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Network Topology

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Review : Computer Network

LAN (Local Area Network)◦A group of computers and

associated devices (printers, etc.) ◦ connected through a wired or

wireless medium◦ by networking devices (hubs,

switches, routers)◦ use protocols for communication

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Topology◦Layout of how devices connect on network Wired Networks

Wireless Networks

Objectives

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Connecting computers on Network - Link Access

Two types of connections: Dedicated or Point-to-point◦Direct connection between two computers

Shared◦Multiple computers share the media

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Topology: Physical layout of network.

Some of the popular network topologies are:◦Star Topology

Distributed Star◦Bus Topology◦Ring Topology◦Tree Topology◦ Mesh

Full Mesh Partial Mesh

Network Topologies

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Dedicated Access - Point to Point connections

Advantages Each network connection is

independent It can be customised to suit the

type of data◦ for example: data speed and

technology It is easy to enforce security and

privacy. DisadvantagesNot scalable for large

networks

Computer A

Point to Point network

Black links show four connections from computer A to all computers in the network

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Star Topology

Individual computers are connected to a central point – a hardware device, called a hub/switch .

Max distance between a computer and hub/switch is restricted based on cable used.◦ With UTP cable, distance limited to

100m. Popular topology for LAN (local area

networks) Adv: Failure of any computer does not

affect other communications in the network

Disadv: Failure of hub/switch can bring the network down, also called SPF( Single Point of Failure)

Star Topology

Extended Star Topology

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Also called a "hierarchical" or "star of stars" topology

Nodes are connected in groups of star-configured workstations that branch out from a single "root,"

The root node usually controls the network and sometimes network traffic flow.

This topology is easy to extend: when new users need to be added

Tree Topology

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Full mesh topology◦ each node is physically

connected to every other node

Adv: Highly fault tolerant: when one node fails, traffic can easily be diverted to other nodes

Disadv: Not scalable for large networks

Partial mesh topologies are popular for backbone networks, where redundancy is desirable

Mesh Topology

Partial Mesh

Full Mesh

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Ring Topology Computers are connected to each other to form a closed loop. Common Examples ◦ FDDI Network

Usually Fibre optic cable based backbone networks◦ Token Ring Network

Example: IBM token ring network Proprietary network

Adding and removing computers disrupts the network. What should be done to provide redundancy in a ring topology ?

computer

cable

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Most wireless implementations are based on◦ Star, tree or line topology

Two modes:◦Ad hoc

No need of central access point Problem: Not scalable

◦ Infrastructure (more common) Central Access Point (AP) is needed Scalable

Many wireless implementations are based onmore than one topology

Topologies relevant to Wireless Networks

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Wireless Topology- Infrastructure

Star • Hotspots, Offices and WISP's• Point to Multipoint• The most common infrastructure in wirelessnetworking

point-2-point • Connecting two wireless clients directly• Building to building (when one has Internetconnection and the other one does not)

point-2-point - RepeatingNecessary when direct line of sight (LOS) is obstructed

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Mesh topologies are an interesting option mainly in◦ dynamic environments

(urban areas) where central infrastructure is hard to implement

◦when redundancy is desired Typical cases are:

municipal networks, campus networks etc.

Wireless Networks – Mesh Topology

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At the center of any cellular technology is the cellular transceiver, an omni-directional antenna whose range projects a circular "footprint." This footprint is the "cell" that gives cellular technology its name

As the cellular user moves from one cell to another, the user's signal is transferred from one antenna to another

Wireless Cellular Technology

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Factors influencing choice of topology?

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What is the role of network card?

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Use packet tracer to set up a network using following Topologies◦ Star◦Distributed Star◦ Point-to-point ◦ Tree

Refer to your task sheet for details

Task: