Homework 6 - Chapter 5

Due: Friday March 2 Monday March 5, 2012 at 5:30pm

Questions are worth 2 pts unless otherwise indicated.

  1. (4 pts) 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.
  2. Describe how choke packets and load shedding differ for congestion control in datagram subnets.
  3. Describe how tunneling can be used in a datagram subnet.
  4. (4 pts) 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.
  5. 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.
  6. 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.
  7. (4 pts) A router has the following entries in its routing table: 
         Address/mask        Interface
     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
    3. 192.168.1.50
    4. 71.138.209.18