M. R. Kharazmi Chapter 1 Data Communications and Networks Overview

Book Computer Networking:A Top Down Approach Featuring the Internet, 3nd edition. Jim Kurose, Keith Ross Addison-Wesley, July Communications and Networking, 3rd edition, Behrouz A Forouzan, McGraw-Hill. ISBN Course Material

Information and Data Information—many meanings Information is: -the necessary property of a message, it includes something to be communicated from the sender to the receiver - any represented pattern -any type of sensory input - Any type of pattern that influences the formation or transformation of other patterns Data Representation of information Symbols with a certain syntax

Communication Sharing or transfer of information “Telecommunication” Communication at a distance Traditionally speach Sound, pictures, text,... “Communications” “The branch of technology concerned with the representation, transfer, interpretation, and processing of data among persons, places, and machines also known as information systems.” ”Data communications” ” the exchange of data between two devices over some form of transmission medium”

A Communications Model Source generates data to be transmitted Transmitter Converts data into transmittable signals Transmission System Carries data Receiver Converts received signal into data Destination Takes incoming data

Communications Tasks Transmission system utilizationAddressing InterfacingRouting Signal generationRecovery SynchronizationMessage formatting Exchange managementSecurity Error detection and correctionNetwork management Flow control

Communications Tasks Ways to transfer information on a link Signal format Addressing Identify sender and receiver Routing Find a path between sender and receiver Buffering Compensate for differences in speed Variations in traffic load Error detection and control If data is lost or corrupted Congestion control To protect the network from being overloaded Management and network operations

Signals

Sine Wave

Time and Frequency Domains

Composite Signals

Fourier Analysis Any composite signal can be represented as a sum of simple sine waves

Bandwidth Important property of a medium Difference between highest and lowest frequency that can pass through the medium Measured in Hertz [Hz] Limits the channel’s capaci

Simplified Communications Model - Diagram

Simplified Data Communications Model

Requirements on Communication

Connectivity

Point-to-point Connections

Multipoint Connection

Networking Aset of nodes connected by links Hosts, switches, routers, stations, Need devices between sender and receiver Signals regeneration and amplification Different equipment, formats, etc Sharing of links Routing, addressing, traffic control,... Links form a topology Distributed processing Tasks are divided among multiple units (computers)

Physical Topologies

Mesh Topology

Star Topology All links to a central node (hub) Common office installation today Advantages Less costly than mesh Easy to install and maintain Disadvantages Hub is single point of failure One cable from each node to hub

Bus Topology

Network Types Classification depends on: Ownership Size and distance Physical architecture

Local Area Networks (LANs)

Metropolitan Area Network (MAN)

Wide Area Networks Large geographical area Crossing public rights of way Rely in part on common carrier circuits Alternative technologies Circuit switching Packet switching Frame relay Asynchronous Transfer Mode (ATM)

Kurose CH.1

Circuit Switching Dedicated communications path established for the duration of the conversation e.g. telephone network

Packet Switching Data sent out of sequence Small chunks (packets) of data at a time Packets passed from node to node between source and destination Used for terminal to computer and computer to computer communications

Frame Relay Packet switching systems have large overheads to compensate for errors Modern systems are more reliable Errors can be caught in end system Most overhead for error control is stripped out

Asynchronous Transfer Mode ATM Evolution of frame relay Little overhead for error control Fixed packet (called cell) length Anything from 10Mbps to Gbps Constant data rate using packet switching technique

Local Area Networks Smaller scope Building or small campus Usually owned by same organization as attached devices Data rates much higher Usually broadcast systems Now some switched systems and ATM are being introduced

LAN Configurations Switched Switched Ethernet May be single or multiple switches ATM LAN Fibre Channel Wireless Mobility Ease of installation

Metropolitan Area Networks MAN Middle ground between LAN and WAN Private or public network High speed Large area

Networking Configuration