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.
�
A mail admin does need to care *that* the service is located, and therefore will care *how* it is located.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...
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.
�
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.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.
�
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. � ��
�
Dave.
--
Dave Cridland - mailto:dave@xxxxxxxxxxxx - xmpp:dwd@xxxxxxxxxxxxxxxxx
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�- http://dave.cridland.net/
Infotrope Polymer - ACAP, IMAP, ESMTP, and Lemonade
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