IFSM 450/650 -- Section 101 -- Spring 2001 -- Test 3



IST 220 – Sample Test 3

Name: ________________________

1. For each question (3 points), there are multiple choices, but only one is correct

1.1) The IP address 191.192.193.194 belongs to class _____

(a) A (b) B (c) C

1.2) The job of a router is to store and forward packets. In order to store packets, a router uses a ____

(a) packet table (b) routing table (c) forwarding table (d) queue (e) NIC with more memory

1.3) A router is different from a LAN switch because _____

a) The router uses a forwarding table, but the LAN switch does not

b) The router uses hierarchical addresses, but the LAN switch does not

c) The router uses physical addresses, but the LAN switch does not

d) The router forwards packets, but the LAN switch does not

1.4) In OSI seven-layer model, the routing layer is called ________

(a) data link layer

(b) physical layer

(c) transport layer

(d) network layer

(e) application layer

2. Please say TRUE or FALSE to each of the following statements ( 3 points each)

2.1) _______ N/A

2.2) _______ A computer cannot be assigned with the IP address 222.200.0.0 since the IP address is a network address.

2.3) _______ Since a phone switch is a special switch, it also does routing using a routing table.

2.4)_______ In OSI seven-layer-model, NIC layer is called network interface layer.

2.5)_______ An internetwork can be smaller than a WAN in terms of the number of computers.

2.6)______ Since IP addresses are hierarchical addresses, IP addresses can make a routing table much smaller than using physical addresses.

2.7) _______ “Nest headers” implies that the IP payload of a packet is always a part of the NIC layer payload of the packet.

2.8) _______ NA

2.9) _______ NA

3. Consider the following internetwork. Assume the Physical Address of NIC-A is E78D45C4FD66, of NIC-E is 7E8D4C544DBB. Assume the IP address of NIC-A is 121.22.230.2, of NIC-C is 192.5.2.2, of NIC-13 is 188.11.135.112, of NIC-E is 200.80.60.40. Assume the distance between R1 and R2 is 90 miles, between R1 and R3 is 150 meters, between R2 and R3 is 80 miles, between R2 and R4 is 300 miles, between R3 and R4 is 400 miles.

Assume computer E now wants to send the message “ER” to computer A. Assume the ASCII code for 'E' is 45, for 'R' is 52. Assume there are no errors during the transmission.

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3.1) How many physical networks are there? Note that leased lines do not cause more networks. (3 points)

3.2) What is device W? Note that in many cases W is inside CO1. (3 points)

3.3) Please list all class C networks in this internetwork. (3 points)

3.4) What is the prefix of the IP address of NIC-42? (3 points)

3.5) What is the network address of the network where computer D is attached? (3 points)

3.6) To send out the message, computer E will first build the frame. Please draw the format of the frame when it leaves NIC-E. (3 points)

3.7) After a while, P-B will get the frame. What will P-B do? (3 points)

3.8) After a while, P-4 will get the frame. Before P-4 does anything on the packet, what is the routing layer payload of this frame? (3 points)

3.9) When this packet leaves P-4, what is the NIC layer header of this frame? ( 3 points)

3.10) What is the routing table inside R3? (4 points)

3.11) After a while, P-1 will get the packet. When P-1 gets the packet, what is the format of the frame? (3 points)

3.12) What will P-1 do next? (3 points)

3.13) After a while, P-A will get the message. During the whole message passing process, how many processors have seen a routing layer header? Please consider all the computers and routers. (3 points)

3.14) During the whole process, how many times is the router layer header changed? (3 points)

3.15) During the whole process, how many times is the message put into a queue? We assume that neither computers nor bridges have queues. (3 points)

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