Download ReviewSheet Midterm2 Last modified January 7

COE 371
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Midterm 2
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Question 1: [15 points]
State whether the following statements are True or False. No explanation needed.
1. ICMP messages are encapsulated inside IP datagrams.
2. In addition to error reporting, ICMP corrects the related errors as well.
3. The ICMP source-quench error message is sent to the source host when there is a problem in
the header field of a datagram.
4. The parameter-problem ICMP message is sent to the source host when a datagram is
undeliverable to the destination.
5. The redirection ICMP message is sent to the source host when a datagram is undeliverable to
the destination.
6. In a Frequency Hopping Spread Spectrum (FHSS) technique, each bit to be transmitted by the
sender is replaced by its chip code.
7. RIP (Routing Information Protocol) is used inside an autonomous system.
8. RIP is based on distance vector routing.
9. The hopping sequence in FHSS (Frequency Hopping Spread Spectrum) is generated by a
pseudorandom number generator.
10. In an ad hoc network, the stations can form a network without the need of access points.
11. In wireless LAN, a collision will always be heard by all stations in the network.
12. An autonomous system is a group of networks and routers under the authority of more than
one administration bodies.
13. In OSPF, each router builds the overall topology of the network.
14. OSPF routing tables are calculated by using Dijkstra’s algorithm.
15. Bluetooth uses FHSS (Frequency Hopping Spread Spectrum) method in the physical layer.
Question 2 (10 points): Circle the correct choice. No explanation needed.
1. In CSMA/CA, each station, before sensing the physical medium to see if it idle, first checks
its ____to see if it has expired. (a) DIFS (b) SIFS (c) NAV (d) RTS (e) none of the above.
2. A wireless LAN uses ____ frames for acknowledgement. (a) management (b) control (c)
data (d) none of the above.
3. In an autonomous system with n areas, how many areas are connected to the backbone? (a) 1
(b) n-1 (c) n (d) n+1.
4. If 8-bit chip code is used in DSSS (Direct Sequence Spread Spectrum) and the user original
data rate is 1 K bits/sec, then the output data rate of the DSSS transmitter will be ___.
(a) 1 Kbits /sec (b) 8 K bits/sec (c) 1 / 8 Kbits/sec (d) none of the above.
5. In DSSS-CDMA, the dot product between two chip codes for two different users will produce
___. (a) 0 (b) +1 (c) –1 (d) none of the above.
6. In CSMA/CA, after receiving RTS frame and waiting for a time period called, ____, the
destination station sends _______frame to the source.
(a) DIFS; RTS (b) DIFS; CTS
(c) SIFS; CTS (d) SIFS; RTS (e) none of the above.
7. Bluetooth devices use ___ technique for exchanging data . (a) Time Division Multiplexing
(b) Time Division Duplexing (c) Frequency Division Multiplexing (d) any of the above.
8. A Bluettoth piconet may have up to ___ Bluetooth devices in total. (a) 1 (b) 2 (c) 7 (d) 8 (e)
none of the above.
9. Link State Packets (LSPs) in link state routing are generated _____ . (a) when there is a
change in the topology of the domain (b) on a periodic basis (c) a and b (d) none of the above.
10. The ____ protocol does not sense the carrier (or channel) before transmitting a frame. (a)
CSMA/ CD (b) CSMA / CA (c) ALOHA (d) none of the above.
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Question 3 (6 points):
A router receives an IP packet with source IP address 130.45.3.33 and destination IP address
201.23.4.33. The router cannot find the destination IP address in its routing table.
(a) Which type of ICMP message will be sent by the router?
(b) Which host will receive the ICMP message (i.e., what will be IP address of the destination
host which will eventually receive the ICMP message)?
Question 4 (7 points):
Draw the topology of the network when the following table is the routing table for router R1.
Mask
/27
/18
Default
Network Address
202.14.17.224
145.23.192.0
Default
Next-hop Address
--130.56.12.4
Interface
m1
m0
m2
Question 5 [7 points]:
Suppose two Bluetooth devices (a master and a slave) are communicating using the following
frequency hopping sequence (all frequencies in GHz): 2.402, 2.411, 2.404, 2.409, 2.405, 2.407,
2.403, 2.401, 2.422, 2.428,… Assume the master and slave take turns. Draw a timing diagram for
first five slots to show which frequency channel will be used in a given slot. The hope rate is
1600 hops/ sec.
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Question 6 (15 points):
The router R1 in a network has the following routing table.
Mask
/32
/26
/25
/24
/8
/0
Network Address
180.70.65.202
180.70.65.192
180.70.65.128
201.4.22.0
202.0.0.0
0.0.0.0
Next-hop Address
---
180.70.65.200
Interface
m1
m0
m3
m5
m4
m2
Which interface at R1 will be used to transmit the packet for the IP packets destined for the hosts
at the following IP addresses?
(a) 182.77.55.66
(b) 180.70.65.140
(c) 180.70.65.203
(d) 180.70.65.202
(e) 16.24.25.26
Question 7: [10 points]
In a 802.11 wireless LAN using CSMA/CA, there are three stations X, Y, and Z. Station Y is in
the coverage range of station X, while Z is not in the coverage range of X. The station Z is in the
coverage range of Y. The station X wants to send a data frame of size 200 bytes to station Y.
Show, with the help of a timing diagram, the sequence of different control and data frames
transmitted or received at X , Y, and Z.
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Question 8 (15 points):
The router A in autonomous system has the following RIP routing table:
To
A
B
C
D
E
Cost
0
10
3
9
7
Next Router
-E
C
C
E
Router A receives the following RIP message from router C. The router C is at cost 3 from A.
To
A
B
C
D
E
Cost
3
4
0
5
8
What would be the contents of the routing table at the router A after the reception of the RIP
message from C. Indicate your results in three column (To, Cost, Next router) in a tabular form?
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Question 9 (15 points):
Apply Dijkstra algorithm to the autonomous system described below and find the link state
routing table for router B. The cost (written on a link) from any element X to Y is the same as for
connecting Y to X.
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