Final Exam    
CS 638-2 Computer Networks   
December 18, 1990

True or False (2 each)

1. An Ethernet must be shut down to add a station. 
2. Ethernet and 802.3 stations cannot be mixed on the same cable.
3. The 802.3 active monitor station provides for retransmission in case of collisions.
4. The 802.3 MAC protocol insures fairness between network stations.
5. 802.3 networks do not require a type field because of the use of 802.2
6. A checksum error leads to automatic retransmission in 802.3.
7. Asynchronous traffic may always be sent by an FDDI station.
8. Multiple frames can simultaneously be on an FDDI network.
9. Multiple frames can simultaneously be on an 802.5 network.
10. The presence of multiple tokens on an 802.5 network means that an error has occurred.  
11. An 802.5 network must be shut down to add a station.
12. Automatic  retransmission occurs in 802.5 when a frame is not copied by the destination.
13. The 802.5 MAC protocol insures fairness between stations at a given priority.
14. In an 802.5 network the destination station removes frames from the network.
15. 802.2 can provide either a connection oriented or a connectionless service.
16. One version of the   802.2 protocol supports retransmission of frames. 

17. (3) Which description does not match slow start? (cwnd = congestion window)

A. cwnd <-- d * cwnd  (where d < 1) on detection of loss
B. cwnd <-- 1 initially
C. receiver's window (w) <--  min (w, cwnd)
D. cwnd <-- cwnd + 1  for each acknowledgment received
E. none of the above

18. (3) A jam

A. is defined by 2 stations transmitting data on the ether at once
B. is a special signal sent by the active monitor when a collision is detected
C. is used to let all stations know that a collision has occurred.
D. occurs at a node when there is congestion in the subnet and inadequate buffer space
E. a & b & c
F. b & c
G. none of the above	

QUESTIONS 19-27 SHOULD BE ANSWERED VERY BRIEFLY. POINTS WILL BE SUBTRACTED FOR LACK OF BREVITY

19. (3)  Why is a minimum frame size required by 802.3? 
20. (3) How do 802.5 and FDDI differ with respect to token regeneration
21. (3) How does an 802.5 station become a "stacking station?" 
22. (3) What is meant by the statement that an 802.5 station is an  active participant on the ring?
23. (3) What is meant by the statement that an 802.3 station is a passive participant on the network?
24. (3) Why do 802.3 networks not scale up well to higher bandwidths?
25. (3) Why do 802.5 networks not scale up well to higher bandwidths?
26. (12) Give three ways in which TP4 and TCP differ.
27. (12) Give three ways in which TP4 and TCP are similar.

28. (16) Assume a connectionless network service.
Assume that the transport protocol is to provide a 
connection-oriented service between users on hosts connected
to a potentially unreliable
internet. 

a. Why is such
a transport protocol more complicated than a link
protocol which provides a connection-oriented link service?

b. Describe two mechanisms employed by such transport protocols
for dealing with the problem of old duplicates.