Subject: [Sip] Possible issue with URL comparison: query for input

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 7 Nov 2001 03:25:20 -0500

Folks,

Discussions have been happening with IESG on SRV usage. One of the oddities
in our current usage is this bit about not using SRV when the URL has a
port, EXCEPT if that port is the default port. That is:

sip:[email-masked]:5099

would use A records, whilst:

sip:[email-masked]:5060

would use SRV. The reason for this odd behavior is rooted in our desire for
the following URLs to be equivalent:

sip:user@foo
sip:user@foo:5060

As the URLs are equivalent, we would expect that their DNS processing should
be the same. Thus, since we use SRV when no port is present, we must also
use SRV if the default port is present.

All of this gets fabulously ugly due to the fact that SIP now has MULTIPLE
default ports that depend on the transport (5060 for UDP and TCP, 5061 for
TLS). The result is that:

sip:user@foo:5061;transport=tls

would use SRV, whilst:

sip:user@foo:5061

would not. Yuck.

The guidance we got was that the far cleaner solution is that:

 a. when the port is present in the URL, always use A records. If there is
no port, use SRV.
 b. as an implication of a., sip:user@foo and sip:user@foo:5060 would *NOT*
be equivalent URLs.

b. above is a change in the URL comparison rules. I am looking to get a
sense whether that would cause interoperability failures in existing and
deployed systems. So, I ask: are there people out there that always put the
5060 as the port in the URL? If so, we will have problems.

Please reply to me privately about what your implementation is doing. I will
collect the results and post the summary to the list.

Thanks,
Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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