B: Answer the following (15 marks) 1- Consider an HTTP client that wants to retrieve a Web document at a given URL. The IP address of the HTTP server is initially unknown. What transport and application-layer protocols besides HTTP are needed in this scenario? 2- What are the main functions of the data plane and control plane? 3- Suppose there are three routers between a source host and a destination host. Ignoring fragmentation, an IP datagram sent from the source host to the destination host will travel over how many interfaces? How many forwarding tables will be indexed to move the datagram from the source to the destination? 4- Describe how loops in paths can be detected in BGP. 5- Suppose users share a 2 Mbps link. Also suppose each user transmits continuously at 1 Mbps when transmitting, but each user transmits only 20 percent of the time. Find the probability that at any given time when three users are transmitting simultaneously. Q2: (15 marks) A: Consider transferring an enormous file of L bytes from Host A to Host B. Assume an MSS of 536 bytes. 1- What is the maximum value of L such that TCP sequence numbers are not exhausted? Recall that the TCP sequence number field has 4 bytes. 2- For the L you obtain in (1), find how long it takes to transmit the file. Assume that a total of 66 1-3 bytes of transport, network, and data-link header are added to each segment before the resulting packet is sent out over a 155 Mbps link. Ignore flow control and congestion control so A can pump out the segments back to back and continuously. B: Consider sending a large file from a host to another over a TCP connection that has no loss. (15 marks) 1- Suppose TCP uses AIMD for its congestion control without slow start. Assuming cwnd increases by 1 MSS every time a batch of ACKS is received and assuming approximately constant round-trip times, how long does it take for cwnd increase from 6 MSS to 12 MSS (assuming no loss events)? 2- What is the average throughout (in terms of MSS and RTT) for this connection up through time=6 RTT