Multipath routing is a technique that allows for computer network communications to be sent over multiple alternate paths. This is in contrast to a single routing protocol, where a data stream is directed along a single path from a source to a destination. With multiple paths, the source and destination pair can use any number of alternate routes to achieve performance enhancements, connection stability, and potential security improvements.
In single-path routing protocols, a network's interior routers direct traffic to the routers on the border of the network which, in turn, connect to another network's border. In order for a network transmission to reach its destination, each route is manually administered on the routers. A transmission then follows the established paths, only choosing an alternate when the regular path becomes unavailable for some reason. This leaves alternate paths with little or nothing to do.
Through multipath routing protocols, the additional available resources can also be implemented. In the case of performance enhancements, the load from a network can be distributed over multiple paths. Through the use of a method known as equal-cost multipath routing, traffic can be distributed equally over connections of varying strength. For example, considering a network that is sharing connectivity among two different service providers, one of which only offers half the speed as the other, one third of the network traffic can be routed to the slower path while the other two thirds go to the faster path.
Network security may also be improved upon when communications are distributed across multiple paths. Here, instead of an intruder observing a common route, the data is spread out among alternate routes. This makes it difficult for an attacker to determine all of the possible routes for a communique and thereby limit their interception of the data to a very small amount if one of the routes is being observed.
Additional multipath routing techniques can monitor packets for better distribution depending on use. For certain types of network communications that require lower delay, such as voice communications or multi-player network gaming, this type of traffic can be routed appropriately through more responsive paths. Other traffic, such as large file downloads, can also be recognized and distributed through multiple routes to balance the load and choose routes that may have higher delay but greater throughput.
Multipath routing has also found use in wireless networking. In these instances, there are limited established connections. A network node may be mobile, or temporary, and give the entire network a somewhat unreliable infrastructure. Allowing for alternate routes to other nodes in such a network improves reliability of the overall wireless network, as nodes are allowed to come and go.
There are a few shortcomings to the multipath routing technique, however. Routers required to monitor alternate routes will have increased overhead with regards to storage and tend to eat up additional processing power by determining and propagating the numerous paths to other routers. There are also additional bandwidth problems, as packets may require more information to be tacked on, increasing their size somewhat.
