Protocol stack
The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. Some of these terms are used interchangeably but strictly speaking, the suite is the definition of the communication protocols, and the stack is the software implementation of them.[1]
Individual protocols within a suite are often designed with a single purpose in mind. This modularization simplifies design and evaluation. 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 interaction with the communications hardware. Each higher layer adds additional capabilities. User applications usually deal only with the topmost layers.[2]
Examples
| Protocol | Layer |
|---|---|
| HTTP | Application |
| TCP | Transport |
| IP | Internet or network |
| Ethernet | Link or data link |
| IEEE 802.3ab | Physical |
Spanning layer
An important feature of many communities of interoperability based on a common protocol stack is a spanning layer, a term coined by David Clark[3]
Certain protocols are designed with the specific purpose of bridging differences at the lower layers, so that common agreements are not required there. Instead, the layer provides the definitions that permit translation to occur between a range of services or technologies used below. Thus, in somewhat abstract terms, at and above such a layer common standards contribute to interoperation, while below the layer translation is used. Such a layer is called a spanning layer in this paper. As a practical matter, real interoperation is achieved by the definition and use of effective spanning layers. But there are many different ways that a spanning layer can be crafted.
In the Internet protocol stack, the Internet Protocol Suite constitutes a spanning layer that defines a best-effort service for global routing of datagrams at Layer 3. The Internet is the community of interoperation based on this spanning layer.
See also
- Cross-layer optimization
- DECnet
- Hierarchical internetworking model
- Protocol Wars
- Recursive Internetwork Architecture
- Service layer
- Signalling System No. 7
- Systems Network Architecture
- Wireless Application Protocol
- X.25
References
- ^ "What is a protocol stack?". WEBOPEDIA. 24 September 1997. Retrieved 2010-02-21.
A [protocol stack is a] set of network protocol layers that work together. The OSI Reference Model that defines seven protocol layers is often called a stack, as is the set of TCP/IP protocols that define communication over the Internet.
- ^ Georg N. Strauß (2010-01-09). "The OSI Model, Part 10. The Application Layer". Ika-Reutte. Archived from the original on 2012-03-20. Retrieved 2010-02-21.
The Application layer is the topmost layer of the OSI model, and it provides services that directly support user applications, such as database access, e-mail, and file transfers.
- ^ David Clark (1997). Interoperation, Open Interfaces, and Protocol Architecture. National Research Council. ISBN 9780309060363.
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