Equal-cost multi-path routing (ECMP) is a

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 ...

strategy where

packet forwarding Packet forwarding is the relaying of packets from one network segment to another by nodes in a computer network. The network layer in the OSI model is responsible for packet forwarding. Models The simplest forwarding modelunicastinginvolves ...

to a single destination can occur over multiple best paths with equal routing priority. Multi-path routing can be used in conjunction with most routing protocols because it is a per-hop local decision made independently at each router. It can substantially increase bandwidth by load-balancing traffic over multiple paths; however, there may be significant problems in deploying it in practice.

History

Load balancing by per-packet

multipath routing Multipath routing is a routing technique simultaneously using multiple alternative paths through a network. This can yield a variety of benefits such as fault tolerance, increased bandwidth, and improved security. Mobile networks To improve pe ...

was generally disfavored due to the impact of rapidly changing latency,

packet reordering In computer networking, out-of-order delivery is the delivery of packet (information technology), data packets in a different order from which they were sent. Out-of-order delivery can be caused by packets following multiple paths through a netwo ...

and

maximum transmission unit In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size that ...

(MTU) differences within a network flow, which could disrupt the operation of many Internet protocols, most notably TCP and

path MTU discovery Path MTU Discovery (PMTUD) is a standardized technique in computer networking for determining the maximum transmission unit (MTU) size on the network path between two Internet Protocol (IP) hosts, usually with the goal of avoiding IP fragmentati ...

. RFC 2992 analyzed one particular multipath routing strategy involving the assignment of flows through

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flow-related data in the

packet header In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header is sometimes called the ''payload'' or ''body''. It is vital ...

. This solution is designed to avoid these problems by sending all packets from any particular network flow through the same path while balancing multiple flows over multiple paths in general.

References

External links

Etutorials: Equal-Cost Multi-Path (ECMP) Routing

Paris-Traceroute: traceroute for ECMP networks

Dublin-Traceroute: NAT-aware traceroute for ECMP networks

Traffic Engineering With Equal-Cost-MultiPath: An Algorithmic Perspective
{{DEFAULTSORT:Equal-Cost Multi-Path routing Routing algorithms

History

See also

References

External links