Data Communications & Networking: Introduction and Network Components, Exercises of Computer Science

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Data Communications & Networking Data Communications & Networking

Chapter 1 Chapter 1

Introduction Introduction

Why Study Why Study Data Communication &Data Communication & Networking? Networking?  (^) Because Data Communication & Networking are changing the way we do business and the way we live

Require immediate access to accurate information

Database, online shopping

Enable long distance communication

Internet, IP phone

Access variable of information (text, voice and

image) Email, messenger, video conference

NetworksNetworks

 Network

 is a collection of computers and devices (Nodes) connected by

communications channels that facilitates communications among users and allows users to share resources with other users  (^) A node can be a computer, printer, or any other device can capable of sending and/or receiving data generated by other nodes on the network. Nodes attached to media through NICNIC (network interface card)

 Distributed Processing

Most network uses distributed processing , in which a task is divided among multiple computers. Instead of a single machine responsible for all aspects of a process, separate

Network ComponentsNetwork Components

 Software components

Communication Protocols

Network Operating System- NOS

peer-to-peer (Windows Xp,Win7) Client-server (Windows server 2003 وLinux)

 Hardware components

 Server

 Workstations

 Connecting Devices

 Cabling system

 Shared resource & peripherals

7 Protocols Protocols  (^) Protocols are set of rules that govern data communication to define What is communicated? How it communicated? When it is communicated?  (^) Key elements  (^) Syntax Structure or format of the data, meaning the order in which they are presented Example: A simple protocol might expect the first byte of data to be the address of the sender, the second byte to be the address of the receiver and the reset of the stream to be the message itself.  (^) Semantics Refers to the meaning of each section of bits. Example: does an address identify the route to be taken or the final destination of the message  (^) Timing When data to should be sent? How fast they can be sent? If a sender produces data at 100Mpbs but the receiver can process data at only 1Mpbs, transmission will overload the receiver and data will be largely lost

Standards Standards

 Standard

provides a model for development

allows for interoperability

Types

De jure/Formal legislated by an officially recognized body De facto Have been adopted as standers through widespread use Established by manufacturers that define the functionality of a new product or technology Standards Organizations  (^) International Organization for Standardization ( ISO )  (^) International Telecommunication Union Telecommunication standard sector ( ITU-T )  (^) American National Standards Institute ( ANSI )  (^) Institute of Electrical and Electronics Engineers ( IEEE )  (^) Electronic Industries Association ( EIA )

HistoryHistory of Internetof Internet

 (^) Experimental work was funded by the U.S. DoD Advanced Research Projects Agency (DARPA).  (^) The goal was to connect the major universities together to share computing resources for improving the cooperation of scientists in joint projects & publications.  (^) ARPA contracted with BBN Corp. (formerly Bolt, Beranek and Newman) to develop “ ARPAnet”. This was the first ever network that was developed by DoD.  (^) The first e-mail program was created in 1972. NSF created a CNET connecting the academic researchers together.  (^) In 1985 the defense withdraw from the network and it became funded by US National Science Foundation. The network was called NSFNET with linked many of the universities, Research labs, Libraries to access their super computers thus establishing the communication. The network grew very rapidly.  (^) It was turned over to private Internet Service Providers (ISP) in 1995.  (^) In early 90’es a new information service, www was developed at CERN by Timothy Berners-Lee. With the graphical browser it changed the whole picture as multimedia capabilities became possible.  (^) Finally giving rise to INTERNET connecting millions of computers together

Effectiveness of data communication depends Effectiveness of data communication depends on on

 Delivery

 System must deliver data to correct destination.

Data must be received by only intended device or user.

 Accuracy

 Data delivered accurately

 Altered data which left uncorrected are unusable.

 Timeliness

 Data delivered in timely manner without delay (real-time)

 Jitter

 variation in packet arrival time, It is the uneven delay

in the delivery of audio or video packets

Passive HubPassive Hub

 Passive hub is just a connector.

 In a star-topology Ethernet LAN, it is just a

point where signals coming from different stations collide.

 The hub is the collision point.

 This type of hub is part of the media

 its location in the Internet model is below the

physical layer.

RepeatersRepeaters

 Operates only in the physical layers

 Can extend the physical length of a LAN

 Receive the signal before it becomes too weak or

corrupted and regenerates the original bit pattern

 Do not actually connect two LANs

 connects two segments of the same LAN

 Segments connected are still part of one single LAN

 A repeater cannot connect two LANs of different

protocols

Active HubsActive Hubs

 Actually a multiport repeater

 Used to create connections between stations in

a physical star topology

 Can also be used to create tree topology to

removes the length limitation of 10Base -T ( m)

ExampleExample

 repeater can overcome 10Base5 Ethernet length

restriction the length of the cable is limited to 500 m divide the cable into (500 m) sections and connect them with repeaters The whole network is still considered one LAN Portions of the network separated by repeaters are called segments Repeaters acts as two-port node and has no filtering capability

BridgeBridge

 Bridge has a table to  (^) Maps address to ports.  (^) Used in filtering decisions

Connecting DevicesConnecting Devices

Network Interface cards Network Interface cards