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Thursday, October 04, 2012

Basic Networking


What is a network?

A computer network is a collection of PCs and other devices connected together with cables, so that they can communicate with each other for the purpose of sharing information and resources. Networks vary in size: some are within a single office, others span the globe.

There are various network technologies, the most common being Ethernet and Fast Ethernet. A network can be made up of one or more of these technologies. Ethernet and Fast Ethernet networks operate in a similar way, the main difference is the speed at which they transfer information; Ethernet operating at 10 Megabits per second (Mbps) and Fast Ethernet operating at 100 Megabits per second (Mbps).

How does a network net work?

Devices on a network communicate by transmitting information to each other in groups of small electrical pulses (known as packets). Each packet contains address information about the transmitting device (the source address) and the intended recipient (the destination address). This address information is used by some of the network equipment to help the packet reach its destination.

Ethernet and Fast Ethernet networks use a protocol called CSMA/CD (Carrier-sense Multiple Access with Collision Detection). This protocol operates by allowing only one device to communicate at any given time. When two devices try to communicate simultaneously, a collision occurs between the transmitted packets, and this is detected by the transmitting devices. The devices stop transmitting and wait before resending their packets. All this is part of normal network operation for Ethernet and Fast Ethernet networks, and is comparable to a conversation between people in a group; if two people speak at the same time, they both stop and then one will start to speak again.

What are the benefits of networking?

Creating a network, by connecting computer equipment together, allows the equipment to communicate and share information and resources. In particular, you can:
·       Share expensive peripherals, such as printers — All of the computers can access the same printer.
·       Pass data between users without the use of floppy disks — Files can be copied and accessed across the network, eliminating the time wasted and inconvenience caused by using floppy disks to transfer files. There is also less restriction on the size of file that can be transferred over the network.
·       Centralize key computer programs, such as finance and accounting programs — It is often important that all users have access to the same program (and not copies of it) so that they can work on it simultaneously (for example, a ticket booking application where one program must be used to ensure that the same tickets are not sold twice). Networking allows offices to have such a central program that all users can access.
·       Automate backup of critical files — It is always essential to keep backups of any important files. You can automate this procedure by having a computer program that backs up the files for you. Without a network, you would have to manually copy files, which is time consuming.

What are the components of a network?

A small network generally consists of:
·       PCs and peripherals (such as printers)
·       Network cables
·       A piece of network equipment such as a hub, that connects your PCs and peripherals
·       A network operating system (NOS) — Windows® 98 can be used as a NOS
Other pieces of network equipment may be required. For example, most PCs are not ready for use in a network; they may require network interface cards (NICs) to provide the connections they need.

What is the difference between a hub and a switch?

Hubs and switches are different types of network equipment that connect devices. They differ in the way that they pass on the network traffic that they receive.


The term ‘hub’ is sometimes used to refer to any piece of network equipment that connects PCs together, but it actually refers to a multi-port repeater. This type of device simply passes on (repeats) all the information it receives, so that all devices connected to its ports receive that information.

Hubs repeat everything they receive and can be used to extend the network. However, this can result in a lot of unnecessary traffic being sent to all devices on the network. Hubs pass on traffic to the network regardless of the intended destination; the PCs to which the packets are sent use the address information in each packet to work out which packets are meant for them. In a small network repeating is not a problem but for a larger, more heavily used network, another piece of networking equipment (such as a switch) may be required to help reduce the amount of unnecessary traffic being generated.


Switches control the flow of network traffic based on the address information in each packet. A switch learns which devices are connected to its ports (by monitoring the packets it receives), and then forwards on packets to the appropriate port only. This allows simultaneous communication across the switch, improving bandwidth.

This switching operation reduces the amount of unnecessary traffic that would have occurred if the same information had been sent from every port (as with a hub).
Switches and hubs are often used in the same network; the hubs extend the network by providing more ports, and the switches divide the network into smaller, less congested sections.

When Should I Use a Hub or Switch?
In a small network (less than 30 users), a hub (or collection of hubs) can easily cope with the network traffic generated and is the ideal piece of equipment to use for connecting the users.
When the network gets larger (about 50 users), you may need to use a switch to divide the groups of hubs, to cut down the amount of unnecessary traffic being generated.

If there is a hub or switch with Network Utilization LEDs, you can use the LEDs to view the amount of traffic on the network. If the traffic is constantly high, you may need to divide up the network using a switch.

When adding hubs to the network (to add more users), there are rules about the number of hubs you can connect together. Switches can be used to extend the number of hubs that you can use in the network.


Making Folders and Drives Shared


This topic describes how to set up shared folders and drives (for example a CD-ROM drive).

Making folders and drives shared

To specify a shared folder or drive, on a PC or laptop:
1.   In the Windows 98 desktop on that PC or laptop, either:
·       Double-click the My Computer icon and locate the folder or drive.
·       Or use Windows Explorer to locate the folder or drive.
To start Windows Explorer, from the Start menu, choose Programs and then Windows Explorer. For information on how to use Windows Explorer, refer to the Windows 98 manual and help system.
2.   When you have located the folder or drive, right-click on it (using the right mouse button) and select Sharing. The Properties dialog box appears with the Sharing tab displayed.
3.   In the Sharing tab, select Shared As.
4.   Select the access type for the folder or drive. This specifies the type of access available to the PCs and laptops that are set up to access it:
·       Full — The users of the network can have read and write access to the folder or drive. You can enter a password in the Password field below it on the screen, to restrict access.
·       Read-only — The users of the network can have read access to the folder or drive (but cannot write to it). You can enter a password in the Password field below it on the screen, to restrict access.
·       Depends on Password — The folder or drive can be accessed either in full or as read-only depending on passwords. You must specify a full password and a read-only password (both must be different) in the Password fields below it on the screen. These passwords are used by the other PCs and laptops to determine their method of access.

Examples of access settings:
·       If you want users to have read and write access to the folder or drive, specify Full access and leave the password field blank.
·       If you want selected users to have read access to the folder or drive (and restrict access to authorized users only), specify Read-only access and type in a password (this password is then used when setting up access for the selected users’ PCs and laptops).

NOTE: A shared folder will provide access to its contents and subfolders.

5.   Click OK.

The folder or drive is now accessible.

Accessing a Shared Folder or Drive


This topic describes how to access shared folders and drives (for example a CD-ROM drive) from other PCs and laptops over a  network.

Accessing a Shared Folder or Drive

To access a shared folder or drive on the network from another PC or laptop:
1.   On the PC or laptop that is to access the folder or drive, double-click the Network Neighborhood icon.
2.   In the Network Neighborhood window, from the View menu select Refresh.
3.   Locate the folder or drive. To do this, double-click the icon for the PC or laptop that has the shared folder or drive on it.
4.   Double-click on the folder or drive and enter a password if required. This is the password that was set up on the PC or laptop (that contains the shared folder or drive) when specifying the folder or drive for shared use. This PC or laptop can now access the folder or drive.
5.   If the user is going to access the folder or drive frequently, it is a good idea to map it to a network drive on the user’s PC or laptop. To do this:
a)   On the PC or laptop, in the Network Neighborhood window, right-click on the folder or drive and select Map Network Drive.
NOTE: Only map the network drive to the main shared folder or drive (and not its subfolders).

Setting Up IP on a PC or Laptop


This subsection describes how to set up an IP address for a PC or laptop you wish to connect to the internet. IP is not normally required for normal peer-to-peer networking.

To connect to the internet you will need a unique IP, or Internet Protocol, address. You usually obtain your IP address from your Internet Service Provider or ISP. If you have no knowledge of IP, consult your network supplier or ISP before going any further.

Setting up IP

To set up an IP address on a PC or laptop:
1.   In the Windows 98 desktop, right-click the Network Neighborhood icon (using the right mouse button) and select Properties. The Network dialog box appears with the Configuration tab displayed.
2.   Click Add.
3.   From the listbox, select Protocol and click Add.
4.   The Select Network Protocol dialog box appears. From the Manufacturer listbox, select Microsoft. From the Network Protocol listbox, select TCP/IP. Click OK.
5.   In the Configuration tab, from the listbox select TCP/IP and click Properties.
6.   The TCP/IP Properties dialog box appears with the IP Address tab displayed. Select Specify an IP address. Specify the IP address and subnet mask, and then click OK.
IP addresses and subnet masks are written in the format xxx.xxx.xxx.xxx, where xxx is a number between 0 and 255.
7.   Click OK. Windows 98 asks you to insert your Windows 98 CD or various Windows 98 disks. Provide them as required. Windows 98 copies the appropriate drivers from the CD or disks.
8.   Restart the PC or laptop as instructed. The IP address has now been set up.

Troubleshooting the IP


To check that a new IP address has been set up correctly on a PC or laptop, you can use PING (Packet INternet Groper) to try and communicate with the PC or laptop from another PC or laptop on the network that already has an IP address.

Checking IP

To check IP:
1.   On the other PC or laptop that already has an IP address, from the Start menu, choose Programs then MS-DOS Prompt. The MS-DOS Prompt Window appears.
2.   Enter the command “ping xxx.xxx.xxx.xxx” (where xxx.xxx.xxx.xxx is the IP address).
The PING application in MS-DOS tries to communicate with the PC or laptop that has the new IP address and displays the results of the operation:
·       If successful, go to step 3.
·       If unsuccessful (indicated by a Request time out message), go to ipconfig.
Close the MS-DOS Prompt Window by entering

Network appears slow
The ability of your network to transfer information is measured in terms of available bandwidth.  It is normal for networks to experience high bandwidth usage from time to time. If someone is transferring a large file across the network, the file may take up most of the available bandwidth and make the network appear slow to other users.

General network response is slow for everyone
There are two main reasons why the network is giving a slow response:
·         There may be a configuration problem or faulty equipment on the network.
·         The network may be unable to cope with the amount of traffic generated.

Configuration problem or faulty equipment on the network
Check that:
a) The network does not break any of the Ethernet or Fast Ethernet configuration rules.
b) There is not a speed mis-match between devices.
c) There is only one path to each device on your network. If there is more than one path, there is an illegal Network Loop.
 d) Devices on the network are working correctly. For example:
· Faulty cables can corrupt traffic on your network and cause requests to fail.
· Faulty devices, such as transceivers, can produce excess traffic that uses up the available bandwidth.

Network unable to cope with the amount of traffic generated
If your device has Utilization LEDs and these LEDs show that 50% or more of the available bandwidth is constantly in use, it is time to reconfigure or upgrade your network. You can:
· Use Ethernet Switches to divide the network into smaller less congested sections.
If this does not solve the problem, check that you have sufficient resources for the type of work you wish to perform.
Ø  You may need more processor power, disk space or memory than is currently available on your PC or laptop.
Ø  You may have a task that is running in the background, which is taking up a lot of processor power.
Ø  Your PC or laptop may have been set up to automatically look for an IP address. The PC or laptop will continually try to get an IP address, and use processor power in the process.
Ø  The PC or laptop may appear slow or even come to a stop. You may see the DHCP error message described in Troubleshooting, Windows 98 Error messages.Network appears slow when users try to access a specific PC/Printer.