Submission Instructions Please submit your homework solutions by EMAIL to me at Russ.Clark@gatech.edu. Make sure to include [CS3251] in subject line.

Late Policy: You have a total of 3-days for a late budget which you may use for any assignment in a minimum of day increments.

1. Question 1

   Consider an IPv4 network using 32-bit host addresses. Suppose a router has four links, numbered 0 through 3, and packets are to be forwarded to the link interfaces as follows:

   Destination Address Range                        Interface
   
   10100100 00000000 00000000 00000000
      through                                           0
   10100100 11111111 11111111 11111111
   
   10100100 00000000 00000000 00000000
      through                                           1
   10100100 00000000 00000000 11111111
   
   10100101 00000001 00000000 00000000
      through                                           2
   10100101 00000001 11111111 11111111
   
      all others                                        3
   

   1. Provide a forwarding table that has four entries, uses longest-prefix matches and forwards packets to the correct link interfaces.
   2. Describe how your forwarding table determines the appropriate link interface for datagrams with the following destination addresses.

      10100100 00100100 01010100 10010100
      10100101 00100100 01010100 10010100
      10100100 00000000 00000000 10110101
      10100101 00000001 11011100 11010100
      10101100 10100100 01010100 10010100
      

2. Question 2

   Re-write the addresses from Question 1 as specified below.

   1. Re-write the forwarding table from the previous question in a.b.c.d/x notation.
   2. Re-write the host addresses in a.b.c.d (dotted quad) notation.

3. Question 3

   Consider the function of a network switch for connecting multiple LAN segments. Recall that this operation is also referred to as transparent bridging.

   This technology is often used to enhance security of a network, specifically privacy.

   1. Explain how a switch might improve network security.
   2. Explain the potential drawbacks to relying on this approach.

4. Question 4

   Assume you make a successful sendto socket call with a 2000 byte buffer via UDP.

   1. Assuming you are connected to the network via Ethernet, determine the length in bytes of the Ethernet frames (including all protocol headers and trailers) that are sent as a result of your sendto call.
   2. Show the fragmentation related fields of the IP header for all packets.
   3. Compute the Protocol Efficiency defined as the number of percentage of user data bytes vs. the total number of bytes transmitted.