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A routing protocol specifies how
routers communicate with each other to distribute information that enables them to select routes between
nodes
In general, a node is a localized swelling (a "knot") or a point of intersection (a Vertex (graph theory), vertex).
Node may refer to:
In mathematics
*Vertex (graph theory), a vertex in a mathematical graph
*Vertex (geometry), a point where two ...
on a
computer network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
. Routers perform the traffic directing functions on the Internet;
data packet
In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the '' payload''. Control inform ...
s are forwarded through the networks of the internet from router to router until they reach their destination computer.
Routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone netw ...
algorithms determine the specific choice of route. Each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the
topology of the network. The ability of routing protocols to dynamically adjust to changing conditions such as disabled connections and components and route data around obstructions is what gives the Internet its
fault tolerance
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...
and
high availability
High availability (HA) is a characteristic of a system which aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period.
Modernization has resulted in an increased reliance on these systems. F ...
.
The specific characteristics of routing protocols include the manner in which they avoid routing loops, the manner in which they select preferred routes, using information about hop costs, the time they require to reach
routing convergence, their
scalability
Scalability is the property of a system to handle a growing amount of work by adding resources to the system.
In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a ...
, and other factors such as relay multiplexing and cloud access framework parameters. Certain additional characteristics such as multilayer interfacing may also be employed as a means of distributing uncompromised networking gateways to authorized ports. This has the added benefit of preventing issues with routing protocol loops.
Many routing protocols are defined in
technical standards documents called
RFCs.
Requirements for IP Version 4 Routers
RFC 1812, F. Baker,June 1995
Types
Although there are many types of routing protocols, three major classes are in widespread use on IP network
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
s:
* Interior gateway protocol
An interior gateway protocol (IGP) or Interior routing protocol is a type of routing protocol used for exchanging routing table information between gateways (commonly routers) ''within'' an autonomous system (for example, a system of corpora ...
s type 1, link-state routing protocol
Link-state routing protocols are one of the two main classes of routing protocols used in packet switching networks for computer communications, the others being distance-vector routing protocols. Examples of link-state routing protocols includ ...
s, such as OSPF
Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous syst ...
and IS-IS
Intermediate System to Intermediate System (IS-IS, also written ISIS) is a routing protocol designed to move information efficiently within a computer network, a group of physically connected computers or similar devices. It accomplishes this b ...
* Interior gateway protocol
An interior gateway protocol (IGP) or Interior routing protocol is a type of routing protocol used for exchanging routing table information between gateways (commonly routers) ''within'' an autonomous system (for example, a system of corpora ...
s type 2, distance-vector routing protocol
A distance-vector routing protocol in data networks determines the best route for data packets based on distance. Distance-vector routing protocols measure the distance by the number of routers a packet has to pass; one router counts as one hop ...
s, such as Routing Information Protocol
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from sour ...
, RIPv2
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from sour ...
, IGRP
Interior Gateway Routing Protocol (IGRP) is a distance vector interior gateway protocol (IGP) developed by Cisco. It is used by routers to exchange routing data within an autonomous system.
IGRP is a proprietary protocol. IGRP was created in ...
.
* Exterior gateway protocol
An exterior gateway protocol is an IP routing protocol used to exchange routing information between autonomous systems. This exchange is crucial for communications across the Internet. Notable exterior gateway protocols include Exterior Gateway ...
s are routing protocols used on the Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
for exchanging routing information between Autonomous Systems
An autonomous robot is a robot that acts without recourse to human control. The first autonomous robots environment were known as Elmer and Elsie, which were constructed in the late 1940s by W. Grey Walter. They were the first robots in history t ...
, such as Border Gateway Protocol
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes ...
(BGP), a path-vector routing protocol
A path-vector routing protocol is a network routing protocol which maintains the path information that gets updated dynamically. Updates that have looped through the network and returned to the same node are easily detected and discarded. This al ...
. Exterior gateway protocols should not be confused with Exterior Gateway Protocol
An exterior gateway protocol is an IP routing protocol used to exchange routing information between autonomous systems. This exchange is crucial for communications across the Internet. Notable exterior gateway protocols include Exterior Gateway ...
(EGP), an obsolete routing protocol.
OSI layer designation
Routing protocols, according to the OSI routing framework, are layer management protocols for the network layer, regardless of their transport mechanism:
* IS-IS
Intermediate System to Intermediate System (IS-IS, also written ISIS) is a routing protocol designed to move information efficiently within a computer network, a group of physically connected computers or similar devices. It accomplishes this b ...
runs on the data link layer (Layer 2)
* Open Shortest Path First
Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous syst ...
(OSPF) is encapsulated in IP, but runs only on the IPv4
Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version de ...
subnet, while the IPv6
Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...
version runs on the link using only link-local addressing.
* IGRP
Interior Gateway Routing Protocol (IGRP) is a distance vector interior gateway protocol (IGP) developed by Cisco. It is used by routers to exchange routing data within an autonomous system.
IGRP is a proprietary protocol. IGRP was created in ...
, and EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary ...
are directly encapsulated in IP. EIGRP uses its own reliable transmission mechanism, while IGRP assumed an unreliable transport.
* Routing Information Protocol
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from sour ...
(RIP) runs over the User Datagram Protocol
In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) network ...
(UDP). Version 1 operates in broadcast mode, while version 2 uses multicast
In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...
addressing.
* BGP
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it mak ...
runs over the Transmission Control Protocol
The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly ...
(TCP).
Interior gateway protocols
Interior gateway protocol
An interior gateway protocol (IGP) or Interior routing protocol is a type of routing protocol used for exchanging routing table information between gateways (commonly routers) ''within'' an autonomous system (for example, a system of corpora ...
s (IGPs) exchange routing information within a single routing domain {{short description, Computer networking concept
In computer networking, a routing domain is a collection of networked systems that operate common routing protocol
A routing protocol specifies how routers communicate with each other to distribut ...
. Examples of IGPs include:
* Open Shortest Path First
Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous syst ...
(OSPF)
* Routing Information Protocol
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from sour ...
(RIP)
* Intermediate System to Intermediate System
Intermediate System to Intermediate System (IS-IS, also written ISIS) is a routing protocol designed to move information efficiently within a computer network, a group of physically connected computers or similar devices. It accomplishes this b ...
(IS-IS)
* Enhanced Interior Gateway Routing Protocol
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietar ...
(EIGRP)
Exterior gateway protocols
Exterior gateway protocol
An exterior gateway protocol is an IP routing protocol used to exchange routing information between autonomous systems. This exchange is crucial for communications across the Internet. Notable exterior gateway protocols include Exterior Gateway ...
s exchange routing information between autonomous systems
An autonomous robot is a robot that acts without recourse to human control. The first autonomous robots environment were known as Elmer and Elsie, which were constructed in the late 1940s by W. Grey Walter. They were the first robots in history t ...
. Examples include:
* Exterior Gateway Protocol
An exterior gateway protocol is an IP routing protocol used to exchange routing information between autonomous systems. This exchange is crucial for communications across the Internet. Notable exterior gateway protocols include Exterior Gateway ...
(EGP)
* Border Gateway Protocol
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes ...
(BGP)
Routing software
Many software implementations exist for most of the common routing protocols. Examples of open-source applications are Bird Internet routing daemon, Quagga
The quagga ( or ) (''Equus quagga quagga'') is a subspecies of the plains zebra that was endemic to South Africa until it was hunted to extinction in the late 19th century. It was long thought to be a distinct species, but early genetic ...
, GNU Zebra
Zebra is a routing software package that provides TCP/IP based routing services with routing protocols support such as RIP, OSPF and BGP. Zebra also supports special BGP Route Reflector and Route Server behavior. In addition to traditional IP ...
, OpenBGPD
OpenBGPD, also known as OpenBSD Border Gateway Protocol Daemon, is a server software program that allows general purpose computers to be used as routers. It is a Unix system daemon that provides a free, open-source implementation of the Border G ...
, OpenOSPFD
OpenOSPFD is an ISC licensed implementation of the Open Shortest Path First Protocol. It is a network routing software suite which allows ordinary general purpose computers to be used as routers exchanging routes with other computer systems spea ...
, and XORP
XORP is an open-source Internet Protocol routing software suite originally designed at the International Computer Science Institute in Berkeley, California. The name is derived from ''eXtensible Open Router Platform''. It supports OSPF, BGP, RI ...
.
Routed protocols
Some network certification courses distinguish between routing protocols and ''routed'' protocols. A routed protocol is used to deliver application traffic. It provides appropriate addressing information in its internet layer
The internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport network packets from the originating host across network boundaries; if necessary, to the destinat ...
or network layer
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.
Functions
The network layer provides the means of transfe ...
to allow a packet to be forwarded from one network to another. Examples of routed protocols are the Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
IP h ...
(IP) and Internetwork Packet Exchange
Internetwork Packet Exchange (IPX) is the network layer protocol in the IPX/SPX protocol suite. IPX is derived from Xerox Network Systems' IDP. It also has the ability to act as a transport layer protocol.
The IPX/SPX protocol suite was very ...
(IPX).
See also
* Static routing Static routing is a form of routing that occurs when a router uses a manually-configured routing entry, rather than information from dynamic routing traffic. In many cases, static routes are manually configured by a network administrator by adding i ...
* Dynamic routing
Dynamic routing, also called adaptive routing,
is a process where a router can forward data via a different route for a given destination based on the current conditions of the communication circuits within a system. The term is most commonly asso ...
* Hierarchical state routing
Hierarchical state routing (HSR), proposed in ''Scalable Routing Strategies for Ad Hoc Wireless Networks'' by Iwata et al. (1999), is a typical example of a hierarchical routing, hierarchical routing protocol.
HSR maintains a hierarchical network ...
* Optimized Link State Routing Protocol
The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad hoc networks, which can also be used on other wireless ad hoc networks. OLSR is a proactive link-state routing protocol, which uses ''hello'' a ...
* B.A.T.M.A.N.
* ZHLS-GF
Notes
References
Further reading
Chapter "Routing Basics"
in the Cisco
Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...
"Internetworking Technology Handbook"
{{Routing_protocols
*
Computer networking
*
routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone netw ...