Chapter 1 Review Questions
There is no difference. 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.
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, she calls 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 either Alice or Bob to politely cancel the engagement if they
have reasonable excuses.
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
The Internet provides its applications a connection-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
Provides reliable data transfer, i.e., all application data sent by one side of the
connection arrives at the other side of the connection in order and without any
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 the network, helping to prevent the Internet from entering a state of