Equal-Cost Multipath Considerations for BGP

BGP routing protocol defined in ([RFC4271]) employs tie-breaking logic to elect single best path among multiple possible. At the same time, it has been common in all practical BGP implementations to allow for "equal-cost multipath" (ECMP) path election and programming of multiple next-hops in routing tables. This documents provides some common considerations for the ECMP logic, with the intent of providing common reference on otherwise unstandardized feature.