Re: [sipcore] Session-timer: Result below an acceptable value

[Christer Holmberg <[e-mail]>]

Hi,


The UAS is not allowed to include Min-SE to begin with (unless it sends a 422 response).


The UAS is currently allowed to reduce the S-E value in the response, as long as it it's larger than the Min-SE value in the corresponding request. My suggestion would be to say that a UAS SHOULD NOT reduce the S-E. Again, assuming the proxies know better how often they want session refreshes, there is no need for the UAS to reduce the value.


Regards,


Christer



________________________________
From: [e-mail] <[e-mail]>
Sent: Thursday, October 4, 2018 4:21 PM
To: Christer Holmberg
Cc: Roman Shpount; OKUMURA Shinji; SIPCORE
Subject: Re: [sipcore] Session-timer: Result below an acceptable value

Hi
Reading this. I understand that the proxy should be allowed to increase the Min SE.
For my understanding.
Following that the UAS cannot lower it again. Correct?
That would be my understanding.

Best Regards
Roland

Am 04.10.2018 20:05 schrieb Christer Holmberg <[e-mail]>:

Hi,


In order to keep track of the suggested RFC modifications, I suggest that we create GitHub issues.


As an example, I created one for Shinji's suggestion to allow a proxy to increase the Min-SE header field value.


https://github.com/cdh4u/draft-sessiontimer-race/issues/1

[https://avatars0.githubusercontent.com/u/9333380?s=400&v=4]<https://github.com/cdh4u/draft-sessiontimer-race/issues/1>

Proxy allowed to increase Min-SE header field value · Issue #1 · cdh4u/draft-sessiontimer-race<https://github.com/cdh4u/draft-sessiontimer-race/issues/1>
github.com
BACKGROUND: Section 8.1 of RFC 4028 says: "A proxy MUST NOT insert a Min-SE header field or modify the value of an existing header field in a proxied request if that request contains a Support...





(As always, any formal decision whether to modify something will be made on the list)


Regards,


Christer




________________________________
From: sipcore <[e-mail]> on behalf of Christer Holmberg <[e-mail]>
Sent: Thursday, October 4, 2018 2:43 PM
To: Roman Shpount
Cc: OKUMURA Shinji; SIPCORE
Subject: Re: [sipcore] Session-timer: Result below an acceptable value


Hi,


Sorry, I read your first e-mail wrong: I thought you said that the proxy would DECREASE Min-SE. But, now I see that you talk about INCREASE 😊


I see no reason why a proxy couldn't increase Min-SE.


As we have learned, the main users of session timer are proxies, not UAs, so a UA should not care if the minimum value is increased.

>Technically speaking UA still care about how often they need to generate refresh since this can result in extra load on the UA.

Sure, but increasing the Min-SE value will not result in extra load - on the contrary it may reduce load :)

>When session timer is negotiated, S-E specifies the max acceptable value and Min-SE specifies min acceptable value, so proxy should be able to increase Min-SE and decrease SE.

Correct.

Regards,

Christer