UNIVERSITY    of     HOUSTON
Department of Computer Science

COSC 4377 - Introduction to Computer Networks
Section 07664
Fall 2001

Assignment 3

Due in the class, on Wednesday, October 31, 2001

Latest Hints:

There are 5 questions, 4 written ones and one experiment. Each question weights 20 points.

  1. Based on Peterson & Davie, Chapter 4, Exercise 12: 
                   3
        A ------------ C
        |              | \
        |              |  \6
        |8        B    |1  \
        |          \   |    F
        |           \2 |
        |            \ |
        D ------------ E
               2

          Figure 4.39
    For the network given in Figure 4.39, give distance-vector tables for node A like Figure 4.6 in Kurose & Ross when
    (a) Each node knows only the distances to its immediate neighbors.
    (b) Each node has reported the information it had in the preceding step to its immediate neighbors.
    (c) Step (b) happens a second time.
  2. From Peterson & Davie, Chapter 4, Exercise 13:
    For the network given in Figure 4.39, show how the link-state algorithm builds the routing table for node D.
  3. From Peterson & Davie, Chapter 4, Exercise 38:

    Table 4.14 (below) is a routing table using CIDR. Address bytes are in hexadecimal. The notation "/12" in C4.50.0.0/12 denotes a netmask with 12 leading 1 bits, that is, FF.F0.0.0. Note that the last three entries cover every address and thus serve in lieu of a default route. State to what next hop of the following will be delivered.

    		-----------------+----------
		Net/MaskLength   |  nexthop
		-----------------+----------
		C4.50.0.0/12     |     A
		C4.5E.10.0/20    |     B
		C4.60.0.0/12     |     C
		C4.68.0.0/14     |     D
		80.0.0.0/1       |     E
		40.0.0.0/2       |     F
		00.0.0.0/2       |     G
		-----------------+----------
		  Table 4.14
    1. C4.5E.13.87
    2. C4.5E.22.09
    3. C3.41.80.02
    4. 5E.43.91.12
    5. C4.6D.31.2E
    6. C4.6B.31.2E
  4. From Peterson & Davie, Chapter 4, Exercise 39:

    5. Suppose P, Q, and R are network service providers, with respective CIDR address allocations (using the notation of Exercise 38) C1.0.0.0/8, C2.0.0.0/8, and C3.0.0.0/8. Each provider's customers initially receive address allocations that are a subset of the provider's. P has the following customers:

    PA, with allocation C1.A3.0.0/16 and
    PB, with allocation C1.B0.0.0/12.

    Q has the following customers:

    QA, with allocation C2.0A.10.0/20, and
    QB, with allocation C2.0B.0.0/16.

    Assume there are no other providers or customers.

    1. Giving routing tables for P, Q, and R assuming each provider connects to both of the others.
    2. Now assume P is connected to Q and Q is connected to R, but P and R are not directly connected. Give tables for P and R.
    3. Suppose customer PA acquires a direct link to Q, and QA acquires a direct link to P, in addition to existing links. Give tables for P and Q, ignoring R.
    Just for reference: You might want to practice Kurose & Ross, Chapter 4, Problems 3, 4, and 6 for the exam also. You don't have to turn in these questions.

5. Traceroute:

This problem requires you to run a traceroute from your computer to some hosts and count number of hops required to reach the destination and also record the latency to reach the destination. You can run "traceroute using any of the following ways.

Here is what you need to do. First of all, pick three (3) of the following hosts and label them as H1, H2, and H3.

Secondly, pick two hosts as routers from www.traceroute.org and label them as R1 and R2. Also, record their host names.

Thirdly, run traceroute from source (R1 and R2) to destination (H1, H2, and H3). Record number of hops and latency between source and destination. You should have 6 values for number of hops and 6 values for latency.

Fourthly, pick a home site. You can use your own PC (running Linux/BSD/Windows 95/98/NT/2000), bayou, or any host from www.traceroute.org (other than R1 and R2). We will label it as HS. Record host name or IP address of HS.

Fifthly, run traceroute from source (HS) to destination (R1, R2, H1, H2, and H3). Record number of hops and smallest latency between source and destination. You should have 5 values for number of hops and 5 values for latency.

Now draw a graph similar to this one. Replace H1, H2, H3, R1, R2, and HS with their host names or IP addresses. Label each link with number of hops and latency.

Finally, calculate the total number of hops and latency between home site (HS) and hosts (H1, H2, and H3). Also, calculate the total number of hops and latency from home site (HS) via routers (R1 or R2) to hosts (H1, H2, and H3). You will have a table like this.

    Paths
    # of hops
    Latency (msec)
    HS-H1   +   HS-H2   +   HS-H3    
    HS-R1-H1   +   HS-R1-H2   +   HS-R1-H3    
    HS-R2-H1   +   HS-R2-H2   +   HS-R2-H3    

Questions you might have:

 

Last modified: October 30, 2001
tihuang at cs . uh . edu