Netword Strategy

• What is a network ?

Networks exists when a group of two or more computers are connected together. There are a few different types of networks.

• Local-area networks(LAN) : Computers are usually close together such as in a library or a school.
• Wide-area Networks(WAN) : The computers are far apart , such as the internet or many schools connected together.
• Campus-area network : Computers are usually in a university campus or military base.
• Metropolitan-area network : Networks restricted to a town or a city area.
• Home area networks : A series of computers connected in a house.

Topology

This is the way in which the computers are connected. It is to do with the physical structure of the network and how the cables are all connected.

Bus (topology)

This is an example of a bus type network. It has a main run of cable with a terminator at each end, the terminators stop the signal bouncing back off the end and causing problems. All networked devices (nodes) are connected to the cable.

Advantages

• Is easy to implement and extend as everything is connected to the main cable.
• They are well suited to temporary networks that must be set up quickly and when costs must be kept to minimum.
• If one node fails , this does not prevent the rest of the network from working normally.

Disadvantages

• Entire network fails if back bone cable fails.
• They require terminators which are an extra finicial burden.
• If the network has a failure it is hard to identify as it could be anywhere on the back bone if all the nodes stopping working.

For these given disadvantages bus topologies are not meant to be used as a stand alone network.

Star (topology)

As shown here is a network than looks similiar to hand drawn star, but this isn’t always the case.

A star network is a network with a series of nodes connected to a central node, usually a switch or a hub. The central node offers a connection from any node to any other one.

Advantages

• Easy to install as everything is connected to central node.
• Easy to detect faults and to remove parts, because if an error occurs it should only effect one node in the network.

Disadvantages

• More cables needed compared to bus network.
• If central node fails , whole network fails.
• More expensive network than bus as you need to purchase an expensive hub or switch.

Ring (topology)

A series of computers connected serially by cable. Meaning one computer is connected to the two computers on either side as shown above.

Advantages

• Can grow without great effect on performance of the system.
• All nodes have equal access to communication.

Disadvantages

• Require specialist hardware to function , which makes it one of the most expensive topology.
• Failure of one node may effect other computers being able to communicate.

Mesh (topology)

Mesh is a topology in which nodes are connected with many reduntant interconnections between the nodes. In a true mesh every node has a connection to every other node in the network.

Advantages

• Mesh topologies provide mutliple physical paths along which data can travel. So if one connection fails there will be another route for the signal to take.

Disadvantages

• Expensive due to many physical links needed in the network.
• Complexity makes the network difficult for the network manger to manage.
• If error occurs can be hard to find problem and fix it.

Tree (topology)

Tree topology is a series of interconnected star topology networks. Meaning tree topology allow for expansion of existing networks.

Advantages

• New nodes can be easily added to indiviual segments, and new segments easily added to the main central node.
• Easy to install and wire.
• No disruptions when connected and disconnecting nodes for the other nodes.
• Easy to detect faults.

Disadvantages

• If central nodes fail whole network fails.
• Overall length of segments governed by type of cables.
• Overall it is the most complicated topology to install.

Protocol

Is the set of rules and signals which governs communication between computers on a network. All networks require protocols to operate. One of the most popular protocols for LANs is called Ethernet. Another one is the IBM token-ring network.

Ethernet

It uses an access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection). This is a system where each computer ‘listens’ to the cable before sending anything through the network. If clear the computer will transmit. Sometimes , two computers attempt to transmit at the same time. When this occurs a collision happens. Each computer backs off and waits a random amount of time before attempting to re-transmit.

Collisions are normal, but the delay is nominal and does not effect the speed.

That was as far as we got today for a more detailed explanation please read the book or contact Jerome .

Cya

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