Protocol stack - Citizendia

A protocol stack (sometimes communications stack) is a particular software implementation of a computer networking protocol suite. A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics The terms are often used interchangeably. Strictly speaking, the suite is the definition of the protocols, and the stack is the software implementation of them.

Individual protocols within a suite are often designed with a single purpose in mind. In computing, a protocol is a convention or standard that controls or enables the connection Communication, and Data transfer between two computing This modularization makes design and evaluation easier. Modular programming is a software design technique that increases the extent to which software is composed from separate parts called modules Because each protocol module usually communicates with two others, they are commonly imagined as layers in a stack of protocols. The lowest protocol always deals with "low-level", physical interaction of the hardware. Every higher layer adds more features. User applications usually deal only with the topmost layers (See also OSI model). The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol

In practical implementation, protocol stacks are often divided into three major sections: media, transport, and applications. A particular operating system or platform will often have two well-defined software interfaces: one between the media and transport layers, and one between the transport layers and applications. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination

The media-to-transport interface defines how transport protocol software makes use of particular media and hardware types ("card drivers"). For example, this interface level would define how TCP/IP transport software would talk to Ethernet hardware. The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs Examples of these interfaces include ODI and NDIS in the Microsoft Windows and DOS environment. The Open Data-Link Interface ( ODI) developed by Apple and Novell, serves the same function as Microsoft and 3COM's Network Driver Interface Specification The Network Driver Interface Specification ( NDIS) is an Application programming interface (API for Network interface cards (NICs Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. DOS, short for "Disk Operating System" is a shorthand term for several closely related Operating systems that dominated the IBM PC compatible market

The application-to-transport interface defines how application programs make use of the transport layers. For example, this interface level would define how a web browser program would talk to TCP/IP transport software. A web browser is a software application which enables a user to display and interact with text images videos music games and other information typically located on a Examples of these interfaces include Berkeley sockets and System V streams in the Unix world, and Winsock in the Microsoft world. The Berkeley sockets Application programming interface (API comprises a library for developing applications in the C programming language that perform Unix System V, commonly abbreviated SysV (and usually pronounced though rarely written as System 5 was one of the versions of the Unix Operating system Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer In computing, the Windows Sockets API, which was later shortened to Winsock, is a technical specification that defines how Windows network

General protocol suite description

  T ~ ~ ~ T
 [A]     [B]_____[C]

Imagine three computers: A, B, and C. A and B both have radio equipment, and can communicate via the airwaves using a suitable network protocol (such as IEEE 802.11. IEEE 80211 is a set of standards for wireless local area network (WLAN computer communication developed by the IEEE LAN/MAN Standards Committee ( IEEE 802 ) B and C are connected via a cable, using it to exchange data (again, with the help of a protocol, for example Ethernet). However, neither of these two protocols will be able to transport information from A to C, because these computers are conceptually on different networks. One, therefore, needs an inter-network protocol to "connect" them.

One could combine the two protocols to form a powerful third, mastering both cable and wireless transmission, but a different super-protocol would be needed for each possible combination of protocols. It is easier to leave the base protocols alone, and design a protocol that can work on top of any of them (the Internet Protocol is an example. The Internet Protocol ( IP) is a protocol used for communicating data across a Packet-switched Internetwork using the Internet Protocol ) This will make two stacks of two protocols each. The inter-network protocol will communicate with each of the base protocol in their simpler language; the base protocols will not talk directly to each other.

A request on computer A to send a chunk of data to C is taken by the upper protocol, which (through whatever means) knows that C is reachable through B. It, therefore, instructs the wireless protocol to transmit the data packet to B. On this computer, the lower layer handlers will pass the packet up to the inter-network protocol, which, on recognizing that B is not the final destination, will again invoke lower-level functions. This time, the cable protocol is used to send the data to C. There, the received packet is again passed to the upper protocol, which (with C being the destination) will pass it on to a higher protocol or application on C. Often an even higher-level protocol will sit on top, and incur further processing.

An example protocol stack and the corresponding layers:

+- - - - - -+       +- - - - - -+
| HTTP      |       |Application|
+- - - - - -+       +- - - - - -+
| TCP       |       | Transport |
+- - - - - -+       +- - - - - -+
| IP        |       | Network   |
+- - - - - -+       +- - - - - -+
| Ethernet  |       | Link      |
+- - - - - -+       +- - - - - -+
| RJ45/CAT5 |       | Physical  |
+- - - - - -+       +- - - - - -+