Physical path tracing for IP traffic using SNMP-a comprehensive solution for end-to-end and multicast streams monitoring

Large-scale enterprise IP networks often involve complex topology consisting of routers, bridges and hosts. Due to multiple redundancies and minimized Single Point of Failure (SPOF), sometimes it is difficult to determine the actual path of a packet even with the most up-to-date physical connectivity diagram. This presents a great challenge for troubleshooting end-to-end traffic flows. This paper describes a novel solution using standard SNMP and a number of powerful algorithms developed for processing MIB data to discover unknown network devices and their physical interconnections, including those between bridges. In the topology diagram delivered by this solution, physical connections are determined at port-level precision. When this is combined with Iayer3 routing information, the entire physical path of an IP packet between any two hosts on the network can be traced. This paper gives detailed elaboration for all algorithms. It also introduces another important feature of the solution, which is the summarization of multicast groups and their routes, which is derived only from the final routing decision of the routers and therefore completely independent of any multicast routing protocols or manual configurations.