ClassLan

Notes 16/06/2006 - Networks

Network Topologies

Bus Topologies Single cable run (coaxial)

Oldest network type

Each station is added until the end of the line

All data has to travel the whole length of the network

Uses Terminators and has to be grounded at one end

If cable breaks no communication is possible

Data throughput is 10Mbps (Coaxial)

Suitable for small networks (10 machines or less)

Easy and cheap to install

Longest cable run for single cable is 185m/1024 PCs

Star Topologies All workstations connect to a central hub or switch

Cable failure only affects directly related PC

Easy to troubleshoot check ‘Link Light’

Hub/switch failure effects all connected PCs

More expensive than Bus – more cabling, hub/switch

Throughput can be: 10, 100, 1000Mbps

Ring Topologies

Bus topology connected together at both ends

(so has the same advantages and disadvantages as a Bus)

The connected ends need special protocols

Mesh Topologies Each ‘node’ is connected to

every other ‘node’ on the Mesh

Used commonly to connect together ISPs via routers

Suitable for Dataflow

Data flows on line on the Mesh with greatest available throughput

Extremely fault tolerant

Difficult to administer

Expensive to setup and maintain

Specialized

Hybrid Topologies Mix of other topographies

Most networks are hybrid

May be more expensive than other networks

Takes best elements of other network topologies

OSI Model (Open Standards Interconnect)

Designed to be a standard for network protocols.

7 Layers The Open Standards Interconnect Network Protocol system

Application File, Print Services/File Sharing, Email, HTTP

Presentation Encryption Keys – Encoding/Decoding

Session Overall Completion of Session – Establishs, controls and

completes session

Transport Error Correction and Troubleshooting

Network IP Addressing/Routing

Data Link MAC Addressing (Media Access Control)

Physical Places data on the 'wire'

IEEE 802 Institute for Electrical and Electronic Engineers (IEEE)

IEEE 802: Specifies each specific network technology standard

IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access/Collision Detection)

Used in Bus Topography networks

Specified 50-ohms coaxial baseboard cable/10Mbps

Data grouped in the Frames.

IEEE 802.5 'Token Ring'

Defined by a physical star, logical ring topology

Uses 'Token' Packets and the related processes

Eliminates collisions

Equal access for all connected machines

Scales very well

Polling Polling Stations are used, PS asks –

‘do you want to transfer data’ to clients.

CMSA/CA (Carrier Sense Multiple Access/Collision Avoidance)

Used by ‘Apple Talk’

posted by ClassLan @ 5:21 PM