Subject: [Sipping] DNS-less clients?

From: "Adam Roach (EUS)" <[email-masked]>
Date: Mon, 25 Jun 2001 17:00:49 -0500

The passage that Sudharsana krishnan P pointed out a while back
(bis03, 16.4.1) raised a red flag for me; specifically:

    "However, in some instances, a UA may not be capable of DNS,
     and therefore may not be able to follow those procedures."

Now, I know there is more to SIP than carrying SDP, but
it can be argued quite strongly that the normal case is
sending SDP in INVITE messages.

Turning our attention to RFC2327, when defining the "c="
parameter:

    "If a unicast data stream is to pass through a network address
     translator, the use of a fully-qualified domain name rather than an
     unicast IP address is RECOMMENDED.  In other cases, the use of an
     IP address to specify a particular interface on a multi-homed host
     might be required.  Thus this specification leaves the decision as
     to which to use up to the individual application, but all
     applications MUST be able to cope with receiving both formats."

So, it seems to me that the prospect of a SIP client incapable
of using DNS is rather improbable, since a SIP client without
DNS would necessarily be in violation of a MUST strength
requirement in SDP (one of only twelve in the whole spec).

I suspect that suggesting that such a client is reasonable in
the SIP specification may cause some unnecessary confusion.

/a

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From: Gonzalo Camarillo <[email-masked]>
Date: Tue, 26 Jun 2001 18:27:34 +0300

Hello Adam,

>      applications MUST be able to cope with receiving both formats."

This has been removed from the SDP draft that is intended to become the
draft standard RFC.

Bottom of page 13:
http://www.ietf.org/internet-drafts/draft-ietf-mmusic-sdp-new-02.txt

Regards,

Gonzalo

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From: Paul Kyzivat <[email-masked]>
Date: Tue, 26 Jun 2001 13:30:16 -0400

Why is this particular change to SDP being made?

	Paul Kyzivat
	Cisco Systems