Network TopologiesNetwork Topologies

What is Topology?What is Topology?

• The topology of a space is the definition of a collection of sets (called the open sets) that include:– the space and the empty set

– the union of any of the sets

– the finite intersection of any of the sets

• “Topological space is a set with the least structure necessary to define the concepts of nearness and continuity”

Types of TopologiesTypes of Topologies

• Bus Topology

• Star Topology

• Ring Topology

• Mash Topology

• Tree Topology

Bus Topology Bus Topology

• A bus topology connects all stations in a linear fashion

Bus TopologiesBus Topologies

• Bus topology advantages:– It is inexpensive– It is easy to design and implement because the

stations are simply daisy-chained together

• Bus topology disadvantages:– It is difficult to troubleshoot– It requires termination

Star TopologiesStar Topologies

• The star network configuration is the most popular physical topology

• In a star configuration, all computers or stations are wired directly to a central location:– Concentrator (a.k.a. hub)– Multistation Access Unit (MAU)

• A data signal from any station goes directly to this central device, which transmits the signal according to the established network access method for the type of network

Star TopologyStar Topology

Star TopologiesStar Topologies

• Star topology advantages:– A break in one cable does not affect all other

stations as it does in bus technologies– Problems are easier to locate because symptoms

often point to one station– The second-easiest topology to design and install– Does not require manual termination

• Instead the media is terminated in the station at the transceiver on the NIC and in the hub or MAU

Star TopologiesStar Topologies

• Star topology disadvantages:– Hubs, which are required for a star topology, are

more expensive than bus connectors– A failure at the hub can affect the entire

configuration and all connected stations– Uses more cable than bus topologies

Star TopologiesStar Topologies

• Bus and star topologies can be combined to form a star/bus or bus/star physical topology

• Hubs that have connectors for coaxial cable as well as for twisted-pair wiring are used to form these types of networks

• When different physical topologies are applied to a network, the result is often called a mixed media network

Ring TopologyRing Topology

• Physical rings– Most often seen in Fiber Distributed Data

Interface (FDDI) networks• FDDI is a WAN technology

– Stations on a ring are wired to one another in a circle around the entire network

Ring TopologyRing Topology

Ring TopologiesRing Topologies

• Ring topology advantages:– It prevents network collisions because of the

media access method or architecture required

– Each station functions as a repeater, so the topology does not require additional network hardware, such as hubs

Ring TopologiesRing Topologies

• Ring topology disadvantages:– As in a bus network, a failure at one point can

bring down the network– Because all stations are wired together, to add a

station the network must be shut down temporarily

– Maintenance on a ring is more difficult than on a star topology because an adjustment or reconfiguration affects the entire ring

Tree TopologyTree Topology

• Characters of bus and star topology

• Different groups

• Backbone cable

Tree TopologyTree Topology

Tree TopologyTree Topology

• Advantages – It provides point to point wiring for individual

segments– It is supported by several hardware and software

venders

Tree TopologyTree Topology

• Disadvantages– Overall length of each segment is limited by the

type of cabling used– If the backbone line breaks the entire segments

goes down– It is more difficult to configure and wire than

other topologies

Mesh TopologyMesh Topology

• Physically connected

• Improved performance and reliability

• Don’t used in local area network

• Used in wide area network

Mesh TopologyMesh Topology

Mesh TopologyMesh Topology

• Advantages– Dedicated link guarantee that each connection

carry its own data load – Eliminates the traffic problems– If one link become unusable it does not harm the

entire system– It is easy to troubleshoot

Mesh TopologyMesh Topology

• Disadvantages– Very expensive– Difficult to install and reconfigure