IP Multimedia Subsystem Part 5 Marek Średniawa

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1 IP Multimedia Subsystem Part 5 Marek Średniawa mareks@tele.pw.edu.pl Institute of Telecommunications Project is co-financed by European Union within the European Social Fund 1

2 Identification in IMS

Identities of the user sip:marek@mydomain.com ms@mobile.

3 Identities of the user tel: IMS subscriber Private User Identity tel: Public User Identities 3

4 Identities of the user and user s service profiles sip:marek@mydomain.com Service Profile 1 IMS subscriber ms@mobile.com Private User Identity tel: Public User Identities sip:ms@pw.com User s Profile related with Private User Identity and with a set of Public User Identities tel: Service Profile 2 User s Profiles 4

5 Identification in IMS A need for a unique identification Private and Public ids. Public User Identity More than one PUI (Public User Identity) SIP URI or TEL URI sip: @telekom.pl; user=phone tel: TEL URI required for IMS-PSTN calls At least one TEL URI and one SIP URI per user 5

6 IMS User Identity (1/2) Each IMS User has at least one private and one or more public User Identities IMS Private User Identity: belongs to the IMS operator not used for routing of SIP messages uses the format defined in RFC 2486 Example: stored on the ISIM card (in the mobile phone) and in the HSS (in the IMS User Profile) 6

7 IMS User Identity (2/2) IMS Public User Identity: public and may be subject to Number Portability used for routing of SIP messages may use the SIP-URI format defined in RFC 3261 and/or the TEL-URI format defined in RFC 2806 Example SIP-URI: Example TEL-URI: tel: At least one Public User Identity is stored on the ISIM card All Public User Identities are stored in the HSS 7

8 Public Service Identities (PSI) Similar to public user identities, but allocated to services (ASs) rather than users Used to identify specific applications Servers (enablers), such as presence or group list servers Typically take the form of a SIP URI or TEL URI sip: songdownload@t-online.de, presence@t-online.de, chat@partner.de tel: PSIs are treated as PUIs, i.e. easy routing of SIP requests to ASs (as end user systems also called service routing ) Public Service Identities are not authenticated i.e., there is no corresponding private user (service) identity 8

9 SIM, USIM and ISIM in 3GPP UMTS terminals feature Universal Integrated Circuit Card (UICC) Stores subscription information, authentication keys, address book, message store Without UICC only emergency calls Logical applications: Subscriber Identity Module (SIM), Universal Subscriber Identity Module (USIM) IP Multimedia Service Identity Module (ISIM) 9

10 ISIM UICC application 3GPP TS Stores IMS data for User authorization and authentication Terminal configuration ISIM might coexist with SIM and USIM 10

11 ISIM Private User Identity Only one Public User Identity One or more SIP URIs assigned to a user Home Network Domain URI SIP URI containing the name of the home domain Used for resolving home network address during registration procedure Only one home network domain Long term secret Authorization and computing of CK and IK keys IMS terminal uses IK and CK respectively for security and ciphering of SIP messages to/from P-CSCF 11

12 User s profile in HSS 12

13 Implementation of services

14 IMS Service Architecture DIAMETER Native SIP Services Service Logic SIP AS Servlet/CPL/API DIAMETER All 3 types of AS behave as SIP AS on ISC interface towards S-CSCF HSS DIAMETER Cx ISC (SIP+) ISC (SIP+) S-CSCF ISC (SIP+) OSA/Parlay Gateway 3rd Party Services OSA API OSA Application Server MAP Legacy IN Services IM SSF CAP CAMEL Service Environment S-CSCF Serving -Call Session Control Function IM SSF IP Multi-media Service Switching Function HSS Home Subscriber Store ISC IMS Service Control Interface 14

15 IMS Service Architecture Networks may contain more than one AS AS may be specialized to certain services S-CSCF communicates with AS via the ISC SIP interface AS can be located in the home network or in the third party networks AS can either act as: originating UA terminating UA SIP proxy SIP redirect server B2BUA Functionality of proxy depends on situation, parameters and configuration as well as on application itself AS may or may not remain in signaling path 15

16 IMS Service Architecture Can be an End-User Service that includes communication service logic & client software Can be a Service Enabler that can be called and shared by many end-user services Includes Software Development Kit (SDK) to allow Service Providers and developers to easily deploy new services Can interact with other AS to generate new composite services via Service Orchestration Framework Pure IMS Applications the new presence based IMS services (e.g. pushto-talk, push-to-video, push-to-text) Hybrid applications bridging between traditional telecom and IMS domain 16

17 IMS Service Architecture SIP based interface between the S-CSCF and the service platforms Supports subscription to event notifications between the AS and S-CSCF Transports presence related messages, according to the Presence Service Platform Allows the AS to be notified of the implicit registered Public User Identities, Registration State and UE capabilities and characteristics S-CSCF performs any filtering (based on information received from the HSS) for ISC interaction Shall be able to convey charging information 17

18 Filter Criteria Filter Criteria determines the services (provide to each other) two types of filter criteria initial filter criteria - ifc subsequent filter criteria - sfc only initial filter criteria are used When S-CSCF receives a first request, S-CSCF evaluates initial filter criteria (i.e. INVITE, OPTIONS) 18

19 Filter Criteria(1/3) HSS stores all the data to a user (user profile) User profile contains Private User Identity User profile is applicable and one or more service profiles Service profiles contains one or more Public User Identities and zero or more filter criteria 19

20 Filter Criteria(2/3) Determines the service that are applicable to the collection of Public User Identity listed Priority be assessed, compared with the same service profile S-CSCF first choose filter criteria higher priority Priority is a unique number Trigger Points to determine whether or not the SIP request will be forwarded to a particular AS A collection of Service Point Triggers Example: (Method = INVITE) AND (Request-URI=sip:user@example.com) 20

21 Filter Criteria(3/3) Service Point Trigger allows to access the information stored in different fields of the SIP request If there is no Trigger Point, SIP request is forwarded to the AS After the Trigger Points, the initial filter criteria contains the AS SIP URI The Service Information field contains transparent data that the AS needs to process the request The user profile XML format 21

22 Structure of Initial Filter Criteria 22

23 An Example of Service Execution A service provided to a particular user(sip:goodguy@example.com) Caller is listed in a black list (sip:badguy@example.com) Sip:goodguy@example.com contains Trigger Point (method = INVITE) AND (P-Asserted-Identity = sip:badguy@example.com) AND (Session Case = Terminating) 23

24 An example of a user profile (XML) 24

3. INVIT E An example of a service IMS home network AS 4. INVIT E 8. 200 OK 7. 200OK MRFC 1. INVITE 2. INVITE 10. 200 OK 9.

25 3. INVIT E An example of a service IMS home network AS 4. INVIT E OK OK MRFC 1. INVITE 2. INVITE OK OK MRFP I-CSCF RTP S -CSCF Based on: G.Carillo, M.A.Garcia-Matin, The 3G IP Multimedia Subsystem (IMS), Wiley,

26 5. INVITE OK Several ASs providing services AS 1 AS 2 AS 3 IMS home network OK 6. INVITE 1. INVITE 2. INVITE 9. INVITE 10. INVITE OK OK OK OK I-CSCF S -CSCF P-CSCF Based on: G.Carillo, M.A.Garcia-Matin, The 3G IP Multimedia Subsystem (IMS), Wiley,

27 Filter Criteria Triggering Example 1. User initiates a SIP session by sending a SIP INVITE with header=a to its S-CSCF 2. S-CSCF evaluates the SPTs and finds a match with the filter criteria X. S-CSCF forwards request to AS1. 3. AS1 performs service logic and sends the SIP request back to the S-CSCF with a service related modification, i.e. change header=a to header=b. 4. S-CSCF evaluates the SPTs and finds a match with the filter criteria Y. S-CSCF forwards the request to AS2. 5. AS2 performs service logic and sends SIP request back to the S- CSCF. 6. No more filter criteria, S-CSCF forwards this request to the next hop based on the route decision. 7. If in step 3, the header was not changed by AS1, then S-CSCF evaluates the SPTs and does not find a match and routes the request to the next hop. AS 1 1 Incoming SIP leg 3 2 INVITE header =A SIP message with header=b S-CSCF Outgoing SIP leg INVITE Match Initial Filter Criteria Filter Criteria X to AS1 SPT HeaderA priority 1 Filter criteria Y to AS2 SPT HeaderB priority AS 2 SIP message possibly modified SIP message forwarded by S-CSCF 27

28 Models of AS operation

29 AS functional model AS HSS Sh /Si Application Logic AS -ILCM AS -OLCM ISC S-CSCF 29

30 AS - terminating UA or Redirect server AS From: X To: Y Call -ID: Z SIP dialog #1 SIP dialog #1 S -CSCF From: X To: Y Call -ID: Z 30

31 AS as initiating UA AS SIP dialog #1 From: X To: Y Call -ID: Z S -CSCF SIP dialog #1 From: X To: Y Call -ID: Z 31

32 AS acting in the SIP proxy mode AS From: X To: Y Call -ID: Z SIP dialog #1 SIP dialog #1 From: X To: Y Call -ID: Z SIP dialog #1 From: X To: Y Call -ID: Z S -CSCF SIP dialog #1 From: X To: Y Call -ID: Z 32

33 AS acting in the 3PCC / B2BUA mode AS From: X To: Y Call -ID: Z SIP dialog #1 SIP dialog #2 From: P To: Q Call -ID: R SIP dialog #1 From: X To: Y Call -ID: Z S -CSCF SIP dialog #2 From: P To: Q Call -ID: R 33

34 AS call model SIP request AS SIP answer AS-ILCM AS-Logic AS-OLCM SIP request SIP answer 34

35 Termination of a session by AS AS SIP BYE SIP 200 OK AS-ILCM AS-Logic AS-OLCM 35

36 Session termination request forwarded by AS From: A To: B Call-ID:Y Cseq:Z SIP BYE AS-ILCM AS AS-Logic AS-OLCM SIP BYE From: A To: B Call-ID:Y Cseq:Z 36

37 Session termination request initiated by AS AS AS-ILCM AS-Logic SIP BYE From: A To: B Call-ID:Y Cseq:Z AS-OLCM SIP BYE From: C To: D Call-ID:W Cseq:X 37

38 IMS - delivery of services - wrap up S-CSCF determines that a call requires enhanced service processing Filtering may be based on: calling / called party other mechanism defined by filtering criteria eg. SIP message type, header fields, etc. Based on FC, the S-CSCF determines the address of the AS and relays the call to the AS function. The AS receives the call and invokes the appropriate service logic taking one of the following actions: Redirects the call to a new destination Send the call back through the S-CSCF in order to monitor subsequent call events (ie. act as a SIP Proxy) The AS, based on some other input, can also set-up calls between other entities in the network i.e. act as a B2BUA 38

39 IMS service platform interfaces Source: T. Magedanz (TU Berlin / Fraunhofer FOKUS) 39

40 EIMS Project is co-financed by European Union within European Social Fund 40

All-IP Core Network Multimedia Domain

GPP X.S00-00-0 Version.0 Version Date: July 00 0 All-IP Core Network Multimedia Domain IP Multimedia (IMS) session handling; IP Multimedia (IM) Call Model; Stage 0 COPYRIGHT NOTICE GPP and its Organizational