Question

A protocol architecture, such as the TCP/IP architecture or OSI, provides a framework for standardization. Within such an architecture, the overall communications function is decomposed into a number of distinct layers with a special design principle used. What is this principle and how does it work? Describe in detail.

Answer 1

The TCP/IP or OSI or protocol architecture or model provides a framework for standardization with an overall communications functions decomposed into a number of distinct layers with a special design principle used.

Definition and description of the principle: The basic principle of this architecture is to ensure the independence of layers defining services provided by the lower layers to their immediate upper layers. This model has one or more protocol standards developed in each layer. This principle further defines the distinct functions performed at each layer and facilitates the standards-making process. The overall function of this protocol architecture is broken up into many modules, making interfaces between modules simpler.

Description of the way how this principle works:
Each layer in either the TCP/IP or OSI architecture, model, suite or protocol stack has its own distinct functions in the four and seven layers of TCP/IP and OSI model respectively.
In the older TCP/IP protocol architecture the four layers are- the Application, Transport (host-to-host), Internet, Network access, and Physical (optional or simply included in the Network access).
Whereas in the OSI protocol architecture the seven layers are Application, Presentation, Session, Transport, Network, Data Link, and Physical Layer. Each layer's functions are well defined, hence standards are developed independently and simultaneously for each layer. Also, the boundaries are well defined between the layers. Hence, the changes in the standards in one layer does not affect the software in another layer.

This architecture uses the design principle of information hiding or simply data abstraction making it seamless. Hence, the upper the layers the more they are independent of and enjoy the lower layers' functions being seamless. The lower layers are concerned about functions in greater detail. Each layer of one party (system) on one end (source machine) implements a protocol to the peer layer in other systems i.e., on the other end or at the destination.