Comments in line :->
Noel Chiappa wrote:
> From: John C Klensin <john-ietf@xxxxxxx>
> Of course, multiple A records works, is out there, and have worked for > years. But they worked better before we introduced routers (i.e., when > the hosts with multiple A records really had interfaces on different > networks). Today, it effectively implies having multiple addresses on > an interface and multiple "local" address prefixes running around on > the same physical LAN segment. > ... > Perhaps more important, as Noel points out, it doesn't scale very well, > at least in terms of the routing fabric.
Sorry? What I said doesn't work for the routing, in terms of scaling to many small sites, is for a multi-homed site to have a single address prefix, which is then globally advertised. (That's the most common tack for multi-homing support in IPv4 to date, which is what you were talking about.)
Having multiple addresses for a host (which has only a single physical interface, but which is in a site which is multi-homed) is in fact the only approach whose effects on the routing does scale (within anything like the current routing architecture, i.e. packets which include only source and destination addresses, as opposed to a source route).
Or you can use SCTP and have seperate interfaces going to seperate ISP's and have the transport use them both....
That is how we designed SCTP.....
> as I tried to point out, address preservation policies have had > trickle-down effects that make it impractical for small enterprises.
It is an interesting point (as Daniel Senie also just pointed out) that multiple addresses -> faster consumption of the address space.
However, since to avoid a size explosion in the routing tables, those multiple addresses do have to be connectivity-dependent (political translation - "provider-dependent"), I don't see how address preservation policies have made this approach "impractical for small enterprises". My understanding of current allocation policies is that ISP's can get enough addresses to cover their customers. If company X is a customer of both ISP P and ISP Q, I would assume that both P and Q don't have a problem getting enough space to cover their customers - including X.
Exactly... When I buy two seperate DSL's from two seperate ISP's the two ISP's hand me an IP address .. they are seperate and don't break or violate any current address allocation policy. I don't ask SBC to advertise my speakeasy address... or vice-versa.. instead I let SCTP handle it all...
R
(Or were you speaking of the "one address block, globally advertized"?)
Noel
-- Randall R. Stewart 815-477-2127 (office) 815-342-5222 (cell phone)