Re: [Ecrit] Expert review of draft-patel-ecrit-sos-parameter-03.txt

["Milan Patel" <milanpa at nortel.com>]

Hi Peter and Gonazalo,

Thank you for the comments provided on the list. I'll provide version
-05 this week based on your feedback.

Best regards,
Milan

Milan Patel
Carrier Networks Core Standards
Nortel
milanpa at nortel.com
Telephone +44 162 843 2381 / ESN 560 2381
Mobile +44 774 053 9261 / ESN 748 9261

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-----Original Message-----
From: Gonzalo Camarillo [mailto:Gonzalo.Camarillo at ericsson.com] 
Sent: 01 May 2009 20:31
To: Dawes, Peter, VF-Group
Cc: Patel, Milan (MOP:EP10); ecrit at ietf.org
Subject: Re: [Ecrit] Expert review of
draft-patel-ecrit-sos-parameter-03.txt

Hi,

inline:

Dawes, Peter, VF-Group wrote:
> Hello Milan, Gonzalo,
> I have read through draft-patel-ecrit-sos-parameter-04 and I have a
few
> comments:
> 
> Section 4.2 says:
>    The "sos" URI parameter is appended to the URI included in the
>    Contact header, thus indicating to the UA that this contact address
>    will be included in the Contact header of an INVITE for emergency
>    call initiation.
> 
> I think it would be clearer to say:
> 
>    The "sos" URI parameter is appended to the URI included in the
>    Contact header, thus indicating to the UA that it MUST include this
> contact address
>    in the Contact header of an INVITE for emergency call initiation.

defining normative behavior in this way is not very clear. I would say 
"it needs to include" instead. Defining what the UA MUST do could be 
placed in a different paragraph or section if needed. The point is that 
separating the specification of UAC behavior from the specification of 
UAS behavior is typically a good thing.

> Also, 4.2 says nothing about whether the PSAP uses the URI in the
> Contact: header for 
> callback. At the end of section 1., it says:
> 
>    A call back from a PSAP would be routed to the registered contact
> address.
> 
> So it seems that for any subsequent callback session initiated by the
> PSAP, the address
>  in the From: or P-Asserted-Identity header fields will be used. I am
> not sure that
>  draft-ietf-ecrit-framework-09 is clear on what to include in the
> Request URI for callback,
> but it suggests that for dropped calls the URI from the Contact:
header
> field may be used. 
> 
>  
> Section 4.3 says:
>    If registration is successful, the 200 (OK) response from a legacy
>    registrar is unlikely to include the "sos" URI parameter in the
>    Contact header.  The UAC is aware of its registered contact address
>    and address-of-record, however, is unable to distinguish between
this
>    registration and a non-emergency registration.
> 
> Does it matter if the UAC gets the "sos" URI parameter back from the
> registrar? I would
> have thought that the disadvantage of a non-supporting registrar is
> limited to not 
> routing callbacks to the contact address marked for emergency use. The
> UAC can still use
> the emergency registered contact address in the Contact: header field
of
> an INVITE request
> for an emergency call.

the thing is that a legacy registrar will treat this registration as a 
non-emergency registration. That is what the text needs to capture.

Cheers,

Gonzalo