Network Topologies

Network Topologies and Types

Topology● The way in which the computers or other devices

that need to communicate are inter-linked together – Topology● Choice of topology depends on following factors

○ Desired Performance of the system○ Desired Reliability of the system○ No. of nodes(computer or devices) in the system○ Cost of maintaining the network○ Routing information from one node to another

Star Topology● It has multiple nodes connected to host

node● Nodes in the network are interconnected

to each other through host node● They (node) can communicate only

through host node● The entire network is control by host node● The logical path for the communication

between two node is define by host node

Star Topology ● Advantage

○ It has minimal line cost because only n-1 lines are required for connecting n nodes

○ Adding new node in network delay the transmission

○ If host node fails network is down● Dis – Advantage

○ Network depends on host node

Ring Topology● It is represented as a circular or ring network● Each node has two communicating

subordinates● No master or host node to control the network● A node receives data from one of its two

adjacent nodes● Data is utilized if it is for it(node), otherwise

passes to the next node.

Ring Topology● Advantage

○ No central node, to control the network or routing decisions

○ It is more reliable than star topology if one of node is fail than the alternative routing is possible

● Dis Advantage○ Addition of node in network increases

communication delay○ Requires special control software than star

topology

Mesh Topology● It is completely connected network● Each node has Personal physical line for

connecting to all other node ● Each Node has a direct link – Point-to-Point

link● Control is distributed with each node

Mesh Topology● Advantage

○ It is very reliable because failure of any node doesn't affects the network

○ Each node of the network need not have individual routing capability

○ Communication very fast between two nodes● Dis Advantage

○ It is most expensive network

Bus Topology● All nodes in network share single

transmission medium i.e same communication channel

● It appends destination address to message and checks whether channel is free

● Also known as ‘multipoint’ or ‘multidrop’ or ‘broadcast’ network

Bus Topology● Advantage

○ It helps in reducing the number of physical lines○ Failure of any node doesn’t affects the network○ Adding of new nodes to the network is easy

● Dis-Advantage○ All the nodes in a network must have good

communication and decision making capability○ If the shared communication line fails, the entire

network fails

Hybrid Topology● Combination of two or more different

network topologies – Hybrid Topology

● Different network Topologies have their own advantages and limitation

● A pure star or ring topology is rarely used

Types of Network

Characteristics LAN WANGeograhpic Distribution

Only few km Extend upto thousand km

Data Rate Much higher rate than WAN (10

mbps) to1 (gbps)

1200 bps to 2 Mbps

Error Rate Fewer HigherCommunication

LinkTwisted pair,

coaxial cable and fiber optic

Telephone lines, microwave link and satellite channels

Ownership Single Organization

Different Organization

Communication Cost Negligible Costly