CDA 4527: Computer Communication Networks
Fall 2006
Homework 2
(assigned 10/26; due: 11/7, submitted in class by hard-copy)
1. Chapter 3, problem 3. You don't need to answer "why is that UDP takes the 1s complement of the sum; that is, why not just use sum?".
2. Consider the cross-country example shown in lecture notes Chapter3-part2.ppt (page 9-11). How big would the window size have to be for the channel utilization to be greater than 90 percent?
3. Chapter 3, problem 19. Justify your answer even if the answer is true. For 19(a), you should justify it by drawing a protocol running example.
4. Chapter 3, problem 20. For 20(b), assume that the network is perfect and there is no error or retransimssion.
5. Write the simple C code to derive the EstimatedRTT based on the equation given on Page 236 in textbook (also on notes Chapter3-part3.ppt page 7). Save the results in the EstimateRTT[], the i-th entry is the data at time i.
Suppose the beginning part of the code is:
#define N 1000 // 1000 points in the data.
double SampleRTT[N]={3, 5, 4.6, 9.8, ....};
double EstimateRTT[N];
print out your code and put in your submitted homework.
6. (a).What are the three classes of router architecture? Write down their names and show the order of their routing speed.
(b).How many bytes used in TCP header? How many bytes used in UDP header?
(c). The impact of DHCP and NAT on Internet measurement: suppose you have a web server. From the web log you know that within the last week, there are connection requests from 1 million different IP addresses. are there exactly 1 million machines connecting to your web server in the last week? How does NAT affect this estimation? How does DHCP affect this estimation? Assume that your web server does not use cookie to track users.
7. Chapter 4, problem 7. For 7(a), the forwarding table you need to provide is similar to the table on Page 14 of Chapter4-part1.ppt, which is derived from the information on Page 13 of the notes.
8. Chapter 4, problem 10.
9. Chapter 4, problem 21. (show your programming code in your submitted homework).
10. Distance vector routing: Suppose a network has 5 nodes denoted as A, B, C, D, and E. The following is the distance table in router E. Answer the following questions:
a). Show the routing table in this router E.
b). Router E directly connects to which routers?
c). If a packet goes out router E directly to router A, and the final destination is router C. What is the cost known by router E?
11. Distance vector routing (no need to generate programming code, just use your hand to manually calculate as shown in the class lecture notes).
Consider the network shown in the figure below with the indicated static link costs. Considering the distance vector routing algorithm, and its current state (right after initialization phase, "-" indicates infinity). Assume that all nodes exchange messages with their neighbors within one time step.
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