[IPv6] Multi6 (no longer RFC 6724 shouldn't prefer partial reachability over reachability)

Brian E Carpenter <brian.e.carpenter@gmail.com> Wed, 22 November 2023 04:03 UTC

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Date: Wed, 22 Nov 2023 17:03:13 +1300
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To: Nick Buraglio <buraglio@forwardingplane.net>, Ole Troan <otroan@employees.org>
Cc: Lorenzo Colitti <lorenzo@google.com>, 6man WG <ipv6@ietf.org>, Michael Richardson <mcr+ietf@sandelman.ca>
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From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Subject: [IPv6] Multi6 (no longer RFC 6724 shouldn't prefer partial reachability over reachability)
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On 22-Nov-23 03:37, Nick Buraglio wrote:
> 
> 
> On Tue, Nov 21, 2023 at 5:45 AM Ole Troan <otroan@employees.org <mailto:otroan@employees.org>> wrote:
> 
>      > The more I think about it, the more I am thinking that it may be a deployable solution for multihoming, with all of the details in appropriate stages of hand waving.
> 
>     The more I think about it, the less I think it is deployable.
> 
>     MHMP:
>     - Rule 5.5 support in all hosts (which as Lorenzo alluded to is complicated)
>     - Application changes to handle failover
>     - No multi-homing policy available to the network
>     - Only works when hosts are directly connected to exit routers. _Any_ other topology requires routers to do SADR or SADR like behaviour
> 
>     I don’t see any realistic way where MHMP can be made deployable.
> 
> 
> Ugh. I had tunnel vision and wasn’t considering upstream routers in my desire to have something simple(ish). Dang, that sucked all of the wind out of my sails.

That's how I felt after finalising the text at https://github.com/becarpenter/book6/blob/main/6.%20Management%20and%20Operations/Multi-prefix%20operation.md

TL;DR: "The need for complex configuration and the resulting failure modes explain why many enterprises have not opted for multi-prefix PA-based multihoming."

    Brian

> 
> 
> 
>     I’d rather we focus on the multi-homing mechanisms that could work.
> 
>     Cheers,
>     Ole
> 
> 
> 
> 
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