Friday, January 13, 2012

ECMP Vs Stateful path switching based load balancing

ECMP stands for equal cost multipath routing. This is a solution when the routing table has two best paths for the same destination address. An example of this could be having two default gateways configured with the same metrics (costs). In such a case, the software on that platform could use a load balancing solution to split traffic across the two paths. However, this could cause additional problems if the two paths meet each other downstream, thus only adding complexity and not increasing the speed by a lot. Also, if the session state is not maintained, it could lead to some problems over the network if the state of the two routes changes dynamically. A solution to this is through explicit stateful switching. Doing switching also improves latencies since it is faster than routing.