Instructor: Seung Bae Im
Closed Book, Closed Notes. Name: ___________________________________
If you have any question, write your assumptions clearly and answer the question.
DO NOT WRITE ON THE BACK OF A PAGE! They will not be graded!
1. (60 Points)
(a) (4 points) An IP layer of a host computer and an IP layer of a router achieve similar functions. What is the main difference?
(b) (6 points) Describe how the TCP’s windowing operates including the word “credit”.
(c) (5 points) Explain how the RARP(Reverse Address Resolution Protocol) operates.
(d) (4 points) Describe how TCP’s timeout value is adjusted dynamically.
(e) (5 points) Explain Data Encapsulation/Decapsulation using TCP/IP protocol layers as the example.
(f) (15 points) Explain how the “socket to socket connections” are established for a concurrent server programs(a server which can serve multiple incoming connections at the same time), including the following terms in your answer: (Socket, Well-known port number, ephemeral port number, local IP address, remote IP address, client program, server program, create a child process). Do not simply explain each term.
(g) (6 points) Describe how “traceroute(tracert on Windows computers)” traces a route for packets. Include the terms; ping, TTL.
(h) (10 points) Routing algorithms can be classified into a) Interior routing algorithms b) Exterior routing algorithms. How are they classified, in other words, what is the difference between them? Also list the popular routing algorithms in each category.
(i) (5 points) Describe the differences between “Link State Routing(e.g. OSPF)” and “Distance Vector(e.g. RIP) routing” in terms of a) “metrics” that are used and b) “size” of networks c) Routing table advertisement ranges(to neighbors, to every routers, …).
2. (20 points)
Let’s assume that you set up a network analyzer program such as a Sniffer on a workstation and set up the filter to capture the packets between your network card’s MAC address and Any MAC addresses. Also assume that you cleared your ARP cache(via arp –d option). Now you “start capture” and then run Internet Explorer which was set up previously with the home address of “www. Yahoo.com” but you are running the browser for the first time today.
After the connection is completed you “stop and display” in Sniffer and “decode(to look at the packets)”.
Assuming an ordinary, no error situations, identify each packet(for example, ARP request packet, DNS request, TCP connection request, …) in a correct order and describe what each packet achieves. Describe at least 10 packets. Hint: In an ordinary situation the following sequence of operations might occur: arp, DNS, TCP connection sequence, http requests and replies(multiple packets will be exchanged to get the content of the current page).
3. (2 points each) Circle the answers on the problems.
1. You work for a government agency that has been assigned a class B network address. Which of the following addresses could be yours?
a. 127.1.0.0
b. 130.92.0.0
c. 193.7.0.0
d. 129.256.0.0
2. Your workstation’s TCP/IP networking is not working properly. Choose the best sequence for checking the connectivity. Given
1) Ping xxx.xxx.xxx.xxx(your workstation’s IP address)
2) Ping 127.0.0.1
3) Ping zzz.zzz.zzz.zzz(your local router’s IP address)
4) Ping www.yahoo.com(or any other URL)
a. 1 à 2 à 3 à 4
b. 3 à 2 à 1 à 4
c. 2 à 1 à 3 à 4
d. 2 à 3 à 1 à 4
e. None of above
3. Your company has a network containing 60 subnets and a Class B address of 132.241.0.0. What subnet mask would you use to allow the largest number of hostids per subnet?
a. 255.255.192.0
b. 255.255.224.0
c. 255.255.240.0
d. 255.255.248.0
e. 255.255.252.0
f. 255.255.255.0
4. RIP(Routing Information Protocol) has the following problems(Choose all that apply).
a. Hop count is not an accurate measure
b. Broadcast storm since RIP routing information is broadcasted to entire network
c. The algorithm has too much overhead
d. Slow Convergence
e. Instability problem(Count to Infinity)
f. Limited size of the networks
g. All of above
5. Which one of the following most accurately describes TCP/IP sockets?
a. A socket designates the connection between two machines
b. A socket is an entry point from IP layer to TCP layer
c. A socket is a Service Access Point that an application uses to invoke the services of UDP or TCP.
d. A socket is a two way communication link between two machines.
6. “Routed protocol” means?
a. Protocols such as RIP, OSPF
b. Protocols that are routed over a network
c. Protocols that routers run
d. Any protocol related to routing
7. Which statement best describes the Internet Control Message Protocol (ICMP)?
a. informs routers that hosts of a specific group are available on a network
b. attempts to report errors and provide feedback on specific conditions on behalf of IP
c. attempts to make IP a reliable protocol
d. responsible for controlling local network and routing packets between hosts
e. All of above
8. A “Gratuitous ARP” is used?
a. To politely ask a neighboring station’s MAC address
b. To find out which station has a dynamically assigned IP address
c. To avoid IP address conflict with other stations on a subnet
d. To find its own IP address in case of a diskless workstation
e. None of above
9. Which are true for routers? Choose all that apply.
a. Routers run only lower 3 layers of OSI 7 layers
b. Routers run all 7 layers even though the lower 3 layers are their main function
c. Routers can also be called as “multihomed device”
d. Routers have more than one Network Adapters(Network Interface Cards)
e. Routers usually have more than one IP address
f. Routers do not use ARP
10. Christine’s company has been assigned the network address 143.5.0.0. Her network will grow to 56 subnets over the next year. Christine’s supervisor tells her to use the subnet mask of 255.255.252.0. How many hostids will be available for each subnet?
a. 1024
b. 1022
c. 62
d. 64
e. None of the above