رقم المادة : cs416 شعبـــــــة : sb spring 2008 spring 2008 الوقت : 8-9...

المادة : المادة :رقم SBSB شعبـــــــة :شعبـــــــة : CS416CS416 رقم

Spring 2008Spring 2008

99--88الوقت : الوقت :

االربعاء – - االثنين االربعاء – - السبت االثنين السبت

Data communication and networkingData communication and networking الكتاب :الكتاب :

الكتاب : الكتاب : لغة EnglishEnglishلغة

المادة المادة درجات درجات

واجب 55 واجب درجات درجات

حضور 55 حضور درجات درجات

أول 1515 أول اختبار اختبار

ثاني 2020 ثاني اختبار اختبار

ثالث 2525 ثالث اختبار اختبار

نهائي 3030 نهائي درجة درجة

Chapter 1Chapter 1

1. Introduction

2. Data Communication

3. Networks

4. Protocols and Standards

5. Standard Organizations

IntroductionIntroduction

Data communications and networking– Change the way we do business and the way we live– Decision depends on accurate information– Business today rely on computer networks and

internetworks

– Before get hooked up, we need to know: How networks operate What types of technologies are available What design best fills which set of needs

IntroductionIntroduction

– Development of the PC changes a lot in business, industry, science and education.

– Same happened to data communication and networking Possible for communications links to carry more and faster

signals Services extended to have telephone services:

– Conference calling– Call waiting– Voice mail– Caller ID

Data CommunicationsData Communications

Communication: Means sharing information

– Local (face to face) or remote (over distance)

Telecommunication – Telephone, telegraph and television

– Means communication at a distance

– Tele is Greek for far


Data: Refers to information

– Presented in any form

– Agreed upon by the parties ( creating & using)

Data communication : is the exchange of data between two devices via some form of transmission medium (wire cable).


– Communication system made up of a combination of hardware (physical equipment) and software (programs)

– Effectiveness of data communication system depends: Delivery : The system must deliver data to correct destination.

– by intended device or user Accuracy: The system must deliver data accurately (no

change).– Data changed is unusable

Timeliness: The system must deliver data in timely manner– Data arrived late are useless

– In the same order (video and audio)

ComponentsComponents

A data communication system is made up of five components


1. Message: the information (data) to be communicated– Consist of text, numbers, pictures, sound, or video– Combination of any

2. Sender: the device that sends the data message– Computer, workstation, telephone handset, video camera …

3. Receiver: the device that receives the message– Computer, workstation, telephone handset, television ….

4. Medium: The transmission medium is the physical path by which a message travels from sender to receiver

– twisted pair, coaxial cable, fiber-optic, radio waves


5. Protocol: a set of rules that govern data communications

– An agreement between the communicating devices– Devices may be connected but not communicating (no protocol)– French speaker with Japanese speaker

Data RepresentationData Representation

TextText

AudioAudio

VideoVideo

NumbersNumbers

ImagesImages

Direction of Data FlowDirection of Data Flow

Communication between two devices can be:– Simplex– Half-Duplex– Full-Duplex

Simplex (one way street)

– The communication is unidirectional– Only one device on a link transmit; the other can only receive

Direction of Data FlowDirection of Data Flow

Half-Duplex (one-lane with two-directional traffic)

– Each station can both transmit and receive, but not at the same time.

– One is sending, the other can only receive, and vice versa– The entire capacity of a channel is take over by the device is

transmitting

Direction of Data FlowDirection of Data Flow Full-Duplex (two-way street)

– Both stations can transmit and receive at same time– Signals going in either direction sharing the capacity of the link– Sharing can occur in two ways:

Link has two physically separate transmission paths– One for sending and the other for receiving

The capacity of the channel is divided between signals traveling in both directions.

NETWORKSNETWORKS

– A Network : A set of devices (nodes) connected by communication links

Nodes : computer, printer

- Distributed Processing : - Most networks used it

- task is divided among multiple computers.

NETWORKSNETWORKS

Network Criteria – Network must meet a certain number of criteria – Performance measured by:

1. transit time: A mount of time required for a message to travel from one device to another

2. response time: Elapsed time between an inquiry and a response Performance depends on :

1- Number of users : large number slow response time.2- Type of transmission medium : fiber-optic cabling faster than others cables.3- Capabilities of the connected hardware : affect both the speed and capacity of transmission.4- Efficiency of the software : process data at the sender and receiver and intermediate affects network performance.

NETWORKSNETWORKS

- Reliability is measured by:

1- Frequency of failure: it is little value to a user.

2- Recovery time of a network after a failure

3- Network’s robustness a Catastrophe: protect by good back up network system

- Security : protecting data from unauthorized access

NETWORKSNETWORKS

Type of connectionDefines the attachment of communication devices to a link

Piont-to-Point Dedicated link between two devices Entire of the link is reserved between those two devices

Use an actual length of wire or cable

NETWORKSNETWORKS

but other such as microwave or satellite is possible

Television remote control

NETWORKSNETWORKSMultipoint (multidrop)Multipoint (multidrop)

o more than two devices share a single linkmore than two devices share a single link

• Capacity is sharedCapacity is shared

•Channel is shared either spatially or temporallyChannel is shared either spatially or temporally

• Spatially shared : if devices use link at same timeSpatially shared : if devices use link at same time

• Timeshare : if users must take turns Timeshare : if users must take turns

NETWORKSNETWORKS

Physical Topology: The way a network is laid out physically– The topology of a network is the geometric representation of the

relationship of all the links and linking devices (nodes) to each other.

– Four topologies : mesh, star, bus, and ring

TopologyTopology

MeshMesh StarStar BusBus RingRing

PHYSICAL TOPOLOGYPHYSICAL TOPOLOGY

Mesh– Every link is dedicated point-to-point link

• To linkTo link n devicesn devices fully connected mesh has n(n-1)/2 fully connected mesh has n(n-1)/2

physical channels physical channels


Example:– 8 devices has links in mesh is n(n-1)/2– number of links = 8 (8-1)/2=28– number of ports per device = n – 1 = 8 –1

= 7


Advantages:– Each connection carry its own data load– A mesh topology is robust– Privacy or security– Fault identification and fault isolation

Disadvantages:– Installation and reconnection are difficult– Big a mount of cabling – Big number of I/O ports– Hardware connect to each I/O could be expensive

It is implemented as a backbone of hybrid network


Star

- Dedicated point-to-point to a central controller (hub)

- No direct traffic between devices– The control acts as an exchange


Advantages:

- Less expensive than mesh ( one I/O port )

- Easy to install and reconfigure

- Less cabling

- Additions, moves and deletions required one connection

- Robustness : one fail not affect others– Easy fault identification and fault isolation

Disadvantages:

- More cabling than other topologies ( ring or bus)

PHYSICAL TOPOLOGYPHYSICAL TOPOLOGYBus

- it is multipoint

- one long cable acts as a backbone

•Nodes connect to cable by drop lines and tapsNodes connect to cable by drop lines and taps

- Limit of number of taps and the distance between taps- Limit of number of taps and the distance between taps

- Signal travels along the backbone and some of its - Signal travels along the backbone and some of its energy is translate to heatenergy is translate to heat


Advantages: - Ease of installation- Less cables than mesh, star topologies

Disadvantages:- Difficult reconfiguration and fault isolation ( limit of taps) adding new device required a modification of the

backbone- Fault or break stops all transmission


Ring- Each device has dedicated point-to-point line configuration

- Each devices incorporates a repeater

- Easy of install and reconfigure - Connect to immediate neighbors

- Move two connection for any moving

- Easy of fault isolation

Disadvantage

- One broken device can disable the entire network (unidirectional)

CATEGORIES OF NETWORKSCATEGORIES OF NETWORKSo Local Area networks

o Metropolitan area networks

O Wide area networks

Local-area networkLocal-area network

(LAN)(LAN)

NetworkNetwork

Metropolitan-area networkMetropolitan-area network

(MAN)(MAN)

Wide-area networkWide-area network

(WAN)(WAN)

CATEGORIES OF NETWORKSCATEGORIES OF NETWORKS

We decide the category depending on:We decide the category depending on:

o o SizeSize

o Ownershipo Ownership

o Distance it covers o Distance it covers

o Physical architectureo Physical architecture

Local Area Network (LAN)Local Area Network (LAN)

• Private owned

• Links the devices in a single office, building or campus

Local Area Network (LAN)Local Area Network (LAN) As simple as two PCs and a printer Limited to few kilometers LAN allow resources to be shared (hardware, software and data) LAN distinguished by:1. Number of Users:

– LAN links a workgroup of task-related computers – Software on a server and accessed by clients– LAN size determined by

Licensing restrictions on the number of user per copy of software Restrictions on the number of users licensed to access the OS

2. LAN uses one type of transmission medium3. LAN topologies : bus, ring and star4. LAN data rate: 4 to 16 Mbps (Today 100 Mbps)

Metropolitan Area Network Metropolitan Area Network ((MANMAN)) Cover a city (company offices in city) MAN could be

– Single network : cable TV network– Many LANs

Example: company uses MAN to connect the LANs in a city Owned by private company or by a public company (telephone

company)

Wide Area Network Wide Area Network ((WANWAN))

Cover country, continent or whole world WAN uses public, leased, or private communication equipment Enterprise network: WAN owned by single company

InternetworksInternetworks

Two or more networks are connected together

THE INTERNETTHE INTERNET

The The InternetInternet has revolutionized many has revolutionized many aspects of our daily lives. It has affected aspects of our daily lives. It has affected the way we do business as well as the way the way we do business as well as the way we spend our leisure time. The Internet is we spend our leisure time. The Internet is a communication system that has brought a communication system that has brought a wealth of information to our fingertips a wealth of information to our fingertips and organized it for our use. and organized it for our use.

THE INTERNETTHE INTERNET Network: group of connected communicating devices (computers and printers) An internet (small i) is two or more networks Notable internet is called the Internet (hundreds of thousands interconnected

networks) – Private individuals + government agencies + school + research facilities + Corporations + libraries in more than 100 countries

This communication system came in 1969 Mid-1960 (ARPA) Advanced Research Projects Agency in (DOD) was

interested to connect mainframes in research organizations 1967, ARPA presented its ideas for ARPANET

– Host computer connecting to (IMP) interface message processor.– Each IMP communicate with other IMP

1969, four nodes (universities) connected via IMPs to form a network– Software (NCP) Network Control Protocol provided communication

between the hosts. 1972, Vint Cerf and Bob Kahn invented (TCP) Transmission Control Protocol

THE INTERNETTHE INTERNET

Later TCP was split to (TCP) Transmission Control Protocol and (IP) Internetworking Protocol

Internet Today Made of many wide- and local-area networks Every day new networks area added and removed (ISP) Internet services Providers offer services to the end users

– International service providers– National service providers– Regional service providers– Local service providers

PROTOCOLS AND STANDARDSPROTOCOLS AND STANDARDS

– Protocols synonymous with rule– Standards are agreed-upon rules

Protocols– Defines:

– What is communicated– How is communicated– What it is communicated

Elements of a protocol are 1- Syntax : structure or format of the data ( order they presented) example : first eight bits is address of sender

second eight address of receiverrest message.

PROTOCOLSPROTOCOLS

2- Semantics : meaning of each section of bits.– How is a particular pattern to be interpreted– What action to be taken based on the interpretation?

Ex : does an address identify route or final destination

3- Timing : identify when data should be sent and how fast they can be sent.

EX: Overloaded and lost if sender 100 Mbps and receiver at 1 Mbps

STANDARDSSTANDARDS

– Essential in creating and maintaining an open and competitive market for equipment manufactures

– Guaranteeing national and international interoperability of data and telecommunication technology and processes

Data communication standards are:

1. De facto standards : (by fact) approved by widespread use

De Jure standards : approved by officially recognized body.

STANDARDSSTANDARDSStandards Organizations developed by: Standard Creation Committees

– (ISO) International Organization for Standardization– (ITU-T) International Telecommunication Union – Telecommunication

Standards Sector– (ANSI) American National Standards Institute – (IEEE) Institute of Electrical and Electronics Engineers– (EIA) Electronic Industries Association

Forums– Created by special-interest groups– Present their conclusions to the standards bodies

Regulatory Agencies– Protect the public by regulating radio, television and wire/cable

communications (FCC – Federal Communications Commission

STANDARDSSTANDARDS

Internet Standards Tested specification that is useful to be adhered by who use the

Internet Formalized regulation the must be followed Specification become Internet standard

– Begins as Internet draft for 6 months– Upon the recommendation from the Internet authorities draft published as

(RFC) Request for Comment

رقم المادة : cs416 شعبـــــــة : sb spring 2008 spring 2008 الوقت : 8-9...

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