Networking Basics

While the underlying principles of networking are somewhat complex, building a network can be very simple, given the right tools and a basic understanding of how they work together. With networks, starting small and planning to grow makes perfect sense. Even a modest network can pay large dividends by saving time, improving communication between employees, customers and suppliers, increasing productivity, and opening new paths to information resources located anywhere in the world. Most people would agree that networks are collections of two or more connected computers. Once their computers are joined in a network, people can share files and peripherals such as modems, printers, tape back-up drives or CD-ROM drives.

Basic network includes:
-at least two computers.
-A network interface on each computer (the device that lets the computer talk to the network? usually called a network interface card (NIC) or adapter).
-A connection medium, usually a wire or cable, but wireless communication between networked computers and peripherals is also possible.
-Network operating system software, such as Microsoft Windows 95 or Windows NT, Novell NetWare, Appleshare or Artisoft LANtastic. Most networks, even those with just two computers, also have a hub or switch to act as a connection point between the computer.

Local Area Networks: Ethernet and Fast Ethernet
Ethernet has been around since the late 1970s and remains the leading network technology for local area networks (LANs). (LAN is a network contained in a building or on a single campus.) Ethernet is based on carrier sense multiple access with collision detection (CSMA/CD)

Simply put, an Ethernet workstation can send data packets only when no other packets are traveling on the network - when the network is "quiet."

Otherwise, it waits to transmit, as a person might wait for another to speak during a conversation.

If multiple stations sense an opening and start sending at the same time, a "collision" occurs. Then, each station waits a random amount of time and tries to send its packet again. After 16 consecutive failed attempts, the original application that sent it has to start over again. As more people try to use the network, the number of collisions, errors, and subsequent retransmits grows quickly, causing a snowball effect.

Collisions are normal occurrences, but too many can start to cause the network to slow down. When more than 50 percent of the network total bandwidth is used, collision rates begin to cause congestion. Files take longer to print, applications take longer to open and users are forced to wait. At 60 percent or higher, the network can slow dramatically or even grind to a halt.

As noted in the previous section, Ethernet bandwidth or data-carrying capacity (also called throughput) is 10 megabits per second (Mbps). Fast Ethernet (or 100Base-T) works the same way - through collision detection, but it provides 10 times the bandwidth- 100 megabits per second.

Shared Ethernet is like a single lane highway with a 10 Mbps speed limit. Shared Fast Ethernet is like a much wider highway with a 100 Mbps speed limit - more room for cars and they can travel at higher speeds. What would Switched Ethernet look like? A multi-lane highway with a speed limit of 10 Mbps in each lane. Switched Fast Ethernet also would be a multi-lane highway, but with a speed limit of 100 Mbps in each lane.

Token Ring
Token Ring is a "token-passing" technology and an alternative to Ethernet collision-detection method. A token travels through the network, which must be set up in a closed ring, and stops at each workstation to ask whether it has anything to send. If not, the token continues to the next point on the network. If there is data to send, the token grabs it and proceeds to the destination without stopping at the other computers along the way. Then it returns to the sending computer to acknowledge the transmission, before beginning its rounds again. Token Ring networks operate at either 4 or 16 Mbps, but with the low cost, ease of use and easy migration to higher performance in Ethernet networks, Token Ring is rarely used for new network installations.

High-Speed LAN Technologies
Today's growing, fast-changing networks are like growing communities - the traffic they create tends to cause congestion and delays. To alleviate these problems, you can install higher-speed LAN technologies in your network, which move traffic more quickly and offer greater data-carrying capacity than Ethernet, Fast Ethernet and Token Ring. Fiber Distributed Data Interface (FDDI) is another "token-passing" technology, operating at 100 Mbps. But since it requires different wiring (fiber) and different hubs and switches from Ethernet, FDDI is losing ground to Fast Ethernet and other high-speed technologies. Asynchronous Transfer Mode (ATM) operates at a range of speeds up to 622 Mbps at present. It is a popular choice for the backbones of extremely demanding or large networks, and it has special features, such as the ability to carry voice and video traffic along with data, and it can be used for wide area networks connecting geographically separated sites. Gigabit Ethernet operates at 1000 Mbps and is fully compatible with Ethernet and Fast Ethernet wiring and applications.

Network Congestion
Congestion is the networking term for too much traffic clogging network pathways. Common causes of congestion in today networks include:

-Too many users on a single networks segment or collision domain.
-High demand from networked applications, such as groupware (for scheduling and appointments) and e-mail with large attached files.
-High demand from bandwidth-intensive applications, such as desktop publishing and multimedia
-The growing number of users accessing the Internet.
-The increased power of new PCs and servers.

These last two issues have arisen only recently. Employees using the Internet may be downloading multi-megabyte image files to move across the network. This can clog pathways created to carry small e-mail and word processing files. Meanwhile, today's Personal Computer Interface (PCI) computers are fast enough to move files like these at 30 to 90 Mbps, easily overloading the actual 8 to 9 Mbps throughput capacity of a shared Ethernet network channel. The speed and bandwidth of these desktop machines, the size of popular Internet files, and the size of attachments sent via e-mail all continue to increase and at an accelerating pace. Your network bandwidth must grow in step to keep up with these advances.

Checklist for Network-building
The following checklists provide a general idea of the components you will need to install your network. These are meant to be rough guidelines only: your own installation will vary based on your needs.

For Building a Small LAN for Small business

-Clients with NICs installed
-Server
-Hub
-Cabling
-Network Operating System software (e.g.,  Linux , Windows NT, Windows 95, Novell Netware, LANtastic, AppleShare, etc.)
-Modem for dialup Internet access (optional)

Typical Office Network

       Networking Glossary

Benefits of network

    A little lecture on TCP/IP