Question 8-2:
Five equal-size datagrams belonging to the same message leave for the destination one after another. However, they travel through different paths as shown in Table 8.1.
We assume that the delay for each switch (including waiting and processing) is 3, 10, 20, 7, and 20 ms respectively. Assuming that the propagation speed is 2 x 10^8 m, find the order the datagrams arrive at the destination and the delay for each. Ignore any other delays in transmission.
Answer:
The order of datagram arrival: 3, 5, 2, 4, 1
1: (3200) / (2 * 108 m/s) + (3 + 20 + 20) = 59.0 ms
2: (11700) / (2 * 108 m/s) + (3 + 10 + 20) = 91.5 ms
3: (12200) / (2 * 108 m/s) + (3 + 10+ 20 + 20) = 114.0 ms
4: (10200) / (2 * 108 m/s) + (3 + 7 + 20) = 81.0 ms
5: (10700) / (2 * 108 m/s) + (3 + 7 + 20 + 20) = 103.5 ms

Question 8-9:
Answer the following questions: a. Can a routing table in a datagram network have two entries with the same destination address? Explain. * There cannot be two entries with the same destination address in a datagram network because they are unique, meaning there is no address alike in the routing table. b. Can a switching table in a virtual-circuit network have two entries with the same input port number? With the same output port number? With the same incoming VCls? With the same outgoing VCls? With the same incoming values (port, VCI)? With the same outgoing values (port, VCI)? * In terms of a virtual-circuit network, Virtual Circuit Identifiers (VCI) are local. They are only considered unique when referencing the relationship between a VCI-to-Port relationship. Therefore, the pair created by this relationship is also unique, meaning there can be multiple entries with the same input or output ports. There can also be multiple entries with the same VCIs, and different ports of course because there cannot be multiple entries with the same combination of ports and VCIs. If this were the case, this would contradict the initial statement of VCI-to-Port relationships being unique, or containing unique VCIs within a VCI-to-port relationship.