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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: [NANOG] OSPF minutia, and, technote publication venues
On Tue, 6 May 2008, Nathan Ward wrote: > This stuff about customers and things sounds too hard. > > Steve, have you actually had to do anycast without having control of > the routing hop in front of your service providing hosts, or is this > getting unnecessarily complicated? I'd imagine that the ability to > install routing equipment would be a pre-requisite for any anycast > service deployment.. Yes I have. Or rather, I've done the network infrastructure for anycast services without having administrative control of the anycasted servers. PCH's anycast platform hosts some blade servers for some other DNS infrastructure operators (in addition to the name servers PCH operates itself). Those operators operate their own servers. PCH operates the routing infrastructure. There is filtering in place to limit the routing announcements from the servers. But also, most of the larger organizations I've worked for have had separate systems and network engineering groups. In general, the network groups haven't wanted to let the systems engineers configure the routers, and the systems groups haven't wanted to let network engineers configure the servers (with good reason). Filtering of routing announcements from anycast servers would be useful in that environment too. To address Paul's point about multipath BGP, I never saw Cisco's implementation of it causing a problem even with full routing tables. I haven't used any other implementations. In the Cisco version (and at least for EBGP; I haven't looked at this with IBGP), it only applies to otherwise identical AS paths. Multiple directly-connected DNS servers sourcing the same announcement with the same AS path and other BGP attributes get load balanced between. Paths learned from different peers had different AS paths and do not get balanced between. I suppose there probably is load balancing in cases where there are multiple sessions with the same peer at the same exchange. That's a relatively rare case in this implementation, and using hash based rather than per-packet load balancing makes it not really matter. -Steve _______________________________________________ NANOG mailing list [email protected] http://mailman.nanog.org/mailman/listinfo/nanog
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