Review Questions for Test-1 (with Answers):

Chapter 1: Introduction to Data Communications

Outline

1.1 Network Basics
1.2 Network Layer Model (most important)
1.3 Network Standards
1.4 Future Trends (least important)

Answers to End-of-Chapter Questions

1. Describe the progression of communications systems from the 1800s to the present.

Communications systems progression from the 1800s to the present: 1837 Invention of the telegraph 1876 Invention of the telephone 1877 Telephone system regulation begins in Canada 1878 Telephone system regulation begins in the United States 1879 Direct dialed long distance service begins 1880 Satellites begin to transmit international telephone calls 1881 Caterfone court decision permits non-Bell telephone equipment to be used 1970 Court permits MCI to provide long distance services 1984 Breakup of AT&T 1985 Cellular phones enter service 1996 Telecommunications Act of 1996 deregulates American telephone system

2. Why are network layers important?

Communication networks are often broken into a series of layers, each of which can be defined separately, to enable vendors to develop software and hardware that can work together in the overall network.

3. Describe the four layers in the network model used in this book and what they do.

• The application layer is the application software used by the user. • The network layer takes the message generated by the application layer and if necessary, breaks it into several smaller messages. It then addresses the message(s) and determines their route through the network, and records message accounting information before passing it to the data link layer. • The data link layer formats the message to indicate where it starts and ends, decides when to transmit it over the physical media, and