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Seputar Bateray Notebook

2011-10-29T22:15:00.000-07:00

Setelah sekian lama g pernah posting lg,,,,,

Perangkat notebook jaman sekarang kebanyakan menggunkan Baterai jenis Lithium (Li-On). Berikut ini adalah karakteristik dari baterai tersebut:

Jika package battere Li-Ion dibuka, sebetulnya didalamnya mengandung beberapa buah battere kecil yang disebut sebagai CELL. Semakin banyak CELL-nya (artinya semakin banyak battere-nya), akan membuat daya tahan-nya lebih lama. Saat ini jumlah CELL pada Baterai Notebook berkisar antara 4, 6 dan 8 Cell.
Jumlah CELL juga akan mempengaruhi berat battere-nya, dan berimbas pada berat notebook secara keseluruhan. Inilah yang menjelaskan kenapa notebook ringan juga menggunakan Baterai dengan jumlah cell sedikit. Misalnya : Notebook ORIS menggunakan Baterai 4-cell.

Baterai Li-Ion TIDAK mengenal “Memory Effect”, yaitu suatu kondisi dimana jika battere tidak di-charge sampai full (100%) maka kemampuannya akan berkurang. Jadi tidak ada istilah bahwa jumlah pemakaian charge akan mempengaruhi kondisi Baterai tsb.
Jika di-charge 100% dan disimpan pada suhu rata-rata 25? maka kemampuan / umur Baterai Li-Ion akan berkurang 20% setiap tahunnya. Ini dalam pemakaian normal.
Pada saat notebook tidak digunakan, maka charge Baterai sebaiknya rata-rata 40% saja (jangan sampai di-charge penuh). Karena jika keadaan full charge, kondisi itu akan membuat battere lebih banyak kehilangan daya tahannya. Ini juga menjelaskan kenapa jika kita membeli notebook / HP baru, battere selalu TIDAK DALAM KEADAAN PENUH.
Battere Li-Ion juga akan berkurang kemampuannya apabila suhu menjadi semakin panas. Ini yang menjelaskan kenapa pada notebook Celeron M, daya tahan Baterai semakin berkurang. Celeron M itu tidak memiliki fitur SpeedStep Technology seperti pada Pentium M / Core Duo, sehingga clock speed tidak bisa diturunkan dan membuat notebook semakin panas.
Teknologi kimia Li-Ion sebetulnya aman apabila digunakan secara wajar dan sesuai petunjuk. Tapi baterai ini juga dapat MELEDAK / TERBAKAR pada kondisi tertentu, seperti pada kondisi panas yang ekstrim dan berlebihan. Sebaiknya jangan meletakkan notebook pada mobil yang terparkir terbuka pada siang hari yg terik !
Berbeda dengan tipe Baterai lainnya seperti Ni-Cd, Li-Ion dapat di-charged berulang kali tanpa kehilangan kualitasnya. Pada saat Notebook tidak digunakan dalam waktu lama, sebaiknya charge Baterai jangan melebihi 40% agar pengurangan umur Baterai tidak terlalu cepat.
Life cycle baterai Lithium (Li-On) adalah sekitar 400-600 cycle charge dan recharge dimana setelah cycle tersebut maka akan terjadi penurunan kualitas Baterai. Karena lithium saat di charge dari kondisi 1% ke 100% itu dianggapnya sama saja dengan charge dari 99% ke 100%, yakni 1x life cycle. Saat life cyclenya semakin banyak, kapasitas baterai akan semakin berkurang jadi perhatikan metoda cycle recharge anda.

Pertanyaan umum dan problem yang sering terjadi pada baterai Notebook:

Saya baru pakai 3 bulan/1tahun kok baterai sudah tidak bisa dipakai :

Baterai dipakai BUKAN BERDASARKAN WAKTU (hari, bulan, tahun), tetapi di-DIHITUNG berdasarkan CYCLE CHARGE-DISCHARGE, setiap satu cycle kemampuan berdasarkan kalkulasi BOARD BATTERY akan berkurang, bukan kemampuan cell baterai. Dimana BOARD BATTERY ada batasan minimum kemampuan baterai yang diperbolehkan. Pada umumnya baterai bisa sampai 400-600 cycle. Jadi kalau dalam satu hari melakukan 30 cycle, kurang lebih baterai dalam 10 hari akan drop

Baterai saya charge kok tidak penuh2x hanya sampai xx% :

Kenapa tidak penuh2x, karena Current Capacity di BOARD BATTERY tidak sinkron/SAMA dengan perhitungan Arus dan Voltage CELL BATTERY (CELL IMPEDANCE). Ada beberapa type yang bisa di kalibrasi ada yang di LOCK oleh MANUFACTURE BATTERY (Bukan Manufacture laptop).

Lampu charge baterai menyala tetapi kalau adaptor di cabut laptop ikut mati / baterai tidak berfungsi normal :

Kondisi ini biasanya karena SAFETY CIRCUIT di BOARD BATTERY sudah rusak, bisa di akibatkan over current (I), over voltage (V) maupun heat atau panas. Dan didalam BOARD BATTERY terdapat safety circuit 3 lapis dan CUKUP CERDAS

Baterai saya simpan (tidak dipasang di laptop) setelah beberapa waktu kok tidak bisa dipakai lagi. Karena KATA ORANG kalau baterai mau awet lebih baik dicabut :

Didalam BOARD BATTERY terdapat “self discharge/day” parameter dimana apabila battery tidak dipakai akan mengurangi “Current Capacity” di BOARD BATTERY , dimana ada minimum CURRENT CAPACITY yang di ijinkan oleh BOARD BATTERY. Apabila terlalu rendah maka BOARD BATTERY akan mengaktifkan SAFETY CIRCUIT, alias bunuh diri.

Tips dalam penggunaan Baterai notebook

Saat mengunakan baterai atau notebook baru discharge sampai kosong daya bawaan dari pabrik kemudia charge penuh dalam kondisi mati dalam waktu 4-8 jam agar cell baterai optimal.
Battere Li-Ion tidak boleh dikosongkan sampai 0% terlalu sering.
Gunakan baterai dengan optimal artinya manfaatkan life cycle dengan baik jangan ketika baterai masih 90% atau 80% langsung di charge.
Jangan di charge sampai 100% kemudia melepas baterai dari notebook, bila ingin meyimpan baterai dengan melepas dari notebook pastikan kondisi baterai dalam kapasitas 40-60%.
Metode melepas baterai ketika menggunakan listrik AC tidak serta merta membuat baterai menjadi awet dibalik itu ada resiko notebook mengalami kerusakan lain saat hanya mengunakan listrik AC dan terjadi pemadaman listrik.
Usahakan gunakan notebook dalam kondisi temperature ruangan yg baik jangan terlalu panas Karena panas merupakan musuh utama baterai Lithium (Li-On) ada baiknya menggunakan perangkat pendingin notebook seperti external cooling notebook.
Lakukan kalibrasi secara berkala terhadap baterai dengan cara melakukan satu kali discharge penuh (dari kapasitas 100% menjadi sekitar 3%) kemudian diikuti pengisian penuh baterai dengan mematikan notebook.

Cisco: How to configure NAT - Network Address Translation

2011-08-24T15:31:00.000-07:00

This brief tutorial will let you configure NAT overload, or how to enable Internet access to multiple PCs of your LAN using only 1 public IP address. This type of NAT can easily be used at home when you have a Cisco 800 series xDSL router.

The first step is to define the addresses that will need to be NAT’d, this is done using a standard access-list:

access-list 1 permit your_lan_address_range
example: access-list 1 permit 192.168.1.0

Now that we defined the addresses that are allowed to use the NAT address we enable the actual NAT:
ip nat inside source list access-list number interface overload
example: ip nat inside source list 1 dialer0 overload

This command states that it will use the addresses from the access-list we defined in step 1 and NAT it to the Public IP address on the interface, e.g. serial 0, dialer 0, ethernet 1,… The overload keyword specifies that multiple LAN addresses can be NAT’d to that address. The router uses the TCP and UDP ports of the hosts [LAN addresses] to translate the public IP address back to the originating local host address.

The last steps we need to configure is to tell the router which our inside and outside addresses. This is achieved using the following commands:
- for the inside
conf t
interface ethernet | fastethernet number
ip nat inside

- for the outside, assume we are dealing with an xDSL router
conf t
interface dialer0
ip nat outside

Now that NAT is configured we can check to see which addresses are being used by using the show ip nat translations commands.

Configuring DHCP to work with Cisco Manager

2011-08-24T15:28:00.000-07:00

In this case from a Windows Server 2000 or 2003 system, with Cisco Call Manager (CCM). When introducing CCM into environments with an exsiting DHCP infrastructure, problems may occur because Cisco IP phones require additional information from the DHCP server when they startup.

Following the steps of DHCP server on the CCM hardware :

1) Start the DHCP server software that is already installed on your server (it comes with Server 2000 or Server 2003) buy clicking on “Start” then “Setting” then “Control Panel”. After the Control Panel open click on the “Administrative Tools” icon, and then the “DHCP” icon.

2) After the DHCP management console opens click on “Action” then select “New Scope…” then “OK” to the “New Scope Wizard”, then type in the name of your scope, this can be almost anything you would like, I named mine “voip_scope”, you can also give it a description if you like, I did not.

3) Then click “Next” and enter a start IP address and a end IP address, then use the up and down arrow buttons to increases or decrees the length of your sub-net mask, (just keep clicking the arrow buttons till you see the sub-net mask you what to use) and then click “Next”.

4) Next you will be asked to enter any address you do not want issue out be the DHCP server, maybe you are saving some static addresses for you router and/or servers. You can enter in just one address by entering the same address in the start and end boxes, or a range of addresses be putting the first or lowest in the start box, and the last or highest in the end box, then click “Next”.

5) You will be asked how long you want the lease to be good for; I leave it to the default and click “Next”.

6) Next you are asked if you want to set up the DHCP options now, these are the options the DHCP server will pass along to the requesting client with it’s new IP address, I select “Yes” and enter the “Router (Default Gateway) IP address, and click “Add” and then click “Next”.

7) Next you can enter and any Domain information you have and then click “Add” then “Next”.

8) You can now add and WINS information you have, I leave mind blank, and click “Next”. The lest question you are asked is if you want to active the scope now, I select “Yes” and click “Next” and then “Finish” to close the “New Scope Wizard”.

9) In the right hand plane of the DHCP management console windows double click on “Scope Options”, the click “Action” and select “Configure Options…” then in the “Scope Options” box click “066 Boot Server Host Name” to check that option, and in the “String value” box enter the IP address of your TFTP server, mine happens to be the same as my CCM, and click OK. Now when a client asked for a new IP address it will also get the TFTP server’s address, which the Cisco IP phones need to boot.

Learning Cisco CCNA with Simulators

2011-08-23T12:06:00.000-07:00

Passing the CCNA is all about knowing the details of how things work, and knowing CSMA/CD theory and how to define collision domains is of the lots of details you have got to master. In the next part of this CCNA tutorial, we'll take a glance at broadcast domains, and how defining broadcast domains in the right places can dramatically cut down on unnecessary traffic on your network.

As you study for your CCNA and CCNP exams, if you are getting hands-on practice in your home lab or rack rental service, you are going to be sending lots of pings. As a CCNA or CCNP candidate, you know that exclamation points (!!) as a ping return indicates that you have IP connectivity to the remote location. periods (\.\...) indicates that you do not have that connectivity.

Students and Professionals that got their CCNA certification will normally finish up in one of categories. The 1st: guys and gals entering the IT world. The 2nd section: individuals who need to make the transition from Local Area Network to Wide Area Network. WAN engineers and administrators make the 3rd section. In the event that they got their CCNA certification, it is because they yearn to move up the ladder.
Keep learning & improving after your've earned your certification. It is simple to quickly forget what you don't use. Feel free to take off a couple days to reward yourself for all that hard work. Then, of work, it is time to strap back in & study. Keep reviewing your CCNA topics, & start on your first CCNP examination. Lots of folks who get that glorious CCNA certificate will basically forget the knowledge they obtained because they gave up studying one time the examination was over.
I give strong recommendation to video tutorials, Exams Testing Engines, Study Guides, Preparation Labs, Q & A for CCNA certification package. Indeed it is a actual worth to money. Here you can get configuration of cisco devices along with proper explanation but the disadvantage is it does not cover everything in examination so you need to go for CCNA CCNA exams training simulators.
Get practice check program

Cisco Simulators
There's free or paid cisco CCNA exams training simulators available on web. It is necessary to get your hands on these simulators so you get on hand experience in configuration cisco devices. In case you have budge you can also build your Cisco home lab.

Today plenty of companies sell practice exams that help to attempt CCNA CCNA examination training. You require to buy them & go for your first check. In the first attempt you may fail but don't get discouraged. Plenty of practice check program are the bank of questions, each divided in to four practice tests. You are necessary to attempt the practice tests four times. Finally you take final practice examination including the all the questions. At this point of time you are prepared to go for actual examination.

If your preparing for career alter & looking for CCNA Training the best online training provider that provide the all the & complete MCTS certification exams training in package, certkingdom self study training kits, save your money on bootcamps, training institutes, It is also save your travelling & time. All training materials are "Guaranteed" to pass your exams & get you certified on the fist attempt, due to best training they become no1 site 2009 & 2010.
In addition I recommend Certkindom.com is best and No1 site of 2008 which provide the complete Windows Server 2003 certified professionals training, Microsoft MCITP, Microsoft MCTS, Cisco CCNA, Cisco CCIE, CompTIA A+, IBM, Citrix, PMP, ISC, and lots more online training self study kits, saving your time and money on all those expensive bootcamps, conventional training institutes where you have take admission pay fees first and if you don't want to continue no refunds no transfer to any other training course, If you planed to take CCNA or specialization in MCSE 2003 all the process starts again; as for getting online training can be much beneficial and you don't need to take for fill any from to switch your training on any desire certification.

4 Tips to Use a CCNA Study Guide

2011-08-23T11:38:00.000-07:00

Try to look for more CCNA study guides & CCNA books. This may help you understand things in over fashion. Reading a range of CCNA study guides about the same idea makes you understand it more & perhaps simple. Go to Amazon & buy CCNA study guides from different study authors as you can.

A CCNA study guide is tremendous gizmo to pass the CCNA Certification examination if used correctly. Regrettably, some CCNA students use CCNA study guides badly, & this leads to confusions related to the CCNA topics & decrease the CCNA candidate's chances to pass the CCNA check. In the upcoming paragraphs, you'll some tips on how to make use of CCNA study guides.

of the ways to benefit from you CCNA study guide is to make use of it as a checklist. all of CCNA study guide provide knowledge that you are supposed to know to pass the CCNA certification examination. In the coursework of your CCNA study journey, try to mark a check to each element in your CCNA study guide when you have comprehended it & configured its related commands. When you finish studying, review you CCNA study guide to see in case you have left or more items unchecked. If yes, use other CCNA books & other networking books on the item or items you still don't understand. You may also do a research on Google & find lots of useful knowledge, document, & even some free CCNA study guides.

Finally, try to build your own CCNA study guide by assembling all the notes you have made as you were studying. In addition, try to share your CCNA study guide with other people studying for the CCNA examination.

Do not make the error of relying on CCNA study guide alone. As historicallyin the past mentioned, CCNA study guides are in no way complete, & you must not treat it as the single source of knowledge to help you pass your CCNA examination. In case you are enrolled in a CCNA boot camp, pay attention in the coursework of your CCNA study activities in the boot camp to help you benefit the most out of your CCNA study guide.

Read more: http://www.articlesbase.com/computers-articles/4-tips-to-use-a-ccna-study-guide-perfectly-4305027.html#ixzz1VsdoxfZE
Under Creative Commons License: Attribution No Derivatives

Classful IP Subnet Calculations

2011-08-23T11:30:00.000-07:00

1. IP Addressing

At this point you should know that IP, the Internet Protocol, is a network layer (OSI layer 3) protocol, used to route packets between hosts on different networks. To suit this purpose, IP must define an addressing scheme, so that a packet's intended destination can be indicated.

An IP address is composed of 32 bits. These 32 bits are divided into 4 octets of 8 bits each. You may have seen an IP address represented like this: 172.68.15.24. We must remember, however, that the computer understands this number only in binary, so we must often deal with them in binary. Many people are intimidated by this initially, but soon find that it is not difficult. If you do not allow yourself to be flustered, you can master this topic.

IP addresses are assigned to orginazations in blocks. Each block belongs to one of three classes: class A, class B, or class C. You can tell what class an IP address is by the value in its first octet.

Class A	1-126
Class B	128-191
Class C	192 -->

An IP address consists of two fields. The first field identifies the network, and the second field identifies the node on the network. Which bits of the address are in the network field and which bits are in the host field is determined by the subnet mask.

When a class A IP license is granted, you are assigned something like this: 99.0.0.0. Only the value of the bits in the first octet are assigned. This means you are free to assign any values you wish in the second, third and fourth octets.

The defualt subnet mask for a class A network is 255.0.0.0. High bits, ones, indicate the bits that are part of the network field of the IP address. The default subnet mask does not create subnets. Therefor, a class A network with the default subnet mask is one network. The three octets that are unassigned and unmasked are part of the host field of the address. There is a total of 24 bits in those three octets. Each bit can be in one of two states. Therefor, 2^24 is the number of host addresses that can be assigned on that network, almost. Two addresses are reserved on every network, x.x.x.0 and x.x.x.255. So the total number of hosts possible on this network is 2^24. 2^24-2=16,777,214 hosts for a class A IP network.

When a class B license is granted, the first two octets are assigned. For example, 172.198.x.x. The default subnet mask for a class B is 255.255.0.0. One network, two octets free, 16 bits for the host address field. 2^16-2=65,534 possible host addresses on a class B IP network.

When a class C license is granted, the first three octets are assigned, for example: 193.52.16.0. The default subnet mask for a class C is 255.255.255.0. Once octet makes up the host address field. 2^8-2=254 host addresses possible on a class C network.

2. Reason for Subnetting

We said that the default subnet mask for a class A IP network is 255.0.0.0. Once octet only of a class A network address identifies the network, with this subnet mask. This leaves three octets of 8 bits each, or 24 bits, to identify the host on that one network. 2^24=16,777,216 addresses. Two addresses are reserved, x.x.x.0 and x.x.x.255. 16,777,214 nodes can be assigned an IP address on this network.

It is highly unlikely that any organization would want one network of 16,777,214 nodes. They might want that many devices connected in a wide area network (WAN), thus capablee of communicating when neccessary, but they will want to subdivide this huge network into mostly self-contained subnetworks of nodes that communicate with each other often. This is called subnetting.

To understand why, consider what would happen in either a broadcast or a token passing network that consisted of over 16,000,000 nodes. Nothing would happen. It simply would not work. Though the problem is not as drastic, class B and class C IP networks are often subnetted, also.

The subnet mask is used to subdivide an IP network into subnets. This is a division that takes place in OSI layer 3, so it is a logical division that is created by the addressing scheme. This logical division is usually combined with a physical division. Many subnets are physically isolated from the rest of the network by a device such as a router or a switch. This aspect of subnetting is discussed in Unit 3--Data Link Layer.

3. How Subnetting Works

The bits of an address that are masked by the subnet mask are the bits that make up the network field of the address. To subnet, the default subnet mask for a network is extended to cover bits of the address that would otherwise be part of the host field. Once these bits are masked, they become part of the network field, and are used to identify subnets of the larger network.

Here is where we begin dealing with both addresses and subnetmasks in binary. Get yourself a cold beverage, stretch, take a deep breath and don't worry. Once you get your brain around the concepts, it is not difficult. You just have to keep trying until the light goes on.

3.1 Translating Binary to Decimal

Both IP addresses and subnet masks are composed of 32 bits divided into 4 octets of 8 bits each. Here is how a single octet translates from binary to decimal. Consider an octet of all ones: 11111111.

128 64 32 16 8 4 2 1 ---  --  --  --  -  -  -  - 1  1  1  1  1  1  1  1  128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255

Here's another: 10111001

128 64 32 16 8 4 2 1 ---  --  --  --  -  -  -  - 1  0  1  1  1  0  0  1 128 +  0 + 32  +16 + 8 + 0 + 0 + 1 = 185

and 00000000

128 64   32   16   8   4   2   1 ---   --   --   --   -   -   -   -  0     0    0    0   0   0   0   0  0  +  0 +  0 +  0 + 0 + 0 + 0 + 0 = 0

3.2 Converting Decimal to Binary

Converting decimal to binary is similar. Consider 175:

128 64  32   16   8   4   2   1 ---   --   --   --   -   -   -   -  1     0    1    0   1   1   1   1 128 +  0 + 32 +  0 + 8 + 4 + 2 + 1 = 175

175=10101111

3.3 Simple Subnetting

The simpliest way to subnet is to take the octet in the subnet mask that covers the first unassigned octet in the IP address block, and make all its bits high. Remember, a high bit, a 1, in the subnet mask indicates that that corresponding bit in the IP address is part of the network field. So, if you have a class B network 172.160.0.0, with the subnet mask 255.255.0.0, you have one network with 65, 534 possible addresses. If you take that subnet mask and make all the bits in the third octet high

128 64   32   16   8   4   2   1 ---   --   --   --   -   -   -   -  1     1    1    1   1   1   1   1 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255

you get the subnet mask 255.255.255.0.

172.60.  0. 0 255.255.255.0

Now the third octet of all the addresses on this network are part of the network field instead of the host field. That is one octet, or eight bits, that can be manipulated to create subnets. 2^8=256 possible subnets now on this class B network.

One octet is left for the host field. 2^8-2=254 possible host addressed on each subnet.

3.4 Advanced Subnetting

That is the simplist way to subnet, but it may not be the most desirable. You might not want 256 subnets on your class B network. Instead, you might use a subnet mask like 255.255.224.0. How many subnets would this give you? The first step is to see how many bits are allocated to the network by this mask.

128 64   32   16   8   4   2   1 ---   --   --   --   -   -   -   -  1     1    1    0   0   0   0   0 128 + 64 + 32 +  0 + 0 + 0 + 0 + 0 = 224

3 bits are allocated. 2^3=8 subnets.

How many hosts on each subnet? Well, 5 bits from this octet are left for the host field, and 8 bits in the fourth octet, for a total of 13 bits in the host field. 2^13-2=8190 possible hosts on each subnet.

The subnet mask is always extended by masking off the next bit in the address, from left to right. Thus, the last octet in the subnet mask will always be one of these: 128, 192, 224, 240, 248, 252, 254 or 255.

Given the IP address of a host and the subnet address for the network, you need to be able to calculate which subnet that host is on. To do this we compare the binary representation of the pertinent octet of the subnet mask witht he binary representation of the corresponding octet in the IP address. Example:

IP address=172.60.50.2 subnet mask=255.255.224.0  50= 00110010 224=11100000

We perform a logical AND on these two numbers. We will be left with only the bits where there is a one in both octets.

00110010 11100000 -------- 00100000=32

This host is on subnet 172.60.32.0.

We also need to be able to find the range of assignable IP addresses on this subnet. To do this, we take the binary that tells us the subnet address, in this case 00100000, and compare it with the subnet mask.

00100000 11100000

The bits convered by the mask we will leave as they are. The rest of the bits we make high. So

00100000 11100000 -------- 0011111=63

The range of assignable IP addresses on the subnet 172.60.32.0 is 172.60.32.1-172.60.63.254.

On every network and subnet, two addresses are reserved. At the low end of the range of addresses for the network or subnet, in this case 172.60.32.0, is the address for the network or subnet itself. The address at the high end of the range of addresses, in this case 172.60.63.255, is the broadcast address. Any message sent to the broadcast address will be received by every host on the network.

4. Sample Problem

Here is a sample problem for you to calculate. When you are done, you can check your answers using an online subnet calcualtor at SubnetOnline.com.

IP address:  154.16.52.16 subnet mask:  255.255.240.0  Find: Number of subnets possible on this network: Number of hosts possible on each subnet: Which subnet this address is on: Range of addresses on that subnet:

Configure your Cisco Router

2011-08-22T10:39:00.000-07:00

If you have just turned on the router, it will be completely unconfigured. If it is already configured, you may want to view its current configuration. Even if it has not been previously configured, you should familiarize yourself with the show commands before beginning to configure the router. Enter privileged mode by issuing the command enable, then issue several show commands to see what they display. Remember, the command show ? will display all the showcommands aavailable in the current mode. Definately try out the following commands:

Router#show interfaces
Router#show ip protocols
Router#show ipv6 protocols
Router#show ip route
Router#show ipv6 route
Router#show ip arp
Router#show ipv6 neighbors

When you enter privileged mode by using the command enable, you are in the top-level mode of privileged mode, also known in this document as "parent mode." It is in this top-level or parent mode that you can display most of the information about the router. As you now know, you do this with the show commands. Here you can learn the configuration of interfaces and whether they are up or down. You can display what IP protocols are in use, such as dynamic routing protocols. You can view the route and ARP tables, and these are just a few of the more important options.

As you configure the router, you will enter various sub-modes to set options, then return to the parent mode to display the results of your commands. You also return to the parent mode to enter other sub-modes. To return to the parent mode, you hit ctrl-z. This puts any commands you have just issued into affect, and returns you to parent mode.

- a.

Global configuration (config)

To configure any feature of the router, you must enter configuration mode. This is the f irst sub-mode of the parent mode. In the parent mode, you issue the command config.

Router#config
Router(config)#

As demonstrated above, the prompt changes to indicate the mode that you are now in.

In connfiguration mode you can set options that apply system-wide, also refered to as "global configurations." For instance, it is a good idea to name your router so that you can easily identify it. You do this in configuration mode with the hostname command.

Router(config)#hostname ExampleName
ExampleName(config)#

As demonstrated above, when you set the name of the host with the hostname command, the prompt immediately changes by replacing Router with ExampleName. (Note: It is a good idea to name your routers with an organized naming scheme.)

Another useful command issued from config mode is the command to designate the DNS server to be used by the router:

ExampleName(config)#ip name-server aa.bb.cc.dd
ExampleName(config)#ctrl-Z
ExampleName#

This is also where you set the password for privileged mode.

ExampleName(config)#enable secret examplepassword
ExampleName(config)#ctrl-Z
ExampleName#

Until you hit ctrl-Z (or type exit until you reach parent mode) your command has not been put into affect. You can enter config mode, issue several different commands, then hit ctrl-Z to activate them all. Each time you hit ctrl-Z you return to parent mode and the prompt:

ExampleName#

Here you use show commands to verify the results of the commands you issued in config mode. To verify the results of the ip name-server command, issue the command show host.

Configuring Cisco router interfaces

Cisco interface naming is straightforward. Individual interfaces are referred to by this convention:

media type slot#/port#

"Media type" refers to the type of media that the port is an interface for, such as Ethernet, Token Ring, FDDI, serial, etc. Slot numbers are only applicable for routers that provide slots into which you can install modules. These modules contain several ports for a given media. The 7200 series is an example. These modules are even hot-swapable. You can remove a module from a slot and replace it with a different module, without interrupting service provided by the other modules installed in the router. These slots are numbered on the router.

Port number refers to the port in reference to the other ports in that module. Numbering is left-to-right, and all numbering starts at 0, not at one.

For example, a Cisco 7206 is a 7200 series router with six slots. To refer to an interface that is the third port of an Ethernet module installed in the sixth slot, it would be interface ethernet 6/2. Therefor, to display the configuration of that interface you use the command:

ExampleName#show interface ethernet 6/2

If your router does not have slots, like a 1600, then the interface name consists only of:

media type port#

For example:

ExampleName#show interface serial 0

Here is an example of configuring a serial port with an IP address:

ExampleName#config
ExampleName(config)#interface serial 1/1
ExampleName(config-if)#ip address 192.168.155.2 255.255.255.0
ExampleName(config-if)#ipv6 address fe80::230:1bff:fe80:b8ea/64
ExampleName(config-if)#ipv6 enable
ExampleName(config-if)#no shutdown
ExampleName(config-if)#ctrl-Z
ExampleName#

Then to verify configuration:

ExampleName#show interface serial 1/1

Note the no shutdown command. An interface may be correctly configured and physically connected, yet be "administratively down." In this state it will not function. The command for causing an interface to be administratively down is shutdown.

ExampleName(config)#interface serial 1/1
ExampleName(config-if)#shutdown
ExampleName(config-if)#ctrl-Z
ExampleName#show interface serial 1/1

In the Cisco IOS, the way to reverse or delete the results of any command is to simply put no infront of it. For instance, if we wanted to unassign the IP address we had assigned to interface serial 1/1:

ExampleName(config)#interface serail 1/1
ExampleName(config-if)#no ip address 192.168.155.2 255.255.255.0
ExampleName(config-if)ctrl-Z
ExampleName#show interface serial 1/1

Configuring most interfaces for LAN connections might consist only of assigning a network layer address and making sure the interface is not administratively shutdown. It is usually not necessary to stipulate data-link layer encapsulation. Note that it is often necessary to stipulate the appropriate data-link layer encapsulation for WAN connections, such as frame-relay and ATM. Serial interfaces default to using HDLC. A discussion of data-link protocols is outside the scope of this document. You will need to look up the IOS command encapsulation for more details.

Configuring Cisco Routing

IP routing is automatically enabled on Cisco routers. If it has been previously disabled on your router, you turn it back on in config mode with the command ip routing.

ExampleName(config)#ip routing
ExampleName(config)#ctrl-Z

To enable IPv6 routing, use the command ipv6 unicast-routing.

ExampleName(config)#ipv6 unicast-routing
ExampleName(config)#ctrl-Z

There are two main ways a router knows where to send packets. The administrator can assign static routes, or the router can learn routes by employing a dynamic routing protocol.

Static routes are generally used in very simple networks or in particular cases that necessitate their use. To create a static route, the administrator tells the router operating system that any network traffic destined for a specified network layer address should be forwarded to a similiarly specified network layer address. In the Cisco IOS this is done with the ip route and ipv6 route commands.

ExampleName#config
ExampleName(config)#ip route 172.16.0.0 255.255.255.0 192.168.150.1
ExampleName(config)#ctrl-Z
ExampleName#show ip route
ExampleName#config
ExampleName(config)#ipv6 route fe80::230:1bff:fe80::/64 fe80::230:1bff:fe80::1
ExampleName(config)#ctrl-Z
ExampleName#show ipv6 route

Two things to be said about this example. First, the packet destination address must include the subnet mask for that destination network. Second, the address it is to be forwarded to is the specified addres of the next router along the path to the destination. This is the most common way of setting up a static route, and the only one this document covers. Be aware, however, that there are other methods.

Dynamic routing protocols, running on connected routers, enable those routers to share routing information. This enables routers to learn the routes available to them. The advantage of this method is that routers are able to adjust to changes in network topologies. If a route is physically removed, or a neighbor router goes down, the routing protocol searches for a new route. Routing protocols can even dynamically choose between possible routes based on variables such as network congestion or network reliability.

There are many different routing protocols, and they all use different variables, known as "metrics," to decide upon appropriate routes. Unfortunately, a router needs to be running the same routing protocols as its neighbors. Many routers can, however, run mutliple protocols. Also, many protocols are designed to be able to pass routing information to other routing protocols. This is called "redistribution."

Routing protocols are a complex topic and this document contains only this superficial description of them. There is much to learn about them, and there are many sources of information about them available. An excelent source of information on this topic is Cisco's website, http://www.cisco.com.

IPv6 configuration with IOS

This is a seperate section because IPv6 is new to most people, and they will be looking specifically for information about configuring IPv6. Examples of configuring IPv6 are included throughout the document, however, alongside IPv4. That is a more accurate reflection of how you will work with IPv6 on a day-to-day basis. Once the newness of IPv6 passes, it will be one more piece in the familiar puzzle.

The important concept to understand when configuring IPv6 is that IPv4 and IPv6 exist in parrallel. One is not a replacement for the other, at least not in the way it is treated by the operating system. A term for this is dual stack. An interface can have an IPv4 address and no IPv6 address. Or an IPv6 address and no IPv4 address. Or both an IPv4 address and an IPv6 address. Examples:

IPv4 only

!
interface FastEthernet0/0
ip address 192.168.1.138 255.255.255.0
!

IPv6 only

!
interface FastEthernet0/0
ipv6 address fe80::230:1bff:fe80::/64
ipv6 enable
!

IPv4 and IPv6

!
interface FastEthernet0/0
ip address 192.168.1.138 255.255.255.0
ipv6 address fe80::230:1bff:fe80::/64
ipv6 enable
!

Notice that there are seperate but similiar commands for IPv4 and IPv6. To assign an IPv4 address,

ExampleName(config-if)#ip address 192.168.1.138 255.255.255.0

To assign an IPv6 address,

ExampleName(config-if)#ipv6 address fe80::230:1bff:fe80::/64

There are some bigger differences between IPv4 and IPv6 IOS commands. For example, the IPv6 equivilant of show ip arp, is show ipv6 neighbors.

3.5 Saving your Cisco Router configuration

Once you have configured routing on the router, and you have configured individual interfaces, your router should be capable of routing traffic. Give it a few moments to talk to its neighbors, then issue the commands show ip route and show ip arp. There should now be entries in these tables learned from the routing protocol.

If you turned the router off right now, and turned it on again, you would have to start configuration over again. Your running configuration is not saved to any perminent storage media. You can see this configuration with the command show running-config.

ExampleName#show running-config

You do want to save your successful running configuration. Issue the command copy running-config startup-config.

ExampleName#copy running-config startup-config

Your configuration is now saved to non-volatile RAM (NVRAM). Issue the command show startup-config.

ExampleName#show startup-config

Now any time you need to return your router to that configuration, issue the command copy startup-config running-config.

ExampleName#copy startup-config running-config

Example Cisco Router configuration

Router>enable
Router#config
Router(config)#hostname N115-7206
N115-7206(config)#interface serial 1/1
N115-7206(config-if)ip address 192.168.155.2 255.255.255.0
N115-7206(config-if)ipv6 address fe80::230:1bff:fe80:b8ea/64
N115-7206(config-if)ipv6 enable
N115-7206(config-if)no shutdown
N115-7206(config-if)ctrl-z
N115-7206#show interface serial 1/1
N115-7206#config
N115-7206(config)#interface ethernet 2/3
N115-7206(config-if)#ip address 192.168.150.90 255.255.255.0
N115-7206(config-if)#no shutdown
N115-7206(config-if)#ctrl-z
N115-7206#show interface ethernet 2/3
N115-7206#config
N115-7206(config)#ip name-server 172.16.0.10
N115-7206(config)#ctrl-z
N115-7206#ping archie.au
N115-7206#config
N115-7206(config)#enable secret password
N115-7206(config)#ctrl-z
N115-7206#copy running-config startup-config
N115-7206#exit

Started with Cisco

2011-08-22T09:45:00.000-07:00

Initially you will probably configure your router from a terminal. If the router is already configured and at least one port is configured with an IP address, and it has a physical connection to the network, you might be able to telnet to the router and configure it across the network. If it is not already configured, then you will have to directly connect to it with a terminal and a serial cable. With any Windows box you can use Hyperterminal to easily connect to the router. Plug a serial cable into a serial (COM) port on the PC and the other end into the console port on the Cisco router. Start Hyperterminal, tell it which COM port to use and click OK. Set the speed of the connection to 9600 baud and click OK. If the router is not on, turn it on.

If you wish to configure the router from a Linux box, either Seyon or Minicom should work. At least one of them, and maybe both, will come with your Linux distribution.

Often you will need to hit the Enter key to see the prompt from the router. If it is unconfigured it will look like this:

Router>

If it has been previously configured with a hostname, it will look like this:

hostname of router>

If you have just turned on the router, after it boots it will ask you if you wish to begin initial configuration. Say no. If you say yes, it will put you in the menu interface. Say no.

- The Cisco IOS command-line interface is organized around the idea of modes. You move in and out of several different modes while configuring a router, and which mode you are in determines what commands you can use. Each mode has a set of commands available in that mode, and some of these commands are only available in that mode। In any mode, typing a question mark will display a list of the commands available in that mode.

When you first connect to the router and provide the password (if necessary), you enter EXEC mode, the first mode in which you can issue commands from the command-line. From here you can use such unprivileged commands as ping, telnet, and rlogin. You can also use some of the show commands to obtain information about the system. In unprivileged mode you use commands like, show version to display the version of the IOS the router is running. Typing show ? will diplay all the show commands available in the mode you are presently in.

Router>show ?

You must enter privileged mode to configure the router. You do this by using the command enable. Privileged mode will usually be password protected unless the router is unconfigured. You have the option of not password protecting privileged mode, but it is HIGHLY recommended that you do. When you issue the command enable and provide the password, you will enter privileged mode.

To help the user keep track of what mode they are in, the command-line prompt changes each time you enter a different mode. When you switch from unprivileged mode to privileged mode, the prompt changes from:

Router>

Router#

This would probably not be a big deal if there were just two modes. There are, in fact, numerous modes, and this feature is probably indispensable. Pay close attention to the prompt at all times.

Within privileged mode there are many sub-modes. In this document I do not closely follow Cisco terminology for this hierarchy of modes. I think that my explanation is clearer, frankly. Cisco describes two modes, unprivileged and privileged, and then a hierarchy of commands used in privileged mode. I reason that it is much clearer to understand if you just consider there to be many sub-modes of privileged mode, which I will also call parent mode. Once you enter privileged mode (parent mode) the prompt ends with a pound sign (#). There are numerous modes you can enter only after entering privileged mode. Each of these modes has a prompt of the form:

Router(arguments)#

They still all end with the pound sign. They are subsumed within privileged mode. Many of these modes have sub-modes of their own. Once you enter priliged mode, you have access to all the configuration information and options the IOS provides, either directly from the parent mode, or from one of its submodes.

computer game

2011-07-25T13:12:00.000-07:00

A personal computer game (also known as a computer game or PC game) is a video game played on a personal computer, rather than on a video game console or arcade machine. Computer games have evolved from the simple graphics and gameplay of early titles like Spacewar!, to a wide range of more visually advanced titles.^[1]

PC games are created by one or more game developers, often in conjunction with other specialists (such as game artists) and either published independently or through a third party publisher. They may then be distributed on physical media such as DVDs and CDs, as Internet-downloadable, possibly freely redistributable, software, or through online delivery services such as Direct2Drive and Steam. PC games often require specialized hardware in the user's computer in order to play, such as a specific generation of graphics processing unit or an Internet connection for online play, although these system requirements vary from game to game.

History

Main article: History of video

Although personal computers only became popular with the development of the microprocessor and microcomputer, computer gaming on mainframes and minicomputers had previously already existed. OXO, an adaptation of tic-tac-toe for the EDSAC, debuted in 1952. Another pioneer computer game was developed in 1961, when MIT students Martin Graetz and Alan Kotok, with MIT student Steve Russell, developed Spacewar! on a PDP-1 mainframe computer used for statistical calculations.^[2]

The first generation of computer games were often text adventures or interactive fiction, in which the player communicated with the computer by entering commands through a keyboard. An early text-adventure, Adventure, was developed for the PDP-11 minicomputer by Will Crowther in 1976, and expanded by Don Woods in 1977.^[3] By the 1980s, personal computers had become powerful enough to run games like Adventure, but by this time, graphics were beginning to become an important factor in games. Later games combined textual commands with basic graphics, as seen in the SSI Gold Box games such as Pool of Radiance, or Bard's Tale for example.

By the late 1970s to early 1980s, games were developed and distributed through hobbyist groups and gaming magazines, such as Creative Computing and later Computer Gaming World. These publications provided game code that could be typed into a computer and played, encouraging readers to submit their own software to competitions.^[4] Microchess was one of the first games for microcomputers which was sold to the public. First sold in 1977, Microchess eventually sold over 50,000 copies on cassette tape.

Like with second-generation video game consoles at the time, early home computer games began gaining commercial success by capitalizing on the success of arcade games at the time with ports or clones of popular arcade games.^[5]^[6] By 1982, the top-selling games for the Atari 400 were ports of Frogger and Centipede, while the top-selling game for the Texas Instruments TI-99/4A was the Space Invaders clone TI Invaders.^[5] That same year, Pac-Man was ported to the Atari 800,^[6] while Donkey Kong was licensed for the Coleco Adam.^[7] In late 1981, Atari attempted to take legal action against unauthorized clones, particularly Pac-Man clones, despite some of these predating Atari's exclusive rights to the home versions of Namco's game.^[6]

[edit] Industry crash

Main article: Video game crash of 1983

As the video game market became flooded with poor-quality cartridge games created by numerous companies attempting to enter the market, and over-production of high profile releases such as the Atari 2600 adaptations of Pac-Man and E.T. grossly underperformed, the popularity of personal computers for education rose dramatically. In 1983, consumer interest in console video games dwindled to historical lows, as interest in computer games rose.^[8] The effects of the crash were largely limited to the console market, as established companies such as Atari posted record losses over subsequent years. Conversely, the home computer market boomed, as sales of low-cost color computers such as the Commodore 64 rose to record highs and developers such as Electronic Arts benefited from increasing interest in the platform.^[8]

The console market experienced a resurgence in the United States with the release of the Nintendo Entertainment System (NES). In Europe, computer gaming continued to boom for many years after.^[8] Computers such as the ZX Spectrum and BBC Micro were successful in the European market, where the NES was not as successful despite its monopoly in Japan and North America. The only 8-bit console to have any success in Europe would be the Sega Master System.^[9] Meanwhile in Japan, both consoles and computers became major industries, with the console market dominated by Nintendo and the computer market dominated by NEC's PC-88 (1981) and PC-98 (1982). A key difference between Western and Japanese computers at the time was the display resolution, with Japanese systems using a higher resolution of 640x400 to accommodate Japanese text which in turn had an impact on game design and allowed more detailed graphics.^[10]

[edit] New genres

Increasing adoption of the computer mouse, driven partially by the success of games such as the highly successful King's Quest series, and high resolution bitmap displays allowed the industry to include increasingly high-quality graphical interfaces in new releases. Meanwhile, the Commodore Amiga computer achieved great success in the market from its release in 1985, contributing to the rapid adoption of these new interface technologies.^[11]

Further improvements to game artwork were made possible with the introduction of FM synthesis sound. Yamaha began manufacturing FM synth boards for computers in the early-mid 1980s, and by 1985, the FM-7 AV computer had built-in FM sound.^[10] The first sound cards, such as AdLib's Music Synthesizer Card, soon appeared in 1987. These cards allowed IBM PC compatible computers to produce complex sounds using FM synthesis, where they had previously been limited to simple tones and beeps. However, the rise of the Creative Labs Sound Blaster card, released in 1989, which featured much higher sound quality due to the inclusion of a PCM channel and digital signal processor, led AdLib to file for bankruptcy by 1992. Also in 1989, the FM Towns computer included built-in PCM sound, in addition to a CD-ROM drive and 24-bit color graphics.^[10]

In 1991, id Software produced an early first-person shooter, Hovertank 3D, which was the company's first in their line of highly influential games in the genre. There were also several other companies that produced early first-person shooters, such as Arsys Software's Star Cruiser,^[12] which featured fully 3D polygonal graphics in 1988,^[13] and Accolade's Day of the Viper in 1989. Id Software went on to develop Wolfenstein 3D in 1992, which helped to popularize the genre, kick-starting a genre that would become one of the highest-selling in modern times.^[14] The game was originally distributed through the shareware distribution model, allowing players to try a limited part of the game for free but requiring payment to play the rest, and represented one of the first uses of texture mapping graphics in a popular game, along with Ultima Underworld.^[15]

While leading Sega and Nintendo console systems kept their CPU speed at 3-7 MHz, the 486 PC processor ran much faster, allowing it to perform many more calculations per second. The 1993 release of Doom on the PC was a breakthrough in 3D graphics, and was soon ported to various game consoles in a general shift toward greater realism.^[16] In the same time frame, games such as Myst took advantage of the new CD-ROM delivery format to include many more assets (sound, images, video) for a richer game experience.

Many early PC games included extras such as the peril-sensitive sunglasses that shipped with The Hitchhiker's Guide to the Galaxy. These extras gradually became less common, but many games were still sold in the traditional over-sized boxes that used to hold the extra "feelies". Today, such extras are usually found only in Special Edition versions of games, such as Battlechests from Blizzard.^[17]

[edit] Contemporary gaming

By 1996, the rise of Microsoft Windows and success of 3D console titles such as Super Mario 64 sparked great interest in hardware accelerated 3D graphics on the IBM PC compatible, and soon resulted in attempts to produce affordable solutions with the ATI Rage, Matrox Mystique and S3 ViRGE. Tomb Raider, which was released in 1996, was one of the first third person shooter games and was praised for its revolutionary graphics. As 3D graphics libraries such as DirectX and OpenGL matured and knocked proprietary interfaces out of the market, these platforms gained greater acceptance in the market, particularly with their demonstrated benefits in games such as Unreal.^[18] However, major changes to the Microsoft Windows operating system, by then the market leader, made many older MS-DOS-based games unplayable on Windows NT, and later, Windows XP (without using an emulator, such as DOSbox).^[19]^[20]

The faster graphics accelerators and improving CPU technology resulted in increasing levels of realism in computer games. During this time, the improvements introduced with products such as ATI's Radeon R300 and NVidia's GeForce 6 Series have allowed developers to increase the complexity of modern game engines. PC gaming currently tends strongly toward improvements in 3D graphics.^[21]

Unlike the generally accepted push for improved graphical performance, the use of physics engines in computer games has become a matter of debate since announcement and 2005 release of the nVidia PhysX PPU, ostensibly competing with middleware such as the Havok physics engine. Issues such as difficulty in ensuring consistent experiences for all players,^[22] and the uncertain benefit of first generation PhysX cards in games such as Tom Clancy's Ghost Recon Advanced Warfighter and City of Villains, prompted arguments over the value of such technology.^[23]^[24]

Similarly, many game publishers began to experiment with new forms of marketing. Chief among these alternative strategies is episodic gaming, an adaptation of the older concept of expansion packs, in which game content is provided in smaller quantities but for a proportionally lower price. Titles such as Half-Life 2: Episode One took advantage of the idea, with mixed results rising from concerns for the amount of content provided for the price.^[25]

[edit] PC game development

Main article: Game development

Game development, as with console games, is generally undertaken by one or more game developers using either standardized or proprietary tools. While games could previously be developed by very small groups of people, as in the early example of Wolfenstein 3D, many popular computer games today require large development teams and budgets running into the millions of dollars.^[26]

PC games are usually built around a central piece of software, known as a game engine,^[27] that simplifies the development process and enables developers to easily port their projects between platforms. Unlike most consoles, which generally only run major engines such as Unreal Engine 3 and RenderWare due to restrictions on homebrew software, personal computers may run games developed using a larger range of software. As such, a number of alternatives to expensive engines have become available, including open source solutions such as Crystal Space, OGRE and DarkPlaces.

[edit] User-created modifications

Main article: Mod (computer gaming)

The multi-purpose nature of personal computers often allows users to modify the content of installed games with relative ease. Since console games are generally difficult to modify without a proprietary software development kit, and are often protected by legal and physical barriers against tampering and homebrew software,^[28]^[29] it is generally easier to modify the personal computer version of games using common, easy-to-obtain software. Users can then distribute their customised version of the game (commonly known as a mod) by any means they choose.

The inclusion of map editors such as UnrealEd with the retail versions of many games, and others that have been made available online such as GtkRadiant, allow users to create modifications for games easily, using tools that are maintained by the games' original developers. In addition, companies such as id Software have released the source code to older game engines, enabling the creation of entirely new games and major changes to existing ones.^[30]

Modding had allowed much of the community to produce game elements that would not normally be provided by the developer of the game, expanding or modifying normal gameplay to varying degrees. Arguably, the most notable example is Counter-Strike, a mod for Half Life. Counter-Strike turned the initial adventure FPS into a round based, tactical FPS.

[edit] Distribution

[edit] Physical distribution

Computer games are typically sold on standard storage media, such as compact discs, DVD, and floppy disks.^[31] These were originally passed on to customers through mail order services,^[32] although retail distribution has replaced it as the main distribution channel for video games due to higher sales.^[33] Cassette tapes^[34] and different formats of floppy disks were initially the staple storage media of the 1980s and early 1990s, but have fallen out of practical use as the increasing sophistication of computer games raised the overall size of the game's data and program files.

The introduction of complex graphics engines in recent times has resulted in additional storage requirements for modern games, and thus an increasing interest in CDs and DVDs as the next compact storage media for personal computer games. The rising popularity of DVD drives in modern PCs, and the larger capacity of the new media (a single-layer DVD can hold up to 4.7 gigabytes of data, more than five times as much as a single CD), have resulted in their adoption as a format for computer game distribution. To date, CD versions are still offered for most games, while some games offer both the CD and the DVD versions.

[edit] Shareware

Main articles: Shareware and Game demo

Shareware marketing, whereby a limited or demonstration version of the full game is released to prospective buyers without charge, has been used as a method of distributing computer games since the early years of the gaming industry and was seen in the early days of Tanarus as well as many others. Shareware games generally offer only a small part of the gameplay offered in the retail product, and may be distributed with gaming magazines, in retail stores or on developers' websites free of charge.

In the early 1990s, shareware distribution was common among fledging game companies such as Apogee Software, Epic Megagames and id Software, and remains a popular distribution method among smaller game developers. However, shareware has largely fallen out of favor among established game companies in favour of traditional retail marketing, with notable exceptions such as Big Fish Games and PopCap Games continuing to use the model today.^[35]

[edit] Online delivery

With the increased popularity of the Internet, online distribution of game content has become more common.^[36] Retail services such as Direct2Drive and Download.com allow users to purchase and download large games that would otherwise only be distributed on physical media, such as DVDs, as well as providing cheap distribution of shareware and demonstration games. Companies such as Real Networks provide a service that allows other websites to use their game catalog and ecommerce backend to publish their own game download distribution sites. Other services, allow a subscription-based distribution model in which users pay a monthly fee to download and play as many games as they wish.

The Steam system, developed by Valve Corporation, provides an alternative to traditional online services. Instead of allowing the player to download a game and play it immediately, games are made available for "pre-load" in an encrypted form days or weeks before their actual release date. On the official release date, a relatively small component is made available to unlock the game. Steam also ensures that once bought, a game remains accessible to a customer indefinitely, while traditional mediums such as floppy disks and CD-ROMs are susceptible to unrecoverable damage and misplacement. The user would however depend on the Steam servers to be online to download its games. According to the terms of service for Steam, Valve has no obligation to keep the servers running. Therefore, if the Valve Corporation shut down, so would the servers. However, they have stated that if the service was to be discontinued, games would no longer require authorization from the servers to run. Nevertheless, they are not obligated to do so.

[edit] PC game genres

[edit] PC gaming technology

An exploded view of a modern personal computer:

Main article: Personal computer

[edit] Hardware

Modern computer games place great demand on the computer's hardware, often requiring a fast central processing unit (CPU) to function properly. CPU manufacturers historically relied mainly on increasing clock rates to improve the performance of their processors, but had begun to move steadily towards multi-core CPUs by 2005. These processors allow the computer to simultaneously process multiple tasks, called threads, allowing the use of more complex graphics, artificial intelligence and in-game physics.^[21]^[38]

Similarly, 3D games often rely on a powerful graphics processing unit (GPU), which accelerates the process of drawing complex scenes in realtime. GPUs may be an integrated part of the computer's motherboard, the most common solution in laptops,^[39] or come packaged with a discrete graphics card with a supply of dedicated Video RAM, connected to the motherboard through either an AGP or PCI-Express port. It is also possible to use multiple GPUs in a single computer, using technologies such as NVidia's Scalable Link Interface and ATI's CrossFire.

Sound cards are also available to provide improved audio in computer games. These cards provide improved 3D audio and provide audio enhancement that is generally not available with integrated alternatives, at the cost of marginally lower overall performance.^[40] The Creative Labs SoundBlaster line was for many years the de facto standard for sound cards, although its popularity dwindled as PC audio became a commodity on modern motherboards.

Physics processing units (PPUs), such as the Nvidia PhysX (formerly AGEIA PhysX) card, are also available to accelerate physics simulations in modern computer games. PPUs allow the computer to process more complex interactions among objects than is achievable using only the CPU, potentially allowing players a much greater degree of control over the world in games designed to use the card.^[39]

Virtually all personal computers use a keyboard and mouse for user input. Other common gaming peripherals are a headset for faster communication in online games, joysticks for flight simulators, steering wheels for driving games and gamepads for console-style games.

[edit] Software

Computer games also rely on third-party software such as an operating system (OS), device drivers, libraries and more to run. Today, the vast majority of computer games are designed to run on the Microsoft Windows family of operating systems. Whereas earlier games written for MS-DOS would include code to communicate directly with hardware, today Application programming interfaces (APIs) provide an interface between the game and the OS, simplifying game design. Microsoft's DirectX is an API that is widely used by today's computer games to communicate with sound and graphics hardware. OpenGL is a cross-platform API for graphics rendering that is also used. The version of the graphics card's driver installed can often affect game performance and gameplay. It is not unusual for a game company to use a third-party game engine, or third-party libraries for a game's AI or physics.

[edit] Multiplayer

[edit] Local area network gaming

Multiplayer gaming was largely limited to local area networks (LANs) before cost-effective broadband Internet access became available, due to their typically higher bandwidth and lower latency than the dial-up services of the time. These advantages allowed more players to join any given computer game, but have persisted today because of the higher latency of most Internet connections and the costs associated with broadband Internet.

LAN gaming typically requires two or more personal computers, a router and sufficient networking cables to connect every computer on the network. Additionally, each computer must have a network card in order to communicate with other computers on the network, and its own copy (or spawn copy) of the game in order to play. Optionally, any LAN may include an external connection to the Internet.

[edit] Online games

Main article: Online game

Online multiplayer games have achieved popularity largely as a result of increasing broadband adoption among consumers. Affordable high-bandwidth Internet connections allow large numbers of players to play together, and thus have found particular use in massively multiplayer online role-playing games, Tanarus and persistent online games such as World War II Online.

Although it is possible to participate in online computer games using dial-up modems, broadband internet connections are generally considered necessary in order to reduce the latency between players (commonly known as "lag"). Such connections require a broadband-compatible modem connected to the personal computer through a network interface card (generally integrated onto the computer's motherboard), optionally separated by a router. Online games require a virtual environment, generally called a "game server". These virtual servers inter-connect gamers, allowing real time, and often fast paced action. To meet this subsequent need, Game Server Providers (GSP) have become increasingly more popular over the last half decade. While not required for all gamers, these servers provide a unique "home", fully customizable (such as additional modifications, settings, etc.) - giving the end gamers the experience they desire. Today there are over 510,000 game servers hosted in North America alone.^[41]

[edit] Emulation

Main article: Emulator

Emulation software, used to run software without the original hardware, are popular for their ability to play legacy video games without the consoles or operating system for which they were designed. The operating system emulators include DOSBox, a DOS emulator which allows playing games developed originally for this operating system and thus not compatible with a modern day OS. Console emulators such as NESticle and MAME are relatively commonplace, although the complexity of modern consoles such as the Xbox or PlayStation makes them far more difficult to emulate, even for the original manufacturers.^[42]

Most emulation software mimics a particular hardware architecture, often to an extremely high degree of accuracy. This is particularly the case with classic home computers such as the Commodore 64, whose software often depends on highly sophisticated low-level programming tricks invented by game programmers and the demoscene.

[edit] Controversy

Main article: Video game controversy

PC games have long been a source of controversy, particularly related to the violence that has become commonly associated with video gaming in general. The debate surrounds the influence of objectionable content on the social development of minors, with organisations such as the American Psychological Association concluding that video game violence increases children's aggression,^[43] a concern that prompted a further investigation by the Center for Disease Control in September 2006.^[44] Industry groups have responded by noting the responsibility of parents in governing their children's activities, while attempts in the United States to control the sale of objectionable games have generally been found unconstitutional.^[45]

Video game addiction is another cultural aspect of gaming to draw criticism as it can have a negative influence on health and on social relations. The problem of addiction and its health risks seems to have grown with the rise of Massively Multiplayer Online Role Playing Games (MMORPGs).^[46] Alongside the social and health problems associated with computer game addiction have grown similar worries about the effect of computer games on education.^[47]

[edit] Computer games museums

There are several computer games museums around the world. In 2011 one opened in Berlin, a computer game museum that documents computer games from the 1970s until today.

Computer Hacking Law & Legal Definition

2011-07-25T13:11:00.000-07:00

Computer hacking is broadly defined as intentionally accesses a computer without authorization or exceeds authorized access. Various state and federal laws govern computer hacking.

The federal Computer Fraud and Abuse Act provides in part as follows:

- . "(a) Whoever--

having knowingly accessed a computer without authorization or exceeding authorized access, and by means of such conduct having obtained information that has been determined by the United States Government pursuant to an Executive order or statute to require protection against unauthorized disclosure for reasons of national defense or foreign relations, or any restricted data, as defined in paragraph y of section 11 of the Atomic Energy Act of 1954, with reason to believe that such information so obtained could be used to the injury of the United States, or to the advantage of any foreign nation, willfully communicates, delivers, transmits, or causes to be communicated, delivered, or transmitted, or attempts to communicate, deliver, transmit or cause to be communicated, delivered, or transmitted the same to any person not entitled to receive it, or willfully retains the same and fails to deliver it to the officer or employee of the United States entitled to receive it;
intentionally accesses a computer without authorization or exceeds authorized access, and thereby obtains--

information contained in a financial record of a financial institution, or of a card issuer as defined in section 1602(n) of title 15, or contained in a file of a consumer reporting agency on a consumer, as such terms are defined in the Fair Credit Reporting Act (15 U.S.C. 1681 et seq.);
information from any department or agency of the United States; or
information from any protected computer if the conduct involved an interstate or foreign communication;

intentionally, without authorization to access any nonpublic computer of a department or agency of the United States, accesses such a computer of that department or agency that is exclusively for the use of the Government of the United States or, in the case of a computer not exclusively for such use, is used by or for the Government of the United States and such conduct affects that use by or for the Government of the United States;
knowingly and with intent to defraud, accesses a protected computer without authorization, or exceeds authorized access, and by means of such conduct furthers the intended fraud and obtains anything of value, unless the object of the fraud and the thing obtained consists only of the use of the computer and the value of such use is not more than $5,000 in any 1-year period;

knowingly causes the transmission of a program, information, code, or command, and as a result of such conduct, intentionally causes damage without authorization, to a protected computer;
intentionally accesses a protected computer without authorization, and as a result of such conduct, recklessly causes damage; or
intentionally accesses a protected computer without authorization, and as a result of such conduct, causes damage;

knowingly and with intent to defraud traffics (as defined in section 1029) in any password or similar information through which a computer may be accessed without authorization, if--

(a)trafficking affects interstate or foreign commerce; or such computer is used by or for the Government of the United States; with intent to extort from any person, firm, association, educational institution, financial institution, government entity, or other legal entity, any money or other thing of value, transmits in interstate or foreign commerce any communication containing any threat to cause damage to a protected computer; shall be punished as provided in subsection (c) of this section. (b) Whoever attempts to commit an offense under subsection (a) of this section shall be punished as provided in subsection (c) of this section. (c) The punishment for an offense under subsection (a) or (b) of this section is--

a fine under this title or imprisonment for not more than ten years, or both, in the case of an offense under subsection (a)(1) of this section which does not occur after a conviction for another offense under this section, or an attempt to commit an offense punishable under this subparagraph; and
a fine under this title or imprisonment for not more than twenty years, or both, in the case of an offense under subsection (a)(1) of this section which occurs after a conviction for another offense under this section, or an attempt to commit an offense punishable under this subparagraph; and

(A) a fine under this title or imprisonment for not more than one year, or both, in the case of an offense under subsection (a)(2), (a)(3), (a)(5)(C), or (a)(6) of this section which does not occur after a conviction for another offense under this section, or an attempt to commit an offense punishable under this subparagraph; and

the offense was committed for purposes of commercial advantage or private financial gain;
the offense was committed in furtherance of any criminal or tortious act in violation of the Constitution or laws of the United States or of any State; or
the value of the information obtained exceeds $5,000;

(B) a fine under this title or imprisonment for not more than 5 years, or both, in the case of an offense under subsection (a)(2), if--

(C) a fine under this title or imprisonment for not more than ten years, or both, in the case of an offense under subsection (a)(2), (a)(3) or (a)(6) of this section which occurs after a conviction for another offense under this section, or an attempt to commit an offense punishable under this subparagraph; and

(A) a fine under this title or imprisonment for not more than five years, or both, in the case of an offense under subsection (a)(4), (a)(5)(A), (a)(5)(B), or (a)(7) of this section which does not occur after a conviction for another offense under this section, or an attempt to commit an offense punishable under this subparagraph; and (B) a fine under this title or imprisonment for not more than ten years, or both, in the case of an offense under subsection (a)(4), (a)(5)(A), (a)(5)(B), (a)(5)(C), or (a)(7)of this section which occurs after a conviction for another offense under this section, or an attempt to commit an offense punishable under this subparagraph; and [former paragraph (4) stricken effective Oct. 11, 1996].

The United States Secret Service shall, in addition to any other agency having such authority, have the authority to investigate offenses under subsections (a)(2)(A), (a)(2)(B), (a)(3), (a)(4), (a)(5), and (a)(6) of this section. Such authority of the United States Secret Service shall be exercised in accordance with an agreement which shall be entered into by the Secretary of the Treasury and the Attorney General."

Computer Software Definition

2011-07-25T13:08:00.000-07:00

Software is a generic term for organized collections of computer data and instructions, often broken into two major categories: system software that provides the basic non-task-specific functions of the computer, and application software which is used by users to accomplish specific tasks.

System software is responsible for controlling, integrating, and managing the individual hardware components of a computer system so that other software and the users of the system see it as a functional unit without having to be concerned with the low-level details such as transferring data from memory to disk, or rendering text onto a display. Generally, system software consists of an operating system and some fundamental utilities such as disk formatters, file managers, display managers, text editors, user authentication (login) and management tools, and networking and device control software.

Application software, on the other hand, is used to accomplish specific tasks other than just running the computer system. Application software may consist of a single program, such as an image viewer; a small collection of programs (often called a software package) that work closely together to accomplish a task, such as a spreadsheet or text processing system; a larger collection (often called a software suite) of related but independent programs and packages that have a common user interface or shared data format, such as Microsoft Office, which consists of closely integrated word processor, spreadsheet, database, etc.; or a software system, such as a database management system, which is a collection of fundamental programs that may provide some service to a variety of other independent applications.

Software is created with programming languages and related utilities, which may come in several of the above forms: single programs like script interpreters, packages containing a compiler, linker, and other tools; and large suites (often called Integrated Development Environments) that include editors, debuggers, and other tools for multiple languages. -

Computer

2011-07-25T13:02:00.000-07:00

A computer is a device that accepts information (in the form of digitalized data) and manipulates it for some result based ओं or sequence of instructions on how the data is to be processed। A computer is a device that accepts information (in the form of digitalized data) and manipulates it for some result based on a program sequence of instructions on how the data is to be processed. Complex computers also include the means for storing data (including the program, which is also a form of data) for some necessary duration. A program may be invariable and built into the computer (and called logic circuitry as it is on microprocesors) or different programs may be provided to the computer (loaded into its storage and then started by an administrator or user). Today's computers have both kinds of programming.

Most histories of the modern computer begin with the Analytical Engine envisioned by Charles Babbage following the mathematical ideas of George Boole, the mathematician who first stated the principles of logic inherent in today's digital computer. Babbage's assistant and collaborator, Ada Lovelace, is said to have introduced the ideas of program loops and subroutines and is sometimes considered the first programmer. Apart from mechanical calculators, the first really useable computers began with the vacuum tube, accelerated with the invention of the transistor, which then became embedded in large numbers in integrated circuits, ultimately making possible the relatively low-cost personal computer.

Modern computers inherently follow the ideas of the stored program laid out by John von Neumann in 1945. Essentially, the program is read by the computer one instruction at a time, an operation is performed, and the computer then reads in the next instruction, and so on. Recently, computers and programs have been devised that allow multiple programs (and computers) to work on the same problem at the same time in parallel. With the advent of the Internet and higher bandwidth data transmission, programs and data that are part of the same overall project can be distributed over a network and embody the Sun Microsystems slogan: "The network is the computer."

Tips Merawat Notebook/Netbook

2011-02-19T21:04:00.000-08:00

Baterai

1. jangan meletakkan baterai di tempat panas (dashboard mobil, dekat sumber panas, terkena panas matahari langsung )

2. charge baterai sesuai dengan buku manual product.

3. Jangan membiarkan baterai terpasang dinotebook lebih dari 1 bulan tanpa menghubungkan dengan adaptor AC4. apabila anda dalam waktu lama tdk pakai notebook, lepaslah baterai simpan ditempat yang aman dan kering.

5. jangan sering mencharge batere jika indikator batere dlm keadaan sudah penuh.

6. Apabila anda igin bekerja untuk waktu cukup lama, lepaskanlah baterai dari notebook dan bekerjalah henya dengan menggunakan adaptor saja. ( dengan syarat listrik cukup aman, tidak sering mati mendadak dan cukup stabil )

7. Pastikan notebook dalam keadaan mati pada saat mengganti baterai.

Harddisk

1. biasakan untuk selalu membackup file data yang ada di harddisk.
2. Instal program anti virus.
3. Jangan memindahkan notebook selama HD sedang bekerja.
4. jangan mengguncang hardisk.

LCD Notebook

1. setelah memakai notebook, biarkan notebook terbuka sekitar 5 menit, baru menutupnya.
2. Sebaiknya gunakan screen saver.

Tips Membersihkan Notebook

1. Untuk membersihkan notebook, pakai kain lembut / kain kaca mata dengan dibasahi sedikit dengan cairan khusus pembersih LCD.

2. Jangan menggunakan alkohol, atau bahan kimia lainnya.

3. Jangan menyemprotkan cairan langsung ke layar LCD,cukup hanya di kain pembersihnya saja.

4. Bersihkan layar dengan penuh hati hati, jangan terlalu ditekan.

Bridging Access Point to Access Point

2011-02-11T08:47:00.000-08:00

Hotspot saat ini bukan lagi merupakan hal yang istimewa dan menherankan bagi para penggemar dunia maya. Cafe, warung internet bahkan rumahan pun saat ini telah menyediakan fasilitas tersebut sebagai salah satu sarana untuk memperlaris atau memudahkan untuk akses internet.
Bridge berasal dari bahasa Inggris, dan sesuai dengan terjemahannya yang berarti jembatan. Metode bridge dalam aplikasi komputer adalah suatu metode yang menjembatani/ menghubungkan dua jaringan LAN kabel menjadi satu sehingga dapat saling berhubungan seperti dalam satu jaringan lan kabel.

Contoh aplikasi sederhana dari metode bridge ini yaitu misalnya kita ingin menghubungkan jaringan LAN di kantor di Gedung A dengan jaringan LAN di gedung B dimana kondisi tidak memungkinkan untuk memasang kabel, maka solusinya hanya menggunakan jaringan radio atau wireless. Pemilihan menggunakan teknologi WIFI ini tidak selamanya mahal karena saat ini sudah banyak produk wireless murah namun berkualitas untuk rumahan atau kantor kecil. Apalagi jika metode ini ingin di terapkan pada lembaga-lembaga non profit seperti gedung-gedung sekolah atau kampus yang tidak mungkin harus mengeluarkan biaya yang sangat besar.

Langkah-langkah sederhana untuk aplikasi yang harus di perhatikan, yaitu :
1. Jarak antar gedung
2. Kondisi sekitar antar gedung apakah terhalang oleh pepohonan atau gedung lain atau tidak.
3. Kondisi alam apakah rawan bahaya petir atau tidak.

Contoh kasus sederhana penerapan aplikasi sederhana point to point pada sebuah gedung sekolah atau kampus. Kondisinya:
1. Gedung A berjarak sekitar 50 s/d 100 meter dengan Gedung B
2. Antar gedung tersebut tidak terhalang oleh pepohonan atau gedung.
3. Kondisi alam sekitar tidak rawan petir.

Pihak sekolah ingin jaringan lan di Gedung A dapat terhubung dengan Gedung B sehingga aplikasi-aplikasi jaringan di dua LAN tersebut dapat di manfaatkan secara optimal bersama-sama.

Maka di pasang dua buah perangkat Akses Point (AP), AP1 di tempatkan di Gedung A dan AP2 di tempatkan di Gedung B. Pemasangan dua AP yang akan di hubungkan tersebutkan di letakan di tempat pada tempat yang saling berhadapan dan di kondisikan tidak ada yang merintangi, misalnya kedua AP tersebut diletakan di langit-langit luar kedua gedung yang saling berhadapan dimana masing-masing AP tersebut terhubung dengan kabel UTP yang menghubungkan dengan masing-masing jaringan LAN.

Garis besar konfigurasi yang harus dilakukan di masing-masing AP yang akan di perlakukan sebagai sarana jembatan koneksi dua LAN tersebut :
1. Pilih konfigurasi mode WAP yaitu sebagai bridge atau point to point
2. Masukan MAC address AP1 di AP2 pada kolom isian MAC AP pasangan, begitu pula sebaliknya MAC address AP2 di masukan ke AP1 kolom isian MAC AP pasang, masing-masing harus di isi MAC address pasangannya.
3. Konfigurasi AP1 dan AP2 sama-sama menggunakan channel radio wireless yang sama, konfigurasi mode keamanan yang sama, seperti jika menggunakan mode keamanan menggunakan WPA PSK atau WPA2PSK masing-masing harus menggunakan konfigurasi dan keyword yang sama.
4. Sesudah dipastikan semua konfigurasi ini sama , cek dan pastikan apakah LAN1 di Gedung A dapat terhubung dengan LAN2 di Gedung B, jika terhubung seharusnya kedua lan ini dapat saling berkomunikasi untuk saling berbagi resource seperti sharing folder, printer , koneksi internet, komputer di LAN1 dapat berhubungan dengan komputer di LAN2. (LAN1 dan LAN2 memiliki subnet mask yang sama meski beda segment)

Jika kondisi antar Gedung terdapat beberapa penghalang seperti daun pepohonan atau jarak yang relative lumayan jauh yang mengurangi kemampuan daya jangkau sinyal AP, maka dapat di lakukan dengan menambahkan antenna high gain directional ke masing-masing AP menggantikan antenna omni bawaan yang kita pasang bahkan adakalanya cukup salah satu AP yang dipasang antenna tersebut (kemampuan antenna dapat dilihat dari DB antenna). Hal lain yang dapat memperkuat sinyal adalah dengan memasang sebuah repeater di tempat antara AP1 dan AP2, biasanya perlakuan ini dilakukan jika kondisi antar gedung penuh dengan penghalang atau inteferensi gangguan sinyal radio lain, maka kita tinggal memilih channel yang cocok untuk bridge kita.

WAP yang umum dijual biasanya transmisi b dan G menggunakan sinyal 2,4 Mhz yang juga di gunakan alat-alat wireless lainnya, namun ada juga WAP yang menyediakan teknologi extended transmisi 2x to 3x eXtended Range dan 108M Super G, serta transmisi N. Juga teknologi transmisi a yang menggunakan sinyal 5 Mhz. Kita tinggal menyesuaikan dengan kondisi yang kita hadapi. Sepasang AP dalam koneksi point to point dapat juga juga dikonfigurasi sebagai Akses Point seperti pada WAP TP-Link TL-WA601G 108M, sehingga pengguna komputer wireless terkoneksi dengan jaringan meski AP tersebut digunakan untuk koneksi point to point, langkah penghematan sederhana.

Bunyi "Tit" dan kerusakan komputer

2011-01-17T17:37:00.000-08:00

Bunyi "tit" pada komputer dapat dijadikan referensi apakah kompuer anda sehat atau tidak. Sama hal nya dengan makan jika porsinya pas maka hidup anda akan sehat, tp kalo kurang atau lebih pasti akan menmbulkan sesuatu yg tidak tepat atau boleh dikatakan bermasalah.

Pada komputer, bunyi tit
(nnti lgi y tak sambung)

Filter MAC Address Mikrotik

2010-10-16T10:41:00.000-07:00

Banyaknya user yang terkadang mengganti-ganti IP Address pada suatu jaringan yg telah ditetapkan alamat IP ny masing-masing. Untuk mengatasi hal ini ada salah satu solusi yang mungkin bisa meminimalisir hal ini, dimana dalam pembahasan kali mengunci MAC hanya dan untuk bisa digunakan oleh IP yang menjadi pasangannya.

MAC filter sendiri metode yang digunakan untuk mengunci MAC address + IP address. Pada contoh kasus sekarang kita akan mengunci :

1. MAC : 00:1D:72:20:E8:1E ke IP : 192.168.5.7
2. MAC : 00:1D:72:C6:AA:F7 ke IP : 192.168.5.8
3. MAC : 00:1F:D0:1E:AB:93 ke IP : 192.168.5.9

Pada contoh kasus di atas digunakan 3 PC dimana masing2 IP telah ditetapkan sesuai MAC nya.

Caranya :
1. Buka WINBOX
2. Masuk ke bagian IP terus klik ARP
3. Step no. 2 digunakan untuk membantu mencari target MAC dan alamat IP-nya ,anda tinggal masuk ke new terminal di winbox anda , kemudian ketik script berikut

/ip firewall filter

Setelah itu ...

Untuk mengunci MAC : 00:1D:72:20:E8:1E ke IP : 192.168.5.7

add chain=forward src-address=192.168.5.7 src-mac-address=!00:1D:72:20:E8:1E action=drop comment=”kunci 192.168.5.7 ke 00:1D:72:20:E8:1E”

add chain=forward src-address=!192.168.5.7 src-mac-address=00:1D:72:20:E8:1E action=drop comment=”kunci 192.168.5.7 ke 00:1D:72:20:E8:1E”

Untuk mengunci MAC : 00:1D:72:C6:AA:F7 ke IP : 192.168.5.8

add chain=forward src-address=192.168.5.8 src-mac-address=!00:1D:72:C6:AA:F7 action=drop comment=”kunci 192.168.5.8 ke 00:1D:72:20:E8:1E”

add chain=forward src-address=!192.168.5.8 src-mac-address=00:1D:72:C6:AA:F7 action=drop comment=”kunci 192.168.5.8 ke 00:1D:72:C6:AA:F7?

Kemudian yang terakhir

Untuk mengunci MAC : 00:1F : D0 : 1E:AB:93 ke IP : 192.168.5.9

add chain=forward src-address=192.168.5.9 src-mac-address=!00:1F:D0:1E:AB:93 action=drop comment=”kunci 192.168.5.9 ke 00:1F:D0:1E:AB:93?

add chain=forward src-address=!192.168.5.9 src-mac-address=00:1F:D0:1E:AB:93 action=drop comment=”kunci 192.168.5.9 ke 00:1F:D0:1E:AB:93?

Setelah langkah-langkah diatas selesai, maka pemilik IP dan MAC yang bersangkutan tidak akan bisa ganti-ganti IP, bahkan menggunakan MAC Clone ato mac address changer sekalipun, karena MAC dan IP-nya terkunci.

Apa itu Cisco router?

2009-06-01T15:44:00.000-07:00

Cisco router adalah peralatan utama yang banyak digunakan pada Jaringan Area Luas atau Wide Area Network (WAN). Dengan cisco router, informasi dapat diteruskan ke alamat-alamat yang berjauhan dan berada di jaringan computer yang berlainan. Untuk dapat meneruskan paket data dari suatu LAN ke LAN lainnya, Cisco router menggunakan tabel dan protocol routing yang berfungsi untuk mengatur lalu lintas data. Paket data yang tiba di router diperiksa dan diteruskan ke alamat yang dituju. Agar paket data yang diterima dapat sampai ke tujuannya dengan cepat, router harus memproses data tersebut dengan sangat tepat.
Untuk itu, Cisco Router menggunakan Central Processing Unit (CPU) seperti yangdigunakan di dalam komputer untuk memproses lalu lintas data tersebut dengan cepat. Seperti komputer, cisco router juga mempunyai sejumlah jenis memori yaitu ROM, RAM, NVRAM dan FLASH, yang berguna untuk membantu kerjanya CPU. Selain itu dilengkapi pula dengan sejumlah interface untuk berhubungan dengan dunia luar dan keluar masuk data. Sistem operasi yang digunakan oleh cisco router adalah Internetwork Operating System (IOS). Memori yang digunakan oleh cisco router masing-masing mempunyai kegunaan sendiri-sendiri sebagai berikut :
• ROM berguna untuk menyimpan sistem bootstrap yang berfungsi untuk mengatur proses boot dan menjalankan Power On Self Test (POST) dan IOS image.
• RAM berguna untuk menyimpan running configuration dan dan sistem operasi IOS yang aktif.
• NVRAM berguna untuk menyimpan konfigurasi awal (start-up configuration)
• FLASH berguna untuk menyimpan IOS image. Dengan menggunakan FLASH, IOS versi baru dapat diperoleh dari TFTP server tanpa harus mengganti komponen dalam router.

Macam-macam Cisco router
Perusahaan cisco membuat router dengan berbagai seri dan model untuk berbagai kelas
atau tingkat penggunaan, seperti :
1. CISCO ROUTER TIPE FIXED TINGKAT AKSES
• Cisco router 700 series
• Cisco router 801-804
• Cisco router 805
• Cisco router 811 dan 813
• Cisco router 827
• Cisco router 1000 series
• Cisco router 2000 series
• Cisco router 2500 series
• Cisco router 3000 series
2. CISCO ROUTER TIPE MODULAR TINGKAT AKSES
• Cisco router 1600 series
• Cisco router 1720 dan 1750
• Cisco router 2500 series
• Cisco router 2600 series
• Cisco router 3600 series
• Cisco router 4000 series
3. CISCO ROUTER TIPE MODULAR TINGKAT INTI
• Cisco router 7000 series, untuk enterprise
• Cisco router 10000 dan 12000 series, untuk enterprise
Umumnya perusahaan cisco memberikan nomor model dengan angka kecil seperti cisco router model 700 untuk jaringan WAN sederhana untuk dipakai oleh perusahaan kecil. Sedangkan nomor dengan angka yang besar seperti cisco router model 12000 digunakan
untuk jaringan WAN kompleks yang dipakai oleh perusahaan besar. Cisco router tipe fixed mempunyai interface tetap yang tidak dapat diganti-ganti sesuai dengan kebutuhan pemakai. Umumnya cisco router jenis modular harganya jauh lebih mahal, tetapi lebih fleksibel dalam penggunaanya. Cisco router 2500 series tersedia dalam
bentuk tipe fixed maupun modular.
Setiap router biasanya mempunyai dua Synchronous Serial port DB-60 (Serial0 dan Serial1) untuk hubungan WAN, satu ethernet port DB-15 (AUI) untuk hubungan LAN, satu Console port RJ-45 untuk akses langsung ke sistem router dan satu Auxiliary Port RJ-45 (AUX) untuk akses ke sistem router dengan modem.

ETOS KERJA

2009-05-09T03:52:00.000-07:00

“ BEBERAPA PENGERTIAN ETOS KERJA ”
1. Keyakinan yang berfungsi sebagai panduan tingkah laku bagi seseorang,
sekelompok orang atau sebuah institusi.
2. Etos Kerja merupakan perilaku khas suatu komunitas atau organisasi,
mencangkup motivasi yang menggerakkan, karakteristik utama, spirit dasar,
pikiran dasar, kode etik, kode moral, kode perilaku,sikap-sikap,aspirasiaspirasi,
keyakinan-keyakinan, prinsip-prinsip, standar-standar.
3. Sehimpunan perilaku positif yang lahir sebagai buah keyakinan fundamental
dan komitmen total pada sehimpunan paradigma kerja yang integral.
“ DELAPAN ETOS KERJA MENURUT JANSEN H SINAMO ”
1. Kerja adalah Rahmat
bekerja tulus penuh syukur.
2. Kerja adalah Amanah
bekerja benar penuh tanggung jawab
3. Kerja adalah Panggilan
bekerja tuntas penuh integritas.
4. Kerja adalah Aktualisasi
bekerja keras penuh semangat.
5. Kerja adalah Ibadah
bekerja serius penuh kecintaan.
6. Kerja adalah Seni
bekerja cerdas penuh kreativitas.
7. Kerja adalah Kehormatan
bekerja tekun penuh keunggulan.
8. Kerja adalah Pelayanan
bekerja paripurna penuh kerendahan hati.

Data Mining Menggali Informasi yang Terpendam

2009-03-02T22:19:00.000-08:00

Data Mining memang salah satu cabang ilmu komputer yang relatif baru. Dan sampai sekarang orang masih memperdebatkan untuk menempatkan data mining di bidang ilmu mana, karena data mining menyangkut database, kecerdasan buatan (artificial intelligence), statistik, dsb. Ada pihak yang berpendapat bahwa data mining tidak lebih dari machine learning atau analisa statistik yang berjalan di atas database. Namun pihak lain berpendapat bahwadatabase berperanan penting di data mining karena data mining mengakses data yang ukurannya besar (bisa sampai terabyte) dan disini terlihat peran penting database terutama dalam optimisasi query-nya.
Lalu apakah data mining itu? Apakah memang berhubungan erat dengan dunia pertambangan…. tambang emas, tambang timah, dsb. Definisi sederhana dari data mining adalah ekstraksi informasi atau pola yang penting atau menarik dari data yang ada di database yang besar. Dalam jurnal ilmiah, data mining juga dikenal dengan nama Knowledge Discovery in Databases (KDD).
Kehadiran data mining dilatar belakangi dengan problema data explosion yang dialami akhir-akhir ini dimana banyak organisasi telah mengumpulkan data sekian tahun lamanya (data pembelian, data penjualan, data nasabah, data transaksi dsb.). Hampir semua data tersebut dimasukkan denganmenggunakan aplikasi komputer yang digunakan untuk menangani transaksi sehari-hari yang kebanyakan adalah OLTP (On Line Transaction Processing). Bayangkan berapa transaksi yang dimasukkan oleh hypermarket semacam Carrefour atau transaksi kartu kredit dari sebuah bank dalam seharinya dan bayangkan betapa besarnya ukuran data mereka jika nanti telah berjalan beberapa tahun. Pertanyaannya sekarang, apakah data tersebut akan dibiarkan menggunung, tidak berguna lalu dibuang, ataukah kita dapat me-‘nambang’-nya untuk mencari ‘emas’, ‘berlian’ yaitu informasi yang berguna untuk organisasi kita. Banyak diantara kita yang kebanjiran data tapi miskin informasi.
Jika Anda mempunyai kartu kredit, sudah pasti Anda bakal sering menerima surat berisi brosur penawaran barang atau jasa. Jika Bank pemberi kartu kredit Anda mempunyai 1.000.000 nasabah, dan mengirimkan sebuah (hanya satu) penawaran dengan biaya pengiriman sebesar Rp. 1.000 per buah maka biaya yang dihabiskan adalah Rp. 1 Milyar!! Jika Bank tersebut mengirimkan penawaran sekali sebulan yang berarti 12x dalam setahun maka anggaran yang dikeluarkan per tahunnya adalah Rp. 12 Milyar!! Dari dana Rp. 12 Milyar yang dikeluarkan, berapa persenkah konsumen yang benar-benar membeli? Mungkin hanya 10 %-nya saja. Secara harfiah, berarti 90% dari dana tersebut terbuang sia-sia.
Persoalan di atas merupakan salah satu persoalan yang dapat diatasi oleh data mining dari sekian banyak potensi permasalahan yang ada. Data mining dapat menambang data transaksi belanja kartu kredit untuk melihat manakah pembeli-pembeli yang memang potensial untuk membeli produk tertentu. Mungkin tidak sampai presisi 10%, tapi bayangkan jika kita dapat menyaring 20% saja, tentunya 80% dana dapat digunakan untuk hal lainnya.
Lalu apa beda data mining dengan data warehouse dan OLAP (On-line Analytical Processing)? Secara singkat bisa dijawab bahwa teknologi yang ada di data warehouse dan OLAP dimanfaatkan penuh untuk melakukan data mining.teknologi data warehouse digunakan untuk melakukan OLAP, sedangkan data mining digunakan untuk melakukan information discovery yang informasinya lebih ditujukan untuk seorang Data Analyst dan Business Analyst (dengan ditambah visualisasi tentunya). Dalam prakteknya, data mining juga mengambil data dari data warehouse. Hanya saja aplikasi dari data mining lebih khusus dan lebih spesifik dibandingkan OLAP mengingat database bukan satu-satunya bidang ilmu yang mempengaruhi data mining, banyak lagi bidang ilmu yang turut memperkaya data mining seperti: information science (ilmu informasi), high performance computing, visualisasi, machine learning, statistik, neural networks (jaringan syaraf tiruan), pemodelan matematika, information retrieval dan information extraction serta pengenalan pola. Bahkan pengolahan citra (image processing) juga digunakan dalam rangka melakukan data mining terhadap data image/spatial.
Dengan memadukan teknologi OLAP dengan data mining diharapkan pengguna dapat melakukan hal-hal yang biasa dilakukan di OLAP seperti drilling/rolling untuk melihat data lebih dalam atau lebih umum, pivoting, slicing dan dicing. Semua hal tersebut diharapkan nantinya dapat dilakukan secara interaktif dan dilengkapi dengan visualisasi.
Data mining tidak hanya melakukan mining terhadap data transaksi saja. Penelitian di bidang data mining saat ini sudah merambah ke sistem database lanjut seperti object oriented database, image/spatial database, time-series data/temporal database, teks (dikenal dengan nama text mining), web (dikenal dengan nama web mining) dan multimedia database.
Meskipun gaungnya mungkin tidak seramai seperti ketika Client/Server Database muncul, tetapi industri-industri seperti IBM, Microsoft, SAS, SGI, dan SPSS terus gencar melakukan penelitian-penelitian di bidang data mining dan telah menghasilkan berbagai software untuk melakukan data mining:
Intelligent Miner dari IBM. Berjalan di atas sistem operasi AIX, OS/390, OS/400, Solaris dan Windows NT. Dijual dengan harga sekitar US$60.000. Selain untuk data IBM juga mengeluarkan produk Intelligent Miner untuk teks. Web site:
www.software.ibm.com/data/iminer/fortext
www-4.inm.com/software/data/iminer/fordata/index.html •
Microsoft juga telah menambahkan fasilitas data mining di Microsoft SQL Server 2000. Web site: www.microsoft.com/sql/productinfo/feaover.htm •
Enterprise Miner dari SAS. Berjalan di atas sistem operasi AIX/6000, CMS, Compaq Tru64 UNIX, HP-UX, IRIX, Intel ABI, MVS, OS/2, Open VMS Alpha, Open VMS Vax, Solaris, dan Windows. Web site: www.sas.com •
MineSet dari Silicon Graphics. Berjalan di atas sistem operasi Windows 9x/NT dan IRIX. Dijual per seat seharga US$995, server (Windows NT) seharga US$35.000 dan untuk IRIX dijual US$50.000. Web site: www.sgi.com/software/mineset •
Clementine dari SPSS. Berjalan di atas sistem operasi UNIX dan Windows NT. Web site: www.spss.com/software/clementine
Beberapa penelitian sekarang ini sedang dilakukan untuk memajukan data mining diantaranya adalah peningkatan kinerja jika berurusan dengan data berukuran terabyte, visualisasi yang lebih menarik untuk user, pengembangan bahasa query untuk data mining yang sedapat mungkin mirip dengan SQL. Tujuannya tidak lain adalah agar end-user dapat melakukan data mining dengan mudah dan cepat serta mendapatkan hasil yang akurat.
Sumber: Yudho Giri Sucahyo, sucahyoy@cs.curtin.edu.au, http://www.ilmukomputer.com/

CakePHP

2009-01-24T02:26:00.000-08:00

CakePHP adalah salah satu framework yang digunakan untuk membuat atau membangun wesbsite berbasis PHP. CakePHP dengan berbagai keunggulannya sangat membantu bagi para pengembang website dalam menyalurkan inspirasi web mereka.
CakePHP Tehe Rapid Development PHP Framework merupakan Wen Framework MVC di dunia PHP yang diinspirasi oleh popularitas RubyonRails. Mencoba menyajikan Rails like Framework di PHP, CakePHP di design mengikuti arsitektur RoR meskipun pastinya terdapat perbedaan.
Kenapa CakePHP menjadi pilihan? Jawabannya adalah ergantung anda sebagai user. CakePHP di design untuk menyelesaikan masalah set solusi yang telah dirangkai dalam paket framework secara tepat dan lengkap.
Itulah sekilas tentang CakePHP, untuk lebih lengkapnya lagi telusuri situs http://www.cakephp.org/ .

Wide Area Network (WAN) dan Router

2008-12-31T01:51:00.000-08:00

Kontribusi Dari Wasi Tri Prasetya
Wednesday, 10 September 2008
Pemutakhiran Terakhir Wednesday, 10 September 2008

Alamat komputer tidak punya network ID yang sama karena berada pada subnet yang berbeda, sehingga untuk mengirimkan paket data tidak bisa menggunakan koneksi hub atau switch. Router dibutuhkan untuk meneruskan paket dari sub-net ke sub-net yang berbeda.

Karakteristik utama WAN

- Menghubungkan peralatan pada tempat yang berjauhan (area luas)
- Menggunakan layanan dengan menyewa, seperti: RBOCs (Perusahan opeasi regional Bell – Regional Bell Operating Company’s), Sprint, MCI, and VPM Internet Services Inc., untuk membangun koneksi antar situs
- Menggunakan koneksi serial dari berbagai jenis untuk mengakses pita lebar dalam lokasi yang berjauhan (luas).
- Bekerja pada layer fisik dan layer datalink dari OSI model
- Melakukan pertukaran paket data dan frames antara ruter dan switch dan LAN yang telah dibangun.

Komponen yang digunakan WAN

- Router dengan beberapa layanan, termasuk interkoneksi dan port-port perantara WAN.
- Modem termasuk perantara layanan voice-grade, unit layanan canel/unit layanan digital (CSU/DSUs), dengan layanan terminal 1/Ethernet 1 (T1/E1), Adapter terminal/terminasi jaringan 1 (TA/NT1s) dengan perantara layanan jaringan digital
terintegrasi (ISDN).
- Server komunikasi pusat dengan dial in and dial out komunikasi antar user

ROUTER

Router adalah jenis khusus dari komputer, yang secara dasar mempunyai komponen yang sama seperti: CPU, memory(ROM, RAM, NVRAM, FLASH), system bus, dan berbagai perantara input/output. Namun router didesain untuk fungsi khusus yang tidak ada di dalam PC, seperti ruter dapat menghubungkan dan menentukan jalur terbaik untuk pengiriman data dalam jaringan.

Seperti juga PC, Router memerlukan sistem operasi untuk menjalankan program aplikasi, router menggunakan Internetwork Operating System (IOS) untuk menjalankan file konfigurasi. File ini berisi instruksi dan parameter yang mengontrol alur lalu lintas data melalui router.

Router menggunakan table dan protokol routing untuk meneruskan paket. File konfigurasi menetapkan seluruh informasi untuk kepastian setup dan menggunakan routing dan routed protocols yang tersedia.

Komponen internal yang utama dari ruter adalah RAM, NVRAM, FLASH MEMORY, ROM dan INTERFACE.

RAM.

- Menyimpan konfigurasi yang sedang berjalan dan sistem ios yang aktif.
- Menyimpan ARP cache (Address Resolution Protocol)
- Menyimpan fast-switching cache
- Menyimpan buffer paket
- Memelihara antrian paket
- Menyimpan memori sementara untuk file konfigurasi ruter selama ruter hidup
- Akan terhapus bila ruter di matikan atau re-start

NVRAM

- Menyimpan file konfigurasi start-up (awal)
- Menyimpan file walau ruter dimatikan atau di re-start.

FLASH MEMORY

- Menyimpan IOS image
- Memungkinkan update software tanpa menghapus dan mengganti chips pada prosesor.
- Menyimpan file walau router dimatikan atau di re-start
- Menyimpan lebih dari satu versi software IOS
- Merupakan alat elektrik yang ROM yang bisa dihapus dan diprogram kembali (EEPROM)

ROM

- Melakukan diagnosa untuk power-on self test (POST)
- Menyimpan program boot dan software sistem operasi dasar
- Untuk upgrade software diperlukan mengganti chips pada motherboard

INTERFACE

- Menghubungkan router ke jaringan untuk meneruskan paket.
- Dapat terpasang pada motherboard ataupun modul terpisah.

Keamanan Sistem Internet

2008-12-25T17:59:00.000-08:00

Untuk melihat keamanan sistem Internet perlu diketahui cara kerja sistem Internet. Antara lain, yang perlu diperhatikan adalah hubungan antara komputer di Internet, dan protokol yang digunakan. Internet merupakan jalan raya yang dapat digunakan oleh semua orang (public). Untuk mencapai server tujuan, paket informasi harus melalui beberapa sistem (router, gateway, hosts, atau perangkat-perangkat komunikasi lainnya) yang kemungkinan besar berada di luar kontrol dari kita. Setiap titik yang dilalui memiliki potensi untuk dibobol, disadap, dipalsukan [22].
Kelemahan sebuat sistem terletak kepada komponen yang paling lemah. Asal usul Internet kurang memperhatikan masalah keamanan. Ini mungkin dikarenakan unsur kental dari perguruan tinggi dan lembaga penelitian yang membangun Internet. Sebagai contoh, IP versi 4 yang digunakan di Internet banyak memiliki kelemahan. Hal ini dicoba diperbaiki dengan IP Secure dan IP versi 6.

Cryptography

2008-12-23T08:13:00.000-08:00

Cryptography comes from the Greek words for "secret writing". It has a long and colorful history going back thousands of years. In this section we will just sketch some of the highlights, as background information for what follows. For a complete history of cryptography, Kahn's (1995) book is recommended reading. For a comprehensive treatment of the current state-of-the-art in security and cryptographic algorithms, protocols, and applications, see (Kaufman et al., 2002). For a more mathematical approach, see (Stinson, 2002). For a less mathematical approach, see (Burnett and Paine, 2001).
Professionals make a distinction between ciphers and codes. A cipher is a character-for-character or bit-for-bit transformation, without regard to the linguistic structure of the message. In contrast, a code replaces one word with another word or symbol. Codes are not used any more, although they have a glorious history. The most successful code ever devised was used by the U.S. armed forces during World War II in the Pacific. They simply had Navajo Indians talking to each other using specific Navajo words for military terms, for example chay-dagahi-nailtsaidi (literally: tortoise killer) for antitank weapon. The Navajo language is highly tonal, exceedingly complex, and has no written form. And not a single person in Japan knew anything about it.
In September 1945, the San Diego Union described the code by saying "For three years, wherever the Marines landed, the Japanese got an earful of strange gurgling noises interspersed with other sounds resembling the call of a Tibetan monk and the sound of a hot water bottle being emptied." The Japanese never broke the code and many Navajo code talkers were awarded high military honors for extraordinary service and bravery. The fact that the U.S. broke the Japanese code but the Japanese never broke the Navajo code played a crucial role in the American victories in the Pacific.

corps, diarists, and lovers. Of these, the military has had the most important role and has shaped the field over the centuries. Within military organizations, the messages to be encrypted have traditionally been given to poorly-paid, low-level code clerks for encryption and transmission. The sheer volume of messages prevented this work from being done by a few elite specialists.
Until the advent of computers, one of the main constraints on cryptography had been the ability of the code clerk to perform the necessary transformations, often on a battlefield with little equipment. An additional constraint has been the difficulty in switching over quickly from one cryptographic method to another one, since this entails retraining a large number of people. However, the danger of a code clerk being captured by the enemy has made it essential to be able to change the cryptographic method instantly if need be.

The messages to be encrypted, known as the plaintext, are transformed by a function that is parameterized by a key. The output of the encryption process, known as the ciphertext, is then transmitted, often by messenger or radio. We assume that the enemy, or intruder, hears and accurately copies down the complete ciphertext.
However, unlike the intended recipient, he does not know what the decryption key is and so cannot decrypt the ciphertext easily. Sometimes the intruder can not only listen to the communication channel (passive intruder) but can also record messages and play them back later, inject his own messages, or modify legitimate messages before they get to the receiver (active intruder). The art of breaking ciphers, called cryptanalysis, and the art devising them (cryptography) is collectively known as cryptology.
It will often be useful to have a notation for relating plaintext, ciphertext, and keys. We will use C = EK(P) to mean that the encryption of the plaintext P using key K gives the ciphertext C. Similarly, P = DK(C) represents the decryption of C to get the plaintext again.

This notation suggests that E and D are just mathematical functions, which they are. The only tricky part is that both are functions of two parameters, and we have written one of the parameters (the key) as a subscript, rather than as an argument, to distinguish it from the message.
A fundamental rule of cryptography is that one must assume that the cryptanalyst knows the methods used for encryption and decryption. In other words, the cryptanalyst knows how the encryption method, E, and decryption, D,of Fig. 8-2 work in detail. The amount of effort necessary to invent, test, and install a new algorithm every time the old method is compromised (or thought to be compromised) has always made it impractical to keep the encryption algorithm secret. Thinking it is secret when it is not does more harm than good.
This is where the key enters. The key consists of a (relatively) short string that selects one of many potential encryptions. In contrast to the general method, which may only be changed every few years, the key can be changed as often as required. Thus, our basic model is a stable and publicly-known general method parameterized
by a secret and easily changed key. The idea that the cryptanalyst knows the algorithms and that the secrecy lies exclusively in the keys is called Kerckhoff's principle, named after the Flemish military cryptographer Auguste Kerckhoff who first stated it in 1883 (Kerckhoff, 1883). Thus, we have: Kerckhoff's principle: All algorithms must be public; only the keys are secret The nonsecrecy of the algorithm cannot be emphasized enough. Trying to keep the algorithm secret, known in the trade as security by obscurity, never works. Also, by publicizing the algorithm, the cryptographer gets free consulting from a large number of academic cryptologists eager to break the system so they can publish papers demonstrating how smart they are. If many experts have tried to break the algorithm for 5 years after itspublication and no one has succeeded, it is probably pretty solid.
Since the real secrecy is in the key, its length is a major design issue. Consider a simple combination lock. The general principle is that you enter digits in sequence. Everyone knows this, but the key is secret. A key length of two digits means that there are 100 possibilities. A key length of three digits means 1000 possibilities, and a key length of six digits means a million. The longer the key, the higher the work factor the cryptanalyst has to deal with. The work factor for breaking the system by exhaustive search of the key space is exponential in the key length. Secrecy comes from having a strong (but public) algorithm and a long key. To prevent your kid brother from reading your e-mail, 64-bit keys will do. For routine commercial use, at least 128 bits should be used. To keep major governments at bay, keys of at least 256 bits, preferably more, are needed.
From the cryptanalyst's point of view, the cryptanalysis problem has three principal variations. When he has a quantity of ciphertext and no plaintext, he is confronted with the ciphertext-only problem. The cryptograms that appear in the puzzle section of newspapers pose this kind of problem. When the cryptanalyst has some matched
ciphertext and plaintext, the problem is called the known plaintext problem. Finally, when the cryptanalyst has the ability to encrypt pieces of plaintext of his own choosing, we have the chosen plaintext problem. Newspaper cryptograms could be broken trivially if the cryptanalyst were allowed to ask such questions as: What is the encryption of ABCDEFGHIJKL?
Novices in the cryptography business often assume that if a cipher can withstand a ciphertext-only attack, it is secure. This assumption is very naive. In many cases the cryptanalyst can make a good guess at parts of the plaintext. For example, the first thing many computers say when you call them up is login: . Equipped with some
matched plaintext-ciphertext pairs, the cryptanalyst's job becomes much easier. To achieve security, the cryptographer should be conservative and make sure that the system is unbreakable even if his opponent can encrypt arbitrary amounts of chosen plaintext.
Encryption methods have historically been divided into two categories: substitution ciphers and transposition ciphers. We will now deal with each of these briefly as background information for modern cryptography.

Intrussion Detection System

2008-12-21T20:32:00.000-08:00

Jaringan atau dalam bahasa inggrisnya network saat ini merupakan salah satu teknologi yang sanagt penting dalam perkembangan IT. Bill Gates dalam bukunya yang berjudul "Speed of Throught" membahas tentang dunia baru yang disebut dengan dunia web, yang menurutnya akan menjadi hal yang sangat penting dan menjadi saraf dalam perkembangan IT.

Jaringan memudahkan user untuk mampu berkomunikasi dalam jarak yang tak terbatas. Antara Indonesia dan Inggris dapat dicapai dengan hitungan detik tanpa kita harus naik pesawat dan berkunjung bertemu dengan Ratu Elisabeth untuk tahu seluk beluk negara Inggris.

perkembangan terknologi ini merupakan akibat dari perkembangan teknolog jaringan yang sudahsnagat pesat saat ini. Mulai dari LAN, MAN, dan WAN yang merupakan spesifikasi jaringan berdasar jarak jangkauan area. Seiring dengan hal ini juga, tingkat keamanan sebuah jaringan menjadi hal yang sangat penting. Keamanan jaringan menjadi hal yang perlu sangat diperhatikan.

Dalam jaringan ada banyak hal yang terkait baik itu dari segi hardware maupun software. pada kesempatan kali ini, saya akan sedikit berbagi tentang apa yang disebut IDS(Intrussion Detection System). IDS merupakan salah satu hal yang menjadi sangat penting mengingat apa yang disebut dengan firewall.

Firewall merupakan pengaman system jaringan dengan prinsip menjaga dan mengamankan jaringan dari kejahatan maupun kejahilan diluar jaringan. Firewall mampu melakukan filtrasi terhadap hal yang tidak dizinkan memasuki jaringan dengan ketentuan-ketentuan tertentu. Hal ini tentunya sungguha akan sangat membantu para ADmin jaringan untuk memantau dan maintenance jaringan.

Tetapi ternyata kejahatn terhadap jaringan bukan hnaya berasal dari luar jaringan saja, tapi juga ancaman dari dalam jaringan itu sendiri. Intrusion detection system (IDS) merupakan penghambat atas semua serangan yang akan menggangu sebuah jaringan. IDS memberi peringatan kepada administrator server saat terjadi sebuah aktivitas tertentu yang tidak diinginkan administrator sebagai penanggung jawab sebuah sistem. Selain memberikan peringatan, IDS juga mampu melacak jenis aktivitas yang merugikan sebuah sistem. Suatu IDS akan melakukan pengamatan (monitoring) terhadap paket-paket yang melewati jaringan dan berusaha menemukan apakah terdapat paket-paket yang berisi aktivitas yang mencurigakan sekaligus melakukan tindak lanjut pencegahan. Pada dasarnya terdapat dua macam IDS, yaitu Host – Based dan Network Based.

IDS host-based bekerja pada host yang akan dilindungi. IDS jenis itu dapat melakukan berbagai macam tugas untuk mendeteksi serangan-serangan yang dilakukan pada host tersebut. keunggulan IDS host-based adalah pada tugas-tugas yanga berhubungan dengan kemanan file, misalnya ada tidaknya file yang telah diubah atau ada tidaknya usaha untuk dapat akses ke file-file yang sensitive.

IDS network-based biasa berupa suatu mesin yang khusus dipergunakan untuk melakukan monitoring terhadap seluruh segmen dari jaringan.IDS network-based akan mengumpulkan paket-paket data yang terdapat pada jaringan dan kemudian menganalisisnya serta menentukan apakah paket-paket tersebut berupa suatu paket yang normal atau suatu serangan atau berupa aktivitas yanga mencurigakan.

Network Security part 2

2008-12-18T18:57:00.000-08:00

Principles of Ciphers

Encryption transforms a message in such a way that it becomes unintelligible to any party that does not have the secret of how to reverse the transformation. The sender applies an encryption function to the original plaintext message, resulting in a ciphertext message that is sent over the network. The receiver applies a secret decryption function—the inverse of the encryption function—to recover the original plaintext. The ciphertext transmitted across the network is unintelligible to any eavesdropper, assuming she doesn’t know the decryption function. The transformation represented by an encryption function and its corresponding decryption function is called a cipher.
Cryptographers have been led to the principle, first stated in 1883, that encryption and decryption functions should be parameterized by a key, and furthermore that the functions should be considered public knowledge—only the key need be secret. Thus, the ciphertext produced for a given plaintext message depends on both the encryption function and the key. One reason for this principle is that if you depend on the cipher being kept secret, then you have to retire the cipher (not just the keys) when you believe it is no longer secret. This means potentially frequent changes of cipher, which is problematic since it takes a lot of work to develop a new cipher. Also, one of the best ways to know that a cipher is secure is to use it for a long time—if no one breaks it, it’s probably secure. (Fortunately, there are plenty of people who will try to break ciphers and who will let it be widely known when they have succeeded, so no news is generally good news.)
Thus, there is considerable cost and risk in deploying a new cipher. Finally, parameterizing a cipher with keys provides us with what is in effect a very large family of ciphers; by switching keys we essentially switch ciphers, thereby limiting
the amount of data that a cryptanalyst (code-breaker) can use to try to break our
key/cipher, and the amount she can read if she succeeds.
The basic requirement for an encryption algorithm is that it turns plaintext
into ciphertext in such a way that only the intended recipient—the holder of the
decryption key—can recover the plaintext. What this means is that encrypted
messages cannot be read by people who do not hold the key.
It is important to realize that when a potential attacker receives a piece of
ciphertext, he may have more information at his disposal than just the ciphertext
itself. For example, he may know that the plaintext was written in English, which
means that the letter e occurs more often in the plaintext that any other letter; the
frequency of many other letters and common letter combinations can also be predicted.
This information can greatly simplify the task of fi nding the key. Similarly,
he may know something about the likely contents of the message; for example,
the word “ login ” is likely to occur at the start of a remote login session. This may enable a known plaintext attack, which has a much higher chance of success
than a ciphertext only attack. Even better is a chosen plaintext attack, which may
be enabled by feeding some information to the sender that you know the sender
is likely to transmit—such things have happened in wartime, for example.
The best cryptographic algorithms, therefore, can prevent the attacker from
deducing the key even when the individual knows both the plaintext and the
ciphertext. This leaves the attacker with no choice but to try all the possible
keys—exhaustive, “ brute-force ” search. If keys have n bits, then there are 2 n possible values for a key (each of the n bits could be either a zero or a one). An attacker could be so lucky as to try the correct value immediately, or so unlucky as to try every incorrect value before fi nally trying the correct value of the key, therefore, she would have tried all 2 n possible values; the average number of guesses to discover the correct value is halfway between those extremes, 2 n /2. This can be made computationally impractical by choosing a suffi ciently large key space and by making the operation of checking a key reasonably costly. What makes this diffi cult is that computing speeds keep increasing, making formerly infeasible computations feasible. Furthermore, although we are concentrating on the security of data as it moves through the network—that is, the data is sometimes vulnerable for only a short period of time—in general, security people have to consider the vulnerability of data that needs to be stored in archives for tens of years. This argues for a generously large key size. On the other hand, larger keys make encryption and decryption slower Most ciphers are block ciphers : they are defi ned to take as input a plaintext block of a certain fi xed size, typically 64 to 128 bits. Using a block cipher to encrypt each block independently—known as electronic codebook (ECB) mode encryption—has the weakness that a given plaintext block value will always result in the same ciphertext block. Hence recurring block values in the plaintext are recognizable as such in the ciphertext, making it much easier for a cryptanalyst to break the cipher.
To prevent this, block ciphers are always augmented to make the ciphertext for a block vary depending on context. Ways in which a block cipher may be augmented are called modes of operation . A common mode of operation is cipher block chaining (CBC), in which each plaintext block is XORed with the previous block’s ciphertext before being encrypted. The result is that each block’s ciphertext depends in part on the preceding blocks (i.e., on its context). Since the first plaintext block has no preceding block, it is XORed with a random number. That random number, called an initialization vector (IV) , is included with the series of ciphertext blocks so that the fi rst ciphertext block can be decrypted. This mode is illustrated in Figure 1.2 . Another mode of operation is counter mode , in which successive values of a counter (e.g., 1, 2, 3, . . .) are incorporated into the encryption of successive blocks of plaintext.
Reference to : Network Security, Know it All.