Version Date: April 26, 2005
This document contains the solutions to review questions and problems for the 3rd edition of Computer Networking: A Top-Down Approach Featuring the Internet by Jim Kurose and Keith Ross. These solutions are being made available to instructorsONLY. Please do NOT copy or distribute this document to others (even other instructors). Please do not post any solutions on a publicly-available Web site. We’ll be happy to provide a copy (up-to-date) of this solution manual ourselves to anyone who asks.
All material © copyright 1996-2005 by J.F. Kurose and K.W. Ross. All rights reserved
Chapter 1 Review Questions
1. There is nodifference. Throughout this text, the words “host” and “end system” are used interchangeably. End systems include PCs, workstations, Web servers, mail servers, Internet-connected PDAs, WebTVs, etc. 2. Suppose Alice, an ambassador of country A wants to invite Bob, an ambassador of country B, over for dinner. Alice doesn’t simply just call Bob on the phone and say, “come to our dinner table now”. Instead, shecalls Bob and suggests a date and time. Bob may respond by saying he’s not available that particular date, but he is available another date. Alice and Bob continue to send “messages” back and forth until they agree on a date and time. Bob then shows up at the embassy on the agreed date, hopefully not more than 15 minutes before or after the agreed time. Diplomatic protocols also allow for eitherAlice or Bob to politely cancel the engagement if they have reasonable excuses. 3. A networking program usually has two programs, each running on a different host, communicating with each other. The program that initiates the communication is the client. Typically, the client program requests and receives services from the server program. 4. The Internet provides its applications aconnection-oriented service (TCP) and a connectionless service (UDP). Each Internet application makes use of one these two services. The two services will be discussed in detail in Chapter 3. Some of the principle characteristics of the connection-oriented service are: • • Two end-systems first “handshake” before either starts to send application data to the other. Provides reliable data transfer, i.e., allapplication data sent by one side of the connection arrives at the other side of the connection in order and without any gaps. Provides flow control, i.e., it makes sure that neither end of a connection overwhelms the buffers in the other end of the connection by sending to many packets to fast. Provides congestion control, i.e., regulates the amount of data that an application can send into thenetwork, helping to prevent the Internet from entering a state of grid lock.
The principle characteristics of connectionless service are: • • • No handshaking No guarantees of reliable data transfer No flow control or congestion control
5. Flow control and congestion control are two distinct control mechanisms with distinct objectives. Flow control makes sure that neither end of aconnection overwhelms the buffers in the other end of the connection by sending to many packets to fast. Congestion control regulates the amount of data that an application can send into the network, helping to prevent congestion in the network core (i.e., in the buffers in the network routers). 6. The Internet’s connection-oriented service provides reliable data transfer by using acknowledgements andretransmissions. When one side of the connection doesn’t receive an acknowledgement (from the other side of the connection) for a packet it transmitted, it retransmits the packet. 7. A circuit-switched network can guarantee a certain amount of end-to-end bandwidth for the duration of a call. Most packet-switched networks today (including the Internet) cannot make any end-to-end guarantees for...