OSI Reference Model Data Communication by Ravinder Nath Rajotiya - September 28, 20210 OSI Reference Model This model is based on a proposal by ISO revised in 1995. The model is called the ISO-OSI(open System Interconnection) as it deals with connecting open systems – that is systems that are open for communication with others. The principles that were applied to arrive at the seven layers can be briefly summarised as: A layers should be created where a different abstraction is needed Each layer should perform a well-defined function The function of each layer should be chosen with an eye toward defining internationally standardised protocols The layer boundaries should be chosen to minimize information flows across the interfaces The number of layers should be large enough that distinct function need not be thrown together in the
Data Communications : Components, Protocols Components Data Communication by Ravinder Nath Rajotiya - September 28, 2021September 28, 20210 Data Communications : Components, protocols Components Outcome : Audience will be able to i. differentiate between data and information ii. To name various components of a communication system iii. To describe the characteristics of the effective communication iv. To differentiate between protocol and standard v. To know various standards organization Data Data is considered to be raw data. It represents ‘values of qualitative or quantitative variables, belonging to a set of items.’ It may be in the form of numbers, letters, or a set of characters. Data is often collected via measurements. In data computing or data processing, data is represented by in a structure, such as tabular data, data tree, a data graph, etc. Categories of Data Data can be analog data or digital data- analog data refers
Service Primitive Data Communication by Ravinder Nath Rajotiya - May 10, 20210 Service Primitive The way in which a layer provide service is by mean of primitive. A service is formally specified by a set of primitives (operations) available to user processes to access the services. These primitives tell the services to perform some action or report on an action taken by a peer entity. Some of the primitives are: Primitive Meaning LISTEN Block waiting for an incoming connection CONNECT Establish a connection with a waiting peer ACCEPT Accept an incoming connection from a peer RECEIVE Block waiting for an incoming message SEND Send a message to the peer DISCONNECT Terminate a connection
Client-Server Communication Data Communication by Ravinder Nath Rajotiya - May 10, 2021May 10, 20210 A simple conversation between client-server is shown in the following figure 2.3
Encapsulation Data Communication by Ravinder Nath Rajotiya - May 10, 20210 Encapsulation – through the use of PDU (protocol data unit) which encapsulates data by adding a header at each layer.