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Addressing & Invocation of IMS-attached ServicesIoannis Fikouras, Roman Levenshteyn,
Salvatore Loreto, Gonzalo CamarilloEricsson Research
IPTComm 2007, 19-20 July, New York
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IMS & non-IMS services
The IP Multimedia Subsystem (IMS) is an IP and IETF protocol based architecture by 3GPP & ETSI TISPAN
IMS was designed as a platform for current & future telecoms & Internet services
Still, a plethora of non IMS-enabled systems and services is and will continue to be available to the subscriber
However, non-IMS services may be accessible locally to IMS terminals
An approach to provide access to such non-IMS services would extend the reach of IMS and is therefore desirable
GGSNEnterprise
BSC
CDMA2000
SIP AS
MSC(Server)RNC
UMTS/GPRS CN
SGSN
MGW
WLAN
MGW
HSS
S-CSCFP-CSCF
IMSIMS
MRF
I-CSCF
MGCF
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Introducing IMS-attached services
Attached services are: not directly addressable e.g. provided by
devices without SIP connectivity, or remotely hosted services, accessible via a
network connection
Introducing Attached Services Identifiers
ASIs support: registration of attached services in the IMS
domain (e.g. on presence servers) discovery of attached services dispatching of service requests for attached
services
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IMS-attached services identifiers
ASIs consist of three components used to:– address the IMS-enabled node (IMS URI),– identify specific types or instantiations of services (LSI)– signify service semantics (feature identifier, e.g. IANA)
Local Service Identifiers (LSI) are required to facilitate:– differentiation between multiple services with the same Feature Identifier– addressing of specific variations of attached services
Attached Serv. Identifier
IMS node URI Feature Identifier LSI
sip:[email protected] 1.3.6.1.8.4.5 (video) LSI3
sip:[email protected] 1.3.6.1.8.4.5 (video) LSI2
sip:[email protected] 1.3.6.1.8.4.1 (audio) LSI1
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Detection of IMS-attached services
Detection of attached services is achieved through:– Local discovery mechanisms for local services provided by devices
connected to an IMS terminal– Remote services can be registered via a network connection to the IMS-
enabled node
The IMS-enabled node creates the Local ASI Mapping Table containing the mapping between ASIs and attached services
Attached Serv. IdentifierAttached Serv. Desc.
IMS node URI Feature Identifier LSI Attached Serv. Address Other
sip:[email protected] 1.3.6.1.8.4.5 (video)
LSI3 192.168.1.123(IP-address)
data
sip:[email protected] 1.3.6.1.8.4.5 (video)
LSI2 192.168.1.100(IP-address)
…
sip:[email protected] 1.3.6.1.8.4.1 (audio)
LSI1 00:20:DF:E0:A3:5A (bluetooth address)
…
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Registration of IMS-attached services
Attached services should be registered in the IMS domain using their ASIs in order to enable:
– Discovery– Invocation
An appropriate registry could be a Presence server or even the CSCF itself.
PresenseServer
Detection
Detection
Detection
Detection
ASI ASD
RegistrationLocal ASI
mapping table
CSCF Registration
ASI
ASI
DiscoveryASI table
CSCF -Discovery ASI
table
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Attached service registrationvia SIP REGISTER REGISTER sip:example.com SIP/2.0 From: sip:[email protected];tag=asd98 To: sip:[email protected] Call-ID: [email protected] CSeq: 9987 REGISTER Max-Forwards: 70 Via: SIP/2.0/UDP
host.example.com;branch=z9hG4bKnashds Contact:
<sip:[email protected]>;audio=LSI1 ;video=LSI2;video=LSI3;actor="msg-taker"
;automata;mobility="fixed" ;methods="INVITE,BYE,OPTIONS,ACK,CANCEL" Content-Length: 0
The Contact header field contains :
the SIP URI in the Contact field is taken from the URI column of the local ASI mapping table
audio and video feature tags are according to IANA classification and are taken from the Feature Identifier column of the local ASI mapping table
LSIs can be omitted, in case only one service with a specific Feature Identifier is registered
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Discovery ASI mapping table
Based on the information provided by the registration process, a table consisting of all registered ASIs for an IMS-enabled node is created and maintained within a registry such as the presence server
Attached Serv. IdentifierOther data
IMS node URI Feature Identifier LSI
sip:[email protected] 1.3.6.1.8.4.5 (video) LSI3 …
sip:[email protected] 1.3.6.1.8.4.5 (video) LSI2 …
sip:[email protected] 1.3.6.1.8.4.1 (audio) LSI1 …
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Discovery ASI mapping flow
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Invocation of IMS-attached services
INVITE sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP 5555::aaa:bbb:ccc:ddd];branch=z9hG4bKnashds7
Max-Forwards: 70 Route: <sip:pcscf1.visited1.net;lr>,
<sip:scscf1.home1.net;lr> From:
<sip:[email protected]>;tag=171828 To: <sip:[email protected]> Call-ID: cb03a0s09a2sdfglkj490333 Cseq: 127 INVITE Contact: <sip:[5555::aaa:bbb:ccc:ddd]> Accept-Contact: audio; video=LSI1 Content-Type: application/sdp Content-Length: 248
Accept-Contact header fields are used to select appropriate attached services for incoming invocations
The set of features specified by the Accept-Contact header field defines the set of attached services to reach
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Conclusions
This paper outlines a method for providing access to attached non-IMS services to all IMS subscribers
The approach enables the IMS terminal to act as gateway for accessing services hosted by other devices
Mechanisms for the detection, registration, discovery and invocation of attached services are presented
The proposed solution opens the way for innovative scenarios and new business cases
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Thank you!
Q&A
For more information please contact: Roman Levenshteyn [email protected]
Ioannis Fikouras [email protected]
Salvatore Loreto [email protected]
Gonzalo Camarillo [email protected]
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