The two, OSI and TCP/IP are Standardized Protocol Architectures developed specifically for: 1.
Devices to communicate
Vendors to have more marketable products
Customers to insist on standards based equipment
The OSI is a reference model whilst TCP/IP is the suite which is the most widely used. Description of Open Systems Interconnection (OSI Model)
Developed by the International Organization for Standardization (ISO) It is made up of seven layers and each layer:
performs a subset of the required communication functions 2.
relies on the next lower layer to perform more primitive functions 3.
provides services to the next higher layer
Changes in one layer should not require changes in other layers
The layers can be summarized as overleaf:
Concerned with transmission of unstructured bit stream over physical medium; deals with the mechanical, electrical, functional, and procedural characteristics to access the physical medium
Physical interface between devices 1.
Provides for the reliable transfer of information across the physical link; sends blocks (frames) with the necessary synchronisation, error control and flow control
Means of activating, maintaining and deactivating a reliable link Error detection and control
Higher layers may assume error free transmission
Provides upper layers with independence from the data transmission and switching technologies used to connect systems; responsible for establishing, maintaining and terminating connections
Transport of information Higher layers do not need to know about underlying technology Not needed on direct links
Provides reliable, transparent transfer of data between end points; provides end-to-end error recovery and flow control.
Exchange of data between end systems Error free
Quality of service
Provides the control structure for communication between applications; establishes, manages and terminates connections (sessions) between cooperating applications
Control of dialogues between applications Dialogue discipline
Provides independence to the application processes from differences in data representation (syntax)
Data formats and coding Data compression
Provides access to the OSI environment for users and also provides distributed information services
Means for applications to access OSI environment
Description of TCP/IP Architecture
The Internet Protocol Suite also known as TCP/IP is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard. IP networking represents a synthesis of several developments that began to evolve in the 1960s and 1970s, namely the Internet and LANs (Local Area Networks), which emerged in the mid- to late-1980s, together with the advent of the World Wide Web in early 1990s. The Internet Protocol Suite, like many protocol suites, may be viewed as a set of layers. Each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted.
TCP/IP architecture does not have an official controlling body but is a defacto model widely used. It is made up of 4 or 5 layers namely: Layer
Physical interface between data transmission device (e.g. computer) and transmission medium or network •
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