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Individual protocols within a suite are often designed with a single purpose in mind. This modularisation makes design and evaluation easier. 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 habitually deal only with the topmost layers. See also OSI model.
In practical implementation, protocol stacks are often divided into three major sections for 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.
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. Examples of these interfaces include ODI and NDIS in the Microsoft Windows and DOS world.
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. Examples of these interfaces include Berkeley sockets and System V streams in the Unix world, and WinsockIn computing, Winsock (also Windows Sockets is a specification that defines how Windows network software should access network services, especially TCP/IP. Winsock intends to provide a single API to which both application developers and network software v in the Microsoft world.
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 like IEEE 802.11IEEE 802. 11 or Wi-Fi denotes a set of Wireless LAN standards developed by working group 11 of IEEE 802. The term is also used specifically for the original version; to avoid confusion that is sometimes called "802. 11 family currently includes three sepa. B and C are connected via a cable, exchanging data over that - 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 our two protocols to form a powerful third mastering both cable and wireless transmission, but we would need a different super-protocol 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 ProtocolThe Internet Protocol IP is a data-oriented protocol used by source and destination hosts for communicating data across a packet-switched internetwork. Data in an IP internetwork are sent in blocks referred to as packets or datagrams (the terms are basica is an example). 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. Often an even higher-level protocol will sit on top, and incur further processing.
A commonly used protocol stack looks like this:
+- - - - - -+ | HTTPHTTP (for HyperText Transfer Protocol is the primary method used to convey information on the World Wide Web. The original purpose was to provide a way to publish and receive HTML pages. Development of HTTP was co-ordinated by the World Wide Web Consortiu | +- - - - - -+ | TCPTransmission Control Protocol (TCP is a connection-oriented, reliable delivery byte-stream transport layer communication protocol, currently documented in IETF RFC 793. It does the task of the transport layer in the simplified OSI model of computer networ | +- - - - - -+ | IPThe Internet Protocol IP is a data-oriented protocol used by source and destination hosts for communicating data across a packet-switched internetwork. Data in an IP internetwork are sent in blocks referred to as packets or datagrams (the terms are basica | +- - - - - -+ | Ethernet | +- - - - - -+
See also: Network protocol design principlesThe topic of this entry is to describe the design principles which had been applied for specifying network protocols. The entry needs rework and has been moved here from Systems engineering. Protocol Layering In modern protocol design, protocols are "laye
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