Re: End-to-end (was Re: Non-Last Small IPv6 Fragments)

[Tom Herbert <[e-mail]>]

On Tue, Jan 15, 2019 at 11:52 PM Fernando Gont <[e-mail]> wrote:
>
> On 15/1/19 19:42, Tom Herbert wrote:
> [....]
> > packets. This uses a modifiable HBH options and is completely
> > idependent of the transport layer.
>
> You cannot use HBH in the public Internet. Well, you can... but there
> high chances your packets will be dropped.
>
Fernando,

By that same thinking we can't use any extension headers at all, any
transport protocol other then TCP (and maybe UDP), ICMP, the TCP
authentication option, TCP fast open, UDP options, or even IPv6 on the
Internet. None these will universally pass through the Internet. But
it's also true that not all such packets are dropped, there are a lot
of networks where these will work and they do conform to the
standards.

We have some workarounds for the problem. We can follow the IPv6 happy
eyeballs approach: if an application see that packets aren't making it
to a destination, then fallback back to using a more rudimentary
protocol with higher probability of success but less service offered
to the user. Encrypting as much of the packet as possible, including
transport layer headers like QUIC does, also helps-- what the network
can't see, it can ossify.

As for HBH, RFC8200 relaxed the requirement that intermediate nodes
need to process them. If a node just wants to get to the transport
layer it can skip over the EH very with a few simple operations. I see
no excuse for new devices being deployed to systematically drop HBH or
destination options EHs. If they are  doing that then their
implementation does not comply with the IPv6 standard and we shouldn't
have any compunction about publically calling them out on that.

Tom

> --
> Fernando Gont
> SI6 Networks
> e-mail: [e-mail]
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
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