SIP IMS Release 6 2004. 6 숭실대학교김영한 ( yhkim@dcn.ssu.ac.kr )
I. 3GPP Overview II. III. IV. 3GPP IMS Architecture IM Subsystem Procedure Difference of CSCF and RFC3261 SIP V. IMS Service
All-IP 네트워크의필요성 Enables rich communications combining multiple media or services New IP-based services, easier & faster service creation and execution Access independency, easier interworking with the Internet Services available over different access technologies One network architecture for accommodating all services Providing and requiring optimized Quality of Service Smooth evolution from today s networks and standards Cost efficiency, evolution for current solutions Openness: both specifications and (distributed) architecture
3GPP TSG 조직구성
3GPP Release 특성
SIP 를통한신규서비스가능성 IMS and Session Initiation Protocol (SIP) offers: Easy integration with other IP protocols and applications Personalized services aware of desired communication capabilities and preferences Straightforward integration of voice, images, video and other interactive communications services Seamless service offering over various access networks
3GPP Rel 5/6 IMS 구조 Legacy SCPs CAMEL,ANSI-41 INAP,TCAP OSA-GW Parlay API Multimedia Services Video Telephony Services IM-SSF Supplemental Video Telephony Services OSA-GW Service Broker SIP-ISC HSS CSCF Signaling Gateway DSL, 802.11, GPRS MRFC MGCF SIP Media Server Media Gaeway Non-SIp Multicast VOD IM,PTT,VOD Video Telephony IM.PTT,VOD Video Telephony
I. 3GPP Overview II. III. IV. 3GPP IMS Architecture IM Subsystem Procedure Difference of CSCF and RFC3261 SIP V. IMS Service
3GPP IM 핵심망서브시스템구조 3GPP Core Network Architecture HSS Media Server Application Server Internet PS IMS MRFP MGCF P-CSCF CSCF Signaling BGCF CSCF Call Session Control Function IM-MGW IM-Media Gateway MGCF MedieaGateway Control Function MRF Media Resource Function BGCF Breakout Gateway Control Function SGSN MRFC IM-MGW GGSN TDM SIP SIP phone PSTN CPE
3GPP IMS Architecture 3GPP IMS 구조 SIP Signaling Interface Service Control Interface Diameter Interface Service Platform ISC : IMS Srvice Control ISC Out / In Bound Proxy Entry Proxy Service Profile Service Proxy To / From terminating Network IMS User P-CSCF I-CSCF S-CSCF Visited Network Home Network
3GPP IMS 구성요소 P-CSCF (Proxy-CSCF) 사용자 (UE) 가 IM 멀티미디어망에접속하는첫포인트지점 UE에게 SIP 메시지를요구또는응답 Bearer 자원의권한검증과 QoS 관리 I-CSCF (Interrogate-CSCF) UE의홈망에접속하는첫포인트지점 타망으로부터수신한 SIP 메시지를 S-CSCF로 routing S-CSCF (Serving-CSCF) 실제등록된 UE의세션상태관리를하면서제어서비스를수행 UE에게서비스자원과관련된정보를제공
3GPP IMS 구성요소 HSS(Home Subscriber Server) 가입자의마스터데이터베이스 호제어를위한가입자의모든정보들을관리 가입자식별자 번호및주소정보 가입자보안정보 인증및권한검증을위한망엑세스 가입자위치정보 등록및Inter-system 레벨의이동정보 가입자서비스프로파일정보 MGCF (Media Gateway Control Function) MGCF는 PSTN/PLMN의종단으로 MGW의미디어채널을위한연결제어에관련된호를제어 기존망에서입력된호에대하여라우팅정보로 CSCF를선택하며기존망과 All-IP 망호제어프로토콜간의프로토콜변환을수행
3GPP IMS 구성요소 IM-MGW CS-MGW의기능은동일하며 IMS에서정의된 MGW VoIP의호가 PSTN으로전달될시에주로사용 BGCF (Breakout Gateway Control Function) CSCF에서어떤PSTN으로나가야하는지를알수있어야하고, 적절하게라우팅이되기위해서적합한 MGCF와 IM-MGW를선택 MRFP (Multimedia Resource Function Processor) Tone Generation, DTMF Detection, Multimedia Announcement, Audio Transcoding, Media Analysis 담당 Multiparty Call을처리하기위하여 Bridge등의정보제공
3GPP IMS 구성요소 MRFC (Multimedia Resource Function Controller) MRFP 의제어를담당 PDF (Policy Decision Function) QoS를 Policy를통하여결정 PDF는 P-CSCF에만존재 Roaming (Visited Network) : P-CSCF 아래 PDF에의해QoS 결정 IP Address Version IPv6 : mandatory IPv4 : optional
3GPP IMS 구성요소 ISC (IMS Service Control Interface) Architecture AS (Application Server) 3rd Party 기반의 IP Multimedia Service 포함 SCIM (Service Capability Interaction Manager) 어플리케이션을통해S-CSCF에연결 S-CSCF와는 ISC 인터페이스를통하여정합 HSS 기존의 CAMEL 기반의지능망서비스와의호환성을위해 IM-SSF( IP Multimedia-Service Service Switching Function) 을사용 IMS SIP AS AS AS SCIM S-CSCF IM-SSF CAMEL Service Environment OSA SCS MRFC OSA AS
I. 3GPP Overview II. III. IV. 3GPP IMS Architecture IM Subsystem Procedure Difference of CSCF and RFC3261 SIP V. IMS Service
IM Subsystem 절차 IM Subsystem Architecture HSS Home Network Diameter S-CSCF I-CSCF DNS SIP UE GPRS P-CSCF Visited Network
IM Subsystem 절차 DHCP / DNS 를이용한 P-CSCF 의발견 UE GGSN DHCP Server DNS Server 1. PDP Context Activation 2. DHCP-Query / Response 2. DHCP-Relay 3. DNS-Query/Response P-CSCF s domain name & DNS server s IP addr.
등록세션 IM Subsystem 절차
IM Subsystem 절차 (Using SIP)
IM Subsystem 절차 발 / 착신세션 세션절차의다양한조합 UE#1 S-CSCF#1 S-CSCF#2 UE#2 -Mobile origination, Home 발신 -Mobile origination, ( 택 1) roaming -PSTN origination One of the MO Invite sequence Information flows Inserted here One of the MT Invite sequence Information flows Inserted here Inter S-CSCF ( 택 1) -Session ori/term same net -Session orig/term Different net One of the S-CSCF to S-CSCF Invite sequence information Flows Inserted here 착신 ( 택 1) -Mobile termination, home -Mobile termination roaming -PSTN termination
IM Subsystem 절차 (Using SIP) UTRAN & packet core Multimedia subsystem GERAN & packet core HSS 3. & 4. Send routing info ACK 1. INVITE 2. 100 Trying 8. Ringing 10. 200 OK 11. ACK CSCF 5. INVITE 6. 100 Trying 7. Ringing 9. 200 OK 12. ACK 13. BYE 16. 200 OK 14. BYE 15. 200 OK
Mobile origination procedure - roaming
I. 3GPP Overview II. III. IV. 3GPP IMS Architecture IM Subsystem Procedure Difference of CSCF and RFC3261 SIP V. IMS Service
CSCF 와 RFC3261 기반 SIP 서버차이점 Release 5기준의 CSCF가제공하는 SIP의기능과 RFC 3261에서제공하는 SIP 기능상의차이점 기존이동통신사업자들이유지해왔던기능에의하여차이 이동통신의과금, 이동통신고유의개인정보보호, 기존 Legacy Network에서유지했던기능이나역할들을최대한 IMS에서도유지하기위한필요성 RFC3261 B2B(Back-to-Back) UA역활요구하지않으나 CSCF는 B2B UA의역할을요구
차이점 1 : P-CSCF initiating BYE Request 문제점 : 무선구간이비정상적인절차로해제시 S-CSCF는무선구간에서호가해제된것을알지못함 P-CSCF는무선구간이끊어진것을인지함 P-CSCF는무선구간이끊어지면바로 BYE 메시지전송 불필요한과금이나망의자원의낭비줄임 BYE 에 Credential 이없는경우 UE 들은 DoS Attack 에노출 해결방안 CSCF는호해제시 BYE 메시지를전송할수있어야한다. UA는 P-CSCF에의한 BYE 메시지를처리할수있어야한다. BYE BYE UE#1 P-CSCF S-CSCF UE#2
차이점 2 : P-CSCF stripping headers 문제점 : UE가 PATH 정보를통해S-CSCF를 Route, Via에서삭제할염려를방지하기위해, P-CSCF가 S-CSCF의경로를추가 이동통신사업자의경우, 사용자의정확한과금부여를위함 SIP end-to-end방식의 S/MIME의 Security 유지못함 Man-in-the-middle attack과같은문제발생 해결방안 IMS Network 의 S-CSCF bypass 를피한다 Register 완료후 S-CSCF 의경로를추가 UE#2 UE#1 P-CSCF S-CSCF
차이점 3 : CSCFs editing SDP 문제점 : SDP 정보를 CSCF 가의도적으로추가 사업자가선호하는코덱정보를삽입 S/MIME Protection이유지되지못함 유선의 UA간공통의 Codec이없을경우 Inter-operation 불가 해결방안 코덱및미디어타입을세션설정중에절충한다 CSCF 가 SDP Editing 을거부할수있도록 CSCF 를설정할수있다
차이점 4 : S-CSCF obfuscating To: and From: 문제점 : 사업자의개인정보보호를위한특수성지원시 ( 예 : 발신번호표시제한, 착신번호표시제한등 ) To: 나 From: 에나타나있는정보를숨김 S-CSCF가 Header 부분을수정함 End-to-end방식의 S/MIME Protection이유지되지못함 해결방안 논의중
차이점 5 : P-CSCF performing identity checks P-CSCF 와 UA 간 Security Association 을형성시 Register를 Authentication하고 Authorization 했을시에사용된 Identity를사용 제 3자의 SIP Server를통한서비스에다른 Identity를사용할수없게되는제약이따름
차이점 6 : Network configuration hiding 문제점 : I-CSCF 가 THIG(topology hiding internetwork GW) 으로동작할경우 Via, Route정보를 encrypt하여 S-CSCF경로숨김 RFC 3261 지원안함 해결방안 Tokenized-by Tag 를사용 (TS-24.229) encrypt 및 decrypt 를지원한다 Encrypt Decrypt Via : SIP/2.0/UDP icscf1_s.home1.net;lr, SIP/2.0/UDP Token(SIP/2.0/UDP scscf1.home1.net;lr, SIP/2.0/UDP pcscf1.home1.net;lr)@home1.net; tokenized-by=home1.net, SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd] Via: SIP/2.0/UDP Token(SIP/2.0/UDP scscf1.home1.net;lr, SIP/2.0/UDP pcscf1.home1.net;lr)@home1.net;tokenized-by=home1.net decrypt Via: SIP/2.0/UDP scscf1.home1.net;lr, SIP/2.0/UDP pcscf1.home1.net;lr
차이점 7 : CSCFs manipulating message bodies AS 와 SIP 메시지를교환할경우 IMS 고유의 Header(P-Headers) 사용 ( 과금, 사용자 ID등을위해 ) SIP Message Body를고유 Header (Ex: P-Charging-Vector Header) 로수정 S/MIME의 Security Protection을유지할수없다
I. 3GPP Overview II. III. IV. 3GPP IMS Architecture IM Subsystem Procedure Difference of CSCF and RFC3261 SIP V. IMS Service
IMS 서비스 Single Application Server triggering (presence.ssu.ac.kr) 4. 200 OK 3. PUBLISH
IMS 서비스 Multiple Application Servers triggering (prepaid.ssu.ac.kr) (messaging.ssu.ac.kr) 3. MESSAGE 4. MESSAGE 6. MESSAGE 7. MESSAGE
IMS 서비스 Service Interactions Servers triggering Initial Filter Criteria of Presence Server Application Server Address : presence.ssu.ac.kr Messaging Server (presence.ssu.ac.kr) Presence Server Trigger point : Event= presence AND Method = SUBSCRIBE AND Request-URI = sip:yhkim@dcn.ssu.ac.kr Handling : Proxy Priority : x 6. Service Control 8. NOTIFY 7. SUBSCRIBE 2. PUBLISH 3. MESSAGE 1. PUBLISH Service Proxy 11. MESSAGE
Presence Service PRESENCE SERVICE accept information, store it, and distribute it PRESENTITY provides PRESENCE INFORMATION WATCHER receives PRESENCE INFORMATION
IMS Watcher registering for event notification
PoC (Push to talk over Cellular) Simple Just push to talk Direct one-to-one and one-to-many voice communication service in the cellular network Main elements PoC-enabled terminal (support to SIP and RTP) Core network (PoC application server)
On demand session Simplified PoC communication based on on demand signalling
결 론 SIP는 3GPP/3GPP2의 IP 기반서비스제어의핵심프로토콜 향후유무선통합환경에서통일된세션제어프로토콜사용됨 IETF에서의 SIP 확장프로토콜요소는 3GPP IMS에계속반영되어신규서비스추가
Commonality and Interoperability support for use of the IMS core by 3GPP IMS 관련표준화 Feature 및계획 other access technologies (SA2, CN1) IMS Local Services support for access to services in visited network (SA2, CN1) IMS to PS Interworking support for interworking with IP endpoints including IPv4/IPv6 interworking, SIP, transcoding, (CN3) IMS to CS Interworking support for SIP/ISUP interworking and CS roaming scenarios (CN3) IMS Conferencing support for IMS based conference provision and control (SA2, CN1) SIP Capabilities Enhancements support for enhanced SIP capabilities such as forking (SA2, CN1) IMS Subscriptions and Access Scenarios requirements on various operator scenarios for IMS deployment (SA1)
Work Plan