Re: [dispatch] draft-jesske-sipping-etsi-ngn-reason-04

[<[e-mail]>]

Hi Dale,
The main probblem is that reasons are currently not allowed in responses. Neither conditionally nor allowed

Please see: http://www.ietf.org/mail-archive/web/sipping/current/msg09682.html

The draft tries to close this gap and allows conditionally Q.850 resasons within Resopnses. So it would be a service provider decision to include Reasons in Responses when mapping from ISUP to SIP.

The following call flow shows an example:

         A                Gateway             Gateway              B 
         |        IAM        |                  |                  | 
         |------------------>|     INVITE       |                  | 
         |                   |----------------->|      IAM         | 
         |                   |     100 Trying   |----------------->| 
         |                   |<-----------------|    100 Trying    | 
         |                   |   403 Decline    |                  |
         |                   |  Reason Q850 #87 |  REL Cause #87   |
         |   REL Cause #87   |                  |<-----------------| 
         |                   |<-----------------|                  | 
         |<----------------- |                  |                  | 
         |                   |                  |                  | 
         |                   |                  |                  | 
         |                   |                  |                  | 

Due to RFC 3398 a 403 will be mapped back to a ISUP Cause 21. With the Reason in responses the Cause Value 87 will be secured and transferred back to ISUP.

Mheanwile I got some indications from some persons who see this issue within the BLISS group due to the fact that this draft solves interoperability issues within SIP and PSTN.

Views?

BR,

Roland
 

-----Ursprüngliche Nachricht-----
Von: Dale Worley [mailto:[e-mail]] 
Gesendet: Freitag, 10. Juli 2009 21:52
An: Jesske, Roland
Cc: [e-mail]
Betreff: Re: AW: [dispatch] draft-jesske-sipping-etsi-ngn-reason-04

On Tue, 2009-07-07 at 07:13 +0200, [e-mail] wrote:
> Hi Dale,
> Within the SIPPING group I had already discussions on that issue.
> The assumption was that the use of the Reason Header within Responses is conditionally allowed. 
> 
> The RFC 3326 says:
>    Initially, the Reason header field defined here appears to be most
>    useful for BYE and CANCEL requests, but it can appear in any request
>    within a dialog, in any CANCEL request and in any response whose
>    status code explicitly allows the presence of this header field.
> 
> 
> So we need a draft where it is stated that a reason header can be included within the SIP Response. That was also the recommendation of that discussion. That is why I wrote a draft.
> Nevertheless some standards already include this behaviour like the ITU-T Q.1912.5 specification.
> Also 3GPP needs the reason header within Responses.

It is still unclear to me what is being changed.  Is the change the
replacement of "conditionally allowed" to "allowed"?  In any case, in my
mind the purpose of the Reason header is to carry Q.850 cause-codes in
failure responses.

The point is that the Abstract is not at all clear about the change from
the status quo (at least to someone who isn't already thoroughly
familiar with how Reason is currently specified).

And the secondary point is that if the Abstract was clearer about what
it is being changed, more people might read and discuss the draft.

Dale