Advanced TCP/IP networks midterm study guide    Midterm: Wed Oct 17, 2001

See the notes file for the topics covered. Essentially we've looked at:
        
        IP routing issues (eg provider-based routing)
        
        TCP:
                Basic algorithms: tahoe, reno, ratehalving, newreno, SACK
                Fairness issues
                Queues: droptail v random-drop
                
                
Some specific sections of Peterson & Davie:

Chapter 4:
    4.2.2 (and some of 4.2.3): basics of IP routing
    4.3.2: CIDR
    
Chapter 6:
    6.1:   Good overview of some issues
    6.2.1: FIFO == droptail
    6.3:   TCP mechanisms, Tahoe & Reno
    6.4:   DecBit, RED, packetpairs
    6.5.1: playback buffers, constant-bit-rate (CBR) traffic, jitter
    
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Some sample questions:

Chapter 6 exercises that are worth at least reading:
5, 6, 11, 15, 24, 25, 27, 28, 39a

1. Explain what is meant by a "phase effect" in TCP, and explain why both
adding a small random delay to packet transmission time ("overhead") and using
random-drop queues both can reduce phase effects. Which of these techniques
reduces phase effects more, and why?


2. Give a timeline showing two packet drops in one TCP window, for both Reno
and NewReno implementations. Identify periods of congestion window "inflation"
(the upper end moves up but the lower end does not) and "deflation" (the lower end
moves up but the upper end does not).

3. Explain why a longer RTT alone, with the same packet-loss risk, 
can mean that a TCP connection gets less bandwidth.

4. Discuss how to arrange for geographical routing in IP.
Discuss how routers in adjacent towns on opposite sides of a state line 
could send traffic to each other directly, while each sends other traffic 
to their state's respective state hub.

5. How might a TCP figure out the "path bandwidth", that is, the smallest bandwidth
along the path to the destination?

What use could a TCP make of this information?


6. (a) How does TCP use IP addresses?
(b) Explain the "Network Address Translation" (NAT) approach to IP address assignment.
Explain the advantages to an organization, in terms of supporting change of provider.
Explain the changes that would have to be made to TCP.