SKR 5302: Advanced Distributed Computing
3. Chapter 3: Networking and Internetworking
3.6. Switching Schemes
- Broadcast
- Involves no switching
- Everything is transmitted to every node, and it’s up to the potential receivers to notice transmissions addressed to them.
- Ethernet
- Wireless networking
- Broadcasts are arranged to reach nodes grouped in cells.
- Circuit switching
- Telephone network
- POTS (plain old telephone system)
- When a caller dialed a number, the pair of wires from the phone to the local exchange was connected by an automatic switch at the exchange to the pair of wires connected to the other party’s phone.
- Packet switching
- Store-and-forward network
- Each packet arriving at a node is first stored in memory at the node and then processed by a program that transmits it on an outgoing circuit;
- which transfers the packet to another node that is closer to its ultimate destination.
- Frame relay
- Problems of switching packets in store-and-forward network
- Switching packet through each network node takes anything from a few tens of microseconds to a few milliseconds.
- Switching delay depends on the packet size, hardware speed, etc.
- Even short Internet packets take up to 200 milliseconds to reach their destinations.
- Delay is too long for telephony and video conferencing (delay less than 50 milliseconds)
- Frame relay
- Overcome the delay problems by switching small packets (frames) on the fly.
- Switching nodes
- Routes frames based on the examination of their first few bits
- Not stored at nodes
- ATM network