Switched network

1. Circuit Switching

A method that lays down a path in advance, like a telephone line, and travels only along that path

• Suited to voice traffic
• Once data transmission is under way, no other logic needs to be considered (transparent)
• Suited to analog communication, poorly suited to digital communication

1. Dedicated path + 3 phases

1. Establish (connection setup)

• As the signal sent by the caller passes through the switching nodes one by one to reach the receiver, a channel is allocated at each node, completing the end-to-end path
• The circuit is held only once the receiver responds

2. Transfer (data transfer)

• Data now flows as if the two devices were connected by a wire. (No re-routing is needed, and intermediate nodes do not need to look at addresses)
• There is no transmission delay and no delay variation (jitter).

3, Disconnect (connection release)

• When the call ends, the circuit is torn down and the channels and resources it held are returned. Other devices can now use this path

Drawbacks

1. Setup takes time
2. Once held, it occupies capacity even while no data is being sent, which is wasteful

2. Blocking & non-blocking

What happens to a new connection request when all paths are in use?

Blocking network

• If all paths are already in use, the new connection is refused
• Based on the assumption that phone calls are short by nature and that only a small fraction of all telephones are in a call at the same time

Non-blocking network

• A structure in which all stations can be connected at the same time
• As long as the other party is free, any connection request is always accepted.
• Unlike phone calls, data communication stays connected for a long time once established, so this approach is used

3. Space Division switching

Transfers signals over physically separate paths

4. Time Division switching

2. Packet Switching

Information is chopped into small pieces, each given just an address and sent off, and the nodes find the way on their own

1. Better line efficiency (link sharing + buffering)

2. Datagram

3. Virtual Circuits

3. Comparison table