1. Consider a network in which for any two nodes directly connected with a link, a message either reaches its destination within T time or gets lost. (a) Give an efficient handshake protocol for connection establishment for this network between two nodes which are directly connected to each other. (b) Discuss the problems which may arise to the protocol in (a) if the two nodes are not directly connected to each other.

2. Consider the arrangement of hosts shown in the Figure. All links are full-duplex, can transmit up to 2Mbps, and all routers are faster and all routers are faster than their links. A wants to send data to D at rate 1Mpbs and E wants to send data to F at rate 2Mbps. What is the throughput for A and E (how much data can they transfer per sec) under the following conditions: (a) The congestion control policy at B employs a single input queue for data coming from both A and E and forwards using the FIFO discipline. (b) The congestion control policy at B employs separate input queues of equal size for A and E and forwards using round robin. Give reasons for your answers.

3. Consider the case where A is connected to B via a wired link and B is connected to C via a wireless link. The bandwidth of the link from A to B is 10 6 bytes/sec and for the link from B to C is 10 5 bytes/sec. The round trip delay is 1sec from A to B and 5 secs from B to C. Assume that A needs to send data to C using B as an intermediate hop. If a standard sliding window protocol is used from A to C, what would be the type of protocol used? If a split-TCP approach is used, what would be the types of protocol used.

4. Assume that you have a set of 4 nodes, A, B, C and D arranged in a ring with A as the requester and B, C and D as responder. The execution proceeds in a sequence of iteration. In each iteration, A asks a question which is to be sent in the clockwise direction in the ring to all responders. On receiving this question, each responder send a response message back to A (which is again sent in the clockwise direction). After receiving all of the responses, A proceeds with the next iteration by asking the next question. You need to design a protocol stack to support this application. Describe the data link layer and routing protocol in sufficient detail for this protocol stack (e.g., type of sliding window protocol, window size, routing strategy). The protocols must be efficient in terms of minimizing the execution/response time.

5. Consider the following protocol for public key distribution. There exists a central authority, CA, whose public key is known to everyone. If Bob wants to obtain Alice’s public key, it sends a message containing the tuple,. to CA, where R is a random number, asking for Alice’s public key. In response, (a) CA sends the message containing the pair,. Is it possible to Trudy to attack this protocol and provide Bob with her public key instead of Alice’s public key? (b) CA sends a the message. Is it possible to Trudy to attack this protocol and provide Bob with her public key instead of Alice’s public key?