Routing protocol: Difference between revisions
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A ''routing protocol'' specifies a source of information for the [[control plane]] of [[routing]]. Specifically, | A '''routing protocol''' specifies a source of information for the [[control plane]] of [[routing]]. Specifically, they are [[protocol (computer)|protocols]] that run among routers, and occasionally hosts as well. | ||
Routers participating in the routing protocol interaction exchange information about the destinations they can directly or indirectly reach. In most cases, the information exchanged also carries information on the relative cost of moving toward the destination from the specific router, and possibly some policy information about what traffic is allowed to take particular paths. | Routers participating in the routing protocol interaction exchange information about the destinations they can directly or indirectly reach. In most cases, the information exchanged also carries information on the relative cost of moving toward the destination from the specific router, and possibly some policy information about what traffic is allowed to take particular paths. | ||
Revision as of 19:49, 14 July 2008
A routing protocol specifies a source of information for the control plane of routing. Specifically, they are protocols that run among routers, and occasionally hosts as well.
Routers participating in the routing protocol interaction exchange information about the destinations they can directly or indirectly reach. In most cases, the information exchanged also carries information on the relative cost of moving toward the destination from the specific router, and possibly some policy information about what traffic is allowed to take particular paths.
Unicast routing protocols
Scope
The most basic type of routing protocol is unicast, which gives destinations to specific addresses, or to address ranges (e.g., IP subnets) that contain specific addresses. Unicast routing protocols can be interior or exterior.
Interior routing protocols are under the control of a single administrative authority that defines the cost factors and policies that will affect the advertising and acceptance of routing information. That scope of control by the single authority is called a routing domain.
More than one routing domain may coexist in an autonomous system, which is a set of routers and addresses, under one or more administrative authorities, that present a single set of route advertisement to the Internet or a private network that interconnects non-public autonomous systems.
Paradigms and protocols
Interior unicast routing protocols use one of two paradigms, with different algorithms and implementations. Three standard, and one proprietary, protocols of this type are in common use:
- Open Shortest Path First (OSPF), an Internet Engineering Task Force (IETF) protocol, which supports hierarchy and primarily uses link state algorithms.[1]
- Intermediate System to Intermediate System (IS-IS), also a IETF link-state protocol but with different assumptions, characteristics, and optimal applications than OSPF.
- Routing Information Protocol (RIP), an IETF protocol using a simple version of the distance vector paradigm. It is far less scalable than the other unicast routing protocols, but is simple and can be useful in small networks.
- Enhanced Interior Gateway Protocol (EIGRP), an advanced distance vector protocol proprietary to Cisco Systems.
One unicast exterior routing protocol is in general use, the IETF-standardized Border Gateway Protocol.