Re: [Sip-implementors] [sipcore] RFC 4028 UAS behavior requirement of Require header

2021-06-01 Thread Hoil Choi 
Thanks Ranjit.  The word "MUST" seems to throw some vendors off.  I saw at 
least one device that behaves this way due to the word "MUST".  Is there way to 
get that reviewed and edited?

Thanks,
Hoil


From: Ranjit Avasarala 
Sent: Friday, May 28, 2021 1:40 PM
To: Hoil Choi 
Cc: Sip-implementors@lists.cs.columbia.edu 
; sipc...@ietf.org 
Subject: Re: [sipcore] RFC 4028 UAS behavior requirement of Require header

Hi Holi

The RFC says UAS should add a Require: timer in response when UAC is the 
refresher to indicate to UAC that it is the refresher. But I think this is 
redundant as UAC anyway knows it is the refresher and does not need a reminder 
from UAS.

On Fri, May 28, 2021 at 3:18 PM Hoil Choi 
mailto:hoil.c...@hotmail.com>> wrote:
Hi Ranjit, thanks for taking a look.

However, I'm more interested in case where UAS is responding to UAC's request 
with refresher as itself (uac).  Consider this case -

UAC  INVITE (Session-Expires: 1800;refresher=uac, Supported: timer) > 
UAS
UAC < 200 OK (Session-Expires: 1800;refresher=uac) - UAS

In this case, the statement in question seems to convey that UAS should also 
add "Require: timer" in its 200 response.  Why would this be, when it's clear 
that UAC declared itself as the refresher and that timer is supported?

For reference, RFC 4028 Section 9 UAS Behavior (or page 16)
If the refresher parameter in the Session-Expires header field in the 2xx 
response has a value of 'uac', the UAS MUST place a Require header field into 
the response with the value 'timer'.

Thanks,
Hoil


From: Ranjit Avasarala mailto:ranjitka...@gmail.com>>
Sent: Friday, May 28, 2021 12:38 PM
To: Hoil Choi mailto:hoil.c...@hotmail.com>>; 
Sip-implementors@lists.cs.columbia.edu
 
mailto:Sip-implementors@lists.cs.columbia.edu>>
Cc: sipc...@ietf.org 
mailto:sipc...@ietf.org>>
Subject: Re: [sipcore] RFC 4028 UAS behavior requirement of Require header

Hi Holi
the presence of the "Require" header with value "timer" from UAS indicates to 
UAC that it (UAC) is performing the refreshing operation. but if the UAS is the 
refresher, then if Require header with value "timer" is present in response 
from UAS, then UAC should send BYE if it does not receive a session refresh 
request from UAS.

Regards
Ranjit



On Fri, May 28, 2021 at 10:02 AM Hoil Choi 
mailto:hoil.c...@hotmail.com>> wrote:
Hello,

I hope this mail finds appropriate person or team for an answer to my question 
on RFC 4028.
I am a SIP enthusiast and always learning a lot about it, but by no means am I 
an expert; so please excuse my ignorance.

I came across an interesting statement In Section 9 UAS Behavior (or page 16).


If the refresher parameter in the Session-Expires header field in the
   2xx response has a value of 'uac', the UAS MUST place a Require
   header field into the response with the value 'timer'.

Statement seems to convey that UAS must place a Require header with value 
'timer' when UAC requests itself to be the refresher.

However, this statement should only be true, if UAC did not put Session-Expire 
with value of 'uac'.

If UAC, in INVITE request, put Session-Expire with value of 'uac' (itself), UAS 
should not bother putting Require header field in the response.  Or to be more 
accurate, UAC should include 'timer' in Supported header, so that UAS doesn't 
have to bother putting Require header field.

What is the reason behind the requirement of Require header, from UAS in this 
case?

Thanks!
Hoil Choi
253-273-5442

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Re: [Sip-implementors] RFC 4028 UAS behavior requirement of Require header

2021-06-01 Thread Paul Kyzivat 

Ranjit,

BTW, did you notice that there is an erata applying to section 9 of 
RFC4028? If you didn't notice, it might be confusing you.


On 5/28/21 5:59 PM, Paul Kyzivat wrote:

On 5/28/21 4:40 PM, Ranjit Avasarala wrote:

Hi Holi

The RFC says UAS should add a Require: timer in response when UAC is the
refresher to indicate to UAC that it is the refresher. But I think 
this is

redundant as UAC anyway knows it is the refresher and does not need a
reminder from UAS.


The UAC makes an offer with Supported:timer and refresher=uac. That says 
it is *willing* to use timer, and is needs to be the refresher *if* 
timer is used for this call. At that point it is still uncertain whether 
timer will be used.


In the case where the UAS does support timer, it consummates the 
negotiation by including Require:timer and including refresher=uac as 
confirmation. It is the Require:timer that is the action that confirms 
timer is to be used. The refresher=uac is pro forma per Table 2 in that 
there is no choice in this case. But the UAC has to say *something* 
about it in the Session-Expires field.


 Thanks,
 Paul


On Fri, May 28, 2021 at 3:18 PM Hoil Choi  wrote:


Hi Ranjit, thanks for taking a look.

However, I'm more interested in case where UAS is responding to UAC's
request with refresher as itself (uac).  Consider this case -

UAC  INVITE (Session-Expires: 1800;refresher=uac, Supported: timer)
> UAS
UAC < 200 OK (Session-Expires: 1800;refresher=uac)
- UAS

In this case, the statement in question seems to convey that UAS should
also add "Require: timer" in its 200 response.  Why would this be, when
it's clear that UAC declared itself as the refresher and that timer is
supported?

For reference, RFC 4028 Section 9 UAS Behavior (or page 16)
If the refresher parameter in the Session-Expires header field in the 
2xx

response has a value of 'uac', the UAS MUST place a Require header field
into the response with the value 'timer'.

Thanks,
Hoil

--
*From:* Ranjit Avasarala 
*Sent:* Friday, May 28, 2021 12:38 PM
*To:* Hoil Choi ;
Sip-implementors@lists.cs.columbia.edu <
Sip-implementors@lists.cs.columbia.edu>
*Cc:* sipc...@ietf.org 
*Subject:* Re: [sipcore] RFC 4028 UAS behavior requirement of Require
header

Hi Holi
the presence of the "Require" header with value "timer" from UAS 
indicates
to UAC that it (UAC) is performing the refreshing operation. but if 
the UAS
is the refresher, then if Require header with value "timer" is 
present in

response from UAS, then UAC should send BYE if it does not receive a
session refresh request from UAS.

Regards
Ranjit



On Fri, May 28, 2021 at 10:02 AM Hoil Choi  
wrote:


Hello,

I hope this mail finds appropriate person or team for an answer to my
question on RFC 4028.
I am a SIP enthusiast and always learning a lot about it, but by no 
means

am I an expert; so please excuse my ignorance.

I came across an interesting statement In Section 9 UAS Behavior (or 
page

16).


If the refresher parameter in the Session-Expires header field in the
    2xx response has a value of 'uac', the UAS MUST place a Require
    header field into the response with the value 'timer'.


Statement seems to convey that UAS must place a Require header with 
value

'timer' when UAC requests itself to be the refresher.

However, this statement should only be true, if UAC did not put
Session-Expire with value of 'uac'.

If UAC, in INVITE request, put Session-Expire with value of 'uac'
(itself), UAS should not bother putting Require header field in the
response.  Or to be more accurate, UAC should include 'timer' in 
Supported

header, so that UAS doesn't have to bother putting Require header field.

What is the reason behind the requirement of Require header, from UAS in
this case?

Thanks!
Hoil Choi
253-273-5442

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Re: [Sip-implementors] [sipcore] RFC 4028 UAS behavior requirement of Require header

2021-06-01 Thread Paul Kyzivat 

On 5/28/21 4:40 PM, Ranjit Avasarala wrote:

Hi Holi

The RFC says UAS should add a Require: timer in response when UAC is the
refresher to indicate to UAC that it is the refresher. But I think this is
redundant as UAC anyway knows it is the refresher and does not need a
reminder from UAS.


The UAC makes an offer with Supported:timer and refresher=uac. That says 
it is *willing* to use timer, and is needs to be the refresher *if* 
timer is used for this call. At that point it is still uncertain whether 
timer will be used.


In the case where the UAS does support timer, it consummates the 
negotiation by including Require:timer and including refresher=uac as 
confirmation. It is the Require:timer that is the action that confirms 
timer is to be used. The refresher=uac is pro forma per Table 2 in that 
there is no choice in this case. But the UAC has to say *something* 
about it in the Session-Expires field.


Thanks,
Paul


On Fri, May 28, 2021 at 3:18 PM Hoil Choi  wrote:


Hi Ranjit, thanks for taking a look.

However, I'm more interested in case where UAS is responding to UAC's
request with refresher as itself (uac).  Consider this case -

UAC  INVITE (Session-Expires: 1800;refresher=uac, Supported: timer)
> UAS
UAC < 200 OK (Session-Expires: 1800;refresher=uac)
- UAS

In this case, the statement in question seems to convey that UAS should
also add "Require: timer" in its 200 response.  Why would this be, when
it's clear that UAC declared itself as the refresher and that timer is
supported?

For reference, RFC 4028 Section 9 UAS Behavior (or page 16)
If the refresher parameter in the Session-Expires header field in the 2xx
response has a value of 'uac', the UAS MUST place a Require header field
into the response with the value 'timer'.

Thanks,
Hoil

--
*From:* Ranjit Avasarala 
*Sent:* Friday, May 28, 2021 12:38 PM
*To:* Hoil Choi ;
Sip-implementors@lists.cs.columbia.edu <
Sip-implementors@lists.cs.columbia.edu>
*Cc:* sipc...@ietf.org 
*Subject:* Re: [sipcore] RFC 4028 UAS behavior requirement of Require
header

Hi Holi
the presence of the "Require" header with value "timer" from UAS indicates
to UAC that it (UAC) is performing the refreshing operation. but if the UAS
is the refresher, then if Require header with value "timer" is present in
response from UAS, then UAC should send BYE if it does not receive a
session refresh request from UAS.

Regards
Ranjit



On Fri, May 28, 2021 at 10:02 AM Hoil Choi  wrote:

Hello,

I hope this mail finds appropriate person or team for an answer to my
question on RFC 4028.
I am a SIP enthusiast and always learning a lot about it, but by no means
am I an expert; so please excuse my ignorance.

I came across an interesting statement In Section 9 UAS Behavior (or page
16).


If the refresher parameter in the Session-Expires header field in the
2xx response has a value of 'uac', the UAS MUST place a Require
header field into the response with the value 'timer'.


Statement seems to convey that UAS must place a Require header with value
'timer' when UAC requests itself to be the refresher.

However, this statement should only be true, if UAC did not put
Session-Expire with value of 'uac'.

If UAC, in INVITE request, put Session-Expire with value of 'uac'
(itself), UAS should not bother putting Require header field in the
response.  Or to be more accurate, UAC should include 'timer' in Supported
header, so that UAS doesn't have to bother putting Require header field.

What is the reason behind the requirement of Require header, from UAS in
this case?

Thanks!
Hoil Choi
253-273-5442

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Re: [Sip-implementors] [sipcore] RFC 4028 UAS behavior requirement of Require header

2021-06-01 Thread Hoil Choi 
Hi Ranjit, thanks for taking a look.

However, I'm more interested in case where UAS is responding to UAC's request 
with refresher as itself (uac).  Consider this case -

UAC  INVITE (Session-Expires: 1800;refresher=uac, Supported: timer) > 
UAS
UAC < 200 OK (Session-Expires: 1800;refresher=uac) - UAS

In this case, the statement in question seems to convey that UAS should also 
add "Require: timer" in its 200 response.  Why would this be, when it's clear 
that UAC declared itself as the refresher and that timer is supported?

For reference, RFC 4028 Section 9 UAS Behavior (or page 16)
If the refresher parameter in the Session-Expires header field in the 2xx 
response has a value of 'uac', the UAS MUST place a Require header field into 
the response with the value 'timer'.

Thanks,
Hoil


From: Ranjit Avasarala 
Sent: Friday, May 28, 2021 12:38 PM
To: Hoil Choi ; Sip-implementors@lists.cs.columbia.edu 

Cc: sipc...@ietf.org 
Subject: Re: [sipcore] RFC 4028 UAS behavior requirement of Require header

Hi Holi
the presence of the "Require" header with value "timer" from UAS indicates to 
UAC that it (UAC) is performing the refreshing operation. but if the UAS is the 
refresher, then if Require header with value "timer" is present in response 
from UAS, then UAC should send BYE if it does not receive a session refresh 
request from UAS.

Regards
Ranjit



On Fri, May 28, 2021 at 10:02 AM Hoil Choi 
mailto:hoil.c...@hotmail.com>> wrote:
Hello,

I hope this mail finds appropriate person or team for an answer to my question 
on RFC 4028.
I am a SIP enthusiast and always learning a lot about it, but by no means am I 
an expert; so please excuse my ignorance.

I came across an interesting statement In Section 9 UAS Behavior (or page 16).


If the refresher parameter in the Session-Expires header field in the
   2xx response has a value of 'uac', the UAS MUST place a Require
   header field into the response with the value 'timer'.

Statement seems to convey that UAS must place a Require header with value 
'timer' when UAC requests itself to be the refresher.

However, this statement should only be true, if UAC did not put Session-Expire 
with value of 'uac'.

If UAC, in INVITE request, put Session-Expire with value of 'uac' (itself), UAS 
should not bother putting Require header field in the response.  Or to be more 
accurate, UAC should include 'timer' in Supported header, so that UAS doesn't 
have to bother putting Require header field.

What is the reason behind the requirement of Require header, from UAS in this 
case?

Thanks!
Hoil Choi
253-273-5442

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