network topologies

1. Topologies

2. Star network
The host node performs
routing function and
centrally controls
communication between
any two other nodes by
establishing a logical path
between
them.

3. Advantages of a Star Topology
► Easy to install and wire.
► Minimal line cost- n-1 lines for n nodes
► No transmission delay by adding new node -2 links connect any 2
nodes
► No disruptions to the network when connecting or removing or failed
devices.
► Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
► If the hub fails, nodes attached are disabled.
► More expensive than linear bus topologies because of the cost of the
hubs

4. • Circular network
• 2 adjacent nodes for
communication
• No master node to control
other nodes
• Receives data from adjacent
nodes
• Node checks If data is
addressed to it, it utilizes it,
Or it passes to next

5. Advantages of a Ring Topology
► Works well if no central node for making routing decisions.
► More reliable than a star network because communication is not
dependent on a single central node.
If a link between any two nodes fails, or if one of the nodes fails,
alternate routing is possible.
Disadvantages of a Ring Topology
► Communication delay is directly proportional to number of nodes
in the network. Hence, addition of new nodes in a network
increases communication delay.
► It requires more complicated control software than star network.

6. Completely connected network
• Direct link called
point-to-point link
• Each node has a control

7. Advantages
► Very reliable because any link failure will affect only direct
communication between 2 nodes connected by that link.
► Each node of the network need not have individual routing
capability.
► Communication is very fast between any two nodes.
Disadvantages
► It is the most expensive network from the point of view of link
cost
If there are n nodes in a network, n(n-1)/2 links are required.

8. Multi-access bus network
► all nodes are connected to a single communication line (Channel)
► Known as broadcast network
Single
Communication
line

9. A node wants to send a message to another node
it appends destination address to the message
checks whether communication line is free
As soon as line becomes free, it broadcasts (places) the message
on the line
each node checks whether the message is addressed to it
The message is picked up by addressee node that sends an
acknowledgement to source node and frees the line

10. Advantages
► It helps in reducing the number of physical lines.
► Failure of a node does not affect communication among
other nodes in the network.
► Addition of new nodes to the network is easy.
Disadvantages
► All nodes in a network must have good communication and
decision-making capability.
► If the shared communication line fails, entire network fails.

11. Hybrid Network

12. ► Different network topologies have their own advantages and limitations.
Hence, in reality, a pure star or ring or Completely connected network is
rarely used.
► An organization normally uses a hybrid network that is a combination of two
or more different network topologies.