CS176A - Introduction to Computer
Communication Networks
Homework Assignment #2
Due BEFORE (2:00pm)
Class on Thursday,
October 23rd, 2003
The purpose of this assignment is to make sure you grasp the
concepts related to the OSI stack model in general, along with a focus on the
physical, data link and network layers.
Some of the questions in this assignment are basic, while
others will require some extra reading/searching (in the book or using Google) so that you could build on the basics that you
know.
Use as much space as needed to answer the following questions.
If you use Google search engine, list the URL's used.
Include your name and e-mail address as the first line of the homework.
- Why do
we have layers in the OSI model and protocols in general? (6 points)
- Mention
the seven layers of the OSI stack, and describe the basic function of each
layer in one sentence. (6 points)
- What
are the differences between the circuit switched and packet switched
networks? Give examples of each. (6
points)
- What
is the difference between hubs, switches, bridges, routers, repeaters and
amplifiers? (10 points)
- What
is the minimum and maximum length for an Ethernet frame? Why do we have those
minimum and maximum lengths? (8
points)
- What
would the string 0111101111101111110 be after bit-stuffing (flag is 01111110)? (4 points)
- Could
there be collisions on a switch? Justify your answer. (6 points)
- Rank
the following LANs from most secure to least secure: Switched LAN,
Wireless LAN and Shared LAN. Explain your reasoning. (6 points)
- What
are the advantages and disadvantages of Manchester
encoding when compared with Binary encoding? Are
there any other encoding schemes that exist? If yes, give at least one
example and briefly explain how it works. (10 points)
- What
would happen if two machines on the same LAN have the same MAC address? (6 points)
- We
know that all our computers (and most routers) nowadays are electronic
based, i.e. they operate with voltages between them, how do we have
optical networks work with such computers or routers since all the optical
signals are based on light (photons) and not voltages? Why is this a challenge for building faster networks? What is
one way this problem could be solved? (10
points)
- What
would happen if two computers in the world had the same IP address?
Justify your answer. (6 points)
- If you
saw the following entries in a routing table: 54.210/16 and 54.211/16. Is
there a way to combine them? If yes, what would the alternative entry or
entries look like? (6 points)
- Assume
each packet has typical TCP and IP headers each 20bytes long. If we have
three computers, A, B and C. The link between A and B has an MTU of 3000
bytes, while the link between B and C has an MTU of 1000 bytes. Consider
the case where a packet needs to be sent from A to C that has a size of
3000 bytes (including headers). How many fragments will we have from B to
C, and how much data will be in each fragment (i.e. excluding headers)? (Note:
assume the network connecting A, B and C is Ethernet)(10 points)
This assignment will be turned in using the CS Department turnin program. From any computer in CSIL type the
following command to turnin your answers to this
homework:
csil-machine>turnin hw2@cs176a hw2.ps
Be sure to use exactly hw2@cs176a for this assignment. However the
last argument is the name of the file containing your homework answers and can
be any name you choose.
This assignment should be turned in a suitable format. Suitable formats
include HTML, PostScript, PDF and plain text. Unfortunately, Microsoft Word
documents are not suitable, they are too prone to
viruses. However, that does not preclude you from using Microsoft Word to type
out your answers. Simply save the Word document as an HTML file or a PostScript
file if you know how. If you have any questions on a format ask the TA's.
Note: See the syllabus for the late turn-in policy. (No late assignments
will be accepted.)