Fundamentals of Networking

Networking is the practice of linking two or more computing devices for the purpose of sharing data which enable more than one user to access shared resources. Whenever you have more than one computer being used at the same location, networking them together makes a lot of sense. Not only can you transfer files between them quickly and easily, but they can also share expensive resources like laser printers, hard disc arrays, backup tape drives, CD and DVD burners, scanners, internet connections and so on.

Network Architectuer

There are two main types of network architectures which are

Server Client

In a server based network, there are computers set up to be primary providers of services such as file service or mail service. The computers providing the service are are called servers and the computers that request and use the service are called client computers.

Peer-to-Peer

In a peer-to-peer network, various computers on the network can act both as clients and servers. For instance, many Microsoft Windows based computers will allow file and print sharing. These computers can act both as a client and a server and are also referred to as peers. Many networks are combination peer-to-peer and server based networks. 

The network operating system uses a network data protocol to communicate on the network to other computers. The network operating system supports the applications on that computer. A Network Operating System (NOS) includes Windows Server family, Windows NT, Novell Netware, Linux, Unix and others.

Network Topologies

The network topology describes the method used to do the physical wiring of the network. The main ones are bus, star, and ring.

 Bus Topology
Allows information to be directed from one computer to another on a single wire each computer is daisy-chained (connected one right after the other) along the same backbone. Information sent from a node travels along the backbone until it reaches its destination node. Each end of a bus network must be terminated with a terminator. A barrel connector can be used to extend it.

Star Topology
In a star network, each computer is connected to a central device called a hub. The hub takes a signal that comes from any node and passes it along to all the other nodes in the network All devices revolve around a central hub, which is what controls the network communications, and can communicate with other hubs. Range limits are about 100 meters from the hub.

Ring Topology
Similar to a bus network, rings have nodes daisy chained, but the end of the network in a ring topology comes back around to the first node, creating a complete circuit. Each node takes a turn sending and receiving information through the use of a token. The token along with any data is sent from the first node to the second node which extracts the data addressed to it and adds any data it wishes to send. Then second node passes the token and data to the third node, etc. until it comes back around to the first node again. Only the node with the token is allowed to send data . All other nodes must wait for the token to come to them.

Hybrid Topology

There are also hybrid networks including a star-bus hybrid, star-ring network, and mesh networks with

connections between various computers on the network. Mesh networks ideally allow each computer to have a direct connection to each of the other computers. The topology this documentation deals with most is star

topology since that is what ethernet networks use.

Network Media

The two different media for transport of data in the networks are

Wired 

Wired networks use either conductive medium or optical medium

The conductive wires transfer data in electrical form of current. The three different types of wires used are 

Coaxial Cables

Are electrical cables with an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis.

Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In addition, it can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial
Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial cable has been popular in
Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network.

Unshielded Twisted Pair

UTP, or Unshielded Twisted Pair, is a type of cable used in telecommunications and computer networks. It consists of different numbers of copper wire that have been twisted into matching pair. It differs from screened and shielded twisted pair, in that the individual pair are not protected with additional protection from interference. Each copper wire is insulated, and the groups of twisted pair have a sheathing holding them together, but no additional insulation is provided.

UTP comes in different types called Categories, often abbreviated as "Cat". The most common are Cat 3, Cat 5e, and Cat 6. The higher the category number, the more twists per foot in the pair, and the better protection from interference. Cat 3 is usually used for home telephone systems. Cat 5e is the industry standard for computer networks and large telephone systems. Cat 6 is an improvement on Cat 5e and is starting to become the favorite for new installs due to its increased speed and protection from interference.

Shielded Twisted Pair

Although UTP cable is the least expensive cable, it may be susceptible to radio and electrical frequency interference (it should not be too close to electric motors, fluorescent lights, etc.). If you must place cable in environments with lots of potential interference, or if you must place cable in extremely sensitive environments that may be susceptible to the electrical current in the UTP, shielded twisted pair may be the solution. Shielded cables can also help to extend the maximum distance of the cables.

Shielded twisted pair cable is available in three different configurations:

1. Each pair of wires is individually shielded with foil.



2. There is a foil or braid shield inside the jacket covering all wires (as a group).


3. There is a shield around each individual pair, as well as around the entire group of wires (referred to as double shield twisted pair).

Fiber Optic Cable

The Optical medium transmits data in the form of packets of light which travel along the length of Fiber Optical Cables from one end of the cable to the other end. The packets of light are tangentially reflected by the inner walls of the fiber cable in form of zig-zag movement.


Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling
The center core of fiber cables is made from glass or plastic fibers  A plastic coating then cushions the fiber center, and kevlar fibers help to strengthen the cables and prevent breakage. The outer insulating jacket made of teflon or PVC.

Wireless

More and more networks are operating without cables, in the wireless mode. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite.

Wireless networks are great for allowing laptop computers or remote computers to connect to the LAN. Wireless networks are also beneficial in older buildings where it may be difficult or impossible to install cables.
The two most common types of infrared communications used in schools are line-of-sight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network. Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks.

Categories of Networks and Networking Devices are further discussed in the next post