chapter 1 Networking and Open Standards

CHAPTER 1

NETWORKING AND OPEN STANDARDS

Brief Summary of the Chapter:

In this chapter we are going to study about computer Networks, associated terminology and related concept along with network devices.

Key Points of the Chapter:

·   Network:   A Computer Network is a number of computers (Usually called terminals
      interconnected by one or more transmission paths.

·  Need of Networking:

1.         Resource Sharing

2.         File and data sharing.

3.         Data security and centralized security

4.         High Reliability :

5.         Communication Media

6.         High Speed

7.         Flexible working environment

8.         Cost factor

·  Application of Networks

1.      Sharing of data, services and resources

2.      Access to remote database

3.      Communication facilities

a.   Elementary Terminology of Networks :

1.    Nodes  (Workstations):- The term nodes refer to the computers that are attached to a

network and are seeking to share the resources.

2.    Server:- A computer that facilitates the sharing of data, software and hardware resources

on the network

3.    Network Interface Unit (NIU) (MAC Address):- A network interface unit is interpreter

that helps in establishing the communication between the server and the client.

4.    IP Address:- Every machine on a TCP   bar IP Network has a unique identifying no.

called an IP Address.

5.    Domain Name:-It is a way to identify and locate the computers connected to the internet.

It must be unique.

a.   NETWORK TOPOLOGIES :    The term Network    Topologies refer to the way in
      which the nodes of a network are physically connected together. The important network
      topologies are

1)     Bus Topology or Linear Topology : In this topology a single leng

medium is used onto which the various nodes are attached. The transmission from any station travels the length of the bus, in both directions and can be received by all other stations. The bus has a terminator at either end which absorbs the signal, removing it from the bus.

Characteristics:

Short cable length and Simple wiring layout

A single cable called trunk is used through which all data propagates and to which all nodes are connected

Easy to extend

There is no central point of failure on a bus because there is no hub.

Entire network shuts down if there is break in the main cable.

Terminators are required at both ends of the backbone cable.

Difficult to identify the problem if the entire network shut down.

Addition of nodes negatively affects the performance of the whole network. Only one computer can send messages at a time

2)   Ring Topology: In a ring topology each node is connected to two and only two neighboring
         nodes.  Data  is  accepted  from  one  of  the  neighboring nodes  and  is  transmitted  onwards  to
         another. Thus data travels only one direction.

Every computer serves as a repeater to boost signals Short cable length.

Suitable for optical fiber
Difficult to add computers
More expensive

If one computer fails,   whole network fails

Data clashes can also occur if two machines send messages at the same time.

3)   Star Topology: A start topology is designed with each node connected directly to the server via hub or switch. This topology is used in most existing information network. Data on a star network passes through the hub or concentrator before continuing to its destination.

Easy to install and wire

No disruptions to the network when connecting or removing devices.

Easy to add new station as each station has direct cable connection to hub or switch.

Depending on the intelligence of hub, two or more   computers may send message at the same
time

One malfunctioning node does not affect the rest of the network. Required more cable length than a linear topology.

All signals transmission through the hub; if down, entire network down

NETWORK DEVICES

1.       MODEM(  MODulator  DEModulator)  :  Modem  is  a  device  that  converts  digital  data

originating  from  a  terminal  or  computer  to  analog  signals  used  by voice  communication network such as the telephone system.

At one end, modems convert the digital pulse to audible tones and convert audio tones        back to digital pulses at the other

2.       RJ -45 Connector:

The RJ-45 is a single line jack for digital transmission over ordinary phone wire. It is a 8 wire connector which is commonly used to connect computers on the LAN(especially Ethernets). RJ - short for Registered Jack - 45

3.       Ethernet Card or NIC or NIU:A NIC(Network Interface card)

board or card that is installed in computer so that it can connected to network. It is suitable for coaxial or twisted pair cables.

4.         Hub: Hub is a device used to connect several computers together. It is a multi-port card. Hubs

forward any data packets including e-mail, word processing documents or print request - they
            receive over one port from one workstation to all of their remaining ports
 5. Switches : Switches are smart hubs that send data directly to the destination rather than
            everywhere  within  network.  When  the  switch  receive  a  packet,  the  switch  examines  the
            destination and source hardware address and compare them to a table of a network segments
            and addresses. If the segments are the same the packet is dropped and if the different then the
            packet is forwarded to the proper segments.

6.         Repeaters :A repeater is a device that amplifies a signal being transmitted on the network.

Since a signal loses strength as it passes along a cable, it if often necessary to boost the signal
with this device.. The repeater electrically amplifies the signal it receives and rebroadcasts it.

7.         Router:

A device that works like a bridge but can handle different protocols, is known as router. It is

used to separate different segments in a network to improve performance and reliability.

Solved Questions:

Q1.     What is MAC Address?

Ans  : In computer networking, a Media Access Control address  (MAC) is a unique identifier
              assigned to most network adapters or network interface cards (NICs) by the manufacturer for
              identification, and used in the Media Access Control protocol sub-layer.
 Q2.     Write two advantages of networks.

Ans:    Advantages:   i)    Data or information can be shared among the users.

ii)    Fast communication can be achieved.

Q3.     Write two disadvantages of networks.
Ans :   Disadvantages of networks:

i. Sophisticated Hardware and software technology is required. ii. Expensive to install network.

Q4.     What is communication channel? Name the basic types of communication channels available.

Ans: What is communication channel? Name the basic types of communication channels available.
            Communication channels mean the connecting cables that link various workstations. There are
            3 basic types of cables: Twisted Pair cables  Coaxial cables    Fiber-optic cables

Q5.     Define a network.

Ans:    A computer network is a system in which computers are connected to share information and
            resources.

Q6.     What is IP address?

Ans      A unique number consisting of 4 parts separated by dots, e.g. 165.113.245.2 Every machine that
            is on the Internet has a unique IP number - if a machine does not have an IP number, it is not
            really on the Internet.

Q7.     What is domain name? How is it alternatively known?

Ans     The unique name that identifies an Internet site. Domain Names always have 2 or more parts,
            separated by dots. The part on the left is the most specific, and the part on the right is the most
            general. E.g.: matisse.net

Q8.     What are the various types of networks?

Ans : Network can be classified on the basis of their size, complexity and geographical spread. On the
            basis of geographical spread it can be classified as Local Area Network, Metropolitan Area
            Network and Wide Area Network.

Q9.     What is the difference between MAN and WAN?

Ans : A metropolitan area network (MAN) is a large computer network that usually spans a city or
            a large campus.

WAN is a network that covers an area larger than a single building or campus such as across the cities or countries.

Q10.    What is meant by Topology? Name some popular topologies.

Ans: Network topology is defined as the interconnection of the various elements (links, nodes, etc.)
            of a computer network. In computer networking, topology refers to the layout of connected
            devices.

•   Bus topology

•   Star topology

•   Ring topology

•   Tree topology

•   Mesh topology

Q11.    What are the similarities and differences between bus and tree topologies?

Ans:    In bus topology each machine is connected to a single cable. Each computer or server is
            connected to the single bus cable through some kind of connector.

Tree topology is a network with the shape of an inverted tree in which a single link between two nodes.

Q12.    What are the limitations of star topology?

Ans     i)    Central node dependency: In this topology central node is a controller of the network. If the
                 central node fails, the entire network will be failed.

ii)    Difficult to expand: The addition of a new node to a network involves a   connection all the
      way to the central node.