Computer Networking

Transport Layer

Switched Networks

Switched networks consist of interconnected nodes. The data is transfer from source to destination through these nodes. As the data is switch from node to node, that’s why, it’s called switched networks.

Types of switched networks

1. Circuit switching

It establishes the dedicated path between two nodes. The entire circuit must be available to transfer data in circuit switching. No other user can use at this time.

 Data sent in circuit switching passes through three stages

  • Establish a connection between sender and receiver before to data transfer.
  • Transfer the data
  • Disconnect the connection

Telephone network is an example of circuit switching. As, when one person calls to other then a connection is establish between two telephones. Secondly two persons can talk with each other. And finally the connection is terminated.

Transmission of data from computer A to B where S1 to S6 are different nodes is explain below in the diagram,

2. Message switching

  • In Message Switching the entire message is transfer as a complete unit through the intermediate nodes to its destination address.
  • Each and every intermediate-node stores the complete message and then forwards it to the next node until it reaches the destination. That’s why, its called store and forward network.
  • No need of establishing a dedicated path between the sender and receiver.
  • The destination address is appended to the message.
  • Message switches are program in such a way the message forward through the most efficient routes.

3. Packet switching

  • The message is divide into smaller pieces, called packets.
  • Packets are given a unique number to identify their order when they reach at the receiving end.
  • Every packet holds some information in its header section i.e. source address, destination address and sequence number.
  • Packets will travel across the intermediate nodes, by choosing the shortest path as possible.
  • All the packets are reassemble again at the receiving end in their sequence order.
  • If any packet is missing or corrupt, then the message will sent back to sender to resend the message.
  • If entire message is receive without any packet missing, then the acknowledgment message will be sent.

Internet network use the packet switching by using TCP/IP protocols.

Circuit Switching VS Packet Switching

Circuit Switching Packet Switching
A physical path is required between source and destination via cabling No physical path is required
Delay is uniform. Delay is not uniform.
Bandwidth is reserved or fixed for data transmission. Bandwidth is shared among users.
Wastage of resources Less wastage of resources
Less efficient more efficient
It does not follow the store and forward technique. It follows the store and forward technique.
Use in telephone network Use in internet networks

Note: S1, S2 … S6 are nodes which may router, switch or hub. And A, B are the devices i.e. computer, mobile, printer etc

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