On Wed, Nov 20, 2019 at 10:20 PM David Schinazi <dschinazi.i...@gmail.com> wrote:
> Hi folks, > > I've chatted with Daniel and Chris offline, and I think there might > have been some miscommunication here. Please allow me to > rephrase what I think is going on, and please let me know if > this accurately represents your views. > > Daniel has a IoT use-case where due to memory constraints, > a client knows it can only handle a certain number of tickets, > and therefore Daniel was wondering if it would make sense to > make the requested number of tickets a required maximum > (as in a RFC 2119 MUST). However, server operators on this > thread have indicated that a MUST would get in the way of > implementing this, due to STEK rotation for example. Daniel > understands this, and is OK with the current mindset of the > document (which is only a hint, not a MUST). Additionally, > Daniel would prefer to see the document move forward. > > In order to try to address Daniel's comments, I attempted > to rephrase the normative section to suggest in more > stronger terms that servers really shouldn't be sending > more than the client's request, but keeping it a SHOULD. > > Here is the PR with the rephrase: > https://github.com/tlswg/draft-ietf-tls-ticketrequest/pull/10 > > Here's a copy of the updated paragraph in the PR: > Clients can use TicketRequestContents.count to indicate the number of > tickets they would prefer to receive. Servers SHOULD NOT send more > tickets than TicketRequestContents.count, as clients will most likely > discard any additional tickets. Servers SHOULD additionally place a > limit on the number of tickets they are willing to send to save > resources. Therefore, the number of NewSessionTicket messages sent > SHOULD be the minimum of the server's self-imposed limit and > TicketRequestContents.count. > > I apology for the late response. This addresses my MUST/SHOULD concern. Thanks David. > Regarding Viktor's suggestion, I personally believe it would increase the > complexity of the proposal, and I don't see use-cases compelling enough > to warrant that complexity. I would rather keep this proposal as simple as > possible. > I particularly like the proposal from Viktor and - at least as I see it - its associated simplicity. I believe it would be beneficial for the document to include it. > > Thanks, > David > > > On Wed, Nov 20, 2019 at 2:48 PM Viktor Dukhovni <ietf-d...@dukhovni.org> > wrote: > >> On Wed, Nov 20, 2019 at 11:53:08AM +0800, Tommy Pauly wrote: >> >> > > Somebody should try to avoid ending up with N new tickets after >> > > every connection, but in could well be the client. >> > >> > Yes, I think that can and ought to be the client. The client is really >> the >> > only party that can know how many tickets have been "consumed" by >> potentially >> > failed attempts to connect that the server didn't see in time or got >> dropped. >> >> OK, in that case, the proposal, is that on resumption, if the proposed >> extension is *absent*, then the server should generally send just one >> rather >> than any larger default. >> >> If the extension is present, it is up to the client to not blindly ask >> for N >> tickets each time, and generally ask for just one ticket on resumption, >> once it >> has sufficiently many tickets for the desired concurrency level, with each >> parallel thread obtaining one replacement ticket its next connection. >> >> As discussed clients that prefer to reuse tickets, can ask for zero, and >> get 1 >> only as-needed. If the server supports reuse then all is well. >> >> If the server does not support and refuses reuse, then it will issue a new >> ticket each time and may only accept it once, but the client may have a >> single-slot cache. If the client makes only one connection at a time, >> this >> also works, but if/when its handshakes with the server overlap (a narrow >> window >> of ~1RTT) and two connections attempt to resume with the same ticket, one >> of >> them will end up doing a full handshake, but only when the client and >> server >> applications have incompatible ticket reuse expectations. Some friction >> when the client and server are mismatched is not the end of the world. >> >> So on the whole I think the proposal still works with just a numeric >> signal >> (tweaked with 0xff == none and 0 == reuse), and the onus to "generally >> send 1" >> on resumption moved to the client (i.e. clients that don't solicit ticket >> reuse >> should request only 1 ticket once they have enough). >> >> -- >> Viktor. >> >> _______________________________________________ >> TLS mailing list >> TLS@ietf.org >> https://www.ietf.org/mailman/listinfo/tls >> > _______________________________________________ > TLS mailing list > TLS@ietf.org > https://www.ietf.org/mailman/listinfo/tls >
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