Computer Techno

IEEE 802.11n

2012-05-26T23:03:00.000+08:00

In response to growing market demand for higher-performance WLANs, the IEEE formed the task group 802.11n. The scope of this task group is to defi ne modifi cations to the PHY and MAC layer to deliver a minimum of 100 Mbps throughput at the MAC service AP (SAP).

802 .11n employs an evolutionary philosophy reusing existing technologies where practical, while introducing new technologies where they provide effective performance improvements to meet the needs of evolving applications. Reuse of legacy technologies such as OFDM, FEC coding, interleaving, and quadrature amplitude modulation mapping have been maintained to keep costs down and ease backward compatibility.

There are three key areas that need to be considered when addressing increases in WLAN performance. First, improvements in radio technology are needed to increase the physical transfer rate. Second, new mechanisms implementing the effective management of enhanced PHY performance modes must be developed. Third, improvements in data transfer efficiency are needed to reduce the improvements achieved with an increase in physical transfer rate.

The emerging 802.11n specification differs from its predecessors in that it provides for a variety of optional modes and configurations that dictate different maximum raw data rates. This enables the standard to provide baseline performance parameters for all 802.11n devices, while allowing manufacturers to enhance or tune capabilities to accommodate different applications and price points. WLAN hardware does not need to support every option to be compliant with the standard.

The first requirement is to support an OFDM implementation that improves upon the one
employed in 802.11a/g standards, using a higher maximum code rate and slightly wider bandwidth. This change improves the highest attainable raw data rate to 65 Mbps from
54 Mbps in the existing standards.

Multi -input, multi-output (MIMO) technology is used in 802.11n to evolve the existing OFDM physical interface presently implemented with legacy 802.11a/g. MIMO harnesses multipath with a technique known as space-division multiplexing (SDM). The transmitting WLAN device splits a data stream into multiple parts, called spatial streams, and transmits each spatial stream through separate antennas to corresponding antennas on the receiving end. The current 802.11n provides for up to four spatial streams, even though compliant hardware is not required to support that many.

Doubling the number of spatial streams from one to two effectively doubles the raw data rate. There are trade-offs, however, such as increased power consumption and, to a lesser extent, cost. The 802.11n specification includes an MIMO power-save mode, which mitigates power consumption by using multiple paths only when communication would benefit from the additional performance. The MIMO power-save mode is a required feature in the 802.11n specification.

There are two features in the specification that focus on improving MIMO performance: (1) beam-forming and (2) diversity. Beam-forming is a technique that focuses radio signals directly on the target antenna, thereby improving range and performance by limiting interference. Diversity exploits multiple antennas by combining the outputs of or selecting the best subset of a larger number of antennas than required to receive a number of spatial streams. The 802.11n specification supports up to four antennas.

Another optional mode in the 802.11n effectively doubles data rates by doubling the width of a WLAN communications channel from 20 to 40 MHz. The primary trade-off is fewer channels available for other devices. In the case of the 2.4-GHz band, there is enough room for three nonoverlapping 20-MHz channels. A 40-MHz channel does not leave much room for other devices to join the network or transmit in the same air space. This means intelligent, dynamic management is critical to ensuring that the 40-MHz channel option improves overall WLAN performance by balancing the high-bandwidth demands of some clients with the needs of other clients to remain connected to the network.

One of the most important features in the 802.11n specifi cation to improve mixed-mode performance is aggregation. Rather than sending a single data frame, the transmitting client bundles several frames together. Thus, aggregation improves effi ciency by restoring the percentage of time that data is being transmitted over the network.

The 802.11n specification was developed with previous standards in mind to ensure compatibility with more than 200 million Wi-Fi (802.11b) devices currently in use. An 802.11n AP will communicate with 802.11a devices on the 5-GHz band as well as 802.11b and 802.11g hardware on 2.4-GHz frequencies. In addition to basic interoperability between devices, 802.11n provides for greater network efficiency in mixed mode over what 802.11g offers.

Because it promises far greater bandwidth, better range, and reliability, 802.11n is advantageous in a variety of network configurations. And as emerging networking applications take hold in the home, a growing number of consumers will view 802.11n not just as an enhancement to their existing network, but as a necessity. Some of the current and emerging applications that are driving the need for 802.11n are voice over IP (VoIP), streaming video and music, gaming, and network attached storage.

Source of Information : Elsevier Wireless Networking Complete

IEEE 802.11b — High-Rate DSSS

2012-05-23T22:38:00.000+08:00

In September 1999, IEEE ratified the 802.11b high-rate amendment to the standard, which added two higher speeds (5.5 and 11 Mbps) to 802.11. The key contribution of the 802.11b addition to the WLAN standard was to standardize the PHY support to two new speeds, 5.5 and 11 Mbps. To accomplish this, DSSS was selected as the sole PHY technique for the standard, since frequency hopping (FH) cannot support the higher speeds without violating current FCC regulations. The implication is that the 802.11b system will interoperate with 1 and 2 Mbps 802.11 DSSS systems, but will not work with 1 and 2 Mbps FHSS systems.

The original version of the 802.11 specifi es in the DSSS standard an 11-bit chipping, called a Barker sequence, to encode all data sent over the air. Each 11-chip sequence represents a single data bit (1 or 0), and is converted to a waveform, called a symbol, that can be sent over the air. These symbols are transmitted at a one million symbols per second (Msps) rate using binary phase shift keying (BPSK). In the case of 2 Mbps, a more sophisticated implementation based on quadrature phase shift keying (QPSK) is used. This doubles the data rate available in BPSK, via improved efficiency in the use of the radio bandwidth.

To increase the data rate in 802.11b standard, advanced coding techniques are employed. Rather than the two 11-bit Barker sequences, 802.11b specifi es complementary code keying (CCK). CCK allows for multichannel operation in the 2.4 GHz band by using existing 1 and 2 Mbps DSSS channelization schemes. CCK consists of a set of 64 8-bit code words. As a set, these code words have unique mathematical properties that allow them to be correctly distinguished from one another by a receiver even in the presence of substantial noise and multipath interference. The 5.5 Mbps rate uses CCK to encode four bits per carrier, while the 11 Mbps rate encodes eight bits per carrier. Both speeds use QPSK modulation and a signal at 1.375 Msps. This is how the higher data rates are obtained.

To support very noisy environments as well as extended ranges, 802.11b WLANs use dynamic rate shifting, allowing data rates to be automatically adjusted to compensate for the changing nature of the radio channel. Ideally, users connect at a full 11 Mbps rate. However, when devices move beyond the optimal range for 11 Mbps operation, or if substantial interference is present, 802.11b devices will transmit at lower speeds, falling
back to 5.5, 2, and 1 Mbps. Likewise, if a device moves back within the range of a higherspeed transmission, the connection will automatically speed up again. Rate shifting is a PHY mechanism transparent to the user and upper layers of the protocol stack.

Source of Information : Elsevier Wireless Networking Complete

Security of IEEE 802.11 Systems

2012-05-18T22:30:00.000+08:00

The IEEE 802.11 provides for MAC access control and encryption mechanisms. Earlier,
the wire line equivalent privacy (WEP) algorithm was used to encrypt messages. WEP uses a Rivest Cipher 4 (RC4) pseudo-random number generator with two key structures
of 40 and 128 bits. Because of the inherent weaknesses of the WEP, the IEEE 802.11i committee developed a new encryption algorithm and worked on the enhanced security and authentication mechanisms for 802.11 systems.

For access control, ESSID (also known as a WLAN service area ID) is programmed into each AP and is required in order for a wireless client to associate with an AP. In addition, there is provision for a table of MAC addresses called an access control list to be included in the AP, restricting access to stations whose MAC addresses are not on the list.

Beyond layer-2, 802.11 WLANs support the same security standards supported by other 802 LANs for access control (such as network operating system logins) and encryption (such as IPSec or application-level encryption). These higher-level technologies can be used to create end-to-end secure networks encompassing both wired LAN and WLAN components, with the wireless piece of the network gaining additional security from the IEEE 802.11i feature set.

Source of Information : Elsevier Wireless Networking Complete

WLAN Technologies

2012-05-15T22:22:00.000+08:00

The technologies available for use in a WLAN include IR, UHF (narrowband), and SS implementation. Each implementation comes with its own set of advantages and limitations.

IR Technology
IR is an invisible band of radiation that exists at the lower end of the visible electromagnetic spectrum. This type of transmission is most effective when a clear line-of-sight exists between the transmitter and the receiver.

Two types of IR WLAN solutions are available: diffused-beam and direct-beam (or line-of-sight). Currently, direct-beam WLANs offer a faster data rate than the diffused-beam networks. Direct-beam is more directional since diffused-beam technology uses reflected rays to transmit/receive a data signal. It achieves lower data rates in the 1 – 2 Mbps range.

IR is a short-range technology. When used indoors, it can be limited by solid objects such
as doors, walls, merchandise, or racking. In addition, the lighting environment can affect
signal quality. For example, loss of communication may occur because of the large amount of sunlight or background light in an environment. Fluorescent lights also may contain large amounts of IR. This problem may be solved by using high signal power and an optimal bandwidth filter, which reduces the IR signals coming from an outside source. In an outdoor environment, snow, ice, and fog may affect the operation of an IR-based system.

UHF Narrowband Technology
UHF wireless data communication systems have been available since the early 1980s.
These systems normally transmit in the 430 – 470 MHz frequency range, with rare systems using segments of the 800 MHz range. The lower portion of this band — 430 – 450 MHz — is referred to as the unprotected (unlicensed), and 450 – 470 MHz is referred to as the protected (licensed) band. In the unprotected band, RF licenses are not granted for specific frequencies and anyone is allowed to use any frequencies, giving customers some assurance that they will have complete use of that frequency.

Because independent narrowband RF systems cannot coexist on the same frequency, government agencies allocate specific RFs to users through RF site licenses. A limited amount of unlicensed spectrum is also available in some countries. In order to have many
frequencies that can be allocated to users, the bandwidth given to a specific user is very small.

The term narrowband is used to describe this technology because the RF signal is sent in a very narrow bandwidth, typically 12.5 or 25 kHz. Power levels range from 1 to 2 W for
narrowband RF data systems. This narrow bandwidth combined with high power results in larger transmission distances than are available from 900 MHz or 2.4 GHz SS systems, which have lower power levels and wider bandwidths. Table 5.4 lists the advantages and disadvantages of UHF technology.

Many modern UHF systems are synthesized radio technology. This refers to the way channel frequencies are generated in the radio. The crystal-controlled products in legacy UHF products require factory installation of unique crystals for each possible channel frequency. Synthesized radio technology uses a single, standard crystal frequency and drives the required channel frequency by dividing the crystal frequency down to a small value, then multiplying it up to the desired channel frequency. The division and multiplication factors are unique for each desired channel frequency, and are programmed into digital memory in the radio at the time of manufacturing. Synthesized UHF-based solutions provide the ability to install equipment without the complexity of hardware crystals. Common equipment can be purchased and specific UHF frequency used for each device can be tuned based upon specific location requirements. Additionally, synthesized UHF radios do not exhibit the frequency drift problem experienced in crystal-controlled UHF radios.

Modern UHF systems allow APs to be individually configured for operation on one of the several preprogrammed frequencies. Terminals are programmed with a list of all frequencies used in the installed APs, allowing them to change frequencies when roaming. To increase throughput, APs may be installed with overlapping coverage but use different frequencies.

Spread Spectrum Technology
Most WLANs use SS technology, a wideband RF technique that uses the entire allotted
spectrum in a shared fashion as opposed to dividing it into discrete private pieces (as with
narrowband). The SS system spreads the transmission power over the entire usable spectrum. This is obviously a less efficient use of the bandwidth than the narrowband approach. However, SS is designed to trade off bandwidth efficiency for reliability, integrity, and security. The bandwidth trade-off produces a signal that is easier to detect, provided that the receiver knows the parameters of the SS signal being broadcast. If the receiver is not tuned to the right frequency, a SS signal looks like background noise.

By operating across a broad range of radio frequencies, a SS device could communicate clearly despite interference from other devices using the same spectrum in the same physical location. In addition to its relative immunity to interference, SS makes eavesdropping and jamming inherently difficult.

In commercial applications, SS techniques currently offer data rates up to 2 Mbps. Because the FCC does not require site licensing for the bands used by SS systems, this technology has become the standard for high-speed RF data transmission. Two modulation schemes are commonly used to encode SS signals: direct sequence SS (DSSS) and frequency-hopping SS (FHSS).

FHSS uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical channel. To an unintended receiver, FHSS appears to be a short-duration impulse noise.

DSSS generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a spreading code . The longer the code, the greater the probability that the original data can be recovered (and, of course, the more bandwidth will be required). To an unintended receiver DSSS appears as low-power wideband noise and is rejected by most narrowband receivers.

Source of Information : Elsevier Wireless Networking Complete

WLAN Equipment

2012-05-11T22:15:00.000+08:00

There are three main links that form the basis of the wireless network. These are:

● LAN adapter : Wireless adapters are made in the same basic form as their wired counterparts: PCMCIA, Card bus, PCI, and USB. They also serve the same function, enabling end-users to access the network. In a wired LAN, adapters provide an interface between the network operating system and the wire. In a WLAN, they provide the interface between the network operating system and an antenna to create a transparent connection to the network.

● AP : The AP is the wireless equivalent of a LAN hub. It receives, buffers, and transmits data between the WLAN and the wired network, supporting a group of wireless user devices. An AP is typically connected with the backbone network through a standard Ethernet cable, and communicates with wireless devices by means of an antenna. The AP or antenna connected to it is generally mounted on a high wall or on the ceiling. Like cells in a cellular network, multiple APs can support handoff from one AP to another as the user moves from area to area. APs have a range from 20 to 500 m. A single AP can support between 15 to 250 users, depending on technology, configuration, and use. It is relatively easy to scale a WLAN by adding more APs to reduce network congestion and enlarge the coverage area. Large networks requiring multiple APs deploy them to create overlapping cells for constant connectivity to the network. A wireless AP can monitor movement of a client across its domain and permit or deny specific traffic or clients from communicating through it.

● Outdoor LAN bridges : Outdoor LAN bridges are used to connect LANs in different
buildings. When the cost of buying a fiber optic cable between buildings is considered, particularly if there are barriers such as highways or bodies of water in the way, a WLAN can be an economical alternative. An outdoor bridge can provide a less expensive alternative to recurring leased-line charges. WLAN bridge products support fairly high data rates and ranges of several miles with the use of line-of-sight directional antennas. Some APs can also be used as a bridge between buildings of relatively close proximity.

Source of Information : Elsevier Wireless Networking Complete

imode Versus WAP

2012-05-08T22:12:00.000+08:00

imode is available only in Japan, whereas Europe and other big markets for 3G mobile service providers are completely WAP-based. In the United States, most service providers have chosen WAP.

The most basic difference between imode and WAP is the different graphic capabilities; imode only supports simple graphics, which is far more than what WAP allows. The imode packet-switched data network is more suited for transferring data than the WAP CS network.

Another major difference is the “ always-on ” capabilities of imode. Since users are not charged for the time they spend on-line, it is more convenient and also less expensive. Since there is no need to dial up before using the various IP-based services, e-mail becomes as instant as SMS. imode uses cHTML, a subset of HTML, while WAP uses WML, a subset of XML. cHTML, while certainly easier to develop from a web-designer standpoint, has its limitations. The downside of WML, on the other hand, is similarly obvious — currently a WAP gateway is required to translate between HTML and WML for almost every data transfer. On the other hand, since WML is derived from XML, it is much more extensible. XML allows for more dynamic content and various different applications. In the future, a WML-based service will be of more advantage than an HTML-based one. So while WAP may currently require more complicated technology, in the long run, it may enable the user to do more with his or her device.

Source of Information : Elsevier Wireless Networking Complete

imode

2012-05-05T00:10:00.000+08:00

imode is a proprietary mobile ISP and portal service from NTT DoCoMo, Japan, with about 50 million subscribers. For imode, DoCoMo adopted the Internet model and protocol. imode uses compact HTML (cHTML) as a page description language. The structure of cHTML means that the user can view traditional HTML and imode sites can be inspected with ordinary Internet web browsers. This is in contrast to WAP, where HTML pages must be translated to WML. imode provides Internet service using personal digital cellular-packet (PDC-P) and a subset of HTML 3.0 for content description.

imode is a packet-switched service (always connected, as long as the user’s handset is reached by imode signal) which includes images, animated images, and colors. In imode, users are charged per packet of downloaded information. imode allows application/content providers to distribute software to cellular phones and also permits users to download appilets (e.g., games). imode uses packet-switched technology for the wireless part of the communication. The wired part of the communication is carried over TCP/IP.

Packet -switched services send and receive information by dividing messages into small blocks called packets and adding headers containing address and control information to each packet. This allows multiple communications to be carried on a communication channel, giving efficient channel usage with low cost. Dopa, DoCoMo’s dedicated data communications service, offers connections to location area network (LAN) and ISPs.

The mobile packet communications system has a network configuration in which a packet communications function is added and integrated into PDC, the digital system for portable and automobile telephones. DoCoMo has developed a data transmission protocol specific to imode. This protocol is used with the PDC-P system. The PDC-P network includes a mobile message packet gateway (M-PGW) to handle conversions between the two protocol formats. Connection between the imode server and the Internet uses TCP/IP. The imode server is regular web server which can reside at NTT DoCoMo or at the enterprise. DoCoMo has been acting as a 1717 portal and normally maintains the imode server.

imode relies on Internet security as provided by SSL/TLS and does not have the ability to
handle server-side authenticated SSL sessions. imode phones are preconfigured with root
collision avoidance keys from public key infrastructure. This will allow for establishment of a server-side authenticated SSL session between the imode device and imode server hosted by the enterprise. imode does not have the capability of handling client-side certifi cates which means that nonrepudiation is not possible with the current implementation of imode.

Applications of WAP

2012-05-01T00:06:00.000+08:00

The first and foremost application of WAP is accessing the Internet from mobile devices.
This is already in use in many mobile phones. This application is gaining popularity daily,
and many web sites already have a WAP version of their site. An application, which is out, is sending sale offers to mobile customers through WAP. The user’s phone will be able to receive any sale prices and offers from the web site of a store.

Games can be played from mobile devices over wireless devices. This application has been implemented in certain countries and is under development in many others. This is an application which has been predicted to gain high popularity. Application to access time sheets and filing expenses claims via mobile handsets are currently being developed. These applications, when implemented, will be a breakthrough in the business world.

Applications to locate WAP customers geographically have been developed. Applications to help users who are lost or stranded by guiding them using their locations are under
consideration. WAP also provides short messaging, e-mail, weather, and traffic alerts based on the geographic location of the customer. These applications are available in some countries but will soon be provided in all countries. One of the biggest applications of WAP under consideration is banking from mobile devices.

These applications will be very popular if they are implemented in a secure manner. The mobile industry appears to be moving forward, putting aside the issues of network and air interface standards, and instead concentrating on laying the foundations for service development, regarded by many as the key driver to multimedia on the move and third generation mobile systems. From that point of view, in the near future WAP and Bluetooth will play fundamental roles.

Source of Information : Elsevier Wireless Networking Complete

WAP Advantages and Disadvantages

2012-04-28T23:59:00.000+08:00

The following are the advantages of WAP:
● Implementation near to the Internet model;
● Most modern mobile telephone devices support WAP;
● Real-time send/receive data;
● Multiplatform functionality (little change is needed to run on any web site since XML is used);
● No hardware obsolescence.

The following are some of the advantages of using WAP CSS on mobile Internet sites:
● Because of WAP 2.0 (XHTML MP/WAP CSS), web programming and WAP programming converge. Learning WAP programming does not require much effort if you already know how to program the web. Web developers can continue to use their familiar web authoring tools and PC web browsers for building mobile Internet sites. This is one major advantage of XHTML MP/WAP CSS over WML.

● You can have greater control on the appearance of WAP pages with WAP CSS than with WML. For example, you can specify the colors, fonts, background, borders, margins, and padding of various elements with WAP CSS.

● If you apply a single CSS to the whole mobile Internet site, a mobile device will download the CSS only once the fi rst time the mobile Internet site is visited. The CSS will then be stored in the cache and it can be accessed later without connecting to the server.

● The file sizes of XHTML MP documents can become smaller if the layout and formatting information is moved to an external WAP CSS style sheet. A small fi le
size has the advantage of a shorter download time.

● Using WAP CSS has the advantage that the content and presentation can be separated. This means you can:
1. Match the layout and style of the same content to the characteristics of different wireless devices easily.
2. Match the layout and style of the same content for different user agents easily.
3. Minimize the effort to maintain a WAP site. When new mobile phone models come onto the market, you can write new WAP CSS style sheets to optimize the layout of the WAP site on these new mobile phones. The content files do not need to be modifed.
4. Apply a single WAP CSS style sheet to multiple WAP pages. Later if you want to change the look and feel of the whole WAP site, just modify the WAP CSS.
5. Reuse the style code in multiple projects.
6. Remotely divide work — someone can focus on look and feel WAP, whereas others can concentrate on contents.

Some of the disadvantages of the WAP are the following:
● Low speeds, security, and very small user interface;
● Not very familiar to the users;
● Business model is expensive;
● Forms are hard to design;
● Third party is included.

Some of the disadvantages of using WAP CSS style sheets on mobile Internet sites are:
● Different WAP browsers have varied levels of support for WAP CSS. One property supported on one WAP browser may not be available on another WAP browser.

● An external WAP CSS style sheet can increase the time required for a page to be
completely loaded the fi rst time the WAP site is visited because of the following
reasons:
1. The external WAP CSS style sheet does not exist in the cache of the mobile phone at the first visit, which means the mobile phone has to download it from the server.
2. An XHTML MP document and its external WAP CSS style sheet have to be downloaded in separate requests.
3. If you make use of a single WAP CSS file to specify all the presentation
information about the mobile Internet site, the fi le size of the WAP CSS file can be quite large.
4. The WAP browser needs to parse the CSS in addition to the XHTML MP document.

Source of Information : Elsevier Wireless Networking Complete

Windows Performance Monitor

2012-04-25T23:14:00.000+08:00

The Performance Monitor in Windows Server 2008 R2, has been modified since Windows Server 2008 as it no longer includes the Reliability Monitor snapin. The Performance Monitor is composed of three main components: monitoring tools such as Performance Monitor, Data Collector Sets, and a reporting component. The Performance Monitor can be launched from within the Windows Server 2008 R2 Server Manager or from the Start, All Programs, Administrative Tools menu.

Using Performance Monitor, administrators can identify bottlenecks and pinpoint resource issues with applications, processes, or hardware. Monitoring these items can help identify and resolve issues, plan for capacity changes, and help establish baselines that can be used for analysis in the future. Upon launching the Performance Monitor, a summary of system performance is displayed, showing current memory, disk, processor, and network loads.

Performance Monitor
Many IT professionals rely on the Performance Monitor because it is bundled with the operating system, and it allows you to capture and monitor every measurable system object within Windows Server 2008 R2. Using the tool involves little effort to become familiar with it. You can find and start the Performance Monitor from within the Performance Monitor program under Monitoring Tools in the console view. The Performance Monitor, is by far the best utility provided in the operating system for capacity-analysis purposes. With this utility, you can analyze data from virtually all aspects of the system both in real time and historically. This data analysis can be viewed through charts, reports, and logs. The log format can be stored for use later so that you can scrutinize data from succinct periods of time.

Data Collector Sets
As mentioned previously, Data Collector Sets are a collective grouping of items to be monitored. You can use one of the predefined sets or create your own to group together
items that you want to monitor. Data Collector Sets are useful for several reasons. First, data collectors can be a common theme or a mix of items. For example, you could have
one Data Collector Set that monitors only memory or a Data Collector Set that contains a myriad of items such as memory, disk usage, processor time, and more. Data Collector Sets can also be scheduled to run when needed.

Reports
As previously discussed, the Performance Monitor includes an updated reporting mechanism and several template performance and diagnostic reports for use. In addition, reports can also be created manually or generated from Data Collector Sets. Three system reports are included for diagnosing and assessing system performance: LAN Diagnostics, System Diagnostics, and System Performance. The following steps outline the process to view a System Diagnostics report.

To create and view reports in Performance Monitor, do the following:
1. Expand Data Collector Sets and System in the console tree of Performance Monitor.

2. Right-click on either the System Diagnostics or System Performance sets and select Start. Windows will begin collecting data for the report.

3. When you have collected enough data, right-click the collection set again, and select Stop.

4. Expand Reports, System and click the collection set you chose earlier. Double-click the report listed under that performance set.

5. The report will be compiled and displayed.

Source of Information : Sams - Windows Server 2008 R2 Unleashed

What’s New in Network Monitor 3.3

2012-04-20T23:07:00.000+08:00

Network Monitor 3.3 is available in ia64, x64, and x86 versions and can run on Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows 7, Windows Vista, and Windows XP systems.

Network Monitor 3.3 expands on the capabilities of the previous versions of Network Monitor by including several more features and fixes for issues that were discovered in the 3.x versions. Network Monitor 3.3 is very flexible and can even stop a capture based on an event log entry in Event Viewer.

The previous versions of Network Monitor included the following:
. An optimized interface that included network conversations and an expandable tree view of frames for the conversation(s)

. A real-time display and updating of captures

. The ability to capture traffic on multiple network cards simultaneously

. The ability to run multiple capture sessions simultaneously

. A script-based protocol parser language

. Support for Windows Server 2008, Windows Vista, Windows XP, and Windows Server 2003 on 32- or 64-bit platforms

. The ability to capture wireless traffic, scan one or all wireless channels supported by the network card, and view signal strength and transfer speed of the connection

. The ability to trace traffic inside of a Windows Vista virtual private network (VPN) tunnel by capturing remote access server (RAS) traffic

. The ability to right-click in the Frame Summary pane and click Add to Filter

. Support for the Windows Update service by periodically checking for updates to the Network Monitor program

. A redesigned filter toolbar

. A redesigned engine for supporting more protocol schemes

. New public parsers like ip1394, ipcp, PPPoE, and more

Some of the new features in Network Monitor 3.3 include the following:

. Support for Windows Server 2008 R2, Hyper-V, and Windows 7

. The ability to capture WWAN and tunnel traffic on Window 7 computers

. Support for both IPv4 and IPV6

Source of Information : Sams - Windows Server 2008 R2 Unleashed

Task Manager

2012-04-16T22:56:00.000+08:00

The Windows Server 2008 R2 Task Manager is similar to its Windows Server 2008 and Windows Server 2003 predecessors in that it offers multifaceted functionality. You can view and monitor processor, memory, application, network, services, user, and process related information in real time for a given system. This utility is a well-known favorite among IT personnel and is great for getting a quick view of key system health indicators with the lowest performance overhead.

To begin using Task Manager, use any of the following methods:

. Press Ctrl+Shift+Esc.

. Right-click on the taskbar and select Start Task Manager.

. Press Ctrl+Alt+Delete and then click Start Task Manager.

The Task Manager window contains the following six tabs:
. Applications—This tab lists the applications that are currently running. You can start and end applications from this tab.

. Processes—On this tab, you can find performance metric information of the processes currently running on the system. Sorting the processes by CPU or memory usage will reveal which processes are consuming the most system resources.

. Services—A recent addition to Windows is the Services tab in Task Manager. Administrators can now see what services are running without having to load Computer Management or the Services Management Console (services.msc) separately.

. Performance—This tab can be a graphical or tabular representation of key system parameters such as kernel usage, paging, CPU cycles, and more—in real time.

. Networking—This tab displays the network traffic coming to and from the machine. The displayed network usage metric is a percentage of total available network capacity for a particular adapter.

. Users—This tab displays users who are currently logged on to the system.

In addition to the Task Manager tabs, the Task Manager is, by default, configured with a status bar at the bottom of the window. This status bar, displays the number of running processes, CPU utilization percentage, and the amount of memory currently being used.

As you can see, Task Manager presents a variety of valuable real-time performance information. This tool is particularly useful for determining what processes or applications are problematic and gives you an overall picture of system health with quick access to terminate applications and processes, or identify potential bottlenecks.

There are limitations, however, which prevent it from becoming a useful tool for long term or historical analysis. For example, Task Manager can’t store collected performance information for future analysis and viewing; it is capable of monitoring only certain aspects of the system’s health, and the information that is displayed pertains only to the local machine. For these reasons alone, Task Manager doesn’t make a prime candidate for capacity planning.

Source of Information : Sams - Windows Server 2008 R2 Unleashed

Establishing Policy and Metric Baselines

2012-04-13T22:34:00.000+08:00

As mentioned earlier, it is recommended that you first begin defining policies and procedures regarding service levels and objectives. Because each environment varies in design, you can’t create cookie-cutter policies—you need to tailor them to your particular business practices and to the environment. In addition, you should strive to set policies that set user expectations and, more important, help winnow out empirical data.

Essentially, policies and procedures define how the system is supposed to be used—establishing guidelines to help users understand that the system can’t be used in any way they see fit. Many benefits are derived from these policies and procedures. For example, in an environment where policies and procedures are working successfully and where network performance becomes sluggish, it would be safe to assume that groups of people weren’t playing a multiuser network game, that several individuals weren’t sending enormous email attachments to everyone in the Global Address List, or that a rogue web or FTP server wasn’t placed on the network.

The network environment is shaped by the business more so than the IT department. Therefore, it’s equally important to gain an understanding of users’ expectations and requirements through interviews, questionnaires, surveys, and more. Some examples of policies and procedures that you can implement in your environment pertaining to end users could be the following:

. Email message size, including attachments can’t exceed 10MB.

. SQL Server databases settings will be enforced with Policy Based Management.

. Beta software, freeware, and shareware can be installed only on test equipment (that is, not on client machines or servers in the production environment).

. Specify what software is allowed to run on a user’s PC through centrally managed but flexible group policies.

. All computing resources are for business use only (in other words, no gaming or personal use of computers is allowed).

. Only business-related and approved applications will be supported and allowed on the network.

. All home directories will be limited in size (for example, 500MB) per user.

. Users must either fill out the technical support Outlook form or request assistance through the advertised help desk phone number.

Policies and procedures, however, aren’t just for end users. They can also be established and applied to IT personnel. In this scenario, policies and procedures can serve as guidelines for technical issues, rules of engagement, or an internal set of rules to abide by. The following list provides some examples of policies and procedures that might be applied to the IT department:

. System backups must include System State data and should be completed by 5:00 a.m. each workday, and restores should be tested frequently for accuracy and disaster preparedness.

. Routine system maintenance should be performed only outside of normal business hours, for example, weekdays between 8:00 p.m. and 12:00 a.m. or on weekends.

. Basic technical support requests should be attended to within two business days.

. Priority technical support requests should be attended to within four hours of the request.

. Any planned downtime for servers should follow a change-control process and must be approved by the IT director at least one week in advance with a five-day lead time provided to those impacted by the change.

Source of Information : Sams - Windows Server 2008 R2 Unleashed

The Benefits of Capacity Analysis and Performance Optimization

2012-04-10T22:29:00.000+08:00

The benefits of capacity analysis and performance optimization are almost inconceivable. Capacity analysis helps define and gauge overall system health by establishing baseline performance values, and then the analysis provides valuable insight into where the system is heading. Continuous performance monitoring and optimization will ensure systems are stable and perform well, reducing support calls from end users, which, in turn, reduces costs to the organization and helps employees be more productive. It can be used to uncover both current and potential bottlenecks and can also reveal how changing management activities can affect performance today and tomorrow.

Another benefit of capacity analysis is that it can be applied to small environments and scale well into enterprise-level systems. The level of effort needed to initially drive the capacity-analysis processes will vary depending on the size of your environment, geography, and political divisions. With a little up-front effort, you’ll save time, expense, and gain a wealth of knowledge and control over the network environment.

Source of Information : Sams - Windows Server 2008 R2 Unleashed

Defining Capacity Analysis

2012-04-06T22:27:00.000+08:00

The majority of capacity analysis is working to minimize unknown or immeasurable variables, such as the number of gigabytes or terabytes of storage the system will need in the next few months or years, to adequately size a system. The high number of unknown variables is largely because network environments, business policy, and people are constantly changing. As a result, capacity analysis is an art as much as it involves experience and insight.

If you’ve ever found yourself having to specify configuration requirements for a new server or having to estimate whether your configuration will have enough power to sustain various workloads now and in the foreseeable future, proper capacity analysis can help in the design and configuration. These capacity-analysis processes help weed out the unknowns and assist you while making decisions as accurately as possible. They do so by giving you a greater understanding of your Windows Server 2008 R2 environment. This knowledge and understanding can then be used to reduce time and costs associated with supporting and designing an infrastructure. The result is that you gain more control over the environment, reduce maintenance and support costs, minimize firefighting, and make more efficient use of your time.

Business depends on network systems for a variety of different operations, such as performing transactions or providing security, so that the business functions as efficiently as possible. Systems that are underutilized are probably wasting money and are of little value. On the other hand, systems that are overworked or can’t handle workloads prevent the business from completing tasks or transactions in a timely manner, might cause a loss of opportunity, or keep the users from being productive. Either way, these systems are typically not much benefit to operating a business. To keep network systems well tuned for the given workloads, capacity analysis seeks a balance between the resources available and the workload required of the resources. The balance provides just the right amount of computing power for given and anticipated workloads.

This concept of balancing resources extends beyond the technical details of server configuration to include issues such as gauging the number of administrators that might be needed to maintain various systems in your environment. Many of these questions relate to capacity analysis, and the answers aren’t readily known because they can’t be predicted with complete accuracy.

To lessen the burden and dispel some of the mysteries of estimating resource requirements, capacity analysis provides the processes to guide you. These processes include vendor guidelines, industry benchmarks, analysis of present system resource utilization, and more. Through these processes, you’ll gain as much understanding as possible of the network environment and step away from the compartmentalized or limited understanding of the systems. In turn, you’ll also gain more control over the systems and increase your chances of successfully maintaining the reliability, serviceability, and availability of your system.

There is no set or formal way to start your capacity-analysis processes. However, a proven and effective means to begin to proactively manage your system is to first establish system wide policies and procedures. Policies and procedures, discussed shortly, help shape service levels and users’ expectations. After these policies and procedures are classified and defined, you can more easily start characterizing system workloads, which will help gauge acceptable baseline performance values.

Source of Information : Sams - Windows Server 2008 R2 Unleashed

The WAP Programming Model

2012-04-03T23:14:00.000+08:00

Before presenting the WAP programming model, we briefl y discuss the WWW model that is the basis for the WAP model.

The WWW Model
The Internet WWW architecture provides a fl exible and powerful programming model. Applications and content are presented in standard data formats, and are browsed by
applications known as web browsers. The web browser is a network application, i.e., it sends requests for named data objects to a network server and the network server responds with encoded data using the standard formats.

The WWW standards specify several mechanisms necessary to build a general-purpose
application environment which includes:

● Standard naming model. All servers and content on the WWW are named with an Internet-standard Uniform Resource Locator ( URL ).

● Content typing. All content on the WWW is given a specific type, thereby allowing web browsers to correctly process the content based on its type.

● Standard content formats. All web browsers support a set of standard content formats. These include (HTML), JavaScript scripting language (ECMAScript, JavaScript), and a large number of other formats.

● Standard protocols. Standard networking protocols allow any web browser to communicate with any web server. The most commonly used protocol on the WWW
is the HTTP. This infrastructure allows users to easily reach a large number of thirdparty
applications and content services. It also allows application developers to easily create applications and content services for a large community of clients.

The WWW protocols defi ne three classes of servers:

1. Origin server: The server on which a given resource (content) resides or is to be created.

2. Proxy: An intermediary program that acts as both a server and a client for the purpose of making requests on behalf of other clients. The proxy typically resides between clients and servers that have no means of direct communication (e.g., across a firewall). Requests are ither serviced by a proxy program or passed on with possible translation to other servers. A proxy must implement both the client and the server requirements of WWW specifications.

3. Gateway: A server which acts as an intermediary for some other server. Unlike a proxy, a gateway receives requests as if it were the origin server for the requested resource. The requesting client may not be aware that it is communicating with a gateway.

The WAP Model
The WAP programming model is similar to the WWW programming model. This provides several benefits to the application developer community, including a familiar programming model, a proven architecture, and the ability to leverage existing tools (e.g.,
web servers, XML tools, etc.). Optimization and extensions have been made in order to match the characteristics of the wireless environment. Wherever possible, existing standards have been adopted or have been used as the starting point for the WAP technology.

WAP content and applications are specified in a set of well-known content formats based on WWW content formats. Content is transported using a set of standard communication
protocols based on WWW communication protocols. A microbrowser in the wireless terminal coordinates the user interface and is analogous to a standard web browser. WAP defines a set of standard components that enable communication between mobile terminals and network servers, including:

● Standard naming model : WWW-standard URLs are used to identify WAP content on origin servers. WWW-standard URLs are used to identify local resources in a device (e.g., call control functions).

● Content typing : All WAP content is given a specifi c type consistent with WWW typing. This allows WAP user agents to correctly process the content based on its type.

● Standard content formats : WAP content formats are based on WWW technology
and include display markup, calendar information, electronic business card objects,
images, and scripting language.

● Standard protocols : WAP communication protocols enable the communication of
browser requests from the mobile terminal to the network web server. The WAP
content types and protocols have been optimized for mass market, hand-held wireless
devices. WAP utilizes proxy technology to connect between the wireless domain and
the WWW.

The WAP proxy typically comprises the following functionality:
● Protocol gateway : The protocol gateway translates requests from the WAP protocol stack to the WWW protocol stack (HTTP and TCP/IP).

● Content encoders and decoders : The content encoders translate WAP content into compact encoded formats to reduce the size of data over the network. This infrastructure ensures that mobile terminal users can browse a wide variety of WAP content and applications, and that the application author is able to build content services and applications that run on a large base of mobile devices. The WAP proxy allows content and applications to be hosted on standard WWW servers and to be developed using proven WWW technologies such as cell global identity (CGI) scripting. While the nominal use of WAP includes a web server, WAP proxy, and WAP client, WAP architecture can easily support other confi gurations. It is possible to create an origin server that includes WAP proxy functionality. Such a server might be used to facilitate end-to-end security solutions, or applications that require better access control or a guarantee of responsiveness.

Source of Information : Elsevier Wireless Networking Complete 2010

AlphaBaby: The Joy of Discovery

2012-03-31T00:37:00.000+08:00

One of any child’s favorite early games has to be the classic “peek-aboo.” Adults love to play this game because they can immediately evoke a positive reaction from a young child and amazingly, it can be played for a while without the child losing much interest.

The reason peek-a-boo works so well is that very young children have an underdeveloped sense of object permanence. You reveal yourself from behind a blanket or your hands over your face and, for the child, he is seeing you all over again. Throw in a funny face and a silly voice, and you’re pure entertainment gold for the child.

Of course, as the child gets older, and the brain starts forming more permanent connections, she can figure out that Mommy and Daddy haven’t really left—they’re just behind the blanket, being silly. A little bit older, and the child may just look at you as if she’s thinking, “Really, Daddy?”

But there’s another element to the fun of peek-a-boo: the joy of discovering that familiar face all over again. That excitement is something that carries forward as the child grows older, and indeed can become the driving force behind much of his behavior as he moves into toddler and preschool age. That’s why he’ll empty out the cookware cabinet onto the kitchen floor, because he has discovered a whole new playground of shiny, noise-making objects that (bonus points!) usually bring the parents running.

AlphaBaby is a remarkably simple app that taps into that excitement of discovery within a more structured format. Toddlers will experience the thrill of discovering new and random objects on the screen (they never know what they’ll see next), with the repetition that will slowly build connections between the letter, number, or shape displayed and the word for that object.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

Apps for Toddler Learning

2012-03-28T00:34:00.000+08:00

From about their first second of life, children can communicate. Any parent will tell you that babies can usually get their intentions known through crying, gestures, and facial expressions. As they grow, they will pick up a vocabulary of hundreds of words, which they will employ to get what they need or want, express their feelings, or simply make conversation. Sometimes, lots and lots of conversation.

It’s well known that kids’ brains are sponges for languages. As parents, we see this every single day. But they can’t do it on their own, nor should they. We, as adults, have a key role in early speech development. This is why interacting with our children and having them watch us interact with others is so important. This is true of both verbal and written language.

It’s not about sitting down with them and practicing reading and writing (though that helps): parents have to convey to their child that such activities can be fun. Skills are all well and good, but in order for children to accomplish their best, they need to embrace these activities. Parents can help make this happen by reading aloud, singing songs, and playing games with language—anything that can bring the spark of interest to a child’s mind will help.

At the same time, a whole other set of concepts is being developed in children’s brains as they are learning language: the building blocks of math. It starts small, of course: children figure out the differences between quantities of objects and start to discover patterns in the world around them. Later, they will start to use these basic foundations to begin working out problems with those objects.

This stems from a basic need of children to start looking around and getting a sense of order about their world. If the world is in order, then all is right with said world. Breaking things down into discrete objects and actions is the beginning of mathematical concepts. The good news is that just normal everyday activities will nurture the development of these mathematical concepts.

Of course, there’s no reason parents can’t help this along, by introducing activities that can increase a child’s mathematical growth. Art, particularly visual arts, is also a key aspect of early childhood development. Parents all marvel at the pretty scribbles our children lovingly hand us, perhaps not realizing that any creative effort a child undertakes has great benefits. Imaginations are stimulated, hand-eye coordination is improved, and overall expression of concepts is markedly improved. This is why parents are encouraged to provide as many opportunities as possible to explore the artistic process.

Such opportunities, really, are what many iPad apps can help you do. Whether art, language, or math, the right iPad apps will expose a child to activities designed to gently reinforce concepts parents are also demonstrating to their children. Using an iPad won’t make your child a super-genius, but it will give that child a variety of activities that will help build a love for language, math, and art, even at this early age.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

Video Mirroring with FaceTime

2012-03-23T00:10:00.000+08:00

Another new hardware feature of the iPad 2, which hasn’t gotten a lot of attention yet, is its capability to send the screen content from the device to another screen, such as a monitor or television screen.

Known as video mirroring, this is very useful if you ever want to run a demonstration of an iPad app for a class, and it’s ideal for broadcasting FaceTime calls to many people at once. The iPad could do this, but only to Apple-compatible devices. The iPad 2 allows video mirroring to a much larger set of monitors.

To use video mirroring, all you need to do is purchase the correct video adapter for your iPad 2. If you want to connect to a computer monitor or TV with a VGA input, you should get the VGA adapter. To connect to an HDTV, purchase the Digital AV connector. Both of these connectors are available for purchase online at the Apple Web site or at any
Apple retail outlet. If you have a widescreen monitor, you can set the iPad 2 to feed to it by following these instructions.

1. Tap the Settings icon on the Home screen. The Settings app will open.

2. Tap the Video setting. The Video settings pane will open.

3. Slide the Widescreen control to On.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

What Is FaceTime?

2012-03-20T00:04:00.000+08:00

FaceTime is not something new to the iPad 2, although the new iPad is the first model that can actually use it, thanks to the new on-board front- and rear-facing cameras. FaceTime was actually created for the iPhone 4 in the summer of 2010, the first device from Apple to feature a dual-camera setup. It’s this double-camera configuration that makes FaceTime work so well. Until recently, most mobile devices, when they had a camera, used a photo/video capture lens that was located on the back of the device—in other words, the side of the device that was on the opposite side of the device’s video screen. Think about a two-video call, and you can quickly imagine such a situation becoming very awkward, very quickly.

With the iPhone 4, and now the iPad 2, FaceTime can enable you and your kids to easily engage in video calls with any FaceTime-enabled device in the world.

But in that statement alone, there are hidden limitations. Note that connectivity is limited to other FaceTime-equipped devices. Right now, that includes all iPad 2 devices, any iPhone 4 (and beyond), fourth-generation iPod Touch devices, and any desktop or laptop with Mac OS X 10.6.6 or higher, so we’re not exactly talking about a small user base.

Still, as of press time, Windows and Linux users were not able to use FaceTime, and don’t look for FaceTime on the Android mobile platform anytime soon, either, given the animosity between Apple and Google over their respective mobile platforms.

This means that as you seek out possible connections for your student, you will need to deliberately search for other students and classrooms that have the correct devices.

Another, perhaps more well-known, limitation is the inability for FaceTime devices to send their signals over any cellular network. This is likely due to the sheer amount of data each video call creates: upwards of 3MB per minute. That number may seem a bit abstract, but think about your own cellular data plan and any financial caps that might exist with it, and you will quickly see why pushing a FaceTime call of any significant length could be a very expensive proposition.

That expense is incurred by the cellular carriers, too. Increasingly, data carriers in North America, Asia, and Europe are learning that unlimited data plans will quickly jam their networks with traffic, and they have taken great pains to limit data traffic to keep their networks clear. This is why, to date, Apple has been unable to negotiate a plan with any cellular carrier.

The result of this behind-the-scenes technical discussion means that anyone who is using FaceTime must connect over a wireless network (or, for Mac users, a wired Ethernet connection will also work). This WiFi-only limitation has gotten quite a bit of knocking in the media, but to be honest, even 3G iPad owners can typically find a wireless network somewhere. Your student, too, is more likely to be at home or school, where such WiFi networks are common.

The good news is, once you find such a network, it is very simple to set up a FaceTime connection. But first, you need to configure FaceTime to be ready to receive and send calls.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

Getting an iPad Device

2012-03-17T00:11:00.000+08:00

If you are fortunate enough to live near one of the hundreds of Apple retail stores, purchasing that needed iPad 2 should be a relatively painless process. Just walk in, pick out the one you want, and then take it home. To date, most U.S. Apple stores have caught up with the huge demand for these devices, and usually have them in stock, although it is still sporadic. Some of the WiFi+3G models are still lagging behind a bit. You may want to call ahead and see if the model you want is in stock before driving in to purchase it.

If you don’t reside near an Apple store, you have two basic options: purchase the iPad 2 online or through an Apple retail partner, such as Target, Wal-Mart, or Best Buy. Be careful about expecting to actually see an iPad 2 at a retail partner, though; these stores often only get a handful of devices at a time, and they are usually snatched up very quickly. The other route you might go is to check an AT&T or Verizon retail store, but here iPad 2s are even more scarce: only the largest stores in a given region will actually have the device in stock, while a big majority of such stores will have to order them from Apple directly. The good news about any of these options is that the cost of the iPad,
either online or at another retail store, is always the same. There’s no markup when you purchase the iPad 2 somewhere other than an Apple store, and the online store will ship iPad 2s free of charge, so there’s no additional cost there.

The bad news is, since most iPad 2 buyers use the online option to get their device, the delivery channel is exceedingly slow. As of this writing, Apple indicated one to two weeks to receive an iPad 2, and while this has been mostly true, anecdotal evidence has suggested otherwise; in some cases, shipping times of three weeks have been reported. The option to go to a partner retailer, if there’s one near you, may not be any better. You should definitely call ahead and see if there’s an iPad 2 in stock. Be sure to specify which model you want. You don’t want to get there and find out the retailer has models that don’t meet your technical or budgetary requirements.

If you are not in a hurry to receive the iPad 2, you should definitely order it online. That way, you’re working directly with Apple, and you won’t have to dodge and weave past other shoppers to get the exact device you want.

Of course, getting an iPad is a little easier. If you find one at a reputable online vendor, you could have the device in your hands in a matter of days, at a lower cost.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

Choosing the Right iPad

2012-03-13T00:06:00.000+08:00

Before you buy an iPad, you need to figure out first which iPad you’re going to get, particularly with the recent release of the iPad 2. A lot of people liked the looks of the iPad and held off buying one until the iPad 2 came out and shoppers mobbed the stores and Web sites looking for them. I am not proud to admit that I was one of those shoppers, and I paid my teenage daughter $50 to go stand in line at another store at the same time, coordinating with text messages. I blame my publisher.

Shopping rushes aside, while all iPads may look alike, there are two key differences found within all iPads that mean you get to choose between a total of six different iPad models.

When choosing an iPad device, you may find yourself gravitating toward an iPad 2, the latest in the iPad family of devices. The good news is that from a retail standpoint, iPad 2s are no more expensive than the first iPad, and each model in the respective device families are similarly priced and with the same basic features.

However, there are key differences between the iPad and iPad 2 that should be taken into consideration.

First, the form factor of the iPad 2 is thinner and lighter than the original iPad. This is not a huge difference, but nonetheless it should be noted. Most of the time, you won’t even notice it, unless you spend your time holding the device in one hand. Then the weight difference can be felt. The two biggest differences between the devices are the faster processor in the iPad 2 and the onboard cameras in the iPad 2.

The faster processor does not change the apps that run on either version of the iPad, but it does increase the speed at which apps will run on the iPad 2. And it is noticeable. iPad apps were never pokey, but when compared with performance on the iPad 2, they are less responsive. Some apps, like Garage Band, can be used on the iPad, but they are recommended for the iPad 2 precisely because of its faster processor.

The cameras on the iPad 2, while not the greatest in the world, do give you the capability to run apps like FaceTime, a two-way videoconferencing app, and Photo Booth, a fun photo-morphing app. Many of the apps you will see in this book also use the cameras to take pictures of children to use as icons within the apps, should you choose. But even without the camera, you can upload an image and use it for the same purpose in the apps on an iPad.

The one big advantage of the iPad versus the iPad 2? Price. While only a year old, first-model iPads are being sold on the secondary market for big discounts from their original prices. Of course, this usually means buying a used iPad, with all the pros and cons of such a transaction. But, if you are on a budget, picking up an iPad on eBay or some other reputable vendor is a great way to get started.

The first choice point for any iPad or iPad 2 model is whether to get a WiFi or a WiFi+3G model. All iPads have the capability to connect to the Internet using WiFi access—the kind found in your home or most public businesses, like the coffee shop on the corner. This is usually pretty adequate, particularly within your own house, which should have its own wireless network.

If you don’t have WiFi, ask your Internet provider. Most home systems include a WiFi network device, so you may have WiFi and not even know it.

iPad WiFi+3G models, on the other hand, can tap into the AT&T cellular network and connect to the Internet anywhere the iPad can receive the AT&T network signal. iPad 2s can use either AT&T or Verizon as a cellular carrier. WiFi+3G models uniformly cost $130 more than their WiFi-only counterparts retail, so using a WiFi-only device is obviously a real cost saver.

The other difference between iPad products is the amount of solid-state storage each device has. The iPad and iPad 2 are currently available with 16, 32, or 64 gigabytes of storage. The price of each model is directly proportional to the amount of memory.

From an education standpoint, you need to factor in how you will use the device. If you are going to be based in one central location, and plan to sync the device with a PC or Mac computer on a regular basis, then you will not need a lot of storage space. You can simply use your computer (and any storage device to which the computer has access) to handle storing files. In such a case, you should stick with one of the 16GB models.

If, however, you plan to be more mobile or otherwise be unable to sync on a regular basis, and will be handling a significant number of files, then consider purchasing one of the larger memory devices. It’s likely that 32GB’s worth of capacity is enough for most mobile use cases, unless you have a huge amount of multimedia files to lug around.

One good way for you to pin down the answer to the memory question is to look at all the files you must have to educate and entertain kids away from home, calculate the amount of memory those files need, and then triple that number. This calculation should account for the original files’ storage and the potential of creating twice as many files while away from your base PC.

As for the decision on WiFi-only versus WiFi+3G, here the recommendation is not really going to be along financial lines. It would be easy to say, for instance, that all stationary iPad users should be fine without plunking down an extra $130 for 3G cellular connectivity. You’ve got WiFi set up in your home or school, so why bother with 3G?

This is where you should ask a key question: What happens when your Internet connection goes down? If losing Internet connectivity would harm your experience on the device, then it may be worth it to spend the extra money and get the WiFi+3G model. Most of the apps in this book, however, do not require always-on Internet connectivity, so you may want to consider that, too.

The final decision in buying an iPad 2 is color: you have a choice between a white or black benzel (screen border) on the new iPad 2. This is strictly a preference issue, but the choice will need to be made, nonetheless. With these choices in mind, you should be able to make an informed choice on getting the iPad or iPad 2 you need.

When 3G May Not Be a Good Idea. If you work in a region where AT&T or Verizon coverage is troublesome or nonexistent, you may need to reconsider the 3G options. One possible work-around, for instance, would be to use a mobile WiFi device from another cellular carrier and connect to the Internet via that device’s WiFi network.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

The Educational Case for the iPad

2012-03-09T23:51:00.000+08:00

With the right apps, the iPad can become more than just a content consumption device for videos, music, and electronic books. It can be an educational and content production device for kids as well, generating documents, spreadsheets, presentations, music, and video, while also giving children a window into a vast array of knowledge.

This ability to make content, given the right apps, immediately increases the iPad’s value as a useful educational device. Students, parents, and teachers can have the tools to learn about new concepts and then turn around and create information based on that learning.

The potential education uses for the iPad are limited only by your ingenuity:

» Parents can let their younger children play with qualified apps that will provide hours of entertainment, while also practicing the basic skills of reading and mathematics.

» Teachers can use the iPad to create lesson plans and present engaging multimedia presentations at home or in the classroom.

» Older students can research new material and put that material together in traditional reports or cutting-edge multimedia presentations of their own.

These, of course, are just a few possible scenarios of iPad use for education. A computer could handle just about all of these tasks, of course, but even laptops can be a hassle to carry around and can require a good chunk of personal space to use. Not to mention the short life of a laptop battery, which often has you looking for a plug. The iPad’s flat form greatly eases transport, and the 10-hour battery life means you won’t be married to an outlet.

Is an iPad device right for every situation? It would be easy to get all excited and say “why yes, yes it is.” But this isn’t always the case. The design of the device itself should make you think about using it in certain instances. For example, an iPad has a large amount of glass, so using it in an environment where that glass can be damaged is obviously not a good idea. Care especially should be taken when younger children are using the device for just this reason. Still, with the right accessory— namely, a good carrying case—and some common sense, even that problem can be solved.

If you see possibilities for using the iPad with your child or students, the first thing you need to do is get yourself an iPad, which sometimes can be easier said than done.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

What Is the iPad?

2012-03-06T23:37:00.000+08:00

When Steve Jobs announced the iPad in January 2010, the initial reaction was rather mixed. After the initial excitement died down, critics pointed out that this “new” device was hardly more than a giant iPod Touch. Sure, the screen was bigger, and the apps looked better, but other than that, what could such a device offer to consumers? Tech pundits didn’t know if they were coming or going with their opinions of this thing.

It turns out, they should have had some faith.

Perhaps the biggest draw to the iPad was the tablet form itself. iPads don’t have physical keyboards, and most applications don’t even require a pen-like stylus to function. All you do is use your fingers to enter text and manipulate objects onscreen. With such a simple interface, and because the device itself is much lighter than laptops, notebooks, and even those itty-bitty, ultra-light netbooks, it is a large-screen device that is much more portable for users of all types.

Besides being large enough to read comfortably and watch the occasional movie, the screen is also a multitouch interface, which can be a unique experience for many electronic device users. In the past, touchscreens on PDAs, smartphones, or even the occasional kiosk were primarily single-touch interfaces, meaning that one and only one touch at a time was registered by the application running on the screen.

Beginning with the iPhone, and continuing with the iPad and iPad 2, there is multitouch, which enables users to touch and manipulate objects on the screen with more than one finger (or device) at a time. This interface enables users to shrink objects by “pinching” them or expand objects by fanning out their fingers. Or they can type capital letters onscreen by virtually “holding down” the Shift key on the keyboard on the screen.

But it’s not just the hardware. Applications are the biggest key to the iPad family’s success, if only by sheer numbers alone. Thousands of applications are available in the Apple App Store, free or otherwise, with a high percentage of them reviewed by other users. This social review system lets you find out quickly what’s really going to work, and what may not. More than that, the stunning variety of apps available makes the iPad highly suitable for any number of uses.

Especially apps for your child.

Source of Information : Cengage-iPad for Kids Using the iPad to Play and Learn 2011

Enhancing Replication and WAN Utilization at the Branch Office

2012-03-02T01:02:00.000+08:00

Windows Server 2008 R2 introduces new technologies and refines existing ones to maximize performance, replication, and file sharing and to reduce WAN bandwidth utilization consumed between branch offices and hub sites. The following technologies that address and improve bandwidth utilization, latency, and reliability of the WAN links at a branch office include the following:

. Read-Only Domain Controllers
. Next Generation TCP/IP
. Distributed File System
. DirectAccess
. Virtualization
. Group Policy
. SMB v2

Read-Only Domain Controllers
As revealed earlier in this chapter, the amount of information replicated over the WAN between a Read-Only Domain Controller residing at a branch office and a writable domain controller at a hub site is significantly minimized. This is because changes do not originate at an RODC, eliminating the need to replicate data from an RODC to a writable domain controller replication partner at a hub site, resulting in a reduction of bandwidth and WAN utilization being used.

Next Generation TCP/IP Stack
A tremendous amount of improvement is seen in the Next Generation TCP/IP stack introduced in Windows Server 2008 R2. Some of the features for the new TCP/IP stack that directly impact and improve branch office WAN utilization and replication include the following:

. Receive Window Auto-Tuning—Support for Receive Window Auto-Tuning is new in the Next Generation TCP/IP stack. Receiver-side throughput is improved through Receive Window Auto-Tuning because this feature is able to calculate the best possible receive window size for each connection by taking into account bandwidth, latency connection, and application retrieval rate. Bandwidth performance naturally improves with better throughput. Bandwidth performance can improve even more if all applications receive TCP data.

. Compound TCP/IP (CTCP)—Compound TCP/IP, which is most often used for TCP connections that have a large receive window size in addition to a large bandwidth delay product, ultimately improves receiver-side throughput. With CTCP, the amount of data sent across connections is significantly greater; however, TCP connections are not impacted negatively. If CTCP and Receive Window Auto-Tuning are used together, even more benefits, including increased link utilization and performance gains for large bandwidth delay connections, can be witnessed.

. ECN support—When a TCP segment is lost, TCP assumes that it was because of congestion at a router, so it performs congestion control. This lowers the TCP sender’s transmission rate. With Explicit Congestion Notification (ECN) in the routing infrastructure, routers experiencing congestion mark the packets as they forward them. TCP peers receiving marked packets lower their transmission rate to ease congestion and prevent segment losses. This increases the overall throughput between TCP peers.

. Improved routing—Path maximum transmission unit (PMTU) black-hole router detection automatically adjusts the PMTU for a connection when large TCP segments are detected.

. RFC optimizations—The TCP/IP stack has better support for RFCs related to TCP communications.

. Neighbor detection—The Next Generation TCP/IP stack supports neighbor unreachability detection for IPv4 traffic. A computer such as a branch office maintains status about whether neighboring computers such as a hub site are reachable. This provides better error detection and recovery when computers are not available.

. Dead Gateway support—Unlike the previous Windows versions of Dead Gateway Detection, the Next Generation TCP/IP Dead Gateway support now provides a failover and failback mechanism when encountering dead gateways.

Distributed File System (DFS)
DFS in Windows Server 2008 R2 builds upon the completely revised replication engine in Windows Server 2003 R2. DFS, which was first introduced with Windows 2000 Server, provides a robust multimaster file replication service that is significantly more scalable and efficient in synchronizing file servers than its predecessor, File Replication Service (FRS).

With Windows Server 2008 R2, DFS includes an impressive list of benefits for both Active Directory and branch office server management, including simplified branch server management, reduction of backups, and more efficient storage management. In addition, DFS Replication (DFSR) enhances branch office implementations because it is possible to schedule and throttle replication schemes, support multiple replication topologies, and utilize Remote Differential Compression (RDC) to increase WAN efficiency. If WAN connections fail, data can be stored and forwarded until WAN connections become available. As a result, WAN replication is reduced and optimized, branch office mission-critical files can be replicated among branch offices, hub sites can reduce the amount of IT management that takes place in the branch office, and the need for backups can also be reduced.

Additionally, a new feature that was introduced in Windows Server 2008 R2 is support for read-only copies of information stored in Distributed File System (DFS) replicas. Because information that is stored on a read-only DFS replica is read-only, users are not able to modify/delete/create the replicated content. Therefore, information that is stored in a read-only DFS replica is protected at branch office locations from accidental modification.

Group Policies
Windows Server 2008 R2 now uses DFSR to replicate Group Policy Objects between domain controllers within a domain. By leveraging DFSR differential replication, changes only occur between two domain controllers and not all of the domain controllers as in the past. As a result, the amount of bandwidth required during Group Policy replication is greatly reduced.

Group policies, which are the traditional Administrative Template files, are now replaced with new XML-based files called ADMX in Windows Server 2008 R2. Moreover, the new ADMX files are stored in a centralized store within SYSVOL. Thus, the new templates, storage of group policies, and utilization of DFSR for replication improve branch office solutions because less data needs to be replicated between the branch office and hub site.

SMB Version 2.0
Another enhancement for Windows Server 2008 R2 branch office deployments is the server message block (SMB) protocol version 2.0. SMB, originally invented at IBM, is an application-level network file-sharing protocol mainly applied when accessing files, printers, serial ports, and miscellaneous communications between computers on a network.

The protocol hasn’t evolved much since it was originally created 15 years ago. As a result, the protocol is considered to be overly chatty and generates unnecessary network traffic between computers on a network. This especially hinders users at branch office implementations when accessing files over the WAN to a hub site, especially if the WAN link is slow or already congested.

Microsoft understands the concerns and limitations with the existing version of SMB and has completely rewritten SMB to meet the demand of today’s branch office needs. The benefits and improvements of the new SMB version 2.0 protocol on WAN network performance and end-user experience when transferring data between the branch office and hub sites include the following:

. Efficiency, performance, and data streaming are improved and are four to five times faster than the older version of SMB.

. The client can increase parallel requests.

. Offline capabilities are included, which is beneficial on slow networks and improves the end-user experience.

. Synchronization performance for offline files is improved.

. Multiple client requests can be compounded into a single round-trip.

. Users can now work in offline mode and synchronize changes on demand.

. Server scalability has been increased by reduced per-connection resource usage.

. The amount of bandwidth required for network communications has been dramatically reduced.

Source of Information : Sams - Windows Server 2008 R2 Unleashed