Re: Usable extension headers

[Havard Eidnes <[e-mail]>]

> So the problem is how do we deploy protocols that aren't necessarily
> supported across all possible paths. I think the answer is already
> known: if we have a priori knowledge that some path supports a
> protocol then use the protocol, if the particular path doesn't support
> a protocol then don't use it and fall back to a degenerative protocol
> more likely to be palatable. There are several examples of this
> technique: Happy Eyeballs for IPv6, QUIC fallback to TCP, UDP DNS
> fallback to TCP DNS, etc.

Those are all mechanisms deployed by hosts, where the probing of
failure or success can be done with some reliability.  If I've
understood correctly, what we're talking about instead is routers
along the path messing with the IPv6 packet in non-standard ways,
and the router which did the messing doesn't under normal
circumstances get the same signal hosts do when a host connection
carried over this path either fails or succeeds.

Regards,

- Håvard