Communication Links Communication Link = Physical connection or Physical Medium Types: Wire Pair or Twisted Pair Coaxial Cable Fiber Optics Bandwidth, Optical Fiber, Light as medium, Low noise susceptibility as compared to others Micro Wave Transmission Satellite Transmission Transponder, Geosynchronous sat. orbits @ 22,300 miles

Microwave and satellite transmission Microwave and satellite transmission. (a) To relay microwave signals, dish-shaped antennas such as these are often located atop buildings, towers, and mountains. Microwave signals can follow a line-of-sight path only, so stations must relay this signal at regular intervals to avoid interference from the curvature of the earth. (b) In satellite transmission, a satellite acts as a relay station and can transmit data signals from one earth station to another. A signal is sent from an earth station to the relay satellite, which changes the signal frequency before transmitting it to the next earth station. Transponder

Mixing and Matching

Protocols Set of rules for the exchange of data between a terminal and a computer or between two computer or precommunication agreement about the form in which messages or data is to be sent and receipt acknowledged. two devices must be able to ask each other questions (Are you ready to receive a message? Did you get my last message? Is there trouble at your end?) and to keep each other informed

Standard Protocol software development can be a nightmare because different vendors use different protocols. Standards help Communications standards exist and are constantly evolving and being updated for new communications forms the most important protocol is the one that makes Internet universality possible called Transmission Control Protocol/ Internet Protocol (TCP/IP)

Network Topologies Physical Layout Node (any computer or component) Types Star Hub computer Message routed through hub computer Ring Unidirectional, one at a time Bus Possible collision, retry if collision

Kinds of Network WAN (wide area network) MAN (Metropolitan area network) Mainframe to PC connection Terminal emulation software Micro to mainframe Host computer File transfer software Download, Upload

Kinds of Network LAN (local area network) Physical Medium Twisted Pair, Co-Axial Cable, Fiber optics etc. Wireless (using infra-red or radio waves) – Easy to install and configure but slow and of short range. NIC (network interface card) The card contains circuitry that handles sending, receiving, and error checking of transmitted data.

Networking Components Bridge Similar networks can be connected by a bridge, a hardware/software combination that recognizes the messages on a network and passes on those addressed to nodes in other networks Router A router is a special computer that directs communications traffic when several networks are connected together. If traffic is clogged on one path, the router can determine an alternative path IP Switch IP used as Protocol routers are being replaced with IP switches, which are less expensive and, since no translation is needed, faster than routers

Networking Components Gateway A gateway is a collection of hardware and software resources that lets a node communicate with a computer on another dissimilar network The main task of Gateway is Protocol conversion

Types of LAN Client Server Peer to Peer Thin client: A computer that has no disk storage ability and is used basically to send input to the server for processing and then receive the output Peer to Peer All computers in a arrangement have equal status

LAN Protocols Ethernet Token Ring the network protocol that dominates the industry uses a high-speed network cable. Ethernet uses a bus topology and is inexpensive and relatively simple to set up. The transmission method used by Ethernet is know as: “carrier sense multiple access with collision detection” or CSMA/CD Token Ring Token needed Token Ring Uses Ring topology

Work of Networking Office Automation E-mail Fax (Facsimile) Groupware Teleconferencing Video conferencing EDI (electronic Data Interchange) Electronic Fund Transfer: Instant Banking ATM machines Telecommuting Online services Weather, news, online ordering of food, clothing etc.