Telecommunications and networking
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Telecommunications and Networking. Network Topologies. What is Topology?. Physical or logical map of devices on a network Physical refers to where each device is physically located and how they are connected to each other

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Telecommunications and Networking

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Telecommunications and networking

Telecommunications and Networking

Network Topologies


What is topology

What is Topology?

  • Physical or logical map of devices on a network

    • Physical refers to where each device is physically located and how they are connected to each other

    • Logical refers to how data is transmitted from one node to another on the network


Topology

Topology

  • When the word topology is used by itself, we typically mean the physical topology

  • Four major topology designs

    • Bus

    • Ring

    • Star

    • Mesh


Telecommunications and networking

Not this…

Bus


Bus topology

Bus Topology

Single cable that connects all nodes on a network

Each node is connected to a common cable

Uses least amount of cable compared to other topologies

Often used as a backbone to link other topologies


Bus topology cont d

Bus Topology Cont’d.

  • Requires a terminator at one end and a grounded resistor at the other

    • If terminator is missing, you experience signal bounce

  • Supports only one channel for communication


Bus topology cont d1

Bus Topology Cont’d.

  • Pros

    • Inexpensive

    • Simple to set up

  • Cons

    • No fault tolerance

    • Not scalable

    • Not practical for more than 10 workstations

    • Difficult to troubleshoot

      • Single point of failure

    • 5-3-3 rule


Use a bus if

Use a Bus if…

Expense is a major issue

A temporary network is required until the primary network is completed and you must have communications

You want to install a backbone to connect two networks


Typical bus layout

Typical Bus Layout


Telecommunications and networking

Not this…

Ring


Ring topology

Ring Topology

  • Network forms a circle

    • First node connects to second node

    • Last node connects to first node

  • Data is (typically) transmitted clockwise

    • Unidirectional

  • Each workstation acts as a repeater

    • Active topology

  • Typically Uses TP or Fiber cabling

  • No fault tolerance


Ring topology cont d

Ring Topology Cont’d.

  • Pros

    • Organized in terms of data transmission

    • Design is simple

    • No need for server/central device

    • Each node has equal access to resources


Ring topology cont d1

Ring Topology Cont’d.

  • Cons

    • Single point of failure

    • Each packet must go through every computer to get to the right receiver

      • Token passing

    • Not very flexible or scalable

    • No fault tolerance


Use a ring if

Use a Ring if…

  • You have a small network that will not expand

    • 10 nodes or less

  • You do not require a central device to manage network


Typical ring layout

Typical Ring Layout


Telecommunications and networking

Not this…

Star


Star topology

Star Topology

  • Every node is connected to a central device

    • Single cable only connects two devices; node to central device

  • Typically built with TP or fiber

  • Supports maximum of 1024 addressable nodes per segment

    • More users = slower performance

    • Uses switches to subdivide segments


Star topology cont d

Star Topology Cont’d.

  • More fault tolerant than Bus or Ring

    • Cable problem will only affect the two devices it connects

    • Failure in central device will affect entire network

      • Single point of failure

    • Single workstation problem will only affect that workstation

  • Flexible and easily scalable


Use star if

Use Star if…

You need fault tolerance

You need maximum scalability

You need/want central network management

You need/want easy troubleshooting


Star topology cont d1

Star Topology Cont’d.

  • Pros

    • Better performance than Bus/Ring

    • Somewhat fault tolerant

    • Easily scalable

    • Centralized control


Star topology cont d2

Star Topology Cont’d.

  • Cons

    • Single point of failure (central device)

    • Cost of equipment/installation

    • More cable required than Bus or Ring

    • Performance and number of nodes supported dependent on central device


Typical star layout

Typical Star Layout


Telecommunications and networking

Not this…

Mesh


Mesh topology

Mesh Topology

  • Each device is connected to every other device on the network

  • Extremely fault tolerant

    • Highest fault tolerance of all topologies

  • Easy to troubleshoot problems

  • Not easily scalable


Mesh topology cont d

Mesh Topology Cont’d.

If a data pathway becomes overloaded or breaks, the network can re-route the data over a different pathway

Central device is optional

EXPENSIVE


Use mesh if

Use Mesh if…

  • Constant network connectivity is critical to your business/environment

  • You have large-scale data transmission

    • Video surveillance


Typical mesh layout

Typical Mesh Layout

Full Mesh

Partial Mesh


Summary

Summary

  • Logical topology represents how the data is transmitted around the network

  • Physical topology represents the physical layout of the network

  • Four major types of networks

    • Bus

    • Ring

    • Star

    • Mesh


Summary cont d

Summary Cont’d.

  • Bus

    • Forms a line

    • Easy to build

    • Inexpensive

    • Not fault tolerant

    • Single cable connects all nodes

    • Single point of failure


Summary cont d1

Summary Cont’d.

  • Ring

    • Forms a circle

    • Easy to build

    • Inexpensive

    • Not fault tolerant

    • Single cable connects all nodes

    • Single point of failure


Summary cont d2

Summary Cont’d.

  • Star

    • All nodes connect to a central device

    • More fault tolerant than Bus or Ring

    • Easily scalable

    • Easy to troubleshoot

    • Expensive

    • Single point of failure


Summary cont d3

Summary Cont’d.

  • Mesh

    • Every device is connected to every other device

    • Extremely fault tolerant

    • Easy to troubleshoot problems

    • Large-scale data transmission

    • Extremely expensive

    • Not easily scalable

    • Difficult to install


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