Hi Bill,
> I'm missing something. > > Wouldn't the route server send withdrawals and updates to the rest of > the participants as soon as its hold timer with the lost router > expires? > I believe the case here is about a situation where peers can talk to RS just fine (no bgp session goes down) however reachability between them is broken. RS to peer path does not need to be congruent with date plane path. Besides, large IXs sometimes use encapsulation between peer's ports while packets to control plane RS may not be subject to it. > Could this not be accelerated by the IXP asking the participants to > keep low keepalive and hold timers with the route server? > Not in the above case. > How would your solution help when two participants at an IXP have > chosen -not- to bilaterally peer, thus needing the route server to > intermediate? They're going to agree to build BFD sessions even though > they don't want BGP sessions? That... doesn't make sense. > It will not. That is why IMO peers should detect NH reachability by unidirectional OAMs. And as mentioned above this would be applicable much wider then in the IXPs. Thx, R. > > The second situation would be to deal with forwarding plane incongruence > > on IXPs, i.e. where router A can reach RS, router B can reach RS, router > A > > cannot reach router B due to a problem on the IXP fabric itself. > Thankfully > > this style of problem has become quite unusual over the last several > years. > > Doesn't seem like it would solve the bouncy link problem. > > Absent bouncy links, simply having a reasonable time out for arp and > ND will assure the router quickly finds its neighbor unreachable, > which is applied as backpressure into BGP. > > Regards, > Bill Herrin > -- > William Herrin > b...@herrin.us > https://bill.herrin.us/ >
