CS2363-Computer Networks

Define computer network.

Computer network is a connection of autonomous computers and network devices for:

Resource sharing (data/devices) in an efficient manner Communication amongst them.

Compare simplex and duplex communication with example.

In simplex mode, the communication is unidirectional (Eg: keyboard, monitor).

In half-duplex mode, each station can both transmit and receive, but not simultaneously (Eg. walkie-talkie).

In full-duplex (also called duplex), both stations can transmit and receive simultaneously (Eg. telephone network). 

List the criteria based on which a network can be assessed.

Performance is based on its throughput (no. of packets delivered) and delay. Reliability is how much the network is fault tolerant.

Security includes preventing unauthorized access and recovery from breaches.

What are the two types of line configuration?

A point-to-point connection provides a dedicated link between two nodes.

In a multipoint connection, more than two nodes share a single link, i.e., bandwidth is shared amongst the nodes..

Classify LAN, WAN, MAN and Internetwork.

LAN is privately owned and links the devices in a single office, building, or campus. The LAN size is limited to a few kilometers. A LAN will use only one type of transmission medium. The speed of LAN is in the range 10–1000 Mbps.

WAN provides long-distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or the whole world.

MAN is a network with a size between a LAN and a WAN. It normally covers the area inside a town or a city. It is designed for customers who need a high-speed connectivity to the Internet, and have endpoints spread over a city or part of city.

When two or more independent networks are connected, it becomes an internetwork or internet.

List the advantages of layering.

It decomposes the problem of building a network into more manageable components.

It provides a more modular design. To add a new service, then it is only needed to modify the functionality at one layer, reusing the functions at all the other layers.

Uses abstraction to hide complexity of network from application.

Define protocol.

The abstract objects that make up the layers of a network system are called protocols. Each protocol defines two different interfaces.

o  Service interface that specifies the set of operations

o    Peer-to-peer interface for messages to be exchanged amongst peers Protocol is a set of rules that govern communications between devices.

What is a protocol graph?

The suite of protocols that make up a network system is represented as a protocol graph. The nodes correspond to protocols and edges represent a depends-on relation.

Define network architecture.

The set of rules governing the form and content of a protocol graph is called network architecture.

Network architecture guides the design and implementation of computer networks. Two commonly used architecture are

o  OSI Architecture

o  Internet or TCP/IP architecture

What purpose do header and trailer serve?

A layer communicates control information to its peer, instructing it how to handle the message when it is received by attaching a header in front of the message.

The trailer usually contains error control information.

A header/trailer is a small data structure consists of a few bytes.

Brief the terms unicast, multicast and broadcast.

The different types of addressing are unicast (one-to-one communication), multicasting (communicating to all members of a group) and broadcast (sending to all nodes on the network).