Source Routing

Source Routing ( Abbr: SR ) is a Wegwahltechnik with which the sender node can determine a complete Wegsequenz to the destination node. This method is the specification of a routing algorithm on the LLC layer.

Overview

It provides a complementary method of Spanning Tree Protocol dar. Thus, it is possible to detect redundant structures. Source routing spanning tree and differ in the information storage, which is necessary for the transport of a data packet from the sender to the destination station. The source refers to the sender of the route, which is to take a package specified. Lest the bridge keeps the information about the route of the data packet, but the transmitting station handling the routing tables of all open ( active ) compounds.

The term " source routing " is used for both Token Ring networks as well as for special options of IP. Source routing is on token ring networks is also a method for path selection with redundant paths between Token Ring switching elements (bridges ) and the different broadcast bits served in the head of the LLC frames. For the optimum design of large token-ring networks, a knowledge of the details of the operation (Broadcast variants SRE versus ARE, hop count limit, Spanning Tree implementation of path cost ) is essential.

Details

In the option field of the IP header following options are set:

The " Record Route " option is closely related to the source routing. If this option is set, then adds each traversed node 's IP (maximum 9 ) to the space provided behind the radio button.

A source route is static, if all routes are statically defined. A source route is dynamic, if all routes are dynamically created and changed after changing the topology.

Security

Source routing is safety concern: a sniffer can enter its IP address in the routing field and thus receives all packets to its host. Therefore, many firewalls and routers discard these packets.