CAMEL in GPRS prepaid service ghlee@alumni.csie.nctu.edu.tw 1 Outline Evolution of IN GPRS overview CAMEL in GPRS Discussion 2 Plain Old Telephone Service Service logic were hardwired in switching systems. Network operators discuss services customers required with switch vendors. (no standard) Once services were implemented, they were not easily modified. service logic hardwired 3 Stored Program Control In the mid-1960s, stored program control (SPC) switching systems were introduced. As a result, it was easier to introduce new services. Service logic was not modular. service logic programmable 4 Common Channel Signaling In the mid-1970s, common channel signaling network (CCSN) was introduced. Signaling system number 7 (SS7) is the protocol that runs over the CCSN. SS7 network separates the call setup information and talk path from the common trunk that runs between switching systems. 5 SS7 network components signal switching points (SSPs)—SSPs are telephone switches equipped with SS7-capable software and terminating signaling links. They generally originate, terminate, or switch calls. signal transfer points (STPs)—STPs are the packet switches of the SS7 network. They receive and route incoming signaling messages to destination. signal control points (SCPs)—SCPs are databases providing information necessary for advanced callprocessing capabilities 6 SS7 network 7 The Introduction of IN During the mid-1980s, Telcordia Technologies responded to RBOCs’s request and developed the concept of Intelligent Network 1 (IN/1). Service logic splits from switching system, now resides in service control points (SCP). service logic now here 8 Call Model PICs represent switching system states that a call goes through from origination to termination. SSPs check TDPs to see if there are any active triggers. If an active trigger is detected, normal switching system call processing is suspended until the SSP and SCP complete communications. SSP suspended,and ask SCP what to do 9 in next step GPRS logical architecture SMS-GMSC SMS-IWMSC E SM-SC C CAMEL GSMSCF Gd MSC/VLR A Gs Iu Uu R TE HLR MT D Ge Gr Iu UTRAN SGSN Gc Gi Gn Gb TE MT R BSS Um SGSN Gn PDN GGSN Ga Ga Gp CGF GGSN Gf TE Billing System EIR Other PLMN Signalling Interface Signalling and Data Transfer Interface 10 Transmission plane in 2.5G Application IP IP Relay SNDCP Radio indep Radio dep SNDCP Multiplexing layer LLC GTP-U UDP UDP IP IP L2 L2 L1 L1 LLC Relay RLC RLC MAC MAC GSM RF BSSGP BSSGP Network Service GSM RF L1bis Network Service L1bis Um MS GTP-U Gb BSS Gn SGSN Gi GGSN Frame relay 11 Signaling plane in 2.5G GMM/SM GMM/SM LLC LLC Relay RLC RLC MAC MAC GSM RF BSSGP BSSGP Network Service GSM RF L1bis Network Service L1bis Um MS Gb BSS 2G-SGSN 12 Multiplexing of network protocols IP/X.25 Signalling Packet Data Protocol SMS Signaling plane Transmission plane N-PDU NSAPI SNDCP SNDC Header NSAPI + Control Data LLC Header Control LLC Information Data SAPI LLC TLLI RLC or BSSGP 13 User plane in 3G Application E.g., IP, PPP E.g., IP, PPP Relay Relay PDCP PDCP GTP-U GTP-U GTP-U GTP-U RLC RLC UDP/IP UDP/IP UDP/IP UDP/IP MAC MAC AAL5 AAL5 L2 L2 L1 L1 ATM ATM L1 L1 Uu MS Iu-PS UTRAN Gn 3G-SGSN ATM Gi 3G-GGSN 14 Control plane in 3G GMM / SM / SMS GMM / SM / SMS Relay RRC RRC RANAP RANAP RLC RLC SCCP SCCP MAC MAC Signalling Bearer Signalling Bearer L1 L1 AAL5 AAL5 ATM ATM Uu MS Iu-Ps RNS 3G SGSN 15 CAMEL architecture Home Network HLR gsmSCF MAP CAP gprsSSF SGSN Interrogating Network MS Visiting Network Home/Interrogating/Visiting Network 16 MAP/CAP protocol stack CAP has the same underlying protocol stack as MAP. Ge interface is first defined in 3G, but didn’t appear in 2.5G. MAP MAP CAP CAP TCAP TCAP TCAP TCAP SCCP SCCP SCCP SCCP MTP3 MTP3 MTP3 MTP3 MTP2 MTP2 MTP2 MTP2 L1 L1 L1 L1 HLR gprsSSF SGSN Gr Ge gsmSCF 17 Overall CAMEL Architecture gsmSCF CAP Interface GPRS Dialogue Handler Internal CAP Interface gprsSSF Internal Interface MobileStation SGSN GTP GGSN 18 Detection Points (DPs) GPRS events maybe made visible to gsmSCF. DPs are points at which these events are detected. DPs can be armed to notify gsmSCF GPRS event was encountered, and to allow gsmSCF to influence subsequent handling of GPRS session/PDP Context. If DP isn’t armed, processing entity continues processing without gsmSCF involvement at the DP. 19 Detection Points (DPs) 3 different types of DP: Trigger Detection Point-Request (TDP-R) Event Detection Point-Request (EDP-R) Event Detection Point-Notification (EDP-N) 20 Detection Points (DPs) TDP-R Statically armed, initiate a CAMEL control relationship When GPRS event is encountered, processing is suspended EDP-R Dynamically armed within CAMEL control relationship When GPRS event is encountered, processing is suspended and gprsSSF waits for inst from gsmSCF EDP-N Dynamically armed within CAMEL control relationship When GPRS event is encountered, processing is not suspended. 21 GPRS Attach/Detach State Model 3 DPs are defined: Detached DP Attach DP Change of Position Detach GPRS session DP Detach Attach request AD_Exception Attach User- or network initiated detach Attached Intra SGSN Routeing area update Inter SGSNRouteing area update Change of Position GPRS Session 22 GPRS PDP Context State Model Idle 4 DPs are defined: PDP Context Setup Req DP PDP Context PDP Context Est. PDP_Context_ Context C_Exception Establishment PDP Setup Disconnection PDP Context DP PDP Context Setup Ack. PDP Context Est. Ack. Establishment Ack User or network PDP_Context_ initiated disc. DP PDP Context Established Disconnection Routeing area update Change of Position Context DP Change of Position Context Routeing area update Change of Position context 23 GPRS CAMEL Scenarios 2 scenarios for CAMEL control of GPRS Scenario 1 Scenario 2 Allows CAMEL control of GPRS session and of multiple PDP contexts within 1 GPRS dialogue Allows CAMEL control of a single PDP contexts Multiple PDP contexts are controlled via multiple GPRS dialogues. Scenario 1 and scenario 2 are mutually exclusive. 24 GPRS CAMEL Scenario 1 Involves Attach/Detach state model Uses less resource (tcap dialogue) More complicated when implementation SGSN / SSP A/D SM PDP#1 SM PDP#2 SM GPRS Dialogue SCP Information flow related to the Session Information flow related to PDP Context #1 Information flow related to PDP Context #2 25 GPRS CAMEL Scenario 2 Doesn’t involves Attach/Detach state model Uses more resource (tcap dialogue) Simpler when implementation SGSN / SSP PDP#1 SM PDP#2 SM GPRS Dialogue #1 SCP Information flow related to PDP context #1 Information flow related to PDP context #2 GPRS Dialogue #2 26 GPRS Attach The message sequence chart is too large to fit in this slide. Please see the supplementary document from 3GPP 23060 spec. Notice the “Insert subscriber data” procedure, GPRSCSI (CAMEL Subscription Information) is sent from HLR to SGSN. 2.5G HLR does not keep GPRS-CSI, nor does it send GPRS-CSI to SGSN. 3G HLR could keep GPRS-CSI, also it sends GPRS-CSI when doing “Insert subscriber data” procedure. 27 GPRS-CSI GPRS-CSI contains following information gsmSCF Address Service Key Default GPRS Handling TDP List CAMEL Capability Handling CSI state Notification flag gsmSCF address list for CSI 28 PDP Context Activation in 2.5G C1 :DP for CAMEL_GPRS_PDP_Context_Establishment C2 :DP for CAMEL_GPRS_PDP_Context_Establishment_Acknowledgement MS BSS 2G-SGSN 2G-GGSN 1. Activate PDP Context Request C1 2. Security Functions 3. Invoke Trace 4. Create PDP Context Request 4. Create PDP Context Response 7. BSS Packet Flow Context Procedures C2 9. Activate PDP Context Accept 29 PDP Context Activation in 3G C1 :DP for CAMEL_GPRS_PDP_Context_Establishment. C2 :DP for CAMEL_GPRS_PDP_Context_Establishment_Acknowledgement MS UTRAN 3G-SGSN 3G-GGSN 1. Activate PDP Context Request C1 4. Create PDP Context Request 4. Create PDP Context Response 5. Radio Access Bearer Setup 6. Invoke Trace 8. Update PDP Context Request 8. Update PDP Context Response C2 9. Activate PDP Context Accept 30 CAMEL procedures for charging activities Procedure ApplyChargingGPRS ApplyChargingReportGPRS InitialDPGPRS ContinueGPRS EventReportGPRS RequestReportGPRSEvent ssf -> scf scf ->ssf - 31 Discussion 32