Subject: Re: [dispatch] Revision ofdraft-allen-dispatch-imei-urn-as-instanceid

From: Ricky Kaura <[email-masked]>
Date: Wed, 02 Feb 2011 19:40:18 +0000

Dear all,

I work for Samsung and attend 3GPP CT1/CT meetings and GSM Association
(GSMA) Interworking, Roaming Expert Group (IREG), Roaming in LTE (RiLTE)
subgroup meetings.

I would like to express my support of draft-montemurro-gsma-imei-urn and
the associated draft-allen-dispatch-imei-urn-as-instanceid for the
following reasons:

*         3GPP has specified IMS emergency calls over LTE and GPRS in
3GPP Release 9. When originating an emergency call over these access
technologies, it is required to include the IMEI-URN as the instance ID
in the "+sip.instance" header field parameter in the Contact header of
the SIP INVITE (see 3GPP TS 23.237 and 3GPP TS 24.237). This is required
in order to support access transfer of emergency calls from the PS
domain to the CS domain. The IMEI is used at the Emergency Access
Transfer Function (EATF) to correlate the original IMS emergency session
with the session transfer request that was initiated from the MSC
(Mobile services Switching Centre) upon handover to the CS domain.
Specifically, in the case of limited service mode, where an IMS
registration does not necessarily occur, the IMEI is the only available
identifier that can be used to allow the EATF to correlate the source
and target access legs.

*         Recently in 3GPP TS 24.229, a CR was approved which states
that if a UE has an IMEI available, it shall always include the IMEI in
the "+sip.instance" header field parameter in the Contact header of the
SIP Register. The requirement for the inclusion of the IMEI came from
GSMA and is included in PRD IR.92. IR.92 is a user-to-network (UNI)
profile of the key 3GPP IMS specifications for voice and SMS over LTE
and has been developed in GSMA IREG RiLTE by a number of operators,
network vendors and device manufacturers. The requirement to include the
IMEI (if available) in the SIP Register is to support operator
requirements for the IMS network to perform an IMEI check when the UE is
IMS registered, as stated in the Stage 1 requirements in 3GPP TS 22.016
(section 5).  

*         3GPP developed a feature in Release 8 called "IMS Centralised
Services" (ICS) (see TS 23.292 and TS 24.292) which allows a user to
have a consistent set of features independent of whether the UE is on PS
access or CS access. 3GPP have defined the MSC server enhanced for ICS
to control voice sessions set up using circuit bearers. To enabled this
feature, the MSC server performs a SIP registration on behalf of the UE
when the UE is in the circuit domain. However, a registration for the
user may also exist in the PS domain. The IMEI included as the Instance
Id is used as a way of allowing the IMS network to identify that the SIP
registrations below to the same UE and to allow correct handling of
session establishment requests using GRUU.

*         The ICS feature in 3GPP also allows the use of specialised
functionality on the UE (i.e. an ICS client). Such a UE is called an ICS
UE. When the ICS UE performs a SIP registration, it identifies itself by
using the IMEI and includes this as the Instance Id in the SIP REGISTER.
When used in conjunction with an MSC server enhanced for ICS, the
application server in IMS can use the GRUU to correlate the SIP
signalling that comes directly from the UE with the SIP signalling that
comes via the MSC server when the ICE UE initiates an ICS session. 

In summary, these drafts are very important for the support of key
features in 3GPP.

I request that this work is progressed as quickly as possible in IETF. 

Regards,

Ricky Kaura.

Principal Standards Engineer

Standands and Industry Affairs (SIA)

Samsung Electronics Research Institute

Tel:   +44 (0) 1784 428 600 Ext 635; Mob: +44 (0) 7760 761514; Fax: +44
(0) 1784 428 610

Email: [email-masked] <mailto:[email-masked]> ; Skype:
rickykaura; Yahoo: rkaura1969

Samsung Electronics (UK) Limited

Registered number: 03086621

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