network topologies michael lunn elias patsalos

Network Topologies

Michael Lunn

Elias Patsalos

James Hardiman

Terminology• Networking – consists of computers, wiring, and other

devices, such as hubs, switches, and routers that make up the network infrastructure.

• Topology – (from the Greek word topos meaning place) is a description of any kind of locality in terms of its layout.

• There are two ways to describe a network topology.

1. Physical topology2. Logical Topology

Client – a computer that allows a user to log onto the network and take advantages of the resources on the network.

Server – Much more powerful computer that provides centralized administration of the network and serves up the resources that are available on the network.

Terminology

Client/Server

Client/Server network operating systems allow the network to centralize functions and applications in one or more file servers

Advantages• Centralized• Scalable• Flexible• Interoperable• Accessible

Disadvantages• Maintenance• Expense• Dependence

Peer to Peer

Each computer acts both as a client and server.

Advantages• Less expense• Easy setup• Decentralized

Disadvantages• Security• Decentralized

Standard Physical Topologies

Star

Ring

Mesh

Bus2223

Bus Topology

• Characterized by a main trunk or backbone line with networked computers attached at intervals along the trunk line.

• Passive topology• Typically use coaxial cable hooked to each computer

using a T-connector.

Bus Topology cont.

Coaxial Cable Connectors

Star Topology

Computers on the network connect to a centralized connectivity device, usually a hub or a switch.

Ring Topology

• Connects the LAN computers one after the other on the wire in a physical circle.

• Moves info on the wire in one direction, considered an active topology.

Mesh Topology

• All nodes are directly connected with all other nodes.

• Best choice when fault tolerance is required.

• Very difficult to setup and maintain.

Standard Logical Topologies

• The way in which data accesses the medium (cable) and transmits packets.

• There are only two: Ring and Bus

Logical Topology: Ring

In the ring logical topology only one node can send information across the network at any given time. This is done by way of a ‘token’.

Each terminal receives this special packet, and if it has data to send, it will do so.

Once it has sent the data, it passes the token to the next station.

• Used for very fast networks• No collisions• Susceptible to faults

Logical Topology: Bus

Each time a node on a network has data for another node the sending node broadcasts to the entire network.

• Stations can always transmit.• Less susceptible to breaks.• Collisions (two stations transmitting at once) have to be

dealt with.

Selecting a TopologyNeeds:Do you need very high speeds?Will you be moving really large files?

Maintenance:Do you want something (relatively) painless?

Cost:Are you on a budget?Do you want replacement parts easily accessible?

Geography:How far is it between stations?Will you be relocating stations often?

Thank you!

Questions?