Ipt Communications Notes

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Communication Systems
Overview:
* Characteristics of communication systems
* Examples of communication systems
* Transmitting and receiving in communication systems
* Other information processes in communication systems
* Issues related to communication systems
Characteristics of a Communication System
* Enables people to send and receive data and information * We use communication systems every day
* Facebook chat: Words/Characters; Wireless Internet; Various friends Text message: Words/Characters; Mobile Network Carrier; Single receiver Mailbox: Physical medium/Paper; Post office; I received the letter PSN: Words/Characters; Wireless Internet/Playstation Network; Single receiver * Must be a sender and receiver

* A protocol is a set of rules which governs the transfer of data between computers. Protocols allow communication between computers and networks * Handshaking is used to establish which protocols to use. Handshaking controls the flow of data between computers * Protocols will determine the speed of transmission, error checking method, size of bytes and whether synchronous or asynchronous * Examples of protocols are: TCP/IP, token ring, CSMA/CD

* Every communication system has 5 basic requirements:
* Data Source: where the data originated
* Transmitter: device used to transmit data
* Transmission Medium: Cable or non-cable
* Receiver: Device used to receive data
* Destination: where the data will be placed
* A protocol is a set of ruled that governs the transmission of data * Different rules are used for different purposes
* Whenever a communication system transfers data, the rules must first be checked * Both sender and receiver must use the same set of rules * Most communication protocols follow internationally accepted standards * One set of standards is the OSI (Open Standards interconnection) reference model * When using the OSI reference model are considered at different levels related to the structure * Modern computer network architecture is highly organised and structured into layers * Each layer has a particular role in the communication system for which it is responsible * The OSI reference model has different layers. They are: * Physical layer – refers to the electrical and physical aspects of devices * Data link layer – the method in which information from then network is broken down and transmitted over the physical layer * Network layer – ensures large files are transferred * Transport layer – ensures system reliability and quality * Session layer – creates and controls sessions between two computers * Presentation layer – programming languages are translated into machine language * Application layer- the user interaction layer where data turns into an application Handshaking

* The exchange in data communication of prearranged signals that defines a protocol between two computers. * Handshaking is used to establish the protocols for the transfer of data. * They must agree on the rules (hence the term ‘handshaking’) * The transmitter and receiver must ‘talk the same language’ * Handshaking occurs on 2 levels of the OSI reference model * Session level

* Opens the handshaking with a query about the readiness of the receiver. The receiver then responds with a query about what the transmitter wants to do. * Application level
* The software goes through the process of verifying the ID and password of the transmitter. * Handshaking is often referred to as flow control as it controls the flow of data. * Handshaking is usually controlled by software over long distance * There are two methods of handshaking used to control the flow of data * Hardware flow control

* Uses a dedicated connection
* Only practical when devices are close enough to be linked with a cable...
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