Comp 346 Midterm Study Guide
Midterm is Wednesday, March 12.

Here is a summary of the sections we have covered:

Chapter 1: 
You should skim all of this; there are some important concepts summarized in 
section 1.3, and the layer model is described in section 1.4.


Chapter 2:
  2.1:  protocols generally, and what they cover
  2.3:  TCP/IP protocols - just general stuff, *not* details like state diagrams
	We did discuss the TCP three-way handshake at some length.
  
  
Chapter 3:
  3.1:  Frequency, bandwidth, spectrum; intro to Fourier analysis
        You are not expected to follow all the math, but you should
        have some idea that any signal can be expressed as a combination
        of sine waves.
  3.2:  Bandwidth requirements, mostly, for voice and video; analog v digital
  3.3:  Transmission impairments: attenuation, distortion, noise
        Nyquist: C = 2B log_2 M         B=bandwidth, M=#levels
        Shannon: C =  B log_2 (1+SNR)
Appendix 3B: decibels


Chapter 4:
  4.1:  Twisted pair
        Coax
        Optical Fiber
  4.2:  microwaves, etc 


Chapter 5:
  5.1:  Digital data, digital signals: 
                NRZ, NRZI, bipolar, Differential Manchester, B8ZS
  5.2:  Digital data, analog signals:
                ASK, FSK, PSK
  5.3:  Analog data, digital signals: digitization
                nonlinear encoding
                delta modulation
  5.4:  Analog data, analog signals
                AM, FM, PM
                
                
Chapter 8:
  8.2:  Synchronous Time-Division Multiplexing (just up through page 250)
  
  
Chapter 9:
  9.1:  basics
  9.2:  circuit switching, trunks, subscriber lines
  9.3:  switches: crossbar, 3-stage space-division switch, etc
  9.4:  circuit-switched routing
  9.5:  Signaling, inband v out-of-band, SS7


Chapter 10:
  10.1: packet basics; packet-size issues, virtual circuits v datagram routing
  10.2: OMIT
  10.3: X.25: omit discussion of different packet formats


You should also know a little about TCP and IP. The notes file would be 
your best source; TCP connection establishment (three-way handshake)
is also outlined in the book on page 632.

Any purely arbitrary distinctions, such as whether 1=low or 1=high, will be
provided to you on the exam.

==============================================  

Here are a few sample questions, intended to complement the questions from hwk1.


1. Give a possible explanation for transmission distortion that is based on 
Fourier analysis.


2. Why is digital data often encoded via an analog signal?


3. Give some advantages of microwaves versus land lines, for long-distance 
transmission.


4. List some disadvantages with NRZ encoding for long lines (>= 10 km). 
Which, if any, are addressed by NRZI?
Which, if any, are not an issue for shorter lines?


5. Suppose we take a 4-kHz voice signal and digitize it to a 56kbps signal.
(a). What frequency bandwidth is needed to transmit this using binary signaling, 
so the signaling rate is also 56kbps?
(b). What bandwidth is needed if we use 16-level signaling? How many bits can
be sent in a single signal element?


6. Consider the following sequence of virtual-circuit routers, and tables.

                                                     D
                                                     |
                                                   link3
                                                     |
                                                    [1]
A------link1-------[0]-B-[1]------link2---------[0]-C-[2]-----link4------E

               vc   vc   port                 vc   vc   port
               in   out  out                  in   out  out
               3    5    1                    5    4     2
               4    2    1                    2    3     1


List the VC used on each link as A sends to D



List the VC used on each link as A sends to E


7. Why is TCP vulnerable to "spoofing" (forged connections appearing to come
from another source) but X.25 is not?


8. Why are virtual circuits called that? That is, why are they like circuits,
and why is the adjective "virtual" there?