Subject: [Asrg] 6. Proposals - LMAP - Similarities in XMPP

From: Yakov Shafranovich <[email-masked]>
Date: Tue, 23 Dec 2003 16:01:48 -0500

While looking at the XMPP draft for IM, I came across a method described 
there about verification of servers via DNS, which sounds awfully like 
LMAP. The original draft can be found here:

http://www.ietf.org/internet-drafts/draft-ietf-xmpp-core-20.txt

In section 10.2, the following snippet:

" There exists no server-to-server stream between the two domains: The
       sender's server (1) resolves the hostname of the foreign domain
       (as defined under Server-to-Server Communications (Section 14.3))
    ...
"

Section 14.3 described the DNS lookups:

"  Inter-domain connections MUST NOT proceed until the DNS hostnames
    asserted by the servers have been resolved. Such resolutions MUST
    first attempt to resolve the hostname using an [SRV] Service of
    "xmpp-server" and Proto of "tcp", resulting in resource records such
    as "_xmpp-server._tcp.example.com. ... If the SRV lookup fails,
    the fallback is a normal IPv4/IPv6 address record resolution to
    determine the IP address, using the "xmpp-server" port of 5269
    registered with the IANA.
"

Now from my reading of "until the DNS hostnames asserted by the servers" 
sounds like this must take place on both on outgoing AND incoming 
messages, which seems to tie in IP addresses to domains, exactly like 
LMAP. This also does not use TXT or RR records, but rather does this via 
SRV records. This is very similar to the method described in 
(http://www.irtf.org/asrg/draft-vixie-repudiating-mail-from.txt) which 
uses the same single RR, MX, for both incoming and outgoing mail.

Of course the XMPP spec recommends TLS and SASL use as well, which has 
already defined for SMTP in RFCs 3207 and 2554.

Yakov
-------
Yakov Shafranovich / asrg <at> shaftek.org
SolidMatrix Technologies, Inc. / research <at> solidmatrix.com
"They that can give up essential liberty to obtain a little temporary 
safety deserve neither liberty nor safety" (Benjamin Franklin)
-------

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