Communications protocols

Communications protocol

A communications protocol defines the formats and rules for exchanging information via a network and typically comprises a complete protocol suite which describes the protocols used at various usage levels. An interesting feature of communications protocols is that they may be – and in fact very often are – stacked above each other, which means that one is used to carry the other. The example for this is HTTP running over TCP over IP over IEEE 802.11, where the second and third are members of the Internet Protocol Suite, while the last is a member of the Ethernet protocol suite. This is the stacking which exists between the wireless router and the home user's personal computer when surfing the World Wide Web.

Communication protocols have themselves various properties, such as whether they are connection-oriented versus connectionless, whether they use circuit mode or packet switching, or whether they use hierarchical or flat addressing.

There exist a multitude of communication protocols, a few of which are described below.

 

Ethernet

Ethernet is a family of connectionless protocols used in LANs, described by a set of standards together called IEEE 802 published by the Institute of Electrical and Electronics Engineers. It has a flat addressing scheme and is mostly situated at levels 1 and 2 of the OSI model. For home users today, the most well-known member of this protocol family is IEEE 802.11, otherwise known as Wireless LAN(WLAN). However, the complete protocol suite deals with a multitude of networking aspects not only for home use, but especially when the technology is deployed to support a diverse range of business needs. MAC bridging (IEEE 802.1D) deals with the routing of Ethernet packets using a Spanning Tree Protocol, IEEE 802.1Q describes V LANs, and IEEE 802.1X defines a port-based Network Access Control protocol which forms the basis for the authentication mechanisms used in V LANs, but also found in W LANs – it is what the home user sees when they have to enter a "wireless access key".

 

Internet Protocol Suite

The Internet Protocol Suite, often also called TCP/IP, is the foundation of all modern internetworking. It offers connection-less as well as connection-oriented services over an inherently unreliable network traversed by datagram transmission at the Internet protocol (IP) level. At its core, the protocol suite defines the addressing, identification, and routing specification in form of the traditional Internet Protocol Version 4 (IPv4) and IPv6, the next generation of the protocol with a much enlarged addressing capability.

 

Asynchronous Transfer Mode

Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous time-division multiplexing and encodes data into small, fixed-sized cells. This differs from other protocols such as the Internet Protocol Suite or Ethernet that use variable sized packets or frames. ATM has similarity with both circuit and packet switched networking. This makes it a good choice for a network that must handle both traditional high-throughput data traffic, and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins.

While the role of ATM is diminishing in favor of next-generation networks, it still plays a role in the last mile, which is the connection between an Internet service provider and the home user.