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Re: [Ecrit] Expert review of draft-patel-ecrit-sos-parameter-03.txt
Hi Milan,
I would like to pick up on Gonzalo's comment below:
> The document does not talk about backwards compatibility. What happens
> if the registrar does not understand the 'sos' parameter? Will it do
> the right thing? Will the UAC detect the failure? Is there a need to
> define an option tag?... the document should address these points.
In the meanwhile, the document does talk about backwards compatibility.
However, the legacy registrar will do the only (right) thing it can do
but from a perspective of the UE that might not be the anticipated
(right) thing.
It is my understanding that an emergency registration can happen at any
time and a UE is not required to immediately follow up the successful
registration with an emergency call or tear down the emergency
registration after the emergency call.
Suppose a UAC has one public user identity and it performs a normal
registration with some feature tags. Subsequently, the same UAC performs
an emergency registration with different feature tags. Would the legacy
registrar "refresh" the binding, then the S-CSCF would apply "emergency"
feature tags to all session requests.
An option tag would prevent this.
If in agreement, I suggest the following changes to the draft (between
<new> and </new> tags):
4.1. REGISTER Request
When the UA sends a REGISTER request for emergency registration, the
"sos" URI parameter MUST be appended to the URI in the Contact
Header<new> and the option-tag "e-reg" must be included in the
Proxy-Require and Require header</new>. This serves as an indication to
the
registrar that the
request is for emergency registration<new> and it is only accepted if
emergency registration is supported</new>.
Example:
Contact: "Alice" <sip:alice at example.com;sos> ;q=0.7; expires=3600
In the event that more than one Contact header field is included in
the REGISTER request, only the contact addresses that include the
"sos" URI parameter shall be considered as emergency registered
contact addresses.
<new>
Upon receipt of a 420 (Bad Extension) response the UAC will use an
existing registration or initiate another registration.
</new>
4.3. Backwards compatibility issues
The backwards compatibility scenario considered in this document is
where a legacy registrar does not support the "sos" URI parameter.
<new>
This document registers an option tag with IANA in section 6.2.
Inclusion of the option tag will prevent a legacy registrar from
handling the request.
</new>
6. IANA Considerations
<new>
6.2 SIP URI parameter
</new>
This specification defines one new SIP URI parameter, as per the
registry created by RFC 3969 [RFC3969]
Parameter Name: sos
Predefined Values: none
Reference: [RFCXXXX]
[NOTE TO IANA: Please replace XXXX with the RFC number of this
specification.]
<new>
6.2 SIP Option Tag
This specification registers a new SIP option tag, as per the guidelines
in Section 27.1 of RFC 3261 [RFC3261].
Name: e-reg
Description: This option tag is used to identify the emergency
registration extension. When used in a Supported header, it indicates
that a User Agent understands the extension. When used in a Require
header field of a REGISTER request, it indicates that the registrar is
not expected to process the registration unless it supports the
emergency registration extension.
</new>
Regards,
John-Luc
-----Original Message-----
From: ecrit-bounces at ietf.org [mailto:ecrit-bounces at ietf.org] On Behalf
Of Milan Patel
Sent: Tuesday, April 28, 2009 8:36 AM
To: Gonzalo Camarillo
Cc: ecrit at ietf.org
Subject: Re: [Ecrit] Expert review of
draft-patel-ecrit-sos-parameter-03.txt
Hi Gonzalo,
Version 4 of draft-patel-ecrit-sos-parameter addresses all the comments
you provided in the expert review. Please can you confirm that you are
OK with its contents and that all the issues you had previously
highlighted are now resolved.
http://tools.ietf.org/html/draft-patel-ecrit-sos-parameter-04
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
For the Companies listed below, The Institute of Chartered Accountants
in England and Wales authorises A R Bloom, S Harris and C Hill to act as
Insolvency Practitioners under section 390(2)(a) of the Insolvency Act
1986 and the Association of Chartered Certified Accountants authorises A
M Hudson to act as an Insolvency Practitioner under section 390(2)(a) of
the Insolvency Act 1986.
The affairs, business and property of the Companies are being managed by
the Joint Administrators, A R Bloom, S Harris, AM Hudson and C Hill who
act as agents of the Companies only and without personal liability.
The Companies are Nortel Networks UK Limited; Nortel Networks SA; Nortel
GmbH; Nortel Networks France SAS; Nortel Networks NV; Nortel Networks
SpA; Nortel Networks BV; Nortel Networks Polska SP Zoo; Nortel Networks
Hispania SA; Nortel Networks (Austria) GmbH; Nortel Networks sro; Nortel
Networks Engineering Service Kft; Nortel Networks Portugal SA; Nortel
Networks Slovensko sro; Nortel Networks Oy; Nortel Networks Romania SRL;
Nortel Networks AB; Nortel Networks International Finance & Holding BV
-----Original Message-----
From: Gonzalo Camarillo [mailto:Gonzalo.Camarillo at ericsson.com]
Sent: 09 March 2009 10:32
To: Patel, Milan (MOP:EP10)
Cc: ecrit at ietf.org; Hannes Tschofenig
Subject: Re: [Ecrit] Expert review of
draft-patel-ecrit-sos-parameter-03.txt
Hi,
the problem with this text is that it specifies behavior for entities
that will not implement this specification. The new section should
describe how a legacy registrar will handle, following regular SIP
rules, a REGISTER request with the sos parameter. However, it cannot
specify extra behavior for such a legacy registrar. That is the whole
point of backwards compatibility: to support unchanged legacy
applications that will not implement the new functionality.
In any case, I believe you can use most of the text you proposed below.
It just needs to be rephrased so that it is more descriptive and non
normative.
Thanks,
Gonzalo
Milan Patel wrote:
> Folks,
>
> In response to Gonzalo's comment on backwards compatibility, I propose
> a subclause "4.3 Backwards compatibility issues" as follows:
>
> ----------------------------------------------------------------------
> --
> ----------------------------------
> 4.3 Backwards compatibility issues
> The backwards compatibility scenario considered in this document is
> where the registrar does not support the "sos" URI parameter. In this
> case, if the registrar receives a REGISTER request that includes the
> "sos" URI parameter in the Contact header, the registrar MUST proceed
> with registration procedures and silently ignore the URI-parameter in
> accordance with RFC 3261. This ensures the user is registered and thus
> can successfully initiate an emergency call.
>
> The drawback of proceeding with registration is if the
> address-of-record is barred or has roaming restrictions applied, then
> these restrictions will not be lifted and thus registration will be
> unsuccessful. This may limit the UAC's ability to successfully place
an emergency call.
>
> If registration is successful, the registrar shall return a 200 (OK)
> response to the UAC and does not include the "sos" URI parameter in
> the Contact header. The UAC is aware of its registered contact address
> and address-of-record, however, cannot distinguish between this
> registration and a non-emergency registration.
> ----------------------------------------------------------------------
> --
> --------------------------------------
>
> Comments/feedback/suggestions for improvement are appreciated. I will
> address Gonzalo's other comments in version -04 of the draft as well.
>
> 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
>
> For the Companies listed below, The Institute of Chartered Accountants
> in England and Wales authorises A R Bloom, S Harris and C Hill to act
> as Insolvency Practitioners under section 390(2)(a) of the Insolvency
> Act
> 1986 and the Association of Chartered Certified Accountants authorises
> A M Hudson to act as an Insolvency Practitioner under section
> 390(2)(a) of the Insolvency Act 1986.
>
> The affairs, business and property of the Companies are being managed
> by the Joint Administrators, A R Bloom, S Harris, AM Hudson and C Hill
> who act as agents of the Companies only and without personal
liability.
>
> The Companies are Nortel Networks UK Limited; Nortel Networks SA;
> Nortel GmbH; Nortel Networks France SAS; Nortel Networks NV; Nortel
> Networks SpA; Nortel Networks BV; Nortel Networks Polska SP Zoo;
> Nortel Networks Hispania SA; Nortel Networks (Austria) GmbH; Nortel
> Networks sro; Nortel Networks Engineering Service Kft; Nortel Networks
> Portugal SA; Nortel Networks Slovensko sro; Nortel Networks Oy; Nortel
> Networks Romania SRL; Nortel Networks AB; Nortel Networks
> International Finance & Holding BV
>
> -----Original Message-----
> From: ecrit-bounces at ietf.org [mailto:ecrit-bounces at ietf.org] On Behalf
> Of Gonzalo Camarillo
> Sent: 19 February 2009 13:57
> To: ecrit at ietf.org
> Subject: [Ecrit] Expert review of
> draft-patel-ecrit-sos-parameter-03.txt
>
> Folks,
>
> I have been asked to perform an expert review of the following draft:
>
> http://tools.ietf.org/id/draft-patel-ecrit-sos-parameter-03.txt
>
> The approach taken by the draft seems OK in general. I have a few
> comments though:
>
> The requirement in Section 3 is too specific because it already
> assumes that the solution will be an indication in the SIP header
> fields. The requirement does not need to make that assumption. I would
> remove "by providing an appropriate indication in the SIP header
fields".
>
> In Section 5, the reference to RFC 2234 should be replaced with one to
> RFC 5234.
>
> Also in Section 5, the formal syntax should be rewritten so that it is
> compatible with the ABNF in RFC 3261. RFC 3261 already defines
> uri-parameter as follows:
>
> uri-parameter = transport-param / user-param / method-param
> / ttl-param / maddr-param / lr-param /
> other-param
>
> other-param = pname [ "=" pvalue ]
> pname = 1*paramchar
> pvalue = 1*paramchar
>
> This document should simply define a new value for pname.
>
> The document does not talk about backwards compatibility. What happens
> if the registrar does not understand the 'sos' parameter? Will it do
> the right thing? Will the UAC detect the failure? Is there a need to
> define an option tag?... the document should address these points.
>
> Cheers,
>
> Gonzalo
>
> _______________________________________________
> Ecrit mailing list
> Ecrit at ietf.org
> https://www.ietf.org/mailman/listinfo/ecrit
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