On Thu, Jul 21, 2011 at 9:57 PM, David Endicott <dendicott@xxxxxxxxx> wrote: >> I have no idea what you might mean by "highly dynamic host environment" in >> this context, but XMPP servers are normally found at the same location >> consistently. However, it is *not* always (or typically) the same location >> as a simple A record lookup: > > That's what I meant. XMPP systems have hosts that change around (for many > reasons) and having a name resolution that handles that is good. > >> >> This property alone is very useful - in a websockets case this would mean >> being able to provide websockets services from a different host (or network) >> to the traditional web services in a simple manner, fully compatible with >> SOP. The fact that this also allows cheap lightweight load balancing and >> fallback control is also useful in other cases; none of this relates to >> dynamic hosts, but simply richer service location. > > Yes, those are all excellent reasons to use DNS SRV. None of them are a > reason to mandate that WS require it. Because something is good for some > (or many) use cases, does not mean it is appropriate for everything and > certainly is not a reason to mandate it as a requirement. > System implementer should be free to pick and choose tools and mechanisms > appropriate for their tasks. DNS SRV would likely be an excellent choice > for many people. But it should not be the one and only choice. That's > really all I'm saying - don't force people to use something without an > overwhelming reason to make it the only option. > >>> >>> I do not oppose DNS's MX records for SMTP as email addresses are >>> name@domain, >>> so obviously the Domain Name System is appropriate. Also, I fail to >>> see >>> why a mail admin should care how the SMTP clients arrive at the server. >>> DNS >>> MX is a reasonable solution, but there may be other methods, any and all >>> of >>> which are irrelevant to the SMTP server. Especially when the SMTP >>> server >>> supports multiple email domains... >>> >> A mail admin does need to care *that* the service is located, and >> therefore will care *how* it is located. >> >> You can be as theoretical as you like, by all means, but in practical >> terms, your email address (and my XMPP address) work because they use a >> defined, interoperable, service location mechanism, which operates via DNS >> record lookup. >> >> (Also, I have no idea what multiple domains has to do with this.) > > Imagine I'm a SMTP server. People connect to me. They do SMTP > transactions. I do not care how they found me. Perhaps they used DNS to > find the MX server. Perhaps they had it cached from before. Perhaps they > guessed. Perhaps it's in a hosts file. I don't care. I answer VRFY > and RCPT TO commands as appropriate. If the "name" they are trying to > mailwith is one I recognize, I process it. If I don't, it's an error. > Just because DNS-MX said that @foobar was handled at <addr>, doesn't mean > the dave@foobar is going to work. > Yes, DNS MX is a well known mechanism for determining what SMTP server to > connect with, but like I tried to say above, it's not mandated by the SMTP > protocol. DNS MX is independent of SMTP and the two mechanisms > operate separately, but with a common goal. I can use DNS to resolve a name > and never send email/message. I can send a email/message via SMTP and never > use DNS to resolve a name. Or I can use one to do the other. > When a SMTP server handles mail for multiple domains, the SMTP server has to > process the @domain part of the RCPT TO request - DNS is not involved at > that point. This process is unrelated to any DNS MX definitions. I used > that as an example of how some name resolutions are sometimes done outside > of any DNS framework. > >>> >>> Since WS is intended as a browser supported protocol, WS should follow >>> the >>> same URI resolution mechanisms as HTTP (or how URI resolution is done in >>> general) Having URLs that could resolve differently for a HTTP request >>> and >>> a WS setup is a problem. >>> >> But they do resolve differently anyway. You don't get a page from a 'ws' >> scheme URI, you get a transport protocol connection. This is good, indeed, >> it's kind of the point. > > > Do they? A http uri and a ws uri have the same host/path construction. > It's really only the scheme that differs - and that identifies the > transport protocol to be used. Resolution of host name/addresses and > mapping of paths "should" be consistent. > WS is a connection that is semantically related to the URI of the request. > > e.g. I could ws://host/davesaid and get live traffic of what Dave is > saying, and then I could ws://host/bobsaid and get traffic of what Bob > says. I wouldn't get Bob on /davesaid and I wouldn't get Dave on /bobsaid. > Dynamic content identified by a URI > And if I http://host/davesaid I could get a <li> of what Dave said. > Static content of a URI. > It could be problematic if ws://host/davesaid resolves to a different > address than http://host/davesaid. (Or it could be advantage - not for > us to decide, however) >> >> Your suggestion of "how URI resolution is done in general" is somewhat >> self-defeating, too, since aside from 'http' and 'https', there are >> 'mailto', which uses MX, 'sip' and 'xmpp', which both use SRV. > > As you just said, the universe is bigger than just xmpp, sip, and http. >> >> I think opponents of SRV records need to mount a stronger argument than >> the kind of luddite argument that if it's hard for one protocol in use by >> the browser, it should be hard for them all. > > I think you misinterpret my position. And I resent the luddite slight. I > think DNS SRV is an awesome tool and would greatly benefit many > implementations. > My position is that it should not be a *requirement*. It should be an > optional mechanism that can be used if desired. Further, since WS is a > bastard cousin to HTTP, they should share a similar name resolution > mechanism. Iñaki's proposal only imposes a requirement on clients, not on server-side WS deployments, since clients will fall back to A/AAAA if no SRV records are available. The mechanism (on the client-side) cannot be optional though, it would make SRV for WS mostly useless in practice. -Philippe. > >> >> Dave. >> -- >> Dave Cridland - mailto:dave@xxxxxxxxxxxx - xmpp:dwd@xxxxxxxxxxxxxxxxx >> - acap://acap.dave.cridland.net/byowner/user/dwd/bookmarks/ >> - http://dave.cridland.net/ >> Infotrope Polymer - ACAP, IMAP, ESMTP, and Lemonade > > > _______________________________________________ > hybi mailing list > hybi@xxxxxxxx > https://www.ietf.org/mailman/listinfo/hybi > > _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf