Subject: [Sip] bis-05: transport mechanisms

From: "Drage, Keith (Keith)" <[email-masked]>
Date: Wed, 5 Dec 2001 23:04:36 -0000

Line 2813 of the bis draft states:

All SIP elements MUST support UDP at a minimum.

When we get to the definition of URL parameters in 3216-3218 we have the
following:

The transport parameter determines the transport mechanism to be used for
sending SIP messages. SIP can use any network transport protocol. Parameter
names are defined for UDP [30], TCP [31], TLS [25], and SCTP [32].

I have seen some readers using the text in 3216-3218 to argue that receivers
must support all four transport mechanisms (or at least TCP as well), and
that the option of supporting only the minimum exists at the sender only. I
am not sure how they think to make this work when they come to provide a
response to a request sent using a transport mechanism they do not support
for sending, but still.

My assumption is that the option exists at both sender and receiver.

If my assumption is correct, can we add some more text around line 2813 to
state that, so that everything is clear. Something along the lines of: 

"SIP implementations MAY support any other defined network transport
protocol, and NEED NOT react to messages received on transport mechanisms
which are not supported."

Keith
Keith Drage
Lucent Technologies
Tel: +44 1793 776249
Email: [email-masked]

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From: Michael Thomas <[email-masked]>
Date: Wed, 5 Dec 2001 15:22:51 -0800 (PST)

> names are defined for UDP [30], TCP [31], TLS [25], and SCTP [32].

I think that placing TLS in the same level of
naming hierarchy as "transport" is asking for
trouble. If we must, we should append the security
layer to the actual L4 transport, as in TCP/TLS or
UDP/IPsec, etc.

		Mike

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From: "Dean Willis" <[email-masked]>
Date: Wed, 5 Dec 2001 17:41:30 -0600

logged as bug 279 in bugzilla.

--
Dean

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From: "Bob Penfield" <[email-masked]>
Date: Fri, 7 Dec 2001 19:50:26 -0500

> All SIP elements MUST support UDP at a minimum.

Should this be "SIP imlementations" instead of SIP elements? I may have an
implementation that supports UDP, but an actual deployed element might be
configured to accept only TCP. Or does this statement make the configured
element non-conforming?