IP Multimedia Subsystem Part 3 Marek Średniawa mareks@tele.pw.edu.pl Institute of Telecommunications Project is co-financed by European Union within the European Social Fund
Charging in IMS
IMS charging and billing Two models: Offline Online Offline Charging info collected after termination of a session Typically - monthly invoicing Online IMS components interwork on-line with a charging system Charging system interacts in real time with user s account 3GPP TR 23.815 - Charging implications of IMS architecture
Charging in IMS
IMS off-line charging Home(A) = Visited(A) Home(B) = Visited(B) BS Bi Bp CCF CGF Rf (Diameter) ACR AS MRFC S-CSCF I-CSCF P-CSCF AS MRFC S-CSCF I-CSCF P-CSCF Rf CCF CGF Bi BS Bp Ga BGCF MGCF BGCF BGCF MGCF BGCF Ga GGSN GGSN SGSN SGSN All components involved in SIP session control can generate off line charging data
IMS offline charging architecture Entities CCF: Charging Collection Function CGF: Charging Gateway Function BS: Billing System. Interface Rf : to send accounting information to a CCF Ga :to send accounting information to a CGF Bi : to send accounting information to a BS Bp :to send accounting information to a BS
Originating Visited Network Originating Home Network IMS Terminal GGSN PCRF P-CSCF C DF S -CSCF CDF (1) INVITE (8) 183 Session Progress (6) AAR (7) AAA (2) INVITE P -Charging-Vector (5) 183 Session Progress P -Charging-Vector (3) INVITE P -Charging-Vector (4) 183 Session Progress P -Charging-Vector (9) RAR (10) RAA (11) PRACK (12) PDP (13) PDP (14) CCR (18) PRACK (19) PRACK (15) CCA (22) 200 OK (16) RAR (17) RAA (21) 200 OK (20) 200 OK (23) UPDATE (24) UPDATE (25) UPDATE (28) 200 OK (27) 200 OK (26) 200 OK (29) 200 OK (35) 200 OK (36) ACK (33) ACR [Start] (34) ACA (30) 200 OK (37) ACK (31) ACR [Start] (32) ACA Session establishment flow (38) ACK
IMS online charging architecture
S-CSCF <-> SCF Online Charging SCF looks like any other AS to the S-CSCF SCF dose not provide services for user in the usual sense. SCF reports accounting information to the Correlation Function. If the user runs out of credit CF informs the SCF SCF terminates the session by acting as a B2BUA
Online Charging AS and the MRFC <-> ECF AS or the MRFC receives the address of the ECF from the S-CSCF in the P-Charging-Function- Address header field
Online Charging Ro interface IEC Based on Diameter Accounting-Request and Answer (ACR,ACA) Immediate Event Charging - IEC Accounting-Record-Type: EVENT_RECORD ECUR Event Charging with Unit Reservation - ECUR Accounting-Record-Type: START_RECORD, INTERIM_RECORD, STOP_RECORD
Charging in IMS - IEC CTF OCF Service request (1) CCR [Event_Request] Service delivery (2) CCA Immediate Event Charging
Charging in IMS - ECUR CTF OCF Service request (1) CCR [INITIAL_REQUEST ] Service delivery starts (2) CCA Service delivery ends (3) CCR [TERMINATION _REQUEST ] (4) CCA Event Charging with Unit Reservation
Charging in IMS CTF OCF Session request (1) CCR [INITIAL_REQUEST] Session delivery starts (2) CCA (3) CCR [UPDATE_REQUEST] Session delivery continues (4) CCA Session delivery ends (5) CCR [TERMINATION_REQUEST] (6) CCA Session Charging with Unit Reservation
AAA in IMS
Authentication, Authorization, and Authentication: Accounting - AAA act of verifying identity of an entity Authorization: act of determining whether a requesting entity will be granted access to a resource Accounting: act of collecting information on resource usage
Diameter base protocol and its applications Credit Control Application Network Access Server Application Mobile IPv 4 Application SIP Application Diameter Base Protocol
Diameter format of a message 0 15 31 Version Message Length Command -Flags Command -Code Application Hop-by-Hop Identifier End-to-End Identifier AVP 1 AVP 2 [...] AVP n
Structure of an AVP 0 15 31 AVP Code Flags AVP Length Vendor-ID (optional) Data
Presence and Instant Messaging and conferencing in IMS
Presence as a catalyst of other services Many services can take advantage of presence info ad hoc conference, PoC, IM, active address list
Presence in IMS IMS terminal plays role of both the watcher and PUA (Presence User Agent) PA is an AS located in the home network Resource List Server (RLS) implemented as AS Functional component accepting and managing presence list subscriptions which enables Watcher applications to subscribe presence info of many presentities using single transaction
IMS presence architecture PUA, Watcher, XDMC Watcher Content Presence Presence Presence RLS RLS Server Server (PS) XDMS Content XDMS XDMS ISC ISC Ut ISC ISC Access Network ISC ISC Sh Access Network P-CSCF S-CSCF HSS SLF Aggregation Proxy Shared XDMS PUA, Watcher XDMC P-CSCF I-CSCF Ut
Watcher subscription to his own list IMS Terminal (1) SUBSCRIBE Originating Visited Network P-CSCF (2) SUBSCRIBE Originating Home Network S -CSCF RLS Evaluation of initial filter criteria (3) SUBSCRIBE (6) 200 OK (9) NOTIFY (10) 200 OK (5) 200 OK (8) NOTIFY (11) 200 OK (4) 200 OK (7) NOTIFY (12) 200 OK Subscription to each of the presentities in the list (15) NOTIFY (16) 200 OK (14) NOTIFY (17) 200 OK (13) NOTIFY (18) 200 OK
Watcher subscription (1) Watcher sends SUBSCRIBE Request contains fields of the Event header S-CSCF analyzes ifc (initial filter criteria) RLS Server authorizing the subscription sends 200 OK RLS sends NOTIFY. Subsequent NOTIFY after receiving new info about change of status of the presentity
The RLS subscribes to a presentity RLS Network Terminating Home Network RLS S -CSCF I-CSCF HSS S -CSCF PS Subscription to the list (1) SUBSCRIBE (10) 200 OK (12) NOTIFY (13) 200 OK Evaluation of initial filter criteria (2) SUBSCRIBE (9) 200 OK (3) LIR (4) LIA (5) SUBSCRIBE (8) 200 OK (11) NOTIFY (14) 200 OK Evaluation of initial filter criteria (6) SUBSCRIBE (7) 200 OK
Watcher subscription (2) RLS sends SUBSCRIBE Request is transferred via S-CSCF to I-CSCF I-CSCF asks HSS to allocate an S-CSCF S-CSCF analyzes ifc and transfers request to PA (Presence Agent) PA sends 200 OK and then NOTIFY
IMS terminal publishing presence information IMS Terminal Originating Visited Network P-CSCF Originating Home Network S-CSCF PS (1) PUBLISH (2) PUBLISH Evaluation of initial filter criteria (3) PUBLISH (6) 200 OK (5) 200 OK (4) 200 OK
Subscription to own Watcher Information IMS Terminal Originating Visited Network P-CSCF Aggregation Proxy Originating Home Network S-CSCF PS/Presence XDMS (1) SUBSCRIBE (2) SUBSCRIBE Evaluation of initial filter criteria (3) SUBSCRIBE (6) 200 OK (9) NOTIFY (5) 200 OK (8) NOTIFY (4) 200 OK (7) NOTIFY (10) 200 OK (19) NOTIFY (11) 200 OK Authorization needed. Subscription in pending state (18) NOTIFY (12) 200 OK (17) NOTIFY (13) SUBSCRIBE (14) 202 Accepted (15) NOTIFY (pending) (16) 200 OK (20) 200 OK (21) 200 OK (22) 200 OK (23) HTTP PUT (24) HTTP PUT (26) 200 OK (25) 200 OK (27) NOTIFY (active) (28) 200 OK
Presence Optimizations Optimizations High Notification Rates Event throttling Presence Optimizations Partial Notification Event Notification Filtering The IMS networks and terminals implement all the extensions
The Ut Interface Runs between an IMS terminal and an Application Server The Ut interface is implemented with HTTP XML Configuration Access Protocol (XCAP)
Pager mode Instant Messaging 3GPP TS 24.229 standard requires IMS terminals to implement MESSAGE method RFC 3428 Optional service feature in S-CSCF and AS Constraints eg. Message size Main goal Enabling S-CSCF or AS to send instant messages to IMS terminals Example AS performs role of a controller in a voice mail service Notification of the user by AS about waiting messages Implementation Registration S-CSCF analyzes ifc S-CSCF sends 3rd party REGISTER message to a selected AS After reception of the REGISTER request, the AS generates MESSAGE request with notification (text info, link,.) MESSAGE transferred via S-CSCF and P-CSCF as each SIP message
Pager mode instant messaging Originating Visited Network Originating Home Network Terminating Home Network Terminating Visited Network IMS Terminal #1 P-CSCF S -CSCF I-CSCF HSS S-CSCF P-CSCF IMS Terminal #2 (1) MESSAGE (2) MESSAGE Evaluation of initial filter criteria (3) MESSAGE (4) Diameter LIR (5) Diameter LIA (6) MESSAGE Evaluation of initial filter criteria (7) MESSAGE (8) MESSAGE (14) 200 OK (13) 200 OK (12) 200 OK (11) 200 OK (10) 200 OK (9) 200 OK Alert user
Pager mode IM based service IMS Terminal P-CSCF I-CSCF HSS S -CSCF AS (1) REGISTER (10) 401 Unauthorized (11) REGISTER (20) 200 OK (25) MESSAGE (26) 200 OK (2) REGISTER (9) 401 Unauthorized (12) REGISTER (19) 200 OK (3) Diameter UAR (4) Diameter UAA (13) Diameter UAR (5) REGISTER (6) Diameter MAR (7) Diameter MAA (8) 401 Unauthorized (14) Diameter UAA (15) REGISTER (24) MESSAGE (27) 200 OK (16) Diameter SAR (17) Diameter SAA (18) 200 OK Evaluation of initial filter criteria (21) REGISTER (22) 200 OK (23) MESSAGE (28) 200 OK
Instant Messaging - session model Instant messaging session initiated by INVITE with SDP media definition for IM Message Session Relay Protocol (MSRP) for transport of messages Two scenarios 1. Terminal IMS establishes a session SIP messages transferred via IMS nodes 2. MRFC i MRFP act as middlemen Charging based on message size or content (MRSP SEND) MRF as chat room server multiparty conference MRSP: VISIT, OK, SEND Later the second user joins the conference and establishes the second session with MRFC
Originating Visited Network Originating Home Network Terminating Home Network Terminating Visited Network IMS Terminal #1 P-CSCF S-CSCF I-CSCF HSS S-CSCF P-CSCF IMS Terminal #2 (1) INVITE (2) 100 (3) INVITE Trying (4) 100 Trying Evaluation of initial filter criteria (5) INVITE (6) 100 Trying (7) Diameter LIR (8) Diameter LIA (9) INVITE Session based IM using MSRP (10) 100 Trying Evaluation of initial filter criteria (11) INVITE (12) 100 Trying (13) INVITE (20) 180 Ringing (19) 180 Ringing (18) 180 Ringing (17) 180 Ringing (16) 180 Ringing (22) 200 OK (14) 100 Trying (15) 180 Ringing (21) 200 OK Alert user Accept session (26) 200 OK (25) 200 OK (24) 200 OK (23) 200 OK (27) ACK (28) ACK (29) ACK (30) ACK (31) ACK (32) MSRP: SEND (33) MSRP: 200 OK (34) MSRP: SEND (35) MSRP: 200 OK
A multi-party session-based conference(chat server) IMS Terminal # 1 Originating Visited Network 1 P-CSCF 1 S-CSCF 1 MRFC MRFP S-CSCF 2 P-CSCF 2 (1) INVITE (2) 100 (3) INVITE Trying (4) 100 Trying Evaluation of initial filter criteria (5) INVITE (6) 100 Trying Originating Home Network (7) H.248 Originating Visited Network 2 IMS Terminal # 2 Session based IM conference chat (10) 200 OK (11) ACK (8) 200 OK (9) 200 OK (12) ACK (13) ACK (14) MSRP: SEND (15) MSRP: 200 OK (18) INVITE (19) 100 Trying Evaluation of initial filter criteria (16) INVITE (17) 100 Trying (20) INVITE (21) 100 Trying (22) H.248 (23) 200 OK (28) ACK (24) 200 OK (27) ACK (29) MSRP: SEND (30) MSRP: 200 OK (25) 200 OK (26) ACK (33) MSRP: SEND (34) MSRP: 200 OK (31) MSRP: SEND (32) MSRP: 200 OK
Conferencing in IMS
Conferencing services in IMS 3GPP TS 24.147 based on SIPPING RFC 4353 XCON RFC 4582 elements utilized BFCP (Binary Floor Control Protocol) Centralized conference server model Tightly coupled conference model Logical distribution of the server into 2 components Signaling Media PSTN interworking Access for PSTN users via MGCF acting as a conference participant SIP for communication with AS/MRFC
IMS conference service architecture AS / MRFC Mp MRFP Conference Server
Conference call using a conference factory URI Alice Bob Conference Server (1) INVITE Conference Factory URI (2) 200 OK Contact : Conference URI (3) ACK (4) INVITE Conference URI (5) 200 OK Contact : Conference URI (6) ACK
Joining a conference using PSI Originating Visited Network Originating Home Network Terminating Home Network IMS Terminal P-CSCF S -CSCF (1) INVITE (2) 100 (3) INVITE Trying (4) 100 Trying Evaluation of initial filter criteria (5) INVITE (6) 100 Trying I-CSCF (7) PSI Location Query (8) Response HSS (9) INVITE (10) 100 Trying AS /MRFC Interaction with MRFP to allocate resources for the conference (14) 183 Session Progress (13) 183 Session Progress (12) 183 Session Progress (11) 183 Sesssion Progress
EIMS Project is co-financed by European Union within European Social Fund