Introduction to Networking

Switched Networks

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

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 it at this time.

 Data sent in circuit switching passes through three stages

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

The telephone network is an example of circuit switching. When one person calls another, then a connection is established between two telephones. Secondly, two persons can talk with each other. Finally, the connection is terminated.

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

2. Message switching

  • In Message Switching, the entire message is transferred 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 it’s called store and forward network.
  • There is no need to establish a dedicated path between the sender and receiver.
  • The destination address is appended to the message.
  • Message switches are programmed in such a way the message is forwarded through the most efficient routes.

3. Packet switching

  • The message is divided 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 possible.
  • All the packets are reassembled again at the receiving end in their sequence order.
  • If any packet is missing or corrupt, then the message will sent back to the sender to resend the message.
  • If the entire message is received without any packet missing, then the acknowledgment message will be sent.

Internet networks use packet switching by using TCP/IP protocols.

Circuit Switching VS Packet Switching

Circuit Switching Packet Switching
A physical path is required between the 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 the telephone network. Use in Internet networks.

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