Basic Communications Overview of communication technology.

Communications Electronically exchanging data or information. zVoice interactive communication zData large volume batch transmissions zImage encoded graphics zVideo streaming media

Telecommunications History zPre 1984 Local and long distance monopoly z1984 AT&T settlement Intense long distance competition z1996 Telecommunications Act Local access competition

Digital Standard Telephone System Analog Network Analog Digital Modem Switch Digital Switch Network

Telephone Changes zRapidly decreasing long distance rates zValue added telephone services zCellular access zFlat rate long distance? zData and voice convergence.

Issue: Access zDedicated lines zStandard voice zIntegrated Services Digital Network zDigital Subscriber Lines zCable Modem zWireless

Voice vs. Data Voice zDelay Sensitive zConstant bit rate zNot error sensitive zGrowth stable (video ??) Data z Delay insensitive z Variable bit rate z Error sensitive z Demand growing

Data Networks NIC LAN Public TELCO WAN POP Switch Router Campus or Metropolitan Area

Application Presentation Session Transport Network Data Link Physical ©”A Guide to Networking Essentials”, 1998, Course Technology. OSI Reference Model Program Functions Wide Area Network Functions LAN Functions Connection Functions

Packet Structure Header(s) Data PayloadTrailer

LAN Operating Protocols (layer 2) zEthernet open standard, cheap, most common zToken Ring IBM proprietary, high quality, expensive zOthers

Network Interface Cards zBuild, send out and accept frames zUsually a daughter board on PC zMust match LAN and CPU zRequire drivers to operate

Network Interface Cards (NIC)

Ethernet Carrier Sense Multiple Access/Collision Detection Header BodyTrailer Listen before transmit Contention access Retransmit on collision

Network Routing Protocols for internetworking.

Two major types zPacket switching (or datagram) yUsually layers 3 and 4 zCircuit switching yUsually layers 1 and/or 2

Packet switching or Datagram Protocols zBest effort zFrames take individual routes zPacket assembly devices needed zError Control zTraffic Management yBuffering yDiscard

Datagram Logic (IP) Packet n Packet 1Packet PAD

IP zBest Effort zAddressing zVariable packet lengths (1500 bytes or less) zIPv4 vs IPv6 zFrame and Header

TCP and UDP Transmission Control Protocol zConnection oriented Assures that packets arrive in order and that they are correct. User Datagram Protocol z Connectionless Sends packets out without confirming that they arrive

Ethernet/TCP/IP Header Structure

Circuit Protocols zAll packets take the same route zNo packet assembly device to reorder packets zNormally layer 2 connection zMay be permanent or switched zAllow guaranteed service quality levels zMay be used to carry datagram protocols

Circuit Logic Source Destination Setup Message & ACK’s Teardown

Inter- networking

Technologies Common WAN technologies.

ISDN Circuit Switched Data and Voice Service

Digital Subscriber Lines DSL uses packet switching technology that operates independent of the voice telephone system, allowing the telephone companies to provide the service and not lock up circuits for long calls.

WAN Costs zCircuit Charges zCommitted Bandwidth zPeak Bandwidth zDiscard Priority zLatency

Representative Prices per MB of traffic (Qwest, Dec. 98) zFrame Relay Non-discard eligible4 cents Discard eligible3 cents zATM Constant bit rate2 cents Variable bit rate (real-time)1.2 cents Variable bit rate (non real-time).75 cents Available bit rate.55 cents Unspecified bit rate.4 cents

Representative Prices per port (Qwest, Dec. 98) z56 Kb Frame Relay$190 zT-1 Frame Relay$1,595 zT-3 Frame Relay$3,190

Client/Server Architecture An architecture in which the client (personal computer or workstation) is the requesting machine and the server is the supplying machine, both of which are connected via a network.

Client/Server Architectures SERVER PROCESSING CLIENT PROCESSING CENTRALIZEDSTAND-ALONE FAT SERVER FAT CLIENT

Client/Server zScalability zInteroperability zUser buy-in zIncreased cost zMulti-tier

One Tier System

Two Tier Client/Server

Three Tier Client/Server

Application Issues zInteroperability (e.g. ODBC) zOS support zMulti-threaded or single threaded zNetwork impact (e.g. chattiness) zQoS demands zDelivery: centralized, clien/server, web

Application Management zStandards ySupported yAccepted yProhibited zVersion Control and Distribution zLicense Management zVirus detection and inoculation