source routing (SR)
Source routing( SR) is a routing algorithm at the LLC level, Logical Link Control (LLC). The method is implemented specifically in Token Ring networks, but can also be used in Token Bus or CSMA/ CD networks. Source routing is a complementary method to the spanning tree protocol for detecting redundant structures.
The main difference between source routing and spanning tree is the information storage required to transport a data packet from the sender to the destination station. As the name implies, the route of a packet is specified by the source, i.e., by its sender. It is not the bridge that holds the information about the route of the data packet, but the sending station that handles the routing tables over all open ( active) connections.
Source routing is equivalent to source bridging because extended bridge functionality is implemented. If source routing takes place over a transparent bridge, by means of an intermediate bridge that translates between the two bridge protocols, it is referred to as source routing with translational bridging.
Source routing with transparent bridging combines the two methods with preset bridging strategy - transparent bridge and source routing bridge. In this method proposed by IBM, both technologies are used in one device to satisfy all end nodes. This method, unlike translational bridging, does not use protocol translation.
A variant of source routing is Dynamic Source Routing( DSR) for mesh networks( WMN), from which Link Quality Source Routing( LQSR) was derived.