A Bridge is another device used to connect LAN cable segments together. Bridge operates at the data link layer of OSI model.

A Bridge provides packet filtering at data link layer, meaning that it only passes the packets that are destinated for the other side of the network.

a Bridge has two or more network interface (own MAC address)connected to different cable segments and operating promiscuous mode.

A Bridge examines each packet as it enteres through one of the ports. It first looks at the MAC address of the sender and creates a mapping between the port and the sender's MAC address. It then looks at the address of the ecipient , comparing the MAC address to the list of all learned MAC address. If the address is in list. the Bridge look up the port number and forwards the packet to the port where it thinks the recipient is connected. If the rrecepient's MAC address is not in the list , the Bridge blocks the data from passing.

Bridge can connect different network architectures like Ethernet and Token Ring.

Types of Bridges.

Three types of Bridges are used in network.

1> Transperent Bridge.

2> Translational Bridge.

3> Source-route Bridge.

Transperent Bridge :

Transperent Bridges is invisible to the other evices on the network. Transperent Bridge only perform the function of blocking or forwarding data based on MAC address. MAC address may also be referred as hardware address or physical address. These addresses are used to built tables and make decision regarding whether a frame should be forward and where it should be forwarded.

Translational Bridge :

Translational Bridges are usefull to connect segments running at different speeds or using different protocols such as token Ring and Ethernet networks. Depending onthe direction of travel, a Translational Bridge can add or remove information and fi elds from frame as needed.

Source-route Bridge :

Source-route Bridges were designed by IBM for use on Token ring networks. the sr Bridge derives the entire route of the frame embedded within the frame. This allows the Bridge to make specific decision about how the frame should be forwarded through the network.

Other than above, there are also Local Bridge, Remote Bridge.

Local Bridge :

A Local Bridge provides paket filtering and repeating services fot the network segments of the same type. this is also called MAC-layer Bridge. This is the simplest type of Bridge because it has no need for packet filtering or buffering. This Bridge simply propagates the incoming packets to the appropriate ports or discard them.

Remote Bridge :

Remote Bridge connects network segments at different locatios, using WAN link such as MODEM or Leased line. The difference in speed between Local and wide area links, a remote Bridge uses internal buffer to store the data received from LAN while it is waiting for transmission to the remote site.

Advantages of Bridges :

1> Bridges are simple and significant.

2> They prevent unnecessary traffic from crossing onto other network segments.

3> Bridge can reduce the amount of network traffic on segments.

4> It also make it possible to isolate a busy network from not-so-busy network.

5> They can connect different network architectures like Ethernet & Token ring.

6> Bridge have ability to look at the physical destination address of the frame and send the frame at the specific port.

7> Bridge can filter the traffic, it increases throughput on a network.

Disadvantages of Bridges :

1> Bridges are slower than Hubs & Repeaters, because they examine each frame's source and deatination addresses.

2> Bridges have no protection against broadcast storms. that is, when a computer needs to send information to all other computers on the networks, it sends a Broadcast frame. Bridges do not have the ability to stop Bridgeoadcast packets from being forwarded. When a Bridge receives a frame with a Broadcast destination address. the Bridge will simply forward the frame out every one of its ports.

3> A Bridge can not make decissions about routes through the network.

Use this trick at your own risks

1.Launch the disk cleanup utility by either:

-"Start">>"Programs">>"Accessories">>System Tools">>Disk Cleanup", or

-"Start">>"Run", enter "cleanmgr" then press enter.

2.Select the disk you want to clean up from the drop - down box (i.e. "Local Disk C") and click "OK"

3.Windows will calculate the space on your selected hard drive. This might take a few minutes depending on the size of your Hard Disk.

4.Once Windows is done with the calculation, Disk Cleanup Utility displays . Here you can select which storage you want to clean up (under "Files to delet") it doesn't hurt if you select them all when yo really need free spaces on your hard drive , Notice the usage size on som of these storage might be huge.

Click "OK" after your selections, then click "Yes" on the prompt.

5. Disk cleanup Utility starts to clean up your hard drive .

This

6.Might take a while depending on the current usage level on the storage . During the cleanup proces, your computer might be very slow, so give it some time. after cleanup your hard disks, perform a disk defrag mentation would really help your PC run faster.

A laptop is a computer which is meant to be carried to any place, unlike the desktop, thus making it more convenient for us to do our computing work at any time.  Here, I would like to discuss the merits and demerits of the laptop and conclude with a few statistics concerning the laptops.

MERITS:

The main benefit of a laptop is its PORTABILITY. There is no separate CPU and as it has a touch pad, there is no necessity to carry even a mouse or a mouse pad. It has an LCD screen as compared to the CRT monitors of the traditional desktops, and hence are lighter. It is handy and can be taken anywhere and everywhere; except perhaps to high altitudes! The other benefits are:

Less power consumption: As it has a rechargeable battery it can be operated on even in the absence of power, though only for a couple of hours.

Built-in Accessories: Almost all of the laptops have a built-in CD drive, graphics card and speakers. A microphone is present in some laptops. Modem and Bluetooth are also integrated into the system.

Less Space: Laptops need less space and hence are suited for homes where there is not much room for gadgets. Furthermore, the number of power connections required is practically nil-only for charging the battery.

Good Time-pass: During journeys, laptops provide a good source of entertainment as movies can be watched on the move.

Preloaded with OS:  Most of the laptops are preloaded with an operating system, thus sparing the users of the trouble of purchasing it separately and installing.

DEMERITS:

More Expensive: Laptops are costlier than desktops due to the LCD screen and other advanced features. Typically a low-end laptop comes at a price of a high-end desktop.

Less availability of Servicing: Servicing of the machine is limited as only the manufactured company will be able to fix a damaged laptop. Even upgradation of some internal parts like processors or hard disks may not be allowed in many cases.

Prone to Theft: As they are portable, they are also liable to be stolen easily. Hence, they need to be guarded with care.

Absence of Floppy: There is no floppy drive in many laptops. However, an external floppy disk can be connected to a USB port on the laptop.

As seen from the above points, the merits outnumber the demerits, hence making the laptops popular day by day. Their sales are indeed growing by the year, with some of the top brands being Acer, HP, IBM,Sony, Dell, Compaq, Lenovo etc.

SOME STATISTICS:

# First laptop: Osborn 1, Osborne Computer Corporations.

# Slimmest laptop: Adamo XPS, manufactured by Dell Corporations (width: 9.99 mm).

# Top Selling laptop brand: HP

WHAT IS THE DIFFERENCE BETWEEN A LAPTOP, A NETBOOK AND A NOTEBOOK?

Notebook computers are those which are smaller in size and are light-weight. They do built in drive and speakers; however, there is no Bluetooth or Wi-Fi integration and the battery lasts longer than in case of laptops.

Netbooks are similar to notebook, but are smaller and do not have a CD- drive. They have relatively slower processors, but the only advantage is that they can run on Linux operating System. Besides, it has a smaller battery and hence, a shorter battery life. Netbooks are basically designed for simpler tasks.