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Data Communications and Networks
Engr. Abdul‐Rahman MahmoodMS, MCP, QMR(ISO9001:2000)
Usman Institute of Technology – University Road KarachiUsman Institute of Technology University Road, [email protected] [email protected] alphapeeler.sf.net/pubkeys/pkey.htm http://alphapeeler.sourceforge.netpk.linkedin.com/in/armahmood http://alphapeeler.tumblr.comp p p pwww.twitter.com/alphapeeler [email protected] www.facebook.com/alphapeeler [email protected]‐sss alphasecure mahmood_cubix [email protected] [email protected]
VC++, VB, ASP
Introduction
DefinitionsThe scope of this course is broad, covering three general areas:
d i i datacommunications, networking, and protocols;protocols;
Data communications deals with the transmission of signals in a reliable and efficient manner.gNetworking deals with the technology and architecture of the communications networks used to interconnect communicating devices.
DefinitionsThis field is generally divided into the topics of local area networks : (LANs) and (WANs).
f h fi ld f 1970s ‐ 1980s : merger of the fields of computer science and data communications:
There is no fundamental difference between data There is no fundamental difference between data processing (computers) and data communications (transmission and switching equipment).There are no fundamental differences among data, voice, and video communicationsThe distinction among single processor computer The distinction among single‐processor computer, multiprocessor computer, local network, metropolitan network, and long‐haul network has blurred
Trendse dsTraffic growth, development of new services, and advances in technology.Service vs throughput rates:
A Communications ModelSource
generates data to be transmittedTransmitter
Converts data into transmittable signalsT i i STransmission System
Carries dataReceiverReceiver
Converts received signal into dataDestinationDestination
Takes incoming data
Simplified Communications M d l DiModel ‐ Diagram
Key Communications TasksTransmission System Utilization (Congestion control)Interfacing (device with comm. sys)Signal Generation (form, intensity, interpretable at the receiver)Signal Generation (form, intensity, interpretable at the receiver)Synchronization (b/t receiver and transmitter)Exchange ManagementE d t ti d tiError detection and correctionFlow controlAddressing and routingRecoveryMessage formattingSecuritySecurityNetwork Management
Simplified Data pCommunications Model
NetworkingPoint to point communication not usually practical
Devices are too far apartLarge set of devices would need impractical number of connections
Solution is a communications networkSolution is a communications network
Simplified Network Model
Wide Area NetworksLarge geographical areaCrossing public rights of wayRely in part on common carrier circuitsAlternative technologies
Circuit switchingPacket switchingF lFrame relayAsynchronous Transfer Mode (ATM)
Circuit SwitchingDedicated communications path established for the duration of the conversation
l h ke.g. telephone network
Packet Switchingac et S tc gData sent out of sequenceSmall chunks (packets) of data at a timeSmall chunks (packets) of data at a timePackets passed from node to node between source and destinationUsed for terminal to computer and computer to computer communications
Frame RelayPacket switching systems have large overheads to compensate for errorsM d li blModern systems are more reliableErrors can be caught in end systemM h d f l i i d Most overhead for error control is stripped outFrame Relay is a standardized wide area network technology that specifies the physical and network technology that specifies the physical and logical link layers of digital telecommunications channels using a packet switching methodology.Uses variable length packets called frames
Asynchronous Transfer ModeATM : sometimes referred to as cell relay, is a culmination of developments in circuit switching and packet switching.Evolution of frame relayEvolution of frame relayLittle overhead for error controlframe relay uses variable‐length packets, called frame relay uses variable length packets, called frames, and ATM uses fixed‐length packets, called cells.
f d f b d h bRange of 10s and 100s of Mbps, and in the Gbps range.Constant data rate using packet switching technique. ATM can also be viewed as an evolution from circuit switching can also be viewed as an evolution from circuit switching. With circuit switching, only fixed‐data‐rate circuits are available to the end system.
Integrated Services Digital g gNetwork
Integrated Services Digital Network (ISDN) is a set of communications standards for simultaneous digital transmission of voice video data and other networktransmission of voice, video, data, and other network.Designed to replace public telecom systemWide variety of servicesWide variety of servicesEntirely digital domain
Local Area NetworksSmaller scope
Building or small campusUsually owned by same organization as attached devicesD t t h hi hData rates much higherUsually broadcast systemsNow some switched systems and ATM are being Now some switched systems and ATM are being introduced
THE INTERNETARPANET, which was developed in 1969 by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defenseof Defense.It was the first operational packet‐switching network.ARPANET began operations in four locations.g pToday the number of hosts is in the hundreds of millions, the number of users in the billions, and the number of
t i ti i ti i countries participating nearing 200.TCP : Vint Cerf and Bob Kahn ‐May of 1974TCP/IP protocol suite This provided the foundation for TCP/IP protocol suite. This provided the foundation for the Internet.
Key Elements of the Internety
Key Elements of the InternetThe purpose of the Internet, of course, is to interconnect end systems, called hosts;Network routers WAN LAN IP datagrams or IP packets Network, routers, WAN, LAN, IP datagrams or IP packets, IP address.LANs are connected to an Internet service provider (ISP) p ( )through a point of presence (POP).The connection is made in a series of steps starting with th t i i t (CPE) Th CPE i the customer premises equipment (CPE). The CPE is the communications equipment located onsite with the host.For home users, the CPE is a 56‐kbps modem, DSL, cable modem, and satellite
