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					Network Topology




                   1
           Introduction
Physical and Logical Topologies
Topologies
  Bus
  Ring
  Star
  Extended Star
  Mesh
  Hybrid

                                   2
 Physical vs. Logical Topology
The actual layout of a network and its media
 is its Physical Topology
The way in which the data access the medium
 and transmits packets is the Logical
 Topology
A glance at a network is not always revealing.
 Cables emerging from a Hub does not make it
 necessarily a Star Topology – it may actually
 be a bus or a ring

                                              3
Bus Topology




               4
          Bus Topology (5)
Advantages                Disadvantages
Inexpensive to install    No longer recommended
Easy to add stations      Backbone breaks, whole
                            network down
Use less cable than       Limited no of devices can
 other topologies           be attached
Works well for small      Difficult to isolate problems
 networks                  Sharing same cable slows
                            response rates
                                                      5
Ring Topology




                6
        Ring Topology (3)
Advantages              Disadvantages
Data packets travel    Requires more cable
 at great speed           than a bus
No collisions          A break in the ring
Easier to fault find     will bring it down
No terminators         Not as common as
 required                 the bus – less
                          devices available
                                          7
Star Topology




                8
           Star Topology (3)
 Advantages                       Disadvantages
 Easy to add devices as the       A star network requires more
  network expands                   cable than a ring or bus
 One cable failure does not        network
  bring down the entire            Failure of the central hub can
  network (resilience)              bring down the entire
 Hub provides centralised          network
  management                       Costs are higher (installation
 Easy to find device and cable     and equipment) than for most
  problems                          bus networks
 Can be upgraded to faster
  speeds
 Lots of support as it is the
  most used
                                                              9
Extended Star Topology
   A Star
  Network
 which has
    been
expanded to
 include an
 additional
hub or hubs.

                         10
Mesh Topology (Web)




                      11
        Mesh Topology (2)
Not common on LANs
Most often used in WANs to interconnect
 LANS
Each node is connected to every other node
Allows communication to continue in the
 event of a break in any one connection
It is “Fault Tolerant”
                                              12
      Mesh Topology (3)
Advantages                   Disadvantages
Improves Fault              Expensive
 Tolerance                   Difficult to install
                             Difficult to
                              manage
                             Difficult to
                              troubleshoot
                  CP2073 Networking            13
Hybrid Topology




                  14
                   Logical Bus


•Modern Ethernet networks are Star Topologies (physically)
•The Hub is at the centre, and defines a Star Topology
•The Hub itself uses a Logical Bus Topology internally, to
transmit data to all segments
                                                             15
              Logical Bus
Advantages                Disadvantages
A single node failure    Collisions can occur
  does not bring the        easily
  network down            Only one device can
Most widely                access the network
  implemented topology      media at a time
Network can be added
  to or changed without
  affecting other
  stations
                                                  16
            Logical Ring
Data in a Star Topology can transmit data
 in a Ring
The MAU (Multistation Access Unit) looks
 like an ordinary Hub, but data is passed
 internally using a logical ring
It is superior to a Logical Bus Hub – see
 later slide
                                        17
Logical Ring (2)




                   18
         Logical Ring (3)
Advantages            Disadvantages
The amount of data A broken ring will
 that can be carried    stop all
 in a single message    transmissions
 is greater than on a A device must wait
 logical bus            for an empty token
There are no           to be able to
 collisions             transmit

                                        19
           Summary
Bus Topology
Ring Topology
Star Topology
Other Topologies
Logical Topologies
Questions and Answers
                         20

				
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posted:9/25/2012
language:English
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