Miniquiz 11/14/2003.  CIS451.  Dr Ott.
You know the drill.
Feel free to use this paper only.
Name on every sheet.


1A What does HDLC stand for?
   High level Data Link Control

1B What does PPP stand for?
   Point to Point Protocol

1C What does IANA stand for?
   Internet Assigned Number Authority

2. BRIEFLY (and I mean it) give the most important reasons 
   you might prefer DSL over cable Modems.

   This is somewhat subjective.
   The reason I stressed in class is that DSL is more private: 

   (1) With a cable Modem, all people with a modem on the same cable can
   see your traffic. (You may need encryption, or watch what you say).
   Also:
   (2) With a cable modem, if many customers using the same cable are 
   active, the performance you see goes down.
   With DSL, you do not share.
   (3) (For me:) Reliability. In the 18 years I have lived in my current
   home, phone has been out once, for a short while.
   Cable is out at least once a month, for several hours.
   Just try to log in to NJIT when your physical connection is down!

But:
   Cable can have better performance. In particular if you have a poor
   quality or long local loop, and if few of your neighbors use cable 
   modems.

Cost is comparable. Where I live, DSL is a bit cheaper. Cable gives the 
option of having a static IP address (against a stiffish surcharge!).
Where I live, DSL only gives dynamic IP addresses.

It certainly is not a clear case. If you want your own website at home,
choose the one that allows a static address. I asked for the arguments 
in favor of DSL.

3. BRIEFLY (and I mean it) describe:

3A The Hidden Station Problem.
   See classnotes.
   Hidden station: A wants to talk to C, C hears B which is talking to D,
   but A does not hear B.
   B is hidden from A. 
   Carrier sense does not work: false negative.


3B The Exposed Station Problem.
   See classnotes.
   Exposed station: A wants to talk to C. A hears B talking to D but 
   does not know that C can not hear B anyhow. 
   B is exposed to A (A is exposed to B).
   Carrier sense does not work: false positive.

 









(Only describe the problems, not the solutions. Make sure to 
have a simple drawing that requires hardly any text.)