Data Communications Study set Chapter 1

What are the three criteria necessary for an effective and efficient network?

performance, reliability, security

What are the two types of line configuration?

point-to-point and multi-point configuration

Why are protocols needed?

protocols are a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese.

In a LAN with a link-layer switch (Figure 1.8b), Host 1 wants to send a message to Host 3. Since communication is through the link-layer switch, does the switch need to have an address? Explain.

write your answer on paper and open the textbook for the correct answer

What are the advantages of a multipoint connection over a point-to-point one?

Advantages of a bus topology include ease of installation. Backbone cable can be laid along the most efficient path, then connected to the nodes by drop lines of various lengths. In this way, a bus uses less cabling than mesh or star topologies

Identify the five components of a data communications system.

1. Message. The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video. 2. Sender. The sender is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on. Figure 1.1 Five components of data communication Transmission medium Message Protocol Protocol Rule 1: Rule 2: ... Rule n: Rule 1: Rule 2: ... Rule n: Sender Receiver 3. Receiver. The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on. 4. Transmission medium. The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves. 5. Protocol. A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese.

What are some of the factors that determine whether a communication system is a LAN or WAN?

A LAN is normally limited in size, spanning an office, a building, or a campus; a WAN has a wider geographical span, spanning a town, a state, a country, or even the world. A LAN interconnects hosts; a WAN interconnects connecting devices such as switches, routers, or modems. A LAN is normally privately owned by the organization that uses it; a WAN is normally created and run by communication companies and leased by an organization that uses it.

Explain the difference between an Internet draft and a proposed standard.

An Internet draft is a working document with no official status and a six-month lifetime. A proposed standard is a specification that is stable, well understood, and of sufficient interest to the Internet community. At this level, the specification is usually tested and implemented by several different groups.

How many point-to-point WANs are needed to connect n LANs if each LAN should be able to directly communicate with any other LAN?

Each LAN should be connected to (n − 1) LANs, which means that we will have n × (n − 1) connections. However, if each connection can be used in both directions, we need only [n × (n − 1)]/2 connections

What is the difference between half-duplex and full-duplex transmission modes?

In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. However, In full-duplex mode (also called duplex), both stations can transmit and receive simultaneously.

Explain the difference between a required RFC and a recommended RFC.

Required. An RFC is labeled required if it must be implemented by all Internet systems to achieve minimum conformance. For example, IP and ICMP (Chapter 19) are required protocols. An RFC labeled recommended is not required for minimum conformance; it is recommended because of its usefulness. For example, FTP (Chapter 26) and TELNET (Chapter 26) are recommended protocols.

Name the four basic network topologies, and cite an advantage of each type.

The Mesh topology: the use of dedicated links guarantees that each connection can carry its own data load, thus eliminating the traffic problems that can occur when links must be shared by multiple devices. The Star topology: If one link fails, only that link is affected. All other links remain active The Ring Topology:To add or delete a device requires changing only two connections The Bus Topology: include ease of installation, and can be laid in the most efficient path.

What is the first principle we discussed in this chapter for protocol layering that needs to be followed to make the communication bidirectional?

The first principle dictates that if we want bidirectional communication, we need to make each layer so that it is able to perform two opposite tasks, one in each direction.

Explain the difference between the duties of the IETF and IRTF.

The Internet Engineering Task Force (IETF) is a forum of working groups managed by the Internet Engineering Steering Group (IESG). IETF is responsible for identifying operational problems and proposing solutions to these problems. IETF also develops and reviews specifications intended as Internet standards. The working groups are collected into areas, and each area concentrates on a specific topic. Currently nine areas have been defined. The areas include applications, protocols, routing, network management next generation (IPng), and security. The Internet Research Task Force (IRTF) is a forum of working groups managed by the Internet Research Steering Group (IRSG). IRTF focuses on long-term research topics related to Internet protocols, applications, architecture, and technology.

Categorize the four basic topologies in terms of line configuration.

The following topologies are point-to-point: mesh topology, star topology, ring topology The following are multi-point topologies: bus topology

When a resident uses a dial-up or DSL service to connect to the Internet, what is the role of the telephone company?

The telephone company acts as an Internet Service provider

What is an internet? What is the Internet?

When two or more networks are connected, they make an internetwork, or internet (lowercase i) versus The Internet (uppercase i) which is composed of thousands of interconnected networks.

For n devices in a network, what is the number of cable links required for a mesh, ring, bus, and star topology?

a. Mesh: n (n - 1) / 2 b. Star: n c. Ring: n - 1 d. Bus: one backbone and n drop lines

When we use local telephones to talk to a friend, are we using a circuit-switched network or a packet-switched network?

circuit-switched network