Re: [Circum-devel] Issues with initial CER/CEA exchange

[Sebastien D. <sde...@ni...>]

Hello Jan,

Thank you for your answer.

> The RFC leaves some open questions, even if just non-normative.
I agree :) In my opinion it makes sense to reply with all the locally
supported applications when the remote peer advertises the Relay
application, so that this relay knows which messages can be routed to
this peer. In any case, if you consider the Relay application as a kind
of wildcard, the intersection of your local application list with this
wildcard would give the same list as a result, which gives the expected
result. But I guess the RFC leaves space for other interpretations here.

> What is one supposed to answer with, 0xffffffff or a list of all supported
> application IDs?
You peer is probably not supposed to answer with 0xfffffff if it does
not support relaying messages (and I believe Circum does not support
this). The list of all locally supported applications makes more sense IMHO.

> Speaking of which, the RFC is also somewhat unclear for non-relay
> cases:
>
> *Either* I am supposed to send the intersection list (because /just
> computing/ it without using it seems pretty pointless), or the list
> of all supported apps, and let the CEA receiver deal with finding the
> intersection.
In my understanding, you compute the intersection just so that you
determine if there is at least one common application. Sending back the
result of the intersection, or the complete list of local applications,
will not have any effect on the remote peer at the moment. It might
change if the Capability-Update application is implemented, however. So,
just to stay on the safe side, I would send the full list of local
applications -- but this is only my personal interpretation, you may
disagree ^^.

Best regards,
Sebastien.

-- 
Sebastien Decugis
Research fellow
Network Architecture Group
NICT (nict.go.jp)