1. The Session Initiation Protocol: Internet-Centric Signaling 네트워크 연구실 류 준 우

2. Introduction (1) Initiates, modifies, and terminates network sessions Focus on interactive multimedia sessions (Internet phone calls or multimedia conferences) Used for instant messaging, event notification or managing other session type (ex. Distributed games)

3. Introduction (2) Peer-to-Peer signaling Protocol SIP URL : e-mail 과 비슷한 형태의 identifier 를 이용하여 사용자를 식별 Personal mobility 같은 id 로 다른 위치나 다른 단말에서 사 용이 가능

4. Components(1) UAC (User Agent Client) - 요청 Msg 로 SIP transaction 을 함 - 요청 Msg 의 존속 기간동안 UAC 로 동 작 UAS (User Agent Server) - SIP 요청 Msg 에 응답 - 요청 메시지의 수용, 거절, 리다이렉트 를 처리함

5. Components (2) Registrars - domain 내의 user 정보를 주고 받는다. - Register 요청 메시지를 수용하는 서버 Proxy Server - application-layer 에서 SIP request, response 를 forwarding 함 Redirect Server - request 를 받아서 다른 주소나 서버로 넘겨준다. Registrars, Proxy Server, Redirect Server 는 같 은 Program 에서 구현 가능하다.

6. Protocol architecture H.323SIPRTSPRTCPRSVP RTP TCPUDP IPv4, IPv6 PPP SONET AAL3/4AAL5 ATMEthernet PPP V.34

7. Signaling SPI request URI 는 email 주소와 비슷하 게 생겼다. user name + host name + parameters Signaling Msg 는 다른 미디어 전송과 전 혀 다른 path 로 전송된다. SIP Msg 는 transfer protocol 에 independent 하게 동작한다.

8. Describing & Changing Session SIP use SDP to describe multimedia sessions. SDP expressed in a simple textual format

9. SIP Message Format SIP 의 Msg format 은 HTTP 처럼 plain text 로 되어 있다. Request Msg. 와 Response Msg 로 볼 수 있다. Request Msg. UAC -> UAS Response Msg. UAC <- UAS

10. SIP Messages

11. Request Messages

12. Response Messages

13. Forking SIP differs from other signaling protocols in that it allows a call request to fork Automatic call distribution (ACD) ex) same number can ring at home and at work.

15. Reliability SIP Msg can be transmitted over unreliable transport protocols SIP has to take care of reliability on its own. INVITE Msg 응답이 올 때까지 Client 는 재전송하고 ACK 때 까지 서버는 Responses 재전송 Response 가 올때까지 Request 재전송

16. Locating Users Location User 는 User Registration 을 통 해서 location mapping 을 만드는 것이다. User agents 주기적으로 SIP REGISTER request 을 사용해 Local registrar server 에 등록 한다.

17. Session Characteristics Overall session caller ’ s name, address, organization callee ’ s name, address session ’ s urgency and subject Media session acceptable media format

18. Security Need to be secured against eavesdropping and alteration. SIP inherits the basic and digest authentication mechanisms from HTTP. Currently, public key cryptography using the PGP format has been defined

19. Security Confidentiality - End-to-end encryption Shared secret 또는 Public key - Hop-by-hop encryption 기존의 security mechanism (TLS/IPSec) Authentication - HTTP authentication mechanism 사용 (RFC2617) - TLS/IPSec 인증 기능 사용

20. Integration with Other Internet Services SIP addresses are regular URLs and can be embedded in Web pages, e-mail, and any other context where URLs are allowed. The message body of requests and responses uses the MIME mechanism familiar from e-mail. SIP messages can thus carry any binary or text object, with servers treating the message body as opaque data.

21. Telephony Service 많은 부가 기능을 가질 수 있는 서비스가 전통적인 Telephony Service 의 기준이상 으로 SIP 에서 제공할 수 있다. 특정 서비스 제공을 위한 요소를 첨가하 기 보단 새로 만들어질 많은 서비스를 제 공할 수 있는 기본적인 요소를 제공하는 방향을 제시

22. Multiparty Sessions Full mesh sends an individual copy of the media stream to the others. Mixer several media streams and replicates them to all participants. Network-layer multicast most efficiently supported by network-layer multicast

23. Expression Caller Preference many of their communications tools and location under a single public identifier.

24. Quality of Service SIP messages and data streams are likely to traverse very different parts of the network SIP 를 set-up resource reservations 에 사용하는건 부적합하다. Can used to negotiate the use of QoS mechanisms

26. Mobility One of the central tasks SIP is to locate one or more IP addresses where a user can receive media streams, given only a generic, locationindependent address identifying a domain. makes it easy to offer precall terminal mobility

27. SIP and MGCP/Megaco MGCP 는 Media Gateway 와 이를 제어하 기 위한 Media Gateway Controller 간에 사용하는 프로토콜입니다

28. Programming SIP Services telephony services have been either hard- coded into switches SIP-based telephony there are at least four choices to create SIP-based services. (language-based APIs, create dedicated languages, SIP servlet is a pice of JAVA code, includesjava applets)

29. The Applicability of SIP There are many functions SIP explicitly does not provide not a session management or conference control protocol. as media transport, voting and polling, virtual microphone passing, chair election, floor control, and feedback on session

30. Related work Telephony signaling protocols channel-associated signaling -> out-of-band signaling. ISUP to set up connections between IP endpoints SIP is related to messaging mechanisms such as Internet e-mail. The ICEBERG project also considers setup of large-scale sessions using multicast, while Elliott discusses session membership propagation.