Homework 4 - Chapter 5

1. Do virtual circuit subnets need to use a routing algorithm that finds a path from any source to any destination? If so, at what point during a virtual circuit connection would this algorithm be needed?
2. Under what circumstances might a packet be delivered to the wrong destination or get lost in transit?
3. A subnet has the same topology as given in Figure 5.13 on page 363. The routers receive the following new link state packets: (A, SEQ, Age, B 7, E 3), (B, SEQ, Age, A 7, C 4, F 4), (C, SEQ, Age, B 4, D 5, E 2), (D, SEQ, Age, C 5, F 6), (E, SEQ, Age, A 3, C 2, F 10), (F, SEQ, Age, B 4, D 6, E 10). Compute the new shortest paths from A to all other routers.
4. Describe how choke packets and load shedding differ for congestion control in datagram subnets.
5. Describe how tunneling can be used in a datagram subnet.
6. An ISP offers static IP services over DSL. In their advertisement, they say they will allocate an 8 address subnet for each subscriber.
   1. What is the netmask for this subnet?
   2. Will all 8 addresses be available for use by the user? Explain your answer.
7. A router has received 206.45.68.0/22, 206.45.72.0/22 and 206.45.76.0/22. All use the same outgoing line. Can the router aggregate them? If so, give the aggregated address. If not, explain why not.
8. A router has an aggregated block with the address 19.28.0.0/17. A set of 1024 addresses within that block, 19.28.60.0 to 19.28.63.255, is assigned to a different outgoing line than the rest of the block. Will the router have to deaggregate 19.28.0.0/17? Explain your answer.
9. A router has the following entries in its routing table:

        Address/mask        Next hop
        138.168.0.0/16      eth0
        192.168.1.0/24      eth1
        71.138.209.16/29    eth2
        default             eth3
   

   Which interface will be used for packets with the following IP addresses?
   1. 136.168.201.110
   2. 71.138.209.157
10. In order to deliver IP packets to the destination host on an Ethernet LAN, the gateway router translates the IP address to a MAC address using ARP. Is ARP part of the data link layer or the network layer?