Problem 1
Give two example computer applications for which connection-oriented service is appropriate. Now give two examples for which connectionless service is best.
Problem 2
Datagram networks route each packet as a separate unit, independent of all others. Virtual-circuit networks do not have to do this, since each data packet follows a predetermined route. Does this observation mean that virtual- circuit networks do not need the capability to route isolated packets from an arbitrary source to an arbitrary destination? Explain your answer.
Problem 3
Give three examples of protocol parameters that might be negotiated when a connection is set up.
Problem 4
Assuming that all routers and hosts are working properly and that all software in both is free of all errors, is there any chance, however small, that a packet will be delivered to the wrong destination?
Problem 8
Give a simple heuristic for finding two paths through a network from a given source to a given destination that can survive the loss of any communication line (assuming two such paths exist). The routers are considered reliable enough, so it is not necessary to worry about the possibility of router crashes.
Problem 10
If costs are recorded as 8-bit numbers in a 50-router network, and distance vectors are exchanged twice a second, how much bandwidth per (full-duplex) line is chewed up by the distributed routing algorithm? Assume that each router has three lines to other routers.
Problem 11
Explain the difference between routing, forwarding, and switching.
Problem 15
In the text it was stated that when a mobile host is not at home, packets sent to its home LAN are intercepted by its home agent on that LAN. For an IP network on an \(802.3\) LAN, how does the home agent accomplish this interception?
Problem 19
Consider two hosts connected via a router. Explain how congestion can occur, even when both hosts and the router use flow control, but no congestion control. Then explain how the receiver can be overwhelmed, even when using congestion control, but no flow control.
Problem 20
As a possible congestion control mechanism in a network using virtual circuits internally, a router could refrain from acknowledging a received packet until (1) it knows its last transmission along the virtual circuit was received successfully and (2) it has a free buffer. For simplicity, assume that the routers use a stop-and-wait protocol and that each virtual circuit has one buffer dedicated to it for each direction of traffic. If it takes \(T\) sec to transmit a packet (data or acknowledgement) and there are \(n\) routers on the path, what is the rate at which packets are delivered to the destination host? Assume that transmission errors are rare and that the host-router connection is infinitely fast so it is not a bottleneck.
