Read Chapter 9 and Chapter 12 as well as Lesson 9a.. Then complete this homework assignment.Work to understand all problems even though all problems may not be assigned.

1. Describe the parts of the local loop in detail.

2. What are the three main features of the telephone system and what are they responsible for?

3. What advantages and disadvantages does a circuit switched network have?

4. How might delay and especially variable delay be bad for an international telephone call?

5. Describe three messages/signals you might get when your telephone call cannot be completed.

6. You are a traffic engineer.  You are redesigning a trunk group that currently supports 96 simultaneous calls.  the trunk group is now reaching maximum capacity and future resources have to be added. 

a) If the demand for resources is growing 10% per year and you wish to install cable plant that will provide adequate support for the next 15 years, how many trunks would you need to add to the current trunk group?

b) How many T1 lines would you add to make sure you could support the expected demand above (round up)?

c) How many trunks would be needed if growth was 35% per year?

7. What are some shortcomings of a circuit switched network when sending data across it?

8. What advantages does packet switching have over circuit switching?

9. Define the following terms:

1. virtual circuit
2. datagram
3. clear-request packet
4. random routing
5. flooding
6. least cost routing
7. routing update
8. oscillation
9. packet sequence

10. What are seven goals of routing?

11. What metrics might be used to determine the least-cost route between two end points?

12. Look at the figure below and answer the questions that follow it

• What is the least cost route from 7 to 1? (Identify the path)
• How about from 1 to 7?
• What would router 2 have to raise each outgoing link cost to so that it no longer carried traffic traveling from 1 to 7?  Identify the new cost for link 2->4 and link 2->3.
• If node 4 failed, what would be the best route from 7 to 1?
• A two way link from 1 to 5 is established.  The costs for both directions are equal.  Traffic traveling back and forth between nodes 1 and 7 do not use this link.  What is the lowest cost that could be set on this link under these conditions?

13. What error and flow control methods are used by X.25

14. Sketch an X.25 packet header and describe the fields.

15. Compare the features of the Bellman-Ford algorithm and Dijkstra's algorithm.

Used with permission of the Author; Copyright (C) Kevin A. Shaffer 1998 - 2018, all rights reserved.