On 23/10/2016 08:37, Michael Richardson wrote: > > Brian E Carpenter <[email protected]> wrote: > > On 21/10/2016 01:56, Michael Richardson wrote: > >> > >> Brian E Carpenter <[email protected]> wrote: > >> >> What I was saying was, *IF* I know how to find a machine with an > open > >> >> GRASP_LISTEN_PORT, and I connect to it, and unicast a DISCOVERY, > that > >> >> I should receive my answer on that connection. > >> > >> > A says discover("B") to C, but C doesn't know where B is. So there > will > >> > be no answer, unless C does extra stuff. > >> > >> So, C would forward the discover("B"), and then when it gets to B, > >> it would connect directly to A, and introduce itself? This is obvious > now > >> that you give this example, but not from the document. I might also > think > >> that B would connect to C, and then C would tell A. > > > But it couldn't do that unless it had already discovered C previously, > in which > > case it could simply reply to A with its cached locator for C. > > >> This clearly fails if A has a LL address only. > > > Yes, but that's why we have discovery relaying. > > Still, I'm more confused now. > > When A has a LL only, we would have to have, not only discovery relaying, but > also response forwarding.
Yes. And if that isn't clear from the text, we (authors) have blown it. Let me look... ... https://tools.ietf.org/html/draft-ietf-anima-grasp-07#page-20 "The discovery results received by the relaying device MUST in turn be sent as a Discovery Response message to the Discovery message that caused the relay action." (which is intentionally recursive, but safe because of the loop suppression rules.) > So does B reply to C (to be relayed to A), or is > it a fail as B tries to connect to A's LL address, and does not connect? > > > >> >> In the 6tisch case doing multicast is either expensive or > unsupported. > >> >> On the other hand, we can quite easily declare that the 6LBR / > >> >> DODAG-root (the router at the top of the tree) will have > >> >> GRASP_LISTEN_PORT open. > >> > >> > Yes, you have topology knowledge in that case. > >> > >> Do you agree that a discovery("C") sent to C over TCP should be > answered > >> over that TCP connection? > > > Oh yes, and that is what should happen under the covers in any case, if > discovery > > is running over the ACP. > > > However, I'm not convinced that we should document this (unicast > discovery). > > At least not yet. > > When? I feel that this is important behaviour that needs to be defined for > the GRASP core system. Well, I don't really know when I would use it, but I have no problem with adding that an initiator MAY send unicast discovery and the recipient will respond accordingly (i.e. treat it just the same as a multicast discovery). Brian _______________________________________________ Anima mailing list [email protected] https://www.ietf.org/mailman/listinfo/anima
