I'm stumped on this one - what makes the origin attribute so important? It seems like a legacy piece of the puzzle that's still being treated as useful more than actually useful in my view. I mean, 33% of the possible values (EGP) are never going to be seen in the wild under normal circumstances (which is a good argument for removing that piece entirely IMO).
It's used in path selection, though as far as I can tell, it's close to being a tie-breaker in that scenario, and seems arbitrary in any case - injected manually versus via redisribution, correct? This is OK, since path selection in gneral after, say, AS path seems to me to be fairly arbitrary ways of just getting a route into the table so it can be used/advertized.
It is well-known and mandatory. This is where I'm stuck. Next-hop is obviously something that *must* be included in bgp routes since bgp routes have to use recursion (no interface listing in a bgp route). AS path agan is obviously mandatory since a) it's the default loop prevention mechanism for bgp, and b) the recieving router has to know where the route came from. But why origin? What makes origin so important that it's considered *mandatory* that it is part of a bgp route?
Anyone have pointers? Obviously this is mostly a curiosity type of question rather than a really important one, but I guess I'm at that point in my studies.