1. Compute end-to-end delay

    2. CIRCUIT SWITCHING

    Set up

    Call Set-up time

    0.2

    Fist bit to arrive

    Number of hops * Prop Delay

    0.004

    Add time to last bit to arrive

    Length of message / Date Rate on links

    0.3333

    Acknowledgement

    Number of hops * Prop Delay + overhead bits per packet / Date Rate on links

    0.00567

    Total

    		 

    0.543

     

  2. What is the average number of hoops between stations for a packet-switch network of N nodes in the following:
  1. Star:

    2. Each connection takes 2 hops – Avg. path is 2 hops

  2. Fully connected:

One hop

 

  1. Flow control mechanisms are used at both levels 2 and 3 of x.25. Are both necessary, or is there a redundancy?

    2. Layer 2 flow control regulates total flow of data between DTE and DCE.

    Layers 3 flow control regulates flow over a single virtual circuit.

  2. In x.25, the virtual-circuit number used by one station of two communicating stations is different from the virtual-circuit number used by the other stations. Why would this be so? After all, it is the same full-duplex virtual circuit.

The virtual circuit number only has local significance (no global management of numbers.)