Homework Answers

Despite being adjacent in a protocol stack, Data Link Layer protocols and Network Layer protocols each employ a number of similar fields in their headers (i.e. a field named 'X' appears in the headers of both layers, and the role of 'X' is similar for both layers).

For each of these three fields:

a. describe its typical role, and

b. provide an example to demonstrate why their 'duplication' does not introduce unnecessary redundancy.

Consider the delivery of messages in an internetworked environment in which the source and destination nodes are many hops apart. Communication between distant nodes passes through a series of routers, and there may be multiple pathways between any source and destination. Large messages must be fragmented and reassembled using one of two possible strategies:

a. the first strategy involves fragmenting each message at the source node, and then reassembling them at the destination node.

b. the second strategy involves fragmenting each message at the source node, reassembling and re-fragmenting them at intermediate routers, and final reassembly at the destination node.

c. For each strategy, describe the fields of a Network Layer header necessary to support the strategy.

d. With reference to two distinct examples, describe circumstances where each of the strategies would be preferred over the other.

View captured traffic in Wireshark