IPv6 addresses for EP or why are exhanges so special ?
Hallgren, Michael michael.hallgren at Teleglobe.com
Wed May 16 13:20:29 CEST 2001
> > > > I have tried to follow this discussion, and stumbeled over a > > fundamental question when trying to reason about this: > > > > * why are exchange points so special? > > My take on this is that "they are not". > > But before plunging on, I would find it useful to distinguish > between the two portions that have been discussed so far: > > o Addresses for the exchange point medium itself (usually a > layer-two network of some sort) > > o Addresses for a "service network", probably used by the > organization which runs the exchange point and which can > provide additional common services of interest to the > connected networks. > > I'll also mention that my experience on the matter is based on > IPv4, so if there are additional quirks that are specific to IPv6 > that I don't know about, you'll have to excuse me. > > For the exchange point medium itself, if the medium is a "multiple- > access broadcast network" it *is* actually a benefit to use the > "natural" way to number such networks, i.e. use a single IP subnet, > as in that case you can use BGP in the "standard configuration". > Starting to muddle with secondary IP addresses and run "multiple > subnet on the same layer-two medium" when you in reality don't have > to, just causes extra complications, and should therefore be > avoided. If your exchange point is implemented using a "multiple- > access non-broadcast network" of some sort, the multiple point-to- > point links, each with their own subnet out of a connected peer's > address block makes sense. > I'm of the same opinion. > Some have said that the IP network used to number the exchange > itself does not have to be announced on the global level. However, > it would appear that practices vary quite widely on this point for > IPv4, and many are announced globally. You mention the possible use > of link-local addresses; I wonder if that won't make it difficult to > handle such things as ICMP; it'll probably be met with similar > issues as folks who use RFC 1918 addresses in today's network (e.g. > breaking Path MTU discovery because RFC 1918-originated datagrams > are often summarily dropped on the floor). > I fear that as well. Of course, however, it's a question of being smallest MTU on path - but for avoiding such potential problems... > I may have misunderstood something fundamental, but I also don't > quite know what's so bad with using IP(v4) addresses out of a > provider's block to number the exchange point medium. > > > As for the "service network", it will of course need global > connectivity, and thus has to get transit service from one or more > ISPs. What I don't understand is why this service network needs to > be so special up and above other normal customers when it comes to > IP address assignment? > Depending on how transit / co-location is provided, yes. Hrm,... maybe I'm wrong, maybe I'm right... but couldn't suitable PI disjunct to IX infra space (and/or close segment) be a choice as well? Thoughts? Kind regards Michael > > Creating these "special cases" as exceptions to the rules just opens > up the floor for other folks who will stand up and say "My Cause is > Extremely Worthy too, so I want some too under those conditions!!". > > > Best regards, > > - Håvard >
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