Reverse Path Forwarding or RPF is a method that serves at least two purposes in routers;

1. Verify loop-free forwarding of multicast packets

The RPF mechanism essentially says “only forward packets  that come in on the interface that is used to reach back to the source” – this guarantees a loop-free distribution path. The idea here is to consult the unicast routing table and perform a lookup by source – i.e. contrary to what routers normally do, lookups by destination. If the source (of the multicast packet) can be reached via the interface through which the packet came in on then proceed with forwarding, otherwise drop the packet. Continue Reading »

When I first studied IP I came across a term whose meaning I didn’t quite fully understand. That term was “traffic plane”. It was a relatively unclear concept and it didn’t make a lot of sense for a beginner. However, after some reading and some experience its meaning  became apparent.

So, in a few words, what is a traffic plane?

The traffic on a network usually performs more than one function. Packets with similar function are said to belong to the same traffic plane. Therefore a plane is a term that identifies the class that the traffic is a member of.  There are at least 4 traffic planes:  Continue Reading »