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
1. Dial-up modem over telephone line: residential; 2. DSL over telephone line:
residential or small office; 3. Cable to HFC: residential; 4. 100 Mbps switched
Etherent: company; 5. Wireless LAN: mobile; 6. Cellular mobile access (for example,
HFC bandwidth is shared among the users. On the downstream channel, all packets
emanate from a single source, namely, the head end. Thus, there are no collisions in
the downstream channel.
Current possibilities include: dial-up; DSL; cable modem; fiber-to-the-home.
Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.
For an X Mbps Ethernet (where X = 10, 100, 1,000 or 10,000), a user can
continuously transmit at the rate X Mbps if that user is the only person sending data.
If there are more than one active user, then each user cannot continuously transmit at
Ethernet most commonly runs over twisted-pair copper wire and “thin” coaxial cable.