On 8/5/11 12:15 AM, Samir Srivastava wrote:
Hi, IMHO presentation of information in tabulated form helps a lot to
starters. Like ABNF it helps parser developers (expert of syntax&
semantic analysis) to develop it without referring each line of SIP
rfc's. 3262 or 100rel should have updated table Ideally each
subsequent RFC should conisder table updation. Tabulation of
information will be done by vendors internally anyway. So do it in
community. SIP needed hitchakers guide. Simplicity for starters
please. Regards Samir
That was the concept that led to the table in the first place.
But history has shown this not to work very well in practice, for a
number of reasons. Here are some:
- it proved impossible to define a table format that expressed
all the nuances. There still had to be text to explain the
complex cases. People tended to believe the table even though
its flagged as having exceptions
- extensions to sip require updates to the table. But the extensions
are done in separate RFCs, not revisions to 3261. So they tended
to specify new rows to the table. These never get rolled up in
one place. Also, extensions that add methods add columns to the
table. When that happens, then you need to specify the values
for the new columns, for rows in 3261 and also in all extensions
that added rows. This is difficult, and was rarely if ever done
right.
- given both a table and text descriptions of what is required,
it was unclear which is the authoritative normative specification.
(I'm certain there are more reasons.)
To be workable we would probably need to move the entire table to an
IANA registry. That also seemed unworkable.
And with text descriptions it is easier to specify the requirements in
ways that will apply to most headers and methods that might be defined
in the future.
The bottom line is that we ultimately decided that the table was a bad
idea and we didn't want to continue maintaining it.
Thanks,
Paul
On 8/4/11, Romel Khan<romel.k...@idt.net> wrote:
So it is useful if one of UAS or UAC requires it, but it does not have to be
mandatory. Some comments:
-- RFC3261 mentions early dialog without mentioning RFC3262. Then it seems
logical to me that it needs to be made clear in this RFC3261 that early
dialog must mean Contact and Record-Route (if Record-Route was received in
INVITE) headers is mandatory in 1xx without reference to 100rel.
-- A UAS could always send 1xx with headers that are required for early
dialog but it doesn't have to enforce 100rel (eg because the origination or
UAS side itself may not support reliable provisional response handling, or
reliable provisioning not really required for its operation). UAS could send
"support:100rel" if it supports it, or it would not send it if it doesn't
support this. In my opinion, if UAC hasn't sent 100rel required, it should
be up to the UAS to decide whether to enforce 100rel
(with "required:100rel") if its application really requires SIP requests
before call answer. If the origination side (UAC) side has a need to send
early requests, like UPDATE, then the UAC should require 100rel from the
termination side (UAS) by sending this in INVITE. In a VoIP service provider
world, these kind of capabilities are configured during interconnect turn
up.
-- I notice that some vendors gateway implementations, even if gateway is
the termination side, require 100rel for the gateway to receive pre-answer
requests such as UPDATE. This really didn't have to be this way. I have
always seen these gateways, when it is the termination side, respond back
SIP 183 with the headers that create early dialog. So if the origination
side received the SIP 183 response, then there is no reason for the
origination side to now not be able to send UPDATE request. Also, no
reason for the termination gateways to not accept the SIP UPDATE without
requiring PRACK.
Thanks.
On Wed, Aug 3, 2011 at 11:46 AM, Robert Sparks<rjspa...@nostrum.com> wrote:
(removing the rfc-editor and trimming the distribution to the lists)
On Aug 2, 2011, at 5:24 PM, Iñaki Baz Castillo wrote:
2011/8/2 Robert Sparks<rjspa...@nostrum.com>:
Further, they're only going to make sense for 1xx that is sent using
100rel.
This has been discussed in sip-implementors, and that assertion seems
incorrect. As I've reported in the errata:
Section 12.1: "Dialogs are created through the generation of
non-failure responses to requests with specific methods. Within this
specification, only 2xx and 101-199 responses with a To tag, where the
request was INVITE, will establish a dialog."
Section 12.1.1: "When a UAS responds to a request with a response that
establishes a dialog (such as a 2xx to INVITE), the UAS MUST copy all
Record-Route header field values from the request into the response
[...]. The UAS MUST add a Contact header field to the response."
So it's clear that a 1xx response to an INVITE creates a dialog and
then it MUST contain a Contact header and mirrored Record-Route
headers, *regardless* the usage of 100rel.
Am I wrong? if so, why?
Not wrong, just incomplete. This will create an (early) dialog at the UAS.
It may or may not create a dialog at the UAC without 100rel since the
message may never get to the UAC. Where I said "make sense" above,
it might have been better if I had said "be useful".
Regards.
--
Iñaki Baz Castillo
<i...@aliax.net>
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_______________________________________________
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This list is essentially closed and only used for finishing old business.
Use sip-implement...@cs.columbia.edu for questions on how to develop a SIP
implementation.
Use dispa...@ietf.org for new developments on the application of sip.
Use sipc...@ietf.org for issues related to maintenance of the core SIP
specifications.
_______________________________________________
Sip mailing list https://www.ietf.org/mailman/listinfo/sip
This list is essentially closed and only used for finishing old business.
Use sip-implement...@cs.columbia.edu for questions on how to develop a SIP
implementation.
Use dispa...@ietf.org for new developments on the application of sip.
Use sipc...@ietf.org for issues related to maintenance of the core SIP
specifications.
