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3GPP and IMS

3GPP and IMS. GPRS Operation and PDP Contexts. MS (mobile station) 는 GPRS attach 절차로 SGSN 에 알림 . Attach 되면 , Packet Data Protocol (PDP) context 를 활성화시킴 . GPRS 에서는 PDP Context Activate message 에 있는 QoS profile 과 자원의 가용도 (availability) 에 근거해서 admission control 을 수행함 PDP context:

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3GPP and IMS

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  1. 3GPP and IMS

  2. GPRS Operation and PDP Contexts • MS (mobile station)는 GPRS attach 절차로SGSN에 알림. • Attach되면, Packet Data Protocol (PDP) context를 활성화시킴. • GPRS에서는 PDP Context Activate message에 있는 QoS profile과 자원의 가용도(availability)에 근거해서 admission control 을 수행함 • PDP context: • PDP: Network layer protocol, is a virtual connection between the MS and GGSN • Includes an identifier (e.g., IP), QoS parameters etc. • Establish a GPRS “tunnel” between GGSN and SGSN using GPRS Tunneling Protocol (GTP) • QoS profile (to each PDP context) consists of: • QoS Profile은 QoS attribute (속성)의 집합임 • Delay: acceptable transfer time from one edge of GPRS system to the other edge • Service precedence: drop preference during network abnormalities • Reliability: tolerance for error rates and need for re-transmission • Mean throughput, peak throughput: specify average rate and maximum rate

  3. PDP Contexts • PDP Context는 Parameter들의 집합으로, 단대단 접속을 설립하는데 필요한 모든 정보로 구성됨 • PDP Type • PDP address type (IPv4 or IPv6) • QoS profile request (이용자가 요청하는 QoS parameters) • QoS profile negotiated (망과 협약된 QoS parameters ) • Authentication type • DNS type • PDP Context Activate가 성공한 경우: • SGSN maps QoS profile into appropriate Radio Link Control (RLC)/Medium Access Control (MAC) priority level to indicate the use in uplink access • SGSN also maps accepted QoS profile into an appropriate IP QoS procedure (e.g., marking in Differentiated Services for QoS provisioning over core networks

  4. 1 3 4 2 3 • MS send a requests to the SGSN to be attached to the network. Capabilities are stated multislot, ciphering algorithms, CS and/or PS required 2. Authentication between terminal and HLR 3. Subscriber data downloaded to MSC/VLR and SGSN 4. SGSN notifies terminal that it is attached, enters READY state GPRS Attach Procedure SCP GMSC BTS BSC with PCU PSTN ISDN BSS HLR AUC Public ISP Corporate RADIUS

  5. juniper.net 2 Juniper.net • MS requests PDP context activation type, APN, QoS 4 2. SGSN validates request against subscription information downloaded from HLR during GPRS Attach 3 3. APN sent to DNS, IP address(s) of suitable GGSNs returned 4. Logical connection using GTP created between SGSN and GGSN. 5. IP address allocated to Mobile via local pools, RADIUS or DHCP- from operators own address range, or other- fixed addresses held in HLR- Proxy to RADIUS server in ISP or corporate domain PDP Context Activationaka “how is the connection set up?” 1 SCP MT GMSC BTS BSC with PCU PSTN ISDN BSS HLR AUC Juniper.net 5 RADIUS Public ISP DNS

  6. PDP Context Procedures • MS initiated • GGSN initiated MS BSS SGSN GGSN Activate PDP Context Request Create PDP Context Request Create PDP Context Response Activate PDP Context Accept Packets from ext. nw. PDU notification req. PDU notification resp. Request PDP Context activation Create PDP Context Request Activate PDP Context Request Create PDP Context Response Activate PDP Context Accept

  7. PDP Context Activation … …

  8. User IP (v4 or v6) Application Server UTRAN SGSN GGSN Terminal Radio Bearer GTP-U GTP-U Transport of IP packets IP tackets are tunnelled through the UMTS/GPRS network (GTP – GPRS tunneling protocol) 응용 IP v4 or v6 IP v4 or v6 IP v4 or v6 Relay Relay PDCP PDCP GTP‑U GTP‑U GTP‑U GTP‑U RLC RLC UDP/IP v4 or v6 UDP/IP v4 or v6 UDP/IP v4 or v6 UDP/IP v4 or v6 MAC MAC AAL5 AAL5 L2 L2 L2 [Source: 3GPP] L1 L1 L1 ATM ATM L1 L1 Uu Iu-PS Gn Gi

  9. IP Transport: Concepts • PDP contexts activation • 데이터 전송전에 UE에 의해서 수행됨 • APN사양과 traffic parameters • GGSN은 IP 주소를 UE에 전달 • set-up of bearers in SGSN and GGSN • activation of multiple PDP contexts possible • Access Point Names (APN) • APN은 외부망의 식별자(logical Gi interface of GGSN) • PDP context activation과정에서, SGSN은 DNS에 문의하여, 단말이 요청한 APN을 지원하는 GGSN을 찾아냄. • DNS응답은 GGSN 주소 목록을 갖고 있으며, SGSN은 이들 중에서 라운드 로빈 방식에 의해 하나의 주소를 선택함. • Traffic Flow Templates (TFTs) • A set of packet filters (source address, subnet mask, destination port range, source port range, TOS (IPv4), Traffic Class (v6), Flow Label (v6) • GGSN이 사용하는 것으로서, 외부 망에서 입력되는 IP 패킷에 적절한 PDP context를 할당하는데 사용됨. • GPRS Tunnelling protocol (GTP) • 모든 UE에 대해서, 신호를 위해서 한 개의 GTP-C tunnel이, 이용자 데이터 전송을 위해서 복수개의 GTP-U tunnels이 설립되는데, GTP-U는 PDP context (i.e., session)마다 하나임.

  10. PDP Context X1 (APN X, IP address X, QoS1) PDP Context X2 (APN X, IP address X, QoS2) GGSN GGSN SGSN Terminal IP Transport: PDP Context & APNs ISP X PDP Context Y (APN Y, IP address Y, QoS) Same PDP (IP) address and APN PDP Context Z (APN Z, IP address Z, QoS) APN X ISP Y PDP Context selectionbased on TFT (downstream) APN Y ISP Z APN Z [Source: 3GPP]

  11. QoS Framework in UMTS R5/R6 외부 IP QoS Domain UMTS IP QoS Domain Policy-based Framework Service Request Authorization Token Service Provision with QoS Gq AF PDF Go IP QoS Parameters IP BS Manager IP BS Manager PDP QoS로 변환 UMTS BS QoS Enforcement RAB Iu BS Backbone BS Gate Function GTP Tunneling Over IP DiffServ or ATM AAL5 GTP Tunneling Over IP DiffServ IP Backbone DiffServ망 UTRAN GERAN RNC

  12. 3GPP Releases • Release '99 • 1999년 12월에 제정완료 • UTRA 정의 및 많은 초기 기능들이 정의됨.( 초기 3G의 기본이 됨) • Release 4 • 2001년 3월에 제정. R99의 개선과 핵심망에서 제어평면과 이용자 평면이 분리됨. • low chip rate TDD mode (TD-SCDMA)정의됨. • Release 5 • 2002.년 3월 제정 • R4의 개선과 함께, • IMS - IP-based Multimedia Services • HSDPA - High Speed Downlink Packet Access • Release 6 • 2004년 제정 • IMS의 2단계로서, 멀티미디어 통신을 위한 다양한 기능을 포함함.

  13. 3GPP 패킷도메인 진화 과정 요약

  14. Uu UTRAN PS PS UTRAN IMS UE UE Domain Domain Session control Signaling (SIP / SDP) Media ( RTP) Real Time Media Control (RTCP) RRC+NAS IMS에 의한 음성통신서비스 사례 • 비교 :R99인 경우 회선교환방식으로 음성제공 • IMS: Uu SF-128 12.2kbps AMR speech 3.4kbps Signalling SF-?? Source: R2-032164

  15. IMS의 음성통신 프로토콜 스택 AMR SIP/SDP RTP RTCP1 UDP UDP UDP IP IP IP SRB#4 SRB#4 SRB#2 SRB#2 SRB#3 SRB#3 SRB#1 SRB#1 RAB/RB #3 RAB/RB #1 RAB/RB #2 - PDCP SAP - PDCP SAP PDCP Entity#1 PDCP Entity#2 PDCP ROHC ROHC ROHC ROHC Comp Decomp Comp Decomp RLC UM RLC UM RLC AM RLC AM RLC AM RLC UM RLC UM RLC AM RLC AM RLC AM RLC AM DTCH#1 DTCH#2 DTCH#3 DTCH#3 DCCH DCCH - D MAC - D - D - - D D MAC MAC MAC MAC DCH#4 DCH#4 DCH#1 DCH#2 DCH#3 DCH#3 Physical Layer Source: R2-032166

  16. R-SGW Applicationsand Services IM Subsystem MultimediaIPNetworks HTTP Others ? ? Sh HSS CSCF BGCF ? SIP SIP Mk ISC SLF Mm SIP TCP UDP Diameter SIP BGCF IM-SSF CAP SIP Mi Cx Dx Mw CS Domain-or-PSTN-or-Legacy-or-External OSA-SCS OSA ? SIP Mj SIP Sc CSCF MGCF T-SGW SIP ? AS PCF Mg H248 Mr R-SGW Mc SIP Mp MAP Sr MRF-C MRF-P COPS SCP ? MGW H248 Gr Gc Go Gm CAP SIP „Gi-Cloud“ GGSN TCP/IP/UDP/RTP/… UE PS Domain AlternativeAccess Networks Gn GERAN MT TE SGSN UTRAN R Uu Iu R5 참조구조

  17. Circuit switchedcall control server 3G Release 6 TS 23.221 BICC H.248 RTPorAAL2 UDP/IP or AAL2 TDM ATM IP Iu cs Iu b NodeB PSTN Iu ps USIM IP/AAL5 IMS enhancements for conversational InternetCorporate Multimedia Broadcast/Multicast Service (MBMS) – conferencing etc Service charging enhancements SIP IP Multimedia CSCF UMTS/GPRS - WLAN Interworking Definition in R6, implementation sooner

  18. Establishing IP-CANfor IMS Signalling GPRS Attach Ready for Internet Access and SIP signalling - UE GGSN link setup - UE’s IP address allocation PDP Context Activation Local P-CSCF Discovery Find a local SIP server User-network authentication and location registration Application Level Registration Ready for IMS Session

  19. DHCP Server DNS Server Local CSCF (P-CSCF) DiscoveryDHCP/DNS Procedure visit1.net 5555::aaa:bbb:ccc:ddd ??? PDP Context Activation Procedure P-CSCF DHCP query pcscf1.visited1.net UDP port 5060 5555::aba:dab:aaa:daa pcscf.visit1.net, IP addr of DNS pcscf.visit1.net NAPTR ? _sip._udp.pcscf.visit1.net _sip._udp.pcscf.visit1.net SRV ? pcscf1.visited1.net , port 5060, 5555::aba:dab:aaa:daa

  20. DHCP Server Local CSCF (P-CSCF) DiscoveryDHCP Procedure with DHCPv6 options for SIP servers visit1.net DHCPv6 options for SIP Servers 5555::aaa:bbb:ccc:ddd PDP Context Activation Procedure DHCP query P-CSCFs IP address list

  21. Local CSCF (P-CSCF) DiscoveryGPRS Procedure visit1.net 5555::aaa:bbb:ccc:ddd Activate PDP Context Request Create PDP Context Request Obtain IP addresses of P-CSCF Create PDP Context Response Activate PDP Context Reponse

  22. AKA: Authentication and Key Agreement

  23. HSS DNS Server Application Level (SIP) Registration ProcedureInitial Registration Home Network REGISTER sip:scscf1.home1.net SIP/2.0 Via: SIP/2.0/UDP icscf1_p.home1.net; SIP/2.0/UDP pcscf1.visit1.net; SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd] Path: <sip:term@pcscf1.visit1.net;lr> S-CSCF scscf1.home1.net Query: Public User Identity Private User Identity Visited Network Identifier Response: S-CSCF list Cx: User reg. status REGISTER sip:registrar.home1.net SIP/2.0 Via: SIP/2.0/UDP pcscf1.visited1.net; SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd Path: <sip:term@pcscf1.visit1.net;lr> I-CSCF icscf1_p.home1.net home1.net pcscf1.visit1.net REGISTER sip:registrar.home1.net SIP/2.0 Via: SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]; From: <sip:user1_public1@home1.net>;tag=4fa3 To: <sip:user1_public1@home1.net> Contact: <sip:[5555::aaa:bbb:ccc:ddd];comp=sigcomp>;expires=600000 Authorization: Digest username="user1_private@home1.net", realm="registrar.home1.net", nonce="", uri="sip:registrar.home1.net", response="" Security-Client: ipsec-3gpp; alg=hmac-sha-1-96; spi-c=23456789; spi-s=12345678; port-c=2468; port-s=1357 Require: sec-agree Proxy-Require: sec-agree DNS: P-CSCF P-CSCF discovery (pcscf1.visited1.net UDP port 5060 5555::aba:dab:aaa:daa ) PDP Context UE#1 visit1.net user1_public1@home1.net user1_private1@home1.net VisitedNetwork 5555::aaa:bbb:ccc:ddd

  24. DNS Server HSS Application Level (SIP) Registration ProcedureChallenge Home Network AV selection Cx: authentication SIP/2.0 401 Unauthorized From: <sip:user1_public1@home1.net>;tag=4fa3 To: <sip:user1_public1@home1.net>; tag=5ef4 Call-ID: apb03a0s09dkjdfglkj49111 WWW-Authenticate: Digest realm="registrar.home1.net", nonce=base64(RAND + AUTN + server specific data), algorithm=AKAv1-MD5, ik="00112233445566778899aabbccddeeff", ck="ffeeddccbbaa11223344556677889900" S-CSCF scscf1.home1.net Querry: Public User Identity Private User Identity S-CSCF name Response: AV list AV=RAND | AUTN | XRES | CK | IK I-CSCF icscf1_p.home1.net home1.net pcscf1.visit1.net P-CSCF SIP/2.0 401 Unauthorized WWW-Authenticate: Digest realm="registrar.home1.net", nonce=base64(RAND + AUTN + server specific data), algorithm=AKAv1-MD5 Security-Server: ipsec-3gpp; q=0.1; alg=hmac-sha-1-96; spi-c=98765432; spi-s=87654321; port-c=8642; port-s=7531 PDP Context UE#1 visit1.net user1_public1@home1.net user1_private1@home1.net VisitedNetwork 5555::aaa:bbb:ccc:ddd

  25. DNS Server HSS Application Level (SIP) Registration ProcedureRegistration with Response (Integrity Protected) Home Network Querry: Public User Identity Private User Identity S-CSCF name Response: User Profile REGISTER sip:scscf1.home1.net SIP/2.0 Authorization: Digest username="user1_private@home1.net", realm="registrar.home1.net", nonce=base64(RAND + AUTN + server specific data), algorithm=AKAv1-MD5, uri="sip:registrar.home1.net", response="6629fae49393a05397450978507c4ef1", integrity-protected="yes" Cx: Reg. notification Authentication S-CSCF scscf1.home1.net Cx: User reg. status Query: Public User Identity Private User Identity Visited Network Identifier Response: S-CSCF list I-CSCF icscf1_p.home1.net home1.net REGISTER sip:registrar.home1.net SIP/2.0 REGISTER sip:registrar.home1.net SIP/2.0 Via: SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]; From: <sip:user1_public1@home1.net>;tag=4fa3 To: <sip:user1_public1@home1.net> Contact: <sip:[5555::aaa:bbb:ccc:ddd];comp=sigcomp>;expires=600000 Authorization: Digest username="user1_private@home1.net", realm="registrar.home1.net", nonce=base64(RAND + AUTN + server specific data), algorithm=AKAv1-MD5, uri="sip:registrar.home1.net", response="6629fae49393a05397450978507c4ef1" Security-Client: ipsec-3gpp; alg=hmac-sha-1-96; spi-c=23456789; spi-s=12345678; port-c=2468; port-s=1357 Security-Verify: ipsec-3gpp; q=0.1; alg=hmac-sha-1-96; spi-c=98765432; spi-s=87654321; port-c=8642; port-s=7531 Require: sec-agree Proxy-Require: sec-agree pcscf1.visit1.net DNS: P-CSCF Generation of Response and Session Key PDP Context UE#1 visit1.net user1_public1@home1.net user1_private1@home1.net VisitedNetwork 5555::aaa:bbb:ccc:ddd

  26. HSS DNS Server Application Level (SIP) Registration Procedure200 OK response Home Network SIP/2.0 200 OK Via: SIP/2.0/UDP icscf1_p.home1.net; SIP/2.0/UDP pcscf1.visited1.net; SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]:1357 Path: <sip:icscf1_p.home1.net;lr>, <sip:term@pcscf1.visited1.net;lr> Service-Route: <sip:icscf1_p.home1.net;lr>, <sip:orig@scscf1.home1.net;lr> P-Associated-URI: <sip:user1_public2@home1.net>, <sip:user1_public3@home1.net>, <sip:+1-212-555-1111@home1.net;user=phone> S-CSCF scscf1.home1.net I-CSCF icscf1_p.home1.net home1.net pcscf1.visit1.net P-CSCF SIP/2.0 200 OK Via: SIP/2.0/UDP pcscf1.visited1.net; SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]:1357 Service-Route: <sip:icscf1_p.home1.net;lr>, <sip:token(orig@scscf1.home1.net;lr)@home1.net;tokenized-by=home1.net> PDP Context UE#1 visit1.net user1_public1@home1.net user1_private1@home1.net VisitedNetwork 5555::aaa:bbb:ccc:ddd

  27. Assigning CSCF for a User • Criteria for assigning a S-CSCF for a User • Required capabilities for user services (provided by the HSS) • Operator preference on a per-user basis (provided by the HSS) • Capabilities of individual S-CSCFs in the home network (internal information) • Topological (i.e. P-CSCF) information of where the user is located (internal information) • Topological information of where the S-CSCF is located (internal information) • Availability of S-CSCFs (internal information) • Assignment of I-CSCF • DNS-based mechanism

  28. AS AS HSS IMS Session Setup: 1. Initial SDP Offer Originating Home Network Terminating Home Network Location Query/Response Service control Service control S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net INVITE sip:[5555::eee:fff:aaa:bbb]:8805 INVITE sip:user2_public1@home2.net Require: precondition, sec-agree Video codec H.263 or MPEG-4 Audio codec AMR P-CSCF P-CSCF user2_public1 @home2.net 5555::eee:fff:aaa:bbb (pcscf1.visited1.net UDP port 5060 5555::aba:dab:aaa:daa ) UE#1 UE#2 visit1.net visit2.net user1_public1@home1.net user1_private1@home1.net Originating Visited Network Terminating VisitedNetwork 5555::aaa:bbb:ccc:ddd

  29. AS AS HSS IMS Session Setup: 2. Offer Response Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net Authorize QoS Resources P-CSCF P-CSCF Authorize QoS Resources 183 Session Progress Video codec H.263 or MPEG-4 Audio codec AMR UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  30. AS AS HSS IMS Session Setup: 3. Response Conf (Opt SDP) Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net PRACK sip:user2_public1@home2.net Video codec H.263 Audio codec AMR visit1.net P-CSCF P-CSCF COPS:RPT COPS: REQ GPRS: Activate PDP Context accept GPRS: Create PDP response COPS:DEC GPRS: Activate PDP Context Resource Reservation GPRS: Create PDP Context UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  31. HSS AS AS IMS Session Setup: 4. Conf ACK (Opt SDP) Terminating Home Network Originating VisitedNetwork S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net P-CSCF P-CSCF 200 OK (PRACK) COPS:RPT COPS: REQ COPS:DEC GPRS: Activate PDP Context accept GPRS: Create PDP response Secondary PDP Context Resource Reservation GPRS: Create PDP Context GPRS: Activate PDP Context UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  32. AS AS HSS IMS Session Setup: 5. Reservation Conf Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net P-CSCF P-CSCF Alert User UPDATE Secondary PDP Context Secondary PDP Context UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  33. AS AS HSS IMS Session Setup: 6. Reservation Conf Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net P-CSCF P-CSCF 200 OK (UPDATE) Secondary PDP Context Secondary PDP Context UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  34. AS AS HSS IMS Session Setup: 7. Ringing Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net P-CSCF P-CSCF Alert User 180 Ringing Secondary PDP Context Secondary PDP Context UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  35. HSS AS AS IMS Session Setup: 8. 200 OK (INVITE) Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net P-CSCF P-CSCF COPS: DEC (Open gate) Start Media Start Media COPS: DEC (Open gate) COPS:RPT 200 OK COPS:RPT Secondary PDP Context Secondary PDP Context Approval of QoS Commit Approval of QoS Commit UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

  36. AS AS HSS IMS Session Setup: 9. ACK Originating Home Network Terminating Home Network S-CSCF I-CSCF I-CSCF S-CSCF I-CSCF I-CSCF home2.net home1.net visit2.net visit1.net P-CSCF P-CSCF ACK UE#1 UE#2 Originating VisitedNetwork Terminating VisitedNetwork

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