CS 656 Homework #2, due 7:20pm April 21st

1. The path vector of a router X is given below
   

   (A, 2, (B K A))
   (B, 2, (B))
   (C, 3, (Z L C))
   (D, 3, (Z L C D))
   (K, 2, (B K))
   (L, 3, (Z L))
   (M, 1, (W M))
   (W, 1, (W))
   (X, -1, ())
   (Y, 1, (W Y))
   (Z, 3, (Z))
   

   X receives via port 2 a vector
   

   (A, 1, (P Q A))
   (B, -1, ())
   (C, 0, (L C))
   (D 4, (D))
   (P, 1 (P))
   (Q, 1 (P Q))
   (Z, 3 (X Z))

   Anaswer the following questions.
   • (20pt) Give the vector of X after processing the incoming vector in the alphabetic order of routers.
   • (10pt) Give the neighboring routers of X.

2. (20pt) Consider the execution of Dijkstra's shortest path algorithm on the graph shown below, using router 7 as the starting point. Give the contents of dist and nhop after the completion of 3 iterations.
   
   

3. (10pt) Describe the function of DNS.
4. (10pt) Describe the function of ARP and how it works.
5. (12pt) Explain why fragmentation is necessary in the Internet. Point out the IP header fields for fragmentation and describe their functions.
6. A host X is configured with the IP address 202.78.55.33/255.255.128.0. Answer the following questions.
   • (5pt) Calculate the length of X's network ID.
   • (5pt) The gateway router of X has the host ID 1. Give the IP address of the gateway.
   • (8pt) X is sending a packet to 302.78.98.40. Will this delivery involve the X's gateway ? Give your reasons.