tony.li at tony.li
Wed Sep 29 20:38:17 CEST 2010
On Sep 29, 2010, at 3:05 AM, Carlos Morgado wrote:
> A decent ISP will have maybe 3 or 4 upstreams. On the all-PA scenario this means 3 or 4 prefixes to manage through the network.
What we proposed was that ISPs get PI.
> I haven't seen any discussion about what this means to end users, do they get 4 prefixes on their home gateways ? This, as far as I know, isn't being covered in CPE development. In fact, the mass deployable equipments I know barely work with autoconfiguration of a single prefix let alone multiple prefixes.
If the end site is multi-homed, yes, exactly, there would be 4 prefixes.
This is the architectural change that we need to make if we want to have scalable multi-homing.
> However this is leaking network topology into the DNS plane which means when a network problem occurs and an upstream is flaky or down the sysops need to update DNS to kill that mapping. Otherwise we get outages similar to what happens now when a site goes down on a dns balanced service.
This is something that could be reasonably automated.
> This is equally valid for end customer addressing, except it's suicide to try to reprovision a customer base in response to an outage with something like a 1 day fix estimate. The average day to day outage an ISP deals with today turns into a massive blackhole.
Well, if ILNP is in use, then it's possible to use any of the locators. So it's not a blackhole.
> On the application side I'm fairly confused as to happens when 2 multihomed machines talk to each other. Even with shims and all that we might get into a ridiculous situation where 2 hosts that share an upstream are talking to each other going halfway across the globe cause that's the addresses they resolved. If you move "route optimization" to the shim you end up with routing policy inside hosts. You might as well have everything running routing protocols.
This is already what can happen. ;-)
If you want optimization, the best known path is to go to MPTCP, which will actually try a variety of paths.
> What I see happening is an all-PA policy driving everybody back to NAT to the great joy of network vendors.
That would cause no joy. No one _wants_ to build NAT.
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