Source routing is a technique that allows a user to route network data packets to a specific destination, but it is susceptible to abuse. It removes decision making from routers and places it in the hands of the user. There are two types of source routing: strict and loose. It is useful for testing and troubleshooting purposes, but can also be used for nefarious purposes. Dynamic source routing (DSR) was devised for wireless networks to quickly discover network paths.
Source routing is a technique used in computer networks that allows a user to route network data packets to a specific destination. Depending on how it is used, packets may be given a specific route to follow or general directions which will allow some of the network’s automatic routing to handle part of the route. While it’s a very useful technique, it’s also very susceptible to abuse, allowing for potential security breaches.
Most normal routing is done by the multitude of devices, known as routers, that make up the many networks that make up the internet. These devices are programmed with protocols that allow them to learn about their neighbors and thus decide on the best possible routes to take when directing network traffic from one computer to another. Source routing, on the other hand, takes advantage of some optional feature of the Internet Protocol (IP) which removes the decision making from the routers and places it in the hands of the user, or source computer.
There are two possible source routing changes a computer can make to a data packet on its way to the network: strict or loose. With strict origin definitions, the exact path a packet should take, from one router to another, is specified before the packet leaves the origin computer. Loose source routing, however, gives the packet a few specific router points and allows other routers to decide along the way. This is useful, for example, if you are sending a packet through routers on a local network to a gateway router and then to a specific address. Local network routers can be omitted, but the gateway and other routers can be specified.
The ability to use source routing is useful for various testing and troubleshooting purposes. One such purpose is similar to neighborhood street learning, whereby the network is discovered by tracing the path of packets from one router to another. It can also be useful for finding out where potential network bottlenecks occur and is often used by Internet Service Providers (ISPs) to ensure unnecessary data traffic is not trying to exploit their main network backbones. The method is also used for nefarious purposes, allowing an attacker to access computers on a private network by pretending to be a computer on that private network.
As wireless networks became popular, another technique called dynamic source routing (DSR) was devised which uses source routing to discover a wireless network. The trick came about because, since network nodes are known to frequently come and go from certain types of wireless networks, those called ad-hoc networks, computers needed a new way to quickly discover network paths. This way, the path from a source computer through a network is discovered on the fly as needed, instead of nodes continually flooding the network with updated information as nodes come and go.
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