CCNA Central

Internet Speed Testing Websites

noreply@blogger.com (Phillip) — Sat, 9 Jul 2011 15:21:00 -0500

A list of internet speed testing websites:

Speedtest.net - The Global Broadband Speed Test

Test your Internet connection bandwidth to locations around the world with this interactive broadband speed test
Speakeasy - Speed Test

Test your Internet Connection with Speakeasy's reliable and accurate broadband speed test. What's your speed?
AT&T High Speed Internet Speed Test

Check the Speed, Quality and Performance of Your Internet Connection with the AT&T Internet Speed Test.
Speed Test Internet Speed Test DSL Speed Test Broadband Speed Test Bandwidth Speed Test

A directory of bandwidth speed test web sites lsited by state and country.
Speed Test | Bandwidth | Broadband Internet Services

Check your Internet connection with Bandwidth Place, the #1 interactive broadband Speed Test. Get real-time prices, and compare services.
Internet Speed Test - Test Internet Speed

Test the download and upload speed of your internet

Subnetting Cheat Sheet

noreply@blogger.com (Phillip) — Tue, 21 Jun 2011 02:38:00 -0500

Subnetting Cheat Sheet For Quick Reference

Subnetting is a method of segmenting hosts within a network and providing additional structure hosts within a network and providing additional structure. Without subnets, an organization operates as a flat network. These flat topologies result in short routing tables, but as the network grows, the use of bandwidth becomes inefficient.

Classes	1st Octet Range	Network Bits	Possible Networks	Host Bits	No. of Hosts per Network
A	1-126	8	126	24	16,777,216
B	128-191	16	16,384	16	65,536
C	192-223	24	2,097,152	8	256

Note: The total number of available hosts on a network can be derived by using the formula 2^n-2, where n is the number of host bits. The -2 accounts for an octet with all 0s, which is reserved for network identification, and all 1s, which is reserved for sending a broadcast message to all hosts.

Cisco Network Magic Pro 5.5

noreply@blogger.com (Phillip) — Wed, 15 Jun 2011 13:16:00 -0500

Features

Easy to use - No IT Expertise Needed

Perform tasks from centralized location

An enhanced interface plus new in-product wizards streamline networking tasks, taking the guesswork and effort out of getting connected, monitoring activity and repairing your network.

Connect to the network

Add a Device

Easily connects all of the devices you use in your daily life; computers, printers, cameras and game consoles to your wireless or broadband network.

Go Wireless

"Go Wireless" helps you connect your computers and devices to a secure network.

NAS Support

Connect Network Attached Storage (NAS) devices to your network, allowing you to easily back up your data.

Share Folders and Printers

Share Printers and Files

Eliminate the need to email yourself to get access to files or print documents from different computers.

Protect

New Security Enhancements

Add protection to your network with wireless protection (encryption support for WPA), enabling you to lock out intruders. Plus, easily change your router password in Network Magic instead of having to log-in to your router admin utility.

Monitor and Control

New Parental Monitoring

Gives parents the ability to monitor their kids' online activity. Restrict Internet access plus take real-time desktop screenshots to track websites visited and programs used, providing peace of mind and a safer online experience.

Network Reports

Viewed detailed activity reports for each computer on your networkl informing you of web sites visited, software application used, and devices added or removed.

Manage and Troubleshoot
- Internet Speed Test
  - Test your Internet speed so you can be aware of service or performance issues.
- Health and Security Alerts
  - Proactively monitors and informs you of your network's activity and health, giving you advice on how to resolve issues and improve your online experience.
- Internet Connection Repair
  - Quickly troubleshoot, pinpoint, and repair Internet connection problems.
Cross-platform Support
- Create a seamless network across Windows 7, Vista, XP and Mac so you can easily share printers and files across alll of your computers.
- Network Magic for MAC Add-on
  - Integrate Macs and PCs into one network.

DOWNLOAD

The Internet Infrastructure and How It Connects

noreply@blogger.com (Phillip) — Tue, 14 Jun 2011 01:32:00 -0500

How The Internet Connects

The internet is connected when a user logs into their pc and browse a website by typing in the url. The URL is known as a Domain Name Server; which maps domain names to their IP address. In order for you to even connect to the internet, you must have a Local ISP or Access Providers. Your Local ISP is connected to a regional access router which pools other local ISPs. The regional access router are connected to back haul providers. Back haul providers is capable of handling the massive amounts of Internet traffic that continues to grow.

Definitions You Should Know

	Access Providers The web is really made of many networks connected in a hierarchy. Local Internet service Providers (ISPs) typically give residential and small business access to the Internet. Regional providers typically connect serveral local ISPs to each other and to back haul providers that connect with other regional poroviders.
	Domain Name Server (DNS) This server maps domain names to their IP addresses. One of the main reasons that the Internet has taken off in use and popularity is because www.ccnacentral.info is much easier to remember than. 34.123.13.3.
	Web Servers All web pages are stored on computers called web servers. Thousands of these servers can be dedicated servers for companies, hosting servers that house many personal pages, or even single computers housing individual pages.
	Back Haul Providers A few back haul providers comprise the high-speed backbone of the Internet. Only a handful of these providers are capable of handling the massive amounts of Internet traffic that continues to grow. Many parts of the back haul providers overlap with each other, which improves both the speed and reliability of the network.

Helpful Sites

How to install DD-WRT onto your Linksys Cisco Home Router

noreply@blogger.com (Phillip) — Sun, 12 Jun 2011 22:54:00 -0500

Installation

Installing DD-WRT on your Linksys Cisco Router is almost as simple as installing a program onto your computer. The bad part is; if done incorrectly, you can brick your router. Installing programs on a router is known as a firmware, is done through flashing. This article will help you install DD-WRT onto your Linksys Cisco Home Router.

Identifying your Linksys Cisco Router

Visit this website to accurately identify which model your Linksys Cisco router is. Start with the brand name Cisco Linksys and go down the list.

Flashing Instructions

First and foremost, you will need to download the DD-WRT file that you've identified is your model and save it to a location that you will be able to locate later to flash your router.
Log into the Linksys stock firmware and choose to reset to defaults.
Do a hard reset on your router (hold the reset button down for 30 seconds.)
After your router has been set to default settings and you've done a hard reset, log into your Linksys firmware by typing 192.168.1.1 into your browser.
Click on the "Administration" tab
Click on the "Firmware Upgrade" sub-tab.
Click the "Browse" button and select the DD-WRT .bin file you downloaded and placed in a location you remembered earlier.
Click the "Upgrade" button.
The router will take a few minutes to upload the file and flash the firmware. You should see the power light flash multiple times, dont panic. This is normal.
Once the firmware has been uploaded, a new page will open confirming that the upload was successful. Now wait about 3-5 minutes before clicking "Continue".
Lastly, do another hard reset on your router.
To check that you've successfully and correctly installed DD-WRT, type in 192.168.1.1 in your web browser to be able to see the DD-WRT web interface.

Reverting Back to Stock

Should you want to revert back to your router's stock firmware, you should be able to download the stock firmwaire from the Linksys's site and flash using the webgui.

Helpful Sites

At-a-Glance: OSI Model

noreply@blogger.com (Phillip) — Thu, 2 Jun 2011 23:45:00 -0500

Why should I Care About the OSI Model?

The OSI model serves as a guideline for creating and implementing network standards, devices, and internetworking schemes. Advantages of using the OSI model include the following:

Breaks up interrelated aspects of network operation into less-complex elements.
Enables companies and individual engineers to specialize design and development efforts on modular functions.
Provides standard interfaces for plug-and-play compatibility and multivendor integration.
Abstracts different layers of the network from each other to provide easier adoption of new technologies within a layer.

Develop mnemonics to help you memorize the layers and their order. Here's an example:

Please Do Not Throw Sausage Pizza Away

What Problems Need to Be Solved?

OSI layers can communicate only with the layer directly above or below it on the stack, and with its peer layer on another device. A process must be used so that information can be passed down the stack, across the network, and back up the stack on the peer device.

Quick IP Cheat Sheet used for Reference

noreply@blogger.com (Phillip) — Mon, 25 Oct 2010 01:55:00 -0500

IP Cheat Sheet

	Hosts	Netmask	Amount of a Class C
/30	4	255.255.255.252	1/64
/29	8	255.255.255.248	1/32
/28	16	255.255.255.240	1/16
/27	32	255.255.255.224	1/8
/26	64	255.255.255.192	1/4
/25	128	255.255.255.128	1/2
/24	256	255.255.255.0	1
/23	512	255.255.254.0	2
/22	1024	255.255.252.0	4
/21	2048	255.255.248.0	8
/20	4096	255.255.240.0	16
/19	8192	255.255.224.0	32
/18	16384	255.255.192.0	64
/17	32768	255.255.128.0	128
/16	65536	255.255.0.0	256

How Computer Networking Can Benefit a Company

noreply@blogger.com (Phillip) — Sun, 13 Jun 2010 01:03:00 -0500

Technology is advancing at a rapid pace in today’s world. Businesses are constantly in high demands of technicians that understand the ebb and flow of information through technical devices and that is able to keep up with the growth and new innovations of demanding vendors. Computer networking is one of the many and perhaps most efficient way that information enters and leaves in the complex world of business.
Like any profession, computer networking is an art and science combined. A graphic designer can strike up a beautiful piece of artwork, but like any artist, whether it be a musician or the next Picasso, passionate artists can capture your emotions or attention. Most of the time, find themselves lost in the zone of their passion. This can be applied to computer networking as well, understanding how a business actually functions and fluctuates from day to day, month to month, and year to year is the first step in determining how to set up a network that is suitable for it. Through planning and drafting sketches, you can produce the best possible routing table and in the process, while keeping in mind how your vendor will use information, you can locate and weed out any possible conflicts or problems you may encounter in setting up this beautiful piece of network master piece. Combined with science and the results are unlimited, that’s why there are many more networking schemes to yet be discovered.
Like chemistry and biology, scientists are still researching on new medicines and cures for existing illnesses and diseases. For example, AIDS and HIV are one of the many researches taking place as one speaks. There are many computer scientists today, researching and developing new innovations in the lab and then test running them on current existing businesses to gain feedback and insights on the next big networking scheme. When implemented correctly, businesses can function properly with information being delivered on time, efficiently, and consistently; most definitely contributing to the success of a business and at the same time, giving them the upper hand in competition. We all know
that when things run smoothly, we can channel our focus on something else; in this case, the ROI of a business. So not only does efficient networking contribute to a business success, it allows it to direct its focus elsewhere, for example; push on sales and focus on net profit for a better return on investment and performance inclination. These are just a few major benefits businesses can gain through use of computer networking; it’s no wonder they spend millions of dollars for technology every year. Take Microsoft Sharepoint for example, last year alone, they spent over millions of dollars on innovations but made over hundreds of millions of dollars back on their returns of investments and profits. Sharepoint, a web-development platform has really proved indispensible to any business owner or business in need of a quick, professional, and functional website. About 5 years ago and the years preceding, you had to fully understand computer language, such as HTML, CSS, JavaScripts, and PHP to create a website Now, you just do it with the dragging and click of a button. Most likely, not as easy as 1, 2, 3, but it’s almost as easy as coloring a book. Although this may prove negatively on current professional designers, it has proved indispensible to businesses around the world, and that’s what new innovations ought to do; make life easier. It has also made the job a lot easier and reduced the cost of spending for website designers to most companies. One can reckon the force of how powerful technology can be, but at the same time how dangerous it could be to society.
In health and pharmaceuticals research, some corrupted scientist could invent a dose of drug that could be harmful or detrimental to society, or in the worst case scenario, wipe out the human population. Computer scientist must always be aware that an innovation of theirs could possibly be the vice versa outcome they had expected. This is where the movies and films such as iRobot and Frankenstein came about. Like all professions, good morals and values is essential to every step in research and development, let alone, life itself.
The ebb and flow of information isn’t just the presence and absence of information. It’s art and science combined, whether complex or compound, its value is crucial and vital on businesses all around the globe. For some it could mean a lot of money, but for the ones that truly have a passion in it, nothing is impossible. It’s the boundary between science and art, like the law of time, gravity, and the universe according to Albert Einstein. Time can only tell, but when solved, cracked, or broken; possibilities and new innovations are endless. For the time being though, they are just floating around, patiently waiting to yet to be discovered by a passionate artist/scientist.

Exam Essential: Internetworking

noreply@blogger.com (Phillip) — Fri, 30 Apr 2010 21:32:00 -0500

Know the possible causes of LAN traffic congestion
Too many hosts in a broadcast domain/storms, multicasting, and low bandwidth are all possible suspects of LAN traffic congestion.

Be able to distinguish the difference between a collision domain and a broadcast domain
Collision domain is an Ethernet term used to describe a network collection of devices in which one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it. On a broadcast domain, a set of all devices on a network segment hear all broadcasts sent on that segment.

Be able to distinguish the difference between a hub, a bridge, a switch, and a router
Hubs create one collision domain and one broadcast domain. Bridges break up collision domains but create one super duper large broadcast domain through use of hardware addresses to filter the network. Switches are really just multiple port bridges with more intelligence. They break up collision domains but create one large broadcast domain by default and also uses hardware addresses to filter the network. Routers break up broadcast domains (as well as collision domains) and use logical addressing to filter the network.

Know the OSI layers
It’s mandatory that you know the OSI layers and the function each layer provides. There are seven layers in the OSI reference model. The upper layers consist of The Application, Presentation, and Session Layers, and are responsible for communicating from a user interface to an application. The bottom layers consist of The Transport, Network, Data Link, and Physical Layers. The transport layer provides for segmentation, sequencing, and virtual circuits. The network layer provides for framing and placing of data on the network medium. Last but not least, the physical layer is responsible for taking 1s and 0s and encoding them into a digital signal for transmission on the network segment.

Remember the types of Ethernet cabling and when to use them
There are three types of cables that can be created from an Ethernet cable:

Straight-through

to connect a PC’s or a router’s Ethernet interface to a hub or switch.

Crossover

to connect hub to hub, hub to switch, switch to switch, or PC to PC.

Rolled

for a console connection from a PC to a router or switch

Understand how to connect a console cable from a PC to a router and commence HyperTerminal
You should know how to do this for the exam: Take a rolled cable and connect it from the COM port of the host to the console port of a router. Start HyperTerminal and set the BPS to 9600 and flow control to none.

Memorize the three layers in the Cisco three-layer model

Core
Distribution
Access

Where do you take the CCNA Exams?

noreply@blogger.com (Phillip) — Sun, 11 Apr 2010 01:15:00 -0500

You can take the CCNA Composite exam at any Pearson VUE authorized testing centers or call 877-404-EXAM (3926).

Follow these steps to register for a CCNA exam:

Determine the number of exam you would like to take. (Composite exam number is 640-802.)
Register with the nearest Pearson VUE testing center. At this time, you will be asked to pay in advance for the exam. The current fee for the exam is $150.00 and must be taken within one year of the time of payment. You may also schedule exams up to six weeks in advance or as late as the day you are planning to take it on. However, if you fail a Cisco exam, you must wait five days before you are allowed to re-schedule for another shot at it. Because life can be unexpected, if something is to pop up on your test day, and you need to cancel or reschedule your exam, contact Prometric or Pearson VUE AT LEAST 24 hours in advance.
Upon scheduling the exam, you will receive instructions regarding all appointment and cancelation procedures, the ID requirements, and information regarding the testing-center location.

Here are some general tips for exam day:

Of course, arrive early at the exam location, so you’re able to relax and get a review in before the test. You should not be trying to study the information on this day.
Read each of the questions carefully. Be certain of what exactly each question is asking before diving in to conclusion.
If you’re stuck on a question, your best bet is to use the process of elimination to get rid of the obviously incorrect answers first. This can greatly improve your odds of choosing the wrong answer.
Because you can no longer move forward or backward through the exams, you will need to double-check your answers before proceeding to the next. Make sure you don’t forget this.
And last but not least, stay focused, attentive, and conscious throughout the whole exam.

The physical layer, hubs, and ethernet

noreply@blogger.com (Phillip) — Sun, 28 Feb 2010 03:53:00 -0600

The main functions of the physical layer is to send bits and receive bits, as well as state transitions.

Bits come in only values of 1 or 0 (morse code with numerical values).
State transitions – changes in voltage from high to low and vice-versa.

Hubs at the physical layer

What is a hub?

A hub is really a multiple port repeater.

Hubs in a network

All devices in the same collision domain.
All devices in the same broadcast domain.
Devices shares some bandwidth.

What is a Physical Star Network?

A physical star network is where the hub is a central device and cables are extended in all directions from it.

Note: Hubs and repeaters can be used to enlarge the area covered by a single LAN segment, however, this is NOT RECOMMENDED.

Ethernet at the physical layer

Created by a group called DIX (Digital, Intel, Xerox)
There are three types of ethernet
- 802.3u – Fast Ethernet
- 802.3ab – Gigabit Ethernet on Category 5
- 802.3ae – 10Gbps over fiber and coax

Electronics Industries Association and The Newer Telecommunications Industry Alliance (EIA/TIA)

The standard body that creates the physical layer/specifications for ethernet.
EIA/TIA specifies that ethernet use a registered jack (RJ) connector with a 4 5 wiring sequence on unshielded twisted pair (UTP) cabling (RJ45).

Cables

Cables are measured in decibals (dB)
Cabling in corporate and home markets is measured in categories.
- A higher quality cable will have a higher rated category and lower attenuation.
  - ex. category 5 > category 3

Key term:

Crosstalk – the unwanted signal interference from adjacent pairs in the cable.

A closer look at the Data-Link layer

noreply@blogger.com (Phillip) — Sun, 14 Feb 2010 01:35:00 -0600

The Data-Link layer provides physical transmission of the data and handles error notifications, network topology, and flow control.

Lets take a closer look at it’s function

Ensures messages are delivered to the proper device on LAN using hardware addresses and will translate messages from the Network layer to transmit.
Transmit messages into pieces called a data frame and adds a customized header containing the hardware destination and source address.
Data-Link uses binary values and hexadecimal values.

Binary Values

Nibble Values	Byte Values
8 4 2 1	128 64 32 16 8 4 2 1

Binary to Decimal Chart

Binary Value	Decimal Value
10000000	128
11000000	192
11100000	224
11110000	240
11111000	248
11111100	252
11111110	254
11111111	255

Hexadecimals

Hex is short for hexadecimal, which is a numbering system that uses the first six letters of the alphabet (A through F) to extend beyond the available ten digits in the decimal system. Hexadecimal has a total of sixteen digits.

Hex to Binary to Decimal Chart

Hexadecimal	Binary	Decimal
0	0000	0
1	0001	1
2	0010	2
3	0011	3
4	0100	4
5	0101	5
6	0110	6
7	0111	7
8	1000	8
9	1001	9
A	1010	10
B	1011	11
C	1100	12
D	1101	13
E	1110	14
F	1111	15

Six major points of Routers

noreply@blogger.com (Phillip) — Sun, 14 Feb 2010 01:07:00 -0600

There are six major points to remember or keep in mind when working with routers or layer 3 devices. You should probably commit these to memory.

Here are the six major points

Routers, by default, will not forward any broadcast or multi-task packets.
Routers use the logical address in the network layer header to determine the next hop router to forward the packet to.
Routers can use access list, created by an administrator to control security on the types of packets that are allowed to enter or exit an interface.
Routers can provide layer 2 bridging functions if needed, and can simultaneously route through the same interface.
Routers provide connections between virtual LANS (VLANS).
Routers provide Quality of Service (QoS) for specific types of network traffic.

A closer look at the Network Layer

noreply@blogger.com (Phillip) — Sun, 14 Feb 2010 00:55:00 -0600

The network layer manages devices addressing, tracks location of devices on the network, and determines the best way to move data, which means the Network layer must transport traffic between devices that aren’t locally attached.

Lets take a closer look at it’s function

Checks a packet when it is first received on a router interface.
If the packet isn’t destined for that particular router, it will look up the destination network address in the routing table.
Once the router chooses an exit interface, the packet will be sent to that interface to be framed and sent out on the local network.
If the router is unable to locate an interface; the packets will be dropped.

Key Terms

Router – a router is a network layer device (layer 3 device) and provides the routing services within an internetwork.

Data packets – are used at the network layer to transport data through the internetwork.

Routed Protocols – are used to support data traffic.

Route Update Packets – are used to update neighboring routers about the networks connected to all routers within the internetwork.

Routing Protocols – are used to send out route updates packets.

Network Address

A protocol specific network address.
A router must maintain a routing table for individual routing protocols because each routing protocols keep track of a network with a different addressing scheme (ex. IP, IPv6, and IPX).

Interface – is the exit interface a packet will take when destined for a specific network.

Metric – is the distance to the remote network.

Visual of Windowing

noreply@blogger.com (Phillip) — Mon, 1 Feb 2010 20:55:00 -0600

Windowing Diagram

Window size of 1 = sending machine waits for an acknowledgement for each data segment it transmit before transmitting another segment.

Window size of 3 = allowed to transmit three data segments before an acknowledgement is actually received.

Types of flow control and a closer look at Windowing

noreply@blogger.com (Phillip) — Thu, 28 Jan 2010 22:15:00 -0600

The three types of flow control consists of:

buffering
windowing
congestion avoidance

A closer look at what windowing is and it's function at the transport layer

Windowing

Windowing is the quantity of data segments (measured in bytes) that the transmitting machine is allowed to send without receiving an acknowledgement for them.
In other words, it's the break of time in between data segments of before and after.
Windowing is used to control the amount of outstanding, unacknowledged data segments.

Note: if hosts fails to receive all segments that it should have acknowledged, the host can improve the communication session by decreasing window size.

Connection-oriented Communication

noreply@blogger.com (Phillip) — Thu, 28 Jan 2010 21:58:00 -0600

Note: Recall that connection-oriented communications takes place in conjunction with flow control. These communication sessions, in combination of the protocols involved, provide for reliable data transports at the transport layer.

Diagram:

This is what we call the "Three Way Handshake"

The 1st "connection agreement" segment is a request for synchronization.
At the 2nd and 3rd connection agreement, segments acknowledge the requests and establishes connection parameters (the rules) between hosts. These segments request that the receiver sequencing is synchronized here as well, resulting in a bidirectional connection.
The final segment is also an acknowledgement. It notifies the destination host that the connection has been established – Data transfer can now begin.

How to identify a connection-oriented communication when you see one

It has a virtual circuit set up. (i.e.. 3 way handshake)
Use sequencing
Use acknowledgements
Use flow control

Question: What happens when a device receives a flooding of datagram's (packets) too quickly for it to process?

Answer: They store them in a memory section called a buffer.

Understanding how flow control operates at the Transport layer

noreply@blogger.com (Phillip) — Thu, 28 Jan 2010 21:30:00 -0600

A quick overview of the Transport layer and its function:

Reliable networking is used at the transport layer
- Reliable networking = using acknowledgements, sequencing, and flow control in the network.
Segments and reassembles data into a data stream from the upper application layer and unites the information into the same data stream for further processing.

Flow Control

Flow control prevents a sending host on one side of the connection from overflowing the buffers in the receiving host.
- an event that can result in data loss
Reliable data transports and employs a connection oriented communications sessions between systems and the protocols involved, to ensure that the following will be achieved:
- Segments delivered are acknowledged back to the sender upon their reception.
- Any segments not acknowledged are re-transmitted.
- Segments are sequenced back into their proper order upon arrival at their destination.
- A manageable data flow is maintained in order to:
  - avoid traffic congestion
  - overloading
  - data loss
The purpose of flow control is to provide means for the receiver to be able to govern the out of data sent by the sender.

Important additional functions of the OSI reference model's upper layers

noreply@blogger.com (Phillip) — Thu, 28 Jan 2010 20:28:00 -0600

Application layer

The application layer acts as an interface between the actual applications programs.
- Example - Microsoft Word – actually does not reside at the application layer, but instead just interfaces at the application layer protocol, using data presented to it by the presentation layer.

Presentation layer

The presentation layer presents data to the application layer up top.
Responsible for data translation and code formatting.
Acts as a translator that presents and provides coding and conversion functions.
- Example – EBCDIC to ASCII
Some presentation layer may also involves multimedia operations too.

Session Layer

The session layer is responsible for setting up, managing, and then tearing down sessions between layer entities.
Coordinates communication between systems and serves to organize their communication by offering THREE different modes:
- Simplex
- Half Duplex
- Full Duplex
Keeps different application data separate from other applications data.

A quick overview of the OSI layers and their functions

noreply@blogger.com (Phillip) — Tue, 26 Jan 2010 03:07:00 -0600

Applications

file
print
message
database
application services

Presentations

data encryption
compression
translation

Session

dialog control

Transport

end-to-end connection

Network

routing

Data Link

framing

Physical

physical topology

Facts and notes on the OSI reference model bottom layers

noreply@blogger.com (Phillip) — Tue, 26 Jan 2010 03:03:00 -0600

The bottom layers of the OSI reference model include

Transport
Network
Data Link
Physical

Functions at each of the bottom layers

Transport
- provides reliable or unreliable delivery
- performs error correction before re-transmit

Network
- provides logical addressing, which routers use for path information

Data Link
- combines packets into bytes and bytes into frames
- provides access to media, using MAC address
- performs error detection, NOT correction

Physical
- moves bits between devices
- specifies voltage, wire speed, and pin-out of cables

The following operates at all seven layers of the OSI reference model

Network Management Stations (NMS)
Web and application servers
Gateways (not default gateways)
Network Hosts

Facts and notes on the OSI reference model

noreply@blogger.com (Phillip) — Tue, 26 Jan 2010 02:55:00 -0600

The OSI reference model has seven layers and is divided into two groups.
The top three layers define how the applications within the end stations will communicate with each other and with users.
The bottom four layers define how data is transmitted end to end.

The upper layers of the OSI reference model include

Application layer
Presentation layer
Session layer

*Note: Users interfaces with computer at the application layer.

*Note: The upper layers are responsible for applications communications between hosts.

Diagram

Advantages of using an OSI reference model

noreply@blogger.com (Phillip) — Sat, 23 Jan 2010 22:40:00 -0600

Advantages of using an OSI model include:

Prevents changes in one layer from affecting other layers.
Divides the network communication process into smaller and simpler components, thus aiding components development, design, and troubleshooting.
Allows multiple-vendor development through standardization of network components.
Encourages industry standardization by defining what functions occur at each layer of the model.
Allows various types of hardware and software to communicate

*Reference model: conceptual blueprint of how communications should take place.

*Binding: communication processes that are related to each other are bounded, or grouped together, at a particular layer.

Tips on network, routers, and switches

noreply@blogger.com (Phillip) — Fri, 22 Jan 2010 15:13:00 -0600

1. Plan your network design carefully.

2. Use network bridge in network to reduce collisions within broadcast domains and to increase the number of collision domains in your network.

3. Using hubs can contribute to traffic congestion.

4. Routers break up collision domains as well as broadcast domains.

5. Although bridges/switches are used to segment networks, they WILL NOT isolate broadcast or multicast domains.

6. Even though you have a switched network, you still need a router to provide your inter-VLAN communication or internetworking.

The OSI reference model and it's seven layers

noreply@blogger.com (Phillip) — Tue, 12 Jan 2010 21:24:00 -0600

The OSI reference model has seven layers:

Application layer (layer 7)
Presentation layer (layer 6)
Session layer (layer 5)
Transport layer (layer 4)
Network layer (layer 3)
Data Link layer (layer 2)
Physical layer (layer 1)

CCNA Central

Internet Speed Testing Websites

Subnetting Cheat Sheet

Subnetting Cheat Sheet For Quick Reference

Cisco Network Magic Pro 5.5

Features

The Internet Infrastructure and How It Connects

How The Internet Connects

Definitions You Should Know

Access Providers

Domain Name Server (DNS)

Web Servers

Back Haul Providers

Helpful Sites

How to install DD-WRT onto your Linksys Cisco Home Router

Installation

Identifying your Linksys Cisco Router

Flashing Instructions

Reverting Back to Stock

Helpful Sites

At-a-Glance: OSI Model

Why should I Care About the OSI Model?

What Problems Need to Be Solved?

Quick IP Cheat Sheet used for Reference

IP Cheat Sheet

How Computer Networking Can Benefit a Company

Exam Essential: Internetworking

Where do you take the CCNA Exams?

The physical layer, hubs, and ethernet

A closer look at the Data-Link layer

Lets take a closer look at it’s function

Six major points of Routers

Here are the six major points

A closer look at the Network Layer

Lets take a closer look at it’s function

Key Terms

Visual of Windowing

Windowing Diagram

Types of flow control and a closer look at Windowing

The three types of flow control consists of:

A closer look at what windowing is and it's function at the transport layer

Connection-oriented Communication

Diagram:

This is what we call the "Three Way Handshake"

How to identify a connection-oriented communication when you see one

Understanding how flow control operates at the Transport layer

A quick overview of the Transport layer and its function:

Flow Control

Important additional functions of the OSI reference model's upper layers

Application layer

Presentation layer

Session Layer

A quick overview of the OSI layers and their functions

Facts and notes on the OSI reference model bottom layers

The bottom layers of the OSI reference model include

Functions at each of the bottom layers

The following operates at all seven layers of the OSI reference model

Facts and notes on the OSI reference model

The upper layers of the OSI reference model include

Diagram

Advantages of using an OSI reference model

Tips on network, routers, and switches

The OSI reference model and it's seven layers