26 Mar
2018
26 Mar
'18
4:55 p.m.
Hi,
This may be more a SIP question than a Kamailio question, but I am
trying to figure out why 407 challenges from Kamailio contain To tags.
I suppose I've not run across it before, and I can't find an RFC-based
rationale. A negative reply to an invite transaction without an
intermediate early dialog-forming reply (e.g. 183 with To tag) does not
form a dialog, nor takes place within a context in which a dialog was
created. So what gives?
Insights appreciated!
-- Alex
--
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
26 Mar
26 Mar
10:27 p.m.
Am Montag, 26. März 2018, 16:55:12 CEST schrieb Alex Balashov:
This may be more a SIP question than a Kamailio
question, but I am
trying to figure out why 407 challenges from Kamailio contain To tags.
I suppose I've not run across it before, and I can't find an RFC-based
rationale. A negative reply to an invite transaction without an
intermediate early dialog-forming reply (e.g. 183 with To tag) does not
form a dialog, nor takes place within a context in which a dialog was
created. So what gives?
Hello Alex,
its indeed that common that it also included in the example RFC 3665, section
3.3. and other.
There is a transaction relationship between the INVITE and the 407. RFC 5057
mandates that the 407 only refers to the transaction, not to any dialog state.
But you are right, if there is no provisional response, there is no (early)
dialog at this state.
But its also included in the 401 (for REGISTERs).
I would think this is normal UAC/UAS behavior for SIP request handling:
RFC 3261, sect. 8.2.6.2:
"However, if the To
header field in the request did not contain a tag, the URI in the To
header field in the response MUST equal the URI in the To header
field; additionally, the UAS MUST add a tag to the To header field in
the response (with the exception of the 100 (Trying) response, in
which a tag MAY be present). This serves to identify the UAS that is
responding, possibly resulting in a component of a dialog ID. "
Or I am wrong?
Henning
10:49 p.m.
On Mon, Mar 26, 2018 at 10:27:35PM +0200, Henning Westerholt wrote:
I would think this is normal UAC/UAS behavior for SIP
request handling:
RFC 3261, sect. 8.2.6.2:
"However, if the To
header field in the request did not contain a tag, the URI in the To
header field in the response MUST equal the URI in the To header
field; additionally, the UAS MUST add a tag to the To header field in
the response (with the exception of the 100 (Trying) response, in
which a tag MAY be present). This serves to identify the UAS that is
responding, possibly resulting in a component of a dialog ID. "
Honestly, in ten years of doing SIP, this is the first time I am
confronting this question. I was accustomed to the notion that To tags
are only added to a reply when it is desirable to form an early dialog
(in the case of a non-100 1xx reply). But the passage you quote seems to
settle it.
--
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
27 Mar
27 Mar
3:30 p.m.
Le 2018-03-26 à 22:49, Alex Balashov a écrit :
On Mon, Mar 26, 2018 at 10:27:35PM +0200, Henning
Westerholt wrote:
An additional question!
Does second authenticated INVITE sent by UAC should also mention this
to tag and the called UA should also accept it as part of the dialog id ?
Or does the second authenticated INVITE open a new dialog ?
Emmanuel
I would think this is normal UAC/UAS behavior for
SIP request handling:
RFC 3261, sect. 8.2.6.2:
"However, if the To
header field in the request did not contain a tag, the URI in the To
header field in the response MUST equal the URI in the To header
field; additionally, the UAS MUST add a tag to the To header field in
the response (with the exception of the 100 (Trying) response, in
which a tag MAY be present). This serves to identify the UAS that is
responding, possibly resulting in a component of a dialog ID. "
Honestly, in
ten years of doing SIP, this is the first time I am
confronting this question. I was accustomed to the notion that To tags
are only added to a reply when it is desirable to form an early dialog
(in the case of a non-100 1xx reply). But the passage you quote seems to
settle it.
9:28 p.m.
Am Dienstag, 27. März 2018, 15:30:01 CEST schrieb Emmanuel BUU:
[..]
Hello Emmanuel,
the first dialog is created at the second successful INVITE. The second INVITE
is just a re-send of the first INVITE with the authentication credentials. To
quote from RFC 3261, section 12.1:
Creation of a Dialog
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. A dialog established by a non-final
response to a request is in the "early" state and it is called an
early dialog.
You will find a good example for a sessions establishment including
authentication and two proxies in RFC 3665, section 3.2.
Best regards,
Henning
Honestly, in ten years of doing SIP, this is the
first time I am
confronting this question. I was accustomed to the notion that To tags
are only added to a reply when it is desirable to form an early dialog
(in the case of a non-100 1xx reply). But the passage you quote seems to
settle it.
An additional question!
Does second authenticated INVITE sent by UAC should also mention this
to tag and the called UA should also accept it as part of the dialog id ?
Or does the second authenticated INVITE open a new dialog ?
2458
days inactive
2459
days old
4 comments
3 participants
participants (3)
-
Alex Balashov -
Emmanuel BUU -
Henning Westerholt