Does circuit switching make sure that all packets follow the same route?I understand that there will be a dedicated path between two end systems before data transfer and all packets are received in order.But does that also mean that they all follow same route ?

I know that in packet switching packets may or may not follow same path and in virtual switch network packets follow same path,but i want to understand about circuit switching whether packets follow same path or not ?

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Circuit switching networks as X.25 or Frame Relay use a mechanism that opens a virtual channel from transmitter to receiver before the data transmission begins.

For example:

If using Frame Relay you want to communicate from London to Paris, your communication device has to send a signal to its next Frame Relay switch indicating that you want to open a channel to Paris, and that switch sends the same signal to the following switch and so on until the signal gets to Paris switch.

Now that the channel is stablished the communication begins. Each frame from London to Paris goes through the designated channel and when the communication ends the switches close the channel.

Packet switching networks as TCP/IP don't open a predefined channel before sending the first frame of communication.

In the same example using London and Paris, your device sends the first frame and the next switch will have to decide what is the best next hop for that frame and every network device will do the same until the frame gets to Paris.

For each frame the switch decides the best next hop so sometimes the frames will go through one path and sometimes through another depending of traffic, congestion, availability, etc.

Packet Switching networks are more flexible than Circuit switching networks because there is not a designated path from start to end.

  • Thanks for your answer @jcbermu. I understand that it will got through designated channel in circuit switching. So does this mean all packets follow same route(Same set of intermediate nodes)? Is there a possibility that the designated path itself having a diverging point where it can either divert packets to either router 1 or router 2?Some packets it sends to router 1 and some to router 2.Although it has captured both the routers for entire communication.Is this possible or all packets has same path? – rahul sharma Aug 18 '17 at 14:55
  • No. frames going through a channel always go through the same path. If the path breaks, for example due to a failing switch then a new path can be stablished and the new path will be used. – jcbermu Aug 18 '17 at 15:01
  • Ok i understood.Can you please tell me why the scenario that i mention in the last comment is invalid? – rahul sharma Aug 18 '17 at 15:16
  • That scenario, by it's very definition, can not exist in a circuit-switched network. Circuit-switched networks have no concept of per-packet forwarding decisions, that is its very definition! If you want diverging paths in a circuit-switched network, you have to build multiple channels, and make forwarding decisions on which circuit to send on before the packet enters into the circuit-switched network. Once the packet enters the channel, it is on a fixed path to the end. This is one of many reasons why circuit-switched networks have largely fallen out of favor compared to packet-switching. – halfmetaljacket Aug 22 '17 at 22:06

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