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Networking Review
1. What is the difference between a circuit-switched network and a packet-switched
network?
2. What is the difference between broadcast and multicast?
3. Write down the seven layers of the protocol stack in ISO OSI Architecture in proper
order.
4. What is the job of the network layer? Give an example of a network layer protocol.
5. Define the following terms: open network, closed network, proprietary network, MAN,
LAN, WAN, bridge, repeater, switch, router, gateway, backbone.
6. Explain the hidden terminal problem for wireless networks. What is a solution?
7. At what layer in the TCP/IP protocol hierarchy would a firewall be placed to filter
messages based on
a. Message content
b. Source address
c. Type of application
8. What is the internet2? Give an example that motivates its creation and use.
9. Translate the IPv4 address 192.207.177.133 into 32-bit binary.
10. List 3 of the most commonly used internet application protocols, and tell or illustrate how
they work.
11. Why is telnet considered an insecure protocol?
12. Why does internet radio require a different protocol from other applications? What is the
most successful protocol?
13. Explain the difference between client/server and peer-to-peer interprocess
communication.
14. Explain how HTTP works with an example.
15. Encode the following binary patterns in dotted decimal notation.
a. 0000 0001 0000 0010 0000 0011
b. 1000 0000 0000 0000
c. 0001 1000 0000 1100
16. What is the Manchester encoding scheme? How does it work?
17. Suppose a 128-Kbps point-to-point link is set up between Earth and a rover on Mars. The
distance from Earth to Mars (when they are closest together) is approximately 55 Gm,
and data travels over the link at the speed of light 3 × 108 m/s.
a. Calculate the minimum RTT for the link.
b. Calculate the delay × bandwidth product for the link.
c. A camera on the rover takes pictures of its surroundings and sends these to Earth.
How quickly after a picture is taken can it reach Mission Control on Earth?
Assume that each image is 5 MB in size.
18. Calculate the total time required to transmit a 1.5 MB file in the following cases. Assume
an RTT of 80ms, a 1 KB packet size and an initial 2 x RTT handshake before data is
sent:
a. Bandwidth is 10 Mbps, data packets can be sent continuously.
b. Bandwidth is 10Mbps, but after each packet we must wait 1 RTT before sending
the next one.
c. Link allows infinitely fast transmit, but limits bandwidth to only 20 packets per
RTT.
d. Link is infinitely fast as in (c), but we can send 1 packet in the first RTT, 2 in the
second, 4 in the third, etc., with exponential increase each RTT.
19. Suppose TCP operates over a 40-Gbps STS-768 link.
a. Assuming TCP can utilize the full bandwidth continuously, how long would it
take the sequence numbers to wrap around completely?
b. Suppose an added 32-bit timestamp field increments 1000 times during the
wraparound time you found above. How long would it take for the timestamp to
wrap around?
20. Suppose we wanted to transmit the message 1011001001001011 and protect it from
errors using the CRC8 polynomial x8+x2+x+1.
a. Use polynomial long division to determine the message that should be
transmitted.
b. Suppose the leftmost bit of the message is inverted due to noise on the
transmission link. What is the result of the CRC calculation? How does the
receiver know that an error has occurred?
21. Suppose we have the forwarding tables shown below for nodes A and F. Assume that all
links have cost 1. Give a diagram of the smallest network consistent with these tables.
Node
B
C
D
A
Cost
1
1
2
NextHop
B
C
B
E
F
3
2
C
C
Node
A
B
C
D
E
F
Cost
2
3
1
2
1
NextHop
C
C
C
C
E
11. Suppose a router has 3 input flows and one output. It receives the following packets as listed
below all about the same time, in the order listed. Assume the port is busy, but all queues are
otherwise empty. Give the order in which the packets are transmitted, assuming:
a. fair queuing
b. Weighted fair queuing, where flow 2 has twice as much share as flow 1, and flow
3 has 1.5 as much share as flow 1. Any ties are resolved in the order flow 1, flow
2, flow 3.
Packet
1
2
3
4
5
6
7
8
Size
200
200
160
120
160
210
150
90
Flow
1
1
2
2
2
3
3
3