iPedia Free Information Center

Information about Routing Protocols

A routing protocol is a protocol that specifies how routers communicate with each other to disseminate information that allows them to select routes between any two nodes on a network. Typically, each router has a priori knowledge only of its immediate neighbors. A routing protocol shares this information so that routers have knowledge of the network topology at large. For a discussion of the concepts behind routing protocols, see: Routing.

The term routing protocol may refer more specifically to a protocol operating at Layer 3 of the OSI model which similarly disseminates topology information between routers.

Many routing protocols used in the public Internet are defined in documents called RFCs.[1][2][3][4]

Routed versus routing protocols

Confusion often arises between routing protocols and routed protocols. While routing protocols help the router in the decision-making on which paths to send traffic, routed protocols are responsible for the actual transfer of traffic between L3 devices.[5] Specifically, a routed protocol is any network protocol that provides enough information in its network layer address to allow a packet to be forwarded from one host to another host based on the addressing scheme, without knowing the entire path from source to destination. Routed protocols define the format and use of the fields within a packet. Packets generally are conveyed from end system to end system. Almost all layer 3 protocols and those that are layered over them are routable, with IP being an example. Layer 2 protocols such as Ethernet are necessarily non-routable protocols, since they contain only a link-layer address, which is insufficient for routing: some higher-level protocols based directly on these without the addition of a network layer address, such as NetBIOS, are also non-routable.

In some cases, routing protocols can themselves run over routed protocols: for example, BGP runs over TCP: care is taken in the implementation of such systems not to create a circular dependency between the routing and routed protocols. That a routing protocol runs over particular transport mechanism does not mean that the routing protocol is of layer (N+1) if the transport mechanism is of layer (N). Routing protocols, according to the OSI Routeing[sic] framework, are layer management protocols for the network layer, regardless of their transport mechanism:
  • IS-IS runs over the data link layer
  • OSPF, IGRP, and EIGRP run directly over IP; OSPF and EIGRP have their own reliable transmission mechanism while IGRP assumed an unreliable transport
  • RIP runs over UDP
  • BGP runs over TCP

Examples

Ad hoc network routing protocols

Ad hoc network routing protocols appear in networks with no or little infrastructure.

Interior routing protocols

Interior Gateway Protocols (IGPs) exchange routing information within a single routing domain. A given autonomous system [6] can contain multiple routing domains, or a set of routing domains can be coordinated without being an Internet-participating autonomous system. Common examples include:
  • IGRP (Interior Gateway Routing Protocol)
  • EIGRP (Enhanced Interior Gateway Routing Protocol)
  • OSPF (Open Shortest Path First)
  • RIP (Routing Information Protocol)
  • IS-IS (Intermediate System to Intermediate System)
Note that IGRP, a Cisco proprietary routing protocol, is no longer supported. EIGRP accepts IGRP configuration commands, but the internals of IGRP and EIGRP are completely different.

Exterior routing protocols

Exterior Gateway Protocols (EGPs) route between separate autonomous systems. Examples include:
  • EGP (the original Exterior Gateway Protocol used to connect to the former Internet backbone network; now obsolete)
  • BGP (Border Gateway Protocol: the current version, BGPv4, dates from around 1995)
  • CSPF (Constrained Shortest Path First)

References

protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication.
..... Click the link for more information.
router is a device that extracts the destination of a packet it receives, selects the best path to that destination, and forwards data packets to the next device along this path.[1] They connect networks together; a LAN to a WAN for example, to access the Internet.
..... Click the link for more information.
A node is a device that is connected as part of a computer network. For example, a node may be a computer, personal digital assistant, cell phone, router, switch, or hub.
..... Click the link for more information.
In general, the term network can refer to any interconnected group or system. Several different types of networks exist, including:

Human network

  • Business network
  • Economic network
  • Entrepreneurial network
  • Old boy network
  • Sexual network

..... Click the link for more information.
Routing (or routeing) is the process of selecting paths in a network along which to send data or physical traffic. Routing is performed for many kinds of networks, including the telephone network, the Internet, and transport networks.
..... Click the link for more information.
Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection (OSI) initiative.
..... Click the link for more information.
Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government
..... Click the link for more information.
Request for Comments (RFC) documents are a series of memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies.
..... Click the link for more information.
protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication.
..... Click the link for more information.
network layer is the third layer out of seven in OSI model and the third layer out of five in TCP/IP model. In the TCP/IP reference model it is called the Internet layer.
..... Click the link for more information.
network layer is the third layer out of seven in OSI model and the third layer out of five in TCP/IP model. In the TCP/IP reference model it is called the Internet layer.
..... Click the link for more information.
Internet protocol may refer to:
  • The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
  • The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs

..... Click the link for more information.
data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. It responds to service requests from the network layer and issues service requests to the physical layer.
..... Click the link for more information.
Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the physical layer, through means of network access at the Media
..... Click the link for more information.
NetBIOS is an acronym for Network Basic Input/Output System. The NetBIOS API allows applications on separate computers to communicate over a local area network. In modern networks, it normally runs over TCP/IP (NBT), giving each computer in the network both a NetBIOS name
..... Click the link for more information.
The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. It works by maintaining a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). It is described as a path vector protocol.
..... Click the link for more information.
The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. TCP provides reliable, in-order delivery of a stream of bytes, making it suitable for applications like file transfer and e-mail.
..... Click the link for more information.
Intermediate system to intermediate system (IS-IS), is a protocol used by network devices (routers) to determine the best way to forward datagrams or packets through a packet-based network, a process called routing.
..... Click the link for more information.
A wireless ad-hoc network is a computer network in which the communication links are wireless. The network is ad hoc because each node is willing to forward data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network
..... Click the link for more information.
An Ad hoc routing protocol is a convention or standard that controls how nodes come to agree which way to route packets between computing devices in a mobile ad-hoc network (MANET).
..... Click the link for more information.
In the original definition and obsolete definition of the Border Gateway Protocol, Version 1[1], it was assumed that "A consistent view of the interior routes of the autonomous system is provided by the intra-AS routing protocol.
..... Click the link for more information.
In the Internet, an autonomous system (AS) is a collection of IP networks and routers under the control of one entity (or sometimes more) that presents a common routing policy to the Internet. See RFC 1930 for additional detail on this updated definition.
..... Click the link for more information.
Interior Gateway Routing Protocol (IGRP) is a kind of IGP which is a distance-vector routing protocol invented by Cisco, used by routers to exchange routing data within an autonomous system.

IGRP is a proprietary protocol.
..... Click the link for more information.
Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary routing protocol loosely based on their original IGRP. EIGRP is an advanced hybrid routing protocol, with optimizations to minimize both the routing instability incurred after topology changes, as well
..... Click the link for more information.
The Open Shortest Path First (OSPF) protocol is a hierarchical interior gateway protocol (IGP) for routing in Internet Protocol, using a link-state in the individual areas that make up the hierarchy.
..... Click the link for more information.
Routing Information Protocol (RIP) was one of the most commonly used interior gateway protocol (IGP) routing protocols on internal networks (and to a lesser extent, networks connected to the Internet), which helps routers dynamically adapt to changes of network connections by
..... Click the link for more information.
Intermediate system to intermediate system (IS-IS), is a protocol used by network devices (routers) to determine the best way to forward datagrams or packets through a packet-based network, a process called routing.
..... Click the link for more information.
The Exterior Gateway Protocol (EGP) is a now obsolete routing protocol for the Internet originally specified in 1982 by Eric C. Rosen of Bolt, Beranek and Newman, and David L. Mills. It was first described in RFC 827 and formally specified in RFC 904 (1984).
..... Click the link for more information.
Internet backbone refers to the main "trunk" connections of the Internet. It is made up of a large collection of interconnected commercial, government, academic and other high-capacity data routes and core routers that carry data across the countries, continents and oceans of the
..... Click the link for more information.
The Border Gateway Protocol (BGP) is the core routing protocol of the Internet. It works by maintaining a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). It is described as a path vector protocol.
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter