Monday, August 17, 2009

Shutdown Faster

XP Tips & Tweaks - Shutdown XP Faster

Like previous versions of windows, it takes long time to restart or shutdown windows XP when the "Exit Windows" sound is enabled. To solve this problem you must disable this useless sound.
• Click Start button.
• Go to settings > Control Panel > Sound, Speech and Audio devices > Sounds and Audio Devices > Sounds.
• Then under program events and windows menu click on "Exit Windows" sub-menu and highlight it. Now from sounds you can select, choose "none" and then click Apply and OK.
Now you should see some improvements when shutting down your system.

Graphics

XP Tips & Tweaks - Stop Jerky Graphics

If you are connected to a LAN and have problems with jerky graphics, this might be the solution:
• Right-click "My Computer".
• Select "Manage".
• Click on "Device Manager".
• Double-click on your NIC under "Network Adapters".
• In the new window, select the "Advanced" tab.
• Select "Connection Type" and manually set the value of your NIC. (Not "Auto Sense" which is default.).
• You should reboot.

Mobility


This diagram allows you to compare the systems we've mentioned in this lesson. The horizontal-axis uses a logarithmic scale to show the bit rate a system offers. The vertical-axis shows the amount of coverage a system offers, from a single room to the whole world.

As you can see, those systems with the lowest mobility, the wireless LAN solutions, offer the highest bit rates, whilst those with higher mobility, such as GSM, offer lower bit rates. The red lines indicate the future developments. For example, GSM currently offers coverage spanning the globe and a bit rate of 9.6kbps. Enhancements, such as GPRS and HSCSD will increase this bit rate.

AMPS offers coverage in several countries across the world with a bit rate similar to that found in GSM. Future enhancements, such as circuit switched data, will offer higher bit rates than are currently available. Metricom's system, which was discussed earlier offers a higher bit rate than current GSM or AMPS systems, but only provides mobility at the metropolitan level.


Universal Mobile Telecommunications System, UMTS, will offer a much higher bit rate than any of today’s systems. Because of the expense of introducing mobile networks, the first implementations will offer patchy coverage. As time progresses, hopes are that UMTS will cover the globe.

Wireless LAN MAN


In the wireless LAN marketplace there are two main solutions, using infra-red or radio waves. None of these solutions pretends to offer mobility - they merely offer a slightly more flexible way of coupling your desktop computer to the LAN. In some cases this wireless flexibility can be very desirable - laptop users do not need to continually plug and
unplug network cables, they can simply move into the covered area and start working. In some older buildings, pulling cable to every desktop can be expensive, so using a

wireless solution can save money. Of course, the usual drawbacks apply - the bit rate is much lower than that offered by other LAN technologies. Typically IR and RF based LANs offer a bit
rate of about 4 Mbps. Compared with Ethernet, which is over 25 years old and yet manages 10 Mbps, that can be a considerable drawback. IR based nets are also further limited by the fact that their connections must be "line-of-sight" based. This is not a problem for RF based LANs.



An interesting solution to the MAN question has been developed by an American company
called Metricom. They've developed a wireless system that breaks away from the usual
wireless network topology that we saw. Instead of building a hierarchical system consisting of base stations, serving nodes and a backbone, Metricom build a semiintelligent mesh consisting of small boxes that sit on top of street light and utility poles. One or more of these pole top boxes is equipped with a fixed connection to the global Internet. When a user sends data it goes to the nearest pole top box. This box then independently routes the information to a box that has a fixed connection. All this routing is done automatically by the meshed network, there is no human intervention and no need for hand crafted routing tables.

Metricom's system currently offers a bit rate of 38 kbps, a speed they hope to increase to 56 kbps some time in 1999.

They offer a public Internet access service in three American urban areas, the Bay Area in California, Seattle and Washington DC. Metricom's solution is also being used by several campus based networks and by Sun Microsystems (among others) to cover their corporate campus. The system uses the license free portion of the RF spectrum and utilizes a patented frequency hopping technique to provide security and maintain good link quality. The pole top boxes are positioned every 400 to 800 meters and take approximately 5 minutes to install. Metricom believe that their system has almost unlimited scalability, and could cover the whole of the states if necessary.

Mobile IP


What is Mobile IP? Well, it's a macro mobility technique that is it can be used to allow movement between two interconnected networks. In this example we are using Mobile IP to allow a portable user to move between two different LANs interconnected by the Internet.

Imagine this scenario. You normally work in you lovely air-conditioned office in Dallas. One
day your boss informs you that you have to go to Ericsson Stockholm to give a presentation. You spend a few hours preparing the presentation, which remains on a server on your home network. You then take your lap top computer across the Atlantic to your meeting in Stockholm. There you plug in to the LAN. Without having to change any configuration parameters or addresses, you can immediately access your home LAN in Dallas and can easily give your presentation. Also, external users can still contact you with your original IP address, as that has moved with you. This transparent mobility is the job of Mobile IP.

So, how does it work? Well, conceptually it's quite simple. Here you can see your home network in Dallas and your foreign network in Stockholm. When you are on your home network you are addressed using the IP address 193.234.210.74. Users on your own network or on other networks connected to the Internet can talk to your computer using that IP address, 193.234.210.74. The router on your home network ensures that packets bearing your IP address are delivered to you.

Now, what happens when you pick up your laptop, spend 10 hours on a plane and arrive at
Ericsson in Stockholm? Well, when you plug your laptop into this new foreign network your laptop talks to the router on the foreign network, which is called the Foreign Agent.

Your laptop basically sends a message to the Foreign Agent saying, "Hi, I'm laptop
193.234.210.74 and I'd like to use your network." The Foreign Agent then sends a message
to the router on the home network, the Home Agent, and says "The mobile with IP address 193.234.210.74 isn't on your network anymore, but it can be reached by sending packets to me at IP address 193.17.213.64." The Home Agent accepts this request and then we're ready to roll.

So, what happens when some host out on the Internet starts to send packets to your laptop? Well, the routers on the Internet have no knowledge of your boss's decision to send you to Stockholm, so they forward the packets to your home network as usual. The router on your home network, the Home Agent, sees these packets and remembers the care-ofaddress it received from the Foreign Agent. So, it takes your IP packets and sends them through an IP tunnel over the Internet to the Foreign Agent. The Foreign Agent looks at the packets and thinks, "This IP address isn't on my network, but I remember receiving information about it, so I can forward it on directly." In this way packets reach the mobile node.

What happens when the mobile node wishes to send packets out to the Internet? Well, this
causes no problem whatsoever, the laptop builds IP packets with the desired destination address and the usual source address (that is, 193.234.210.74) and sends them directly out to the Internet as usual.

Of course Mobile IP isn't perfect. One of the biggest drawbacks is the routing inefficiency it
introduces. Packets destined for our laptop pass through the Internet to our home network and then back out onto the Internet to our foreign network. This doglegged routing means that received packets suffer from higher latency than normal. It also means that the Internet is loaded more as the same packets must pass through it twice. There are also some important security implications to consider with Mobile IP. The mobile node must be carefully verified to ensure that packets are not forwarded to impostors intent on stealing others information.

Mobile IP is only one of a host of macro mobility techniques. Others, such as Dynamic DNS, L2TP and IP security are also capable of solving the problem of nodes moving between interconnected networks.

Macro


Micro and macro mobility are terms used to describe different methods of dealing with mobility management. Micro mobility techniques are used when mobiles move between individual base stations - micro means small and so micro mobility techniques are used for small moves.


Macro means big, so macro mobility techniques are used for large moves between different
networks. So, for example, when you take your GSM telephone from your home network in Sweden, and move to a new network in a different country, for example in England, you are moving to a new network and therefore the mobility management is solved using macro mobility techniques.


Now, you may have spotted there is a grey area in this definition. If micro mobility is moving between base stations and macro mobility is moving between networks, what term do we use for moving between different serving nodes?


There is no right and wrong answer here; it depends on the techniques implemented in the
network. For example, in a GSM network the same techniques are used when mobiles move between base stations and between serving nodes. So, GSM solves the problem of moving between serving nodes with micro mobility techniques. Conversely, PDC, the Japanese mobile telephone standard, uses macro mobility techniques for mobiles moving between serving nodes, so moving from one serving node to another and moving from one network to another both use the same technique. It's simply a question of how the network is standardized.

Generic Wireless Network


Although all wireless networks are different they do share some common characteristics. Here we try and illustrate those parts, which most systems share.


Most wireless applications consist of a user wishing to communicate with a server at some

remote location. The user's terminal is connected to the wireless network via a radio link to a base station. The server is connected to a network, be it the Internet or some corporate
Intranet. Now, each base station is connected to something called a serving node. The terminology differs depending on which mobile network you look at, but the idea is almost always the same. Note that one serving node can be attached to several base stations. On the
other side of the diagram we have the network attached to some gateway. Finally, tying the
pieces together we have the backbone network to which both the gateway and the serving
node are connected. Note that the backbone can be connected to several serving nodes and
several gateways. Using this network a wireless user can communicate with a remote server.


Other things are also attached to the network backbone. For example, there is some kind of
subscription register to store information on the mobile users. There is also some operations
and maintenance equipment to allow network monitoring, charging etc.

Tag

Assignment Lanka Tag Cloud
Computer Networks The History of Local Area Networks, LAN, The Topologies of a Networks, LANs describe different types of transmission Medias, Local Area Networks Access Methods, Carrier Sense Multiple Access with Collision Detect, Development of LAN Technologies. LAN -Token Ring, LAN Ethernet Digital, LAN - Ethernet Sun microsystems, LAN - Ethernet Mixed Environment, LAN - Token Ring was introduced by IBM LAN - IBM implementation of Token Ring, Token Ring Novell, LAN Token Ring - in a mixed environment, LAN - Fiber Distributed Data Interface, LAN - ATM, LAN Components, LAN Switching Methods, Virtual Local Area Network, Port based VLAN, Mac based VLAN, Protocol based VLAN, User Base VLAN, PC networks Components, PC networks Shared resources, PC Network operating systems, PC networks Novell Netware, PC networks Windows NT, PC networks IBM LAN Server Computer Programming Languages HTML Language, The Generations of Programming Languages, Different types of High Level Languages, Different types of High Level Languages Disadvantages
Computer Networks - IBM LAN Server, Windows NT Networks, Novell Netware, Network operating systems, Networks Shared, Networks Components, User Base, Protocol based, Mac based, Port based, VLAN, LAN Switching, LAN Components, ATM, Fiber Data, Token Ring, Token Ring Novell, IBM implementation, Ethernet, Sun microsystems, Ethernet Digital, Token passing, LAN Technologies, CSMA/CD, Access Methods, Transmission, Networks, The History of Local Area Networks, LAN