On Wed, Aug 31, 2022 at 4:39 AM, Brian Dickson < brian.peter.dick...@gmail.com> wrote:
> Here are some proposed text changes, per Warren's invitation to send text: > Um, no. Warren said: "can we craft a sentence (or possibly two) which only clarify what is already written?". This is a significantly larger set of changes than that. The Section 3 changes in particular are (IMO) much more than a clarification. These may or may not be good changes, but anything approaching that level of change would have to be in a -bis document… W > In section 1.2, change: > > 2. TargetName: The domain name of either the alias target (for > AliasMode) or the alternative endpoint (for ServiceMode). > > to: > > 2. TargetName: Either the domain name of the alias target (for > AliasMode) or the host name of the alternative endpoint (for > ServiceMode). > > In section 2.4.2, change: > > As legacy clients will not know to use this record, service operators > will likely need to retain fallback AAAA and A records alongside this > SVCB record, although in a common case the target of the SVCB record > might offer better performance, and therefore would be preferable for > clients implementing this specification to use. > > to: > > As legacy clients will not know to use this record, service operators > will likely need to retain fallback AAAA and A records at the service > name, > although in a common case the target of the SVCB record > might offer better performance, and therefore would be preferable for > clients implementing this specification to use. > > > In section 2.4.3, change: > > In ServiceMode, the TargetName and SvcParams within each resource > record associate an alternative endpoint for the service with its > connection parameters. > > to: > > In ServiceMode, the TargetName and SvcParams within each resource > record associate an alternative endpoint for the service with its > connection parameters. The TargetName MUST be a host name > (as defined in [DNSTerm].) > > In section 3, the following changes are proposed; they introduce a new > term LASTNAME to be used to disambiguate the $QNAME reference so as to > remove ATTRLEAF prefixes from the appended target: > > > 1. Let $QNAME be the service name plus appropriate prefixes for the > scheme (see Section 2.3). > > becomes: > > 1. Let $QNAME be the service name plus appropriate prefixes for the > scheme (see Section 2.3). Let $LASTNAME be the service name without > any prefixes. > > > > 3. If an AliasMode SVCB record is returned for $QNAME (after > following CNAMEs as normal), set $QNAME to its TargetName > (without additional prefixes) and loop back to step 2, subject to > chain length limits and loop detection heuristics (see > Section 3.1). > > becomes: > > 3. If an AliasMode SVCB record is returned for $QNAME (after > following CNAMEs as normal), set $QNAME to its TargetName > (without additional prefixes), set $LASTNAME to this new $QNAME and > loop back to step 2, subject to > chain length limits and loop detection heuristics (see > Section 3.1). > > > Once SVCB resolution has concluded, whether successful or not, SVCB- > optional clients SHALL append to the priority list an endpoint > consisting of the final value of $QNAME, the authority endpoint's > port number, and no SvcParams. (This endpoint will be attempted > before falling back to non-SVCB connection modes. This ensures that > SVCB-optional clients will make use of an AliasMode record whose > TargetName has A and/or AAAA records but no SVCB records.) > > becomes: > > Once SVCB resolution has concluded, whether successful or not, SVCB- > optional clients SHALL append to the priority list an endpoint > consisting of the final value of $LASTNAME, the authority endpoint's > port number, and no SvcParams. (This endpoint will be attempted > before falling back to non-SVCB connection modes. This ensures that > SVCB-optional clients will make use of an AliasMode record whose > TargetName has A and/or AAAA records but no SVCB records.) > > If the client is SVCB-optional, and connecting using this list of > endpoints has failed, the client now attempts to use non-SVCB > connection modes. > > becomes: > > If the client is SVCB-optional, and connecting using this list of > endpoints has failed, the client MAY attempt to use non-SVCB > connection modes, using the origin name (without prefixes), > > the authority endpoint's port number, and no SvcParams. > > > One additional suggested addition to the end of section 3.1 is: > > If DNS responses are cryptographically protected, and at least > one HTTPS AliasMode record has been received successfully, > clients MAY apply Section 9.5 (HSTS equivalent) restrictions > even when reverting to non-SVCB connection modes. Clients > > also MAY treat resolution or connection failures subsequent > > to the initial cryptographically protected AliasMode record > > as fatal. > > [Brian's note: this last would provide some guidance to implementers of > clients: a signed HTTPS AliasMode record is a strong signal that the DNS > operator is discouraging fallback, albeit at a "MAY" level.] > > NB: The 2.4.3 change could be removed as it is mostly independent, as > could the last addition to 3.1. > The 1.2 change is very minor, is not too important but presents a succinct > clarification on the hostname vs domain name thing. > The 2.4.2 change and section 3 changes together are fixes for the > prefix/no-prefix issue (which was basically a scrivener's error, and does > not change the semantics at all.) They should stay or go as one unit. > > Brian > > On Tue, Aug 30, 2022 at 12:08 AM Brian Dickson <brian.peter.dickson@gmail. > com> wrote: > >> >> >> On Sat, Aug 27, 2022 at 3:00 PM Ben Schwartz <bem...@google.com> wrote: >> >>> >>> >>> On Fri, Aug 26, 2022 at 10:49 PM Brian Dickson <brian.peter.dickson@ >>> gmail.com> wrote: >>> >>>> >>>> Fail fast may not be appealing, but in some (probably the majority of) >>>> cases, it may be the most correct option. >>>> >>>> It may also be the case that the zone owner knows whether this is the >>>> case. >>>> I think it is much more likely that explicitly declaring the situation >>>> (if known) is more useful than having several billion clients independently >>>> attempting to infer whether the first option will even work, let alone >>>> provide a useful alternative to the second or third. >>>> >>> >>> In fact, there is one way for the zone owner to disable fallback: enable >>> ECH. Fallback is not compatible with ECH, so ECH-aware clients will >>> disable fallback when the ServiceMode records contain ECH. >>> >>> >> Wait, what? >> >> This whole discussion was raised from the perspective of zone owners >> publishing AliasMode apex records. >> Those owners would not be operating the CDN, which is the whole point of >> using a CNAME or AliasMode. >> I.e., the zone owner would be the one wanting to disable fallback, but >> would not be in a position to do what you suggest. >> >> The domain's contents are served via a CDN, where the CDN requires >> delegation of control, most often with CNAME (or AliasMode at the apex). >> The ServiceMode records are placed on the CDN operated zone (in order to >> avoid the first connection to establish the AltSvc stuff). >> >> The AliasMode record cannot be combined with ECH, since no SvcParams are >> allowed. The zone owner is not using ServiceMode, that is the declared >> assumption. >> >> If that (ECH) is the only way to disable fallback, that's what the >> focused discussion needed to elicit, and I think some slight adjustments >> are needed to at least facilitate zone owners preventing fallback. The >> mechanism doesn't need to be added to the draft, but likely would get put >> into a separate draft or a -bis document. However, there needs to be some >> daylight between the fallback method and the mandatory SVCB/HTTPS >> components, in order to allow for that development. >> >> BTW, the concern is less about singleton zone owners than it is about >> large scale integrated DNS management of zones in order to accommodate CDN >> usage. >> >> Note also, this issue is not strictly limited to vertical integration >> among products/services of the DNS operator; there are large scale >> inter-provider (DNS and other services) open partnerships (controlled by >> their mutual customers) that have need for the programmatic ability to >> assign CDNs and enable/disable fallback (if fallback is part of the >> specification). >> (For those interested, the not-yet-an-IETF standard for interoperability >> between DNS and service providers is Domain Connect. The intent is to >> revive the draft for that, which previously lived in the REGEXT WG.) >> >> I think converting the fallback in the draft into MAY, and having active >> discussions, dev, test, and deployment on a voluntary basis outside of the >> scope of the current draft, is the fastest path to solving the "no >> fallback" signaling issue, and to getting the draft published (with a few >> minor tweaks). >> >> I'll review the other comments, as well as Warren and Viktor's recent >> messages, and see if I can come up with some proposed text to make very >> limited changes to the draft. >> >> Brian >> >
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