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Data Communication Network

MCA – II SEM

Ms Jyoti

Deptt. of IT

Biyani Girls College, Jaipur

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Published by :

Think Tanks

Biyani Group of Colleges

Concept & Copyright :

Biyani Shikshan Samiti

Sector-3, Vidhyadhar Nagar, Jaipur-302 023 (Rajasthan) Ph : 0141-2338371, 2338591-95 Fax : 0141- E-mail : acad@biyanicolleges.org Website :www.gurukpo.com; www.biyanicolleges.org

Edition : 2012

Leaser Type Setted by : Biyani College Printing Department

While every effort is taken to avoid errors or omissions in this Publication, any mistake or omission that may have crept in is not intentional. It may be taken note of that neither the publisher nor the author will be responsible for any damage or loss of any kind arising to anyone in any manner on account of such errors and omissions.

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Syllabus

Overview, evolution of computer networks, computer telephony. Data communications – advantages of digital communication, transmission media, and fundament ales of digital communications, transmission media, modulation techniques and modems. The OSI seven layer network model, LAN technologies – protocols and standards, LAN hardware, TCP/IP and the Internet, Internet Architecture, Internet protocol and datagram., Routing protocols, UDP, Internet standard services, DNS. Networking Technologies, ISDN, Cable Modem System, DSL, SMDS, Frame relay, fast Ethernet, 100VG-anyLAN and Gigabit Ethernet, FDDI and CDDI, Asynchronous Transfer, SONET, DWDM Switching and Virtual LAN, Non-ATM Virtual LANs, IEEE 802.1Q VLAN standard, Network Performance, Analytical approaches, simulation, traffic monitoring. Network Management – SNMP, RMON and RMNv2, TMN, Directory services and network management. Issues related to network reliability and security, SSL and VPN, Introduction only to firewalls and Kerberos, Cyber Laws.

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Content

UNIT 1 – Data Communication

digital communication, advantages of digital communication communication, communication system Twisted pairs cable ,Advantages, disadvantages, uses ,types Coaxial cable, Advantages, disadvantages ,uses ,types Optical fiber cable, Advantages, disadvantages, uses, types transmission media, Advantages, disadvantages ,uses ,types modem, types of modems ,modulation data communication ,advantages ,disadvantages transmission mode, refraction

UNIT 2 – Network Protocol (OSI Model)

UNIT 3 – Networking Technologies

UNIT 4 -- Network Switching

UNIT 5 – Network Management

UNIT 6 – Network Security

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A communication system itself can be either analog or digital (or a combination of two). The information can be transmitted in either in analog from or in digital form within the communication networks. The technique by which a digital signal is converted to its analog form is known as modulation. The reverse processes, i.e. the conversation of analog signal to its digital form at the destination devices are called demodulation.

Q. 3 What are the advantages of digital communication? Ans. Advantages of Digital communication: (1) The voice data, music and images can be combined to make more efficient use of the same circuit and equipment. (2) Much higher data transmission rates are possible using existing telephones lines. (3) Digital communication is much cheaper than analog data transmission and also it is not necessary to accurately reproduce on analogue wave form after it has passed through potentially hundreds if reports a transcontinental call. (4) Maintenance of a digital system is easier received correctly or not , making it simpler to track document the problems. (5) A digital signals can pass through an arbitrary number of regenerators with no loss is signals and there travels long distances with no information loss.

Q. 4 Explain the following terms with their advantages and disadvantages? (a) Twisted pairs cable (b) Coaxial cable (c) Optical fiber cable

Ans. (a) TWISTED PAIRS :-- It has two types Unshielded twisted pair Shielded twisted pair  Unshielded twisted pair:--A twisted pair consist of four insulated copper wires, typically about 1mm thick. The wires are twisted together in helical.

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The purpose of twisting the curies is to reduce the electric interference from similar pairs close by. Twisted pair wires are commonly used for digital data transmission over short distances up to 1km.when many twisted pairs run in parallel for a substantial distance, such as all the wires coming from a multistory apartment building to the telephone exchange, they are bundled together and encased in a protective sheath. The pairs in these bundles would interface with one another. it wire not for the twisting.

UNSHEILDED TWISTED PAIR

 Shielded twisted pair:--Shielded wire is typically is used in an electrically noisy environment to limit the effects of noise absorption .unshielded pair commonly referred to as UTP is by far the more common of the two configuration twisted pair wiring is more commonly used for local area network. Twisted pair cabling comes in several varieties. Computer network ,true of these are important category-3 twisted pairs consist of two insulated wires gently twisted together .Four such pairs are typically grouped together in a plastic sheath for protection and to keep the eight wires together.

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kinds of coaxial cable are widely used .one kind 50-ohm cable is commonly used for digital transmission. The other kind, 75-ohm cables, is commonly used for analog transmission in cable TV transmission. Coaxial cable is difficult to connect to network devices and generally requires more planning than twisted pair system. Many coaxial systems require the connectors on the main cable to be attached directly to the adapter on the PCs. This reduces flexibility in locating workstation and server.

ADVANTAGES:--

(a) It has better shielding than twisted pairs, so it can span longer distances at higher data bps.

(b) It can be used both analog data transmission as well as digital data transmission for analog ,75ohm.broadband coaxial is used and for digital data transmission 50ohm cable, baseband cable is used. (c) Coaxial cable has higher bandwidth and excellent noise amenity. (d) It is relatively expensive as ax pared to fiber optic cables and easy to handle. (e) Coaxial cable has a bandwidth in the range of 300-400MHz,it is capable of carrying over 50 standard 6MHz color TV channels or thousand of channels of voice grade and 1 or low speed data over a single cable.

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DISADVANTAGE:--

(a) Installation costs, while dropping, are still high. (b) Special test equipment is often required. (c) Susceptibility to physical damage. (d) Wildlife damage to fiber optic cables.

(b) OPTICAL FIBER: -- optical fiber is the newest form of bounded media .this media is superior in data handling and security characteristics .the fiber optic cable transmits light signals rather than electrical signals. it is for more efficient than the other network transmission media. Each fiber has an inner core of glass or plastic that conducts light. There are two types of light sources for which fiber cables are available. These sources of light are: a- Light emitting diodes b- Light amplification by stimulated emission radiation.

The system basically consists of fiber optic cables that are mode of tine threads of glass or plastic in a single mode fiber, the wire is 8 to 10 microns about the size of hair in multimode fibers, the core is of about 50microns in diameters. Towards its sources side is a convert that converter that converts electrical signals into light waves. These light waves are transmitted over the fiber. Another converter placed near the sink converts the light waves back to electrical signals are amplified and sent to the receiver each fiber has a inner core of glass or plastic that conducts light. The inner core is surrounded by cladding. Cladding is layer of glass that reflects the light back in to the core.

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(b) Fiber is not being affected by power surges, electromegnatic interference or power failures. Nor it is affected by corrosive chemicals in the air, making it ideal for harsh factory environments. (c) Fiber is lighter than copper. (d) Fiber does not wake light and are quit difficult to tap. This gives an excellent security against potential wire tapper.

DISADVANTAGES of fiber optic cable over copper wire:--

(a) Fiber is an unfamiliar technology requiring skills most engineers do not have. (b) Since optical transmission is inherently unidirectional ,two ways communication requires either two fibers of fours frequency bands on one fiber. (c) fiber interfaces cost more than electrical interfaces.

Q. 5 Explain transmission media? Ans Transmission media :-media is the general term used to describe the data path that forms the physical channel between sender and the receiver.media can be twisted pair wire such as that used for telephone installation ,coaxil cabel of various sizes and electrical characterstics, fiber optics and wireless supporting either light waves or radio waves. Band width is similar to the concept of frequence response in a stereo amplifier— the greater the frequance response, the higher the band width according to a fundamental princepal of information theory ,higher band width communication channels support higher data rates.

Q.6 Explain the types of transmission media? Ans There are several types of physical channels (communication media)through which data can be transmitted from one point to another .some of the most common data transmission media are as follow :--  Guided media electrical  Twisted pair cable  coaxial cable

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optical  single mode and multimode

coaxial cable

 Unguided media electromagnetic waves in air  radio  microwaves

Twisted Pair Various forms of data path can be used depend on the type of coputers connected and the data rate.i.e number of bits passed in one second.there are thus main types of communication media.these are bounded and unbounded media.in the case of boundedmedia,the data is transferred in the limited space whereas in the case of unbounded media,there is no restriction on the space.

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Modems convert communications signals from a form the computer can understand to a form the phone system can convey and vice versa .modems speed is often discussed in baud rates or bps , which are similar terms but they do not mean exactly the same baud rate refers to the oscillation of a sound wave on which a single bit of data is carried. bits per second is the amount of data transferred in a second. When a computer wishes to send digital data over a dial up line ,the data must first be converted to analog form by a modem for transmission over the local loop ,then convert to digital form for transmission over the long – haul trunks ,then back to analog over the local loop at the receiving end.

MODE

A modem can be installed internally in the computer in which case it is called an internal modem ,or it can be a external device that is connected to the computer with a serial cable.

Q.10 Explain the types of modems? Ans Modems can be of following types : (a)Landline modems (b)wireless modems (c)LAN modems

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=> Landline modems are modems which connect to the public switched telephone network (PSTN).to connect to PSTN, these modems have have a jack known as RJ-11jack or regular phone jack. Landline modems can be further classified into the following types : (a)internal modems (b)external modems (c)PCMCIA modems (d)voice/data/modems

=>wireless modems are redio transmitters/receivers installed into mobile computing devices(i.e.devices that are used while you are moving such as mobile phones,laptops etc)

=>Lan modems allow shared remote access to lan resources.lan modems comes fully preconfigured for asingle particular network architecture such as Ethernet or token ring.

LAN

Q.11 Explain the modem standards? Ans There are two modem standards .these are : (a) B ell modems (b)ITU-T modems First commercially available modems were developed by Bell telephone company in the early 1970s.Being the first modem manufacturer, they defined the developed of the technology and provided the standard which subsequent manufactures followed. some major Bell modems include the 103/113series,202series,212series,201series. Many of today’s popular modems are based on the standards published by ITU- T.v.21,v.22,v.23,v.32 modems are ITU-T modems.

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5- Protocol:-- a protocol is a set of rules that govern data communication devices.without a protocol ,two devices may be connected but not communicating,just as a person speaking french can not be understand by a person who speaks only japanese.

Q.14 Define data communication network? Ans Data Communication network :--the task of network designers is to selected and coordinate the network components is that the necessarydata are module to the right place,at the right time,with minimum of errors and at the lowest possible cost.a number of communication processor are used by network designers to achieve this goal. Communication system is the combination of hardware,software and data transfer units that make up a communication facility for transferring data in an efficient manner.

Q.15 What are the characteristics of data communication system? Ans Fundamentals characteristics of data communication system : 1- Delivery : the system must deliver data to the correct destination.data must be received by the intended devices or user and only by that device or user. 2- Accuracy : the system must deliver data accuratly. data that have been altered in transmission and left uncorrected are unusable. 3- Timeliness : the system must deliver data in a timely manner data delivered late are useless. in the case of videos, audios, and voice data. timly deliverly means delivering data as they are produced in the same order that they are produced and without significant delay. this kind of delivery is called real time transmission.

Q.16 Write down the transmission mode? Ans T he term transmission mode is used to define the direction of signal flow between two linked devices.there are three types of transmission modes : 1- Simplex 2- Half-duplex 3- Full-duplex

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1- SIMPLEX :--in this mode,the communication is undirectional,as on a one-way communication transmission.television transmission is avery good example of simplex communication.the main transmitter sends out a signal(broadcast),but it does not expect a reply as the receving units can not issue reply back to the transmitter.exam: include a data collection terminal one a factory floor or a line printer. 2- HALF-DUPLEX :-- in half-duplex mode,both units communicate our same medium,but only one unit can send at a time.while one is in send mode,the other unit is in receiving mode.it is like true polite people talking to each other-one talk the other listen,but both of them could not talk at the same time – thus a half duplex line can alternately sen and receive data.it requires two wires it is used to connect a terminal with computer.the terminal might transmit data and them the computer responds with an acknowledgement.the transmission of data to and from a hard disk is also done in half duplex mode. 3- FULL-DUPLEX :-- a half-duplex system,the line must be ―turned around ‖each time the direction is requires. This involves a special switching circuit and requires a small amount of time with high speed capabilities of the computer this turn around time is unacceptable in many instances. also,some application requires simultaneously transmission in both direction in such cases a full duplex system is used that allows information to flow simultaneously in both direction on the transmission path. use of full-duplex line improves efficiency as the line turnaround time required in a half-duplex arrangement is eliminated also requires four wires for full-duple.