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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: