North American Network Operators Group|
Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical
Re: with a flap flap here and a flap flap there...
Marc Slemko <[email protected]> writes: > But the loop avoidance from having paths constrains you to the width of > the Internet in terms of ASes. It isn't completely a distance vector > protocol. Yakov Rekhter also made a similar observation. I was caught up in rhetoric and was imprecise. (I could also be wrong; it happens.) BGP records paths and the loop avoidance scheme prevents a count-to-infinity problem in a way slightly better than RIP with split horizons does. In a network like this: C /| A--B< | \| D if A-B goes down in a split-horizons RIP network, there can still be a count-to-infinity problem between C and D announcing reachability to A. BGP does not have this problem. However, a withdrawal of a network from D can cause A to see a transition from ABD to ABCD to unreachable. This effect is what was complained about in the message I initally followed-up to. BGP is also not formally a distance vector protocol because the AS_PATH attribute is a trail of breadcrumbs rather than a distance. However, I argue that in common practice, it is a distance, and offer up AS-path prepending to affect path selection remotely as evidence. > I guess I'm just suprised at how wide the Internet has grown and at the > lack of noticeable public acknowledgment of the resulting problems. I'm not so surprised by the first bit, and I think I have become jaded about the second. Sean.