Re: [tsvwg] Way forward for UDP option FRAGs with limited router hardwara

["C. M. Heard" <[e-mail]>]

On Tue, Apr 12, 2022 at 8:44 AM Joe Touch wrote:
> On Apr 12, 2022, at 8:20 AM, Christian Huitema wrote:
> > Joe, you should stop mentioning Teredo. We have established that
> > Teredo packets just use UDP to carry a Teredo payload with no
> > trailers. The Teredo packets themselves are the assembly of IPv6
> > packets and Teredo extensions, but that usage is not the same as
> > the proposed Teredo options. So, no, when it comes to measuring
> > the prevalence of packet filtering, Teredo is not a precedent.
>
> I’m speaking of Teredos trailers, not UDP ones.

Right. Just so that we do not talk past each other in the discussion,
it may be useful to note that there are two very distinct concerns
being raised against trailers:

1.) There is a concern that some devices likely to be used to terminate
tunnels cannot access the trailers to process them. This, as I
understand it, is Tom Herbert's concern. It applies equally to Teredo
trailer options and UDP trailer options. So in this context, it's fair
game to cite Teredo as a precedent for the use of trailer options.

2.) There is a concern that packets with UDP trailers -- i.e., where
the IP Payload Length exceeds the UDP Length -- will be filtered in
intermediate systems. If I understand correctly, this is the concern
(or at least one of the concerns) that Christian Huitema has raised.
The Aberdeen group has actually investigated this matter, and Tom Jones
presented the results at a MAPRG meeting several years ago. I'll search
my archives and provide appropriate pointers to that work in a bit.

Mike Heard