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) (5 points) State why “Bridges” cannot be used to route packets on Internet.
(b) (5 points) Describe why TCP connection initialization(when TCP establishes a connection) needs 3-way handshaking.
(c) (5 points) Explain how the ARP(Address Resolution Protocol) operates. Also state what it achieves.
(d) (10 points) Internet address space(IPv4) is running out. What are the three solutions available? List them and explain each.
(e) (15 points) Explain how the “socket to socket connections” are established. Include the following terms in your answer: Socket, Well-known port number, ephemeral port number, local IP address, remote IP address, client, server. Do not simply explain each term.
(f) (5 points) What is a subnet mask? Describe how it is used.
(g) (10 points) Routing algorithms can be classified into a) Interior routing algorithms b) Exterior routing algorithms. How are they classified? Also list the popular routing algorithms in each category.
(h) (5 points) Describe the differences between “Link State Routing(OSPF)” and “Distance Vector(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. (14 points)
Let’s assume that you set up a network analyzer program such as a Sniffer and set up the filters to capture the packets between your IP address and Any IP 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 with the home address of “www. Yahoo.com”.
After the connection is completed you “stop and display” in Sniffer and “decode(to look at the packets)”.
Assuming an ordinary, no error situations, list the names of packets in a correct order and describe what each packet achieves. Describe at least 7 packets. Hint: In an ordinary situation the following operations will occur: arp, DNS, TCP connection sequence.
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. 129.2.0.0
c. 193.7.2.0
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 20 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
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
e. None of above
7. RARP(Reverse Address Resolution Protocol) is used in?
a. When a station does not know its own IP address
b. When a station wants to find the hardware(MAC) address of a neighboring station
c. When a router is trying to find a neighboring router
d. When a station does not know its MAC address
e. None of above
8. 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
9. A “Gratuitous ARP” is used in?
a. To politely ask a neighboring stations MAC address
b. To find out which station has a fixed IP address
c. To avoid IP address conflict
d. To find its own IP address in case of a diskless workstation
e. None of above
10. When making the determination to subnet a given network, which of the following must you consider? Choose all that apply.
a. the types of computers used on the network.
b. the IP address class
c. the number of physical segments(subnets) on your network
d. the potential for network growth
e. the types of LANs, e.g. Ethernet or Token ring, FDDI, ….
f. All of above
11. 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 cannot be called as “multihomed device”
d. Routers have more than on Network Adapters(Network Interface Cards)
e. Routers usually have more than one IP address
f. Routers do not use ARP
12. 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
13. Ben receives a complaint from an employee in subnet E that when they retrieve files from a server in subnet F, it takes twice as long as when they retrieve files from a server in subnet D. What can Ben use to identify the path that the data packets take as they pass through the routers?
a. ping
b. netstat
c. traceroute
d. nslookup