sip (session initiation protocol) 순천향대학교 정보기술공학부 이상정

SIP(Session Initiation

Protocol)

순천향대학교 정보기술공학부

이상정

순천향대학교 정보기술공학부 이 상 정 2

2004-2

SIP 개요

Session Initiation Protocol 호 (call), 세션 설정 프로토콜 Peer-to-peer signaling protocol SIP-URL

• e-mail 형태의 주소를 이용해 사용자를 식별 사용자 이동성 제공

• 동일한 SIP 주소 , 다른 위치 ( 단말 ) 에서 연결• 현재 사용자의 위치 등록 , 수정 , 삭제 , 검색 기능

하위 전송 프로토콜에 독립적

2004-2

SIP 개발단계 1996

• Mark Hadley’s SIP(Session Invitation Protocol)• Henning Schulzrinne’s SCIP(Simple Conference Control Proto

col) 1999. 3.

• RFC 2543 by IETF MMUSIC WG 1999. 9.

• IETF SIP WG 2000. 6

• RFC 2543bis 2002. 6

• RFC 3261

2004-2

SIP 구성요소 UAC (User Agent Client)

• 요청 메시지로 SIP transaction 을 개시하는 논리적 실체• 요청 메시지의 존속기간동안 UAC 로 동작

UAS (User Agent Server)• SIP 요청 메시지에 응답하는 논리적 실체• 요청 메시지 수용 , 거절 , 리다이렉트

UA (User Agent) = UAC + UAS Redirect Server

• SIP 요청 메시지의 주소를 0 개 이상의 새로운 주소로 매핑 , 클라이언트에게 새로운 주소 반환

Proxy Server• 요청 메시지를 내부적으로 처리하거나 다른 서버로 전달• 요청 메시지를 해석하고 포워딩 전에 재작성 가능

Registrar • REGISTER 요청 메시지를 수용하는 서버• Proxy 나 Redirect Server 와 함께 구현될 수 있음

2004-2

SIP 아키텍처

SIP Client (UAC:User Agent Client)

SIP RedirectServer

SIP Proxy

SIP ProxySIP Client

(User Agent Server)

Location Service

Request

Response

LocationServer

2004-2

SIP 메시지

2004-2

SIP 메시지 형식

2004-2

SIP 구문

session_id version IP4

2004-2

SIP 헤더

Via : 응답 시 경유될 호스트 명시 From, To Call-ID: 각 호 (call) 을 구분하는 유일한 ID Cseq: 각 요청 마다 증가되는 값

2004-2

Session Description Protocol 메시지 바디에서 미디어 세션을 기술 주요 미디어 형태를 표현하기 위해 RTP/AVP

Profiles 을 사용• 0 : PCM u-law• 3 : GSM• 4 : G.723

2004-2

SIP 요청 메시지

2004-2

SIP 응답 메시지

2004-2

End-to-End SIP Model

2004-2

Simple Call Flow

2004-2

Simple Call Flow – 미디어 기술 예

2004-2

코덱 협상

2004-2

등록

2004-2

Redirect Server 에서의 세션 설정

cs.tu-berlin.de

cs.columbia.edu

location server

hgs@play

cz@cs.tu-berlin

1. INVITEhenning@cs.colombia.edu

4. 302 Moved tempoarilycontact : hgs@play

5. ACKhenning@cs.colombia.edu

6. INVITEhenning@play.cs.colombia.edu

7. 200 OK

8. ACK henning@play.cs.colombia.edu

3. hgs@play. cs.columbia.edu

2. henning@cs.columbia.edu

2004-2

Proxy Server 에서의 세션 설정

cs.tu-berlin.de

cs.columbia.edu

location server

hgs@play

playcz@cs.tu-berlin

1. INVITE henning@cs.colombia.edu

6. 200 OK

4. INVITEhenning@play.cs.colombia.edu

5. 200 OK

7. ACK henning@cs.colombia.edu

3. hgs@play.cs.columbia.edu2. henning@

cs.columbia.edu

7. ACK henning@play.cs.colombia.edu

2004-2

Overview of OperationAlice’s

softphoneatlanta.com

proxybiloxy.com

proxyBob’s

SIP Phone

100 F3

INVITE F1

180 F7

INVITE F2

100 F5INVITE F4

180 F6

180 F8 200 OK F9200 OK F10

200 OK F11

ACK F12

Media Session

BYE F13

200 OK F14

2004-2

Overview of Operation

INVITE sip:bob@biloxi.com SIP/2.0Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@biloxi.com>From: Alice <sip:alice@atlanta.com>;tag=1928301774Call-ID: a84b4c76e66710@pc33.atlanta.comCSeq: 314159 INVITEContact: <sip:alice@pc33.atlanta.com>Content-Type: application/sdpContent-Length: 142

Request-Line : Method SP Request-URI SP SIP-Version CRLF

2004-2

SIP/2.0 200 OKVia: SIP/2.0/UDP server10.biloxi.com ;branch=z9hG4bKnashds8;received=192.0.2.3Via: SIP/2.0/UDP bigbox3.site3.atlanta.com ;branch=z9hG4bK77ef4c2312983.1;received=192.0.2.2Via: SIP/2.0/UDP pc33.atlanta.com ;branch=z9hG4bK776asdhds ;received=192.0.2.1To: Bob <sip:bob@biloxi.com>;tag=a6c85cfFrom: Alice <sip:alice@atlanta.com>;tag=1928301774Call-ID: a84b4c76e66710@pc33.atlanta.comCSeq: 314159 INVITEContact: <sip:bob@192.0.2.4>Content-Type: application/sdpContent-Length: 131

Status-Line : SIP-Version SP Status-Code SP Reason-Phrase CRLF

2004-2

Via• Expecting to receive responses• Branch parameter that identifies this transaction

Call-ID• Globally unique identifier for this call• Random string

CSeq• Increment for each new request within a dialog

Contact• Tells other elements where to send future requests

Max-Forwards• Limit the number of hops

2004-2

Dialogs

Dialog • Peer to Peer SIP relationship between two user

agents• < Call-ID, From tag, To tag >

Early Dialog• Established by a non-final response to a request

Transaction• From the first request sent from the client to

the server up to a final(non-1xx) response sent from the server to client

• Occur between a client and a server

2004-2

SIP to SIP through two proxiesF1 INVITE A -> Proxy 1 INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com> Call-ID: 12345601@here.com CSeq: 1 INVITE Contact: <sip:UserA@100.101.102.103> Content-Type: application/sdp Content-Length: 147

F2 407 Proxy Authorization Required Proxy 1 -> User A SIP/2.0 407 Proxy Authorization Required Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=3flal12sf Call-ID: 12345601@here.com CSeq: 1 INVITE Proxy-Authenticate: Digest realm="wcom.com", nonce="f84f1cec41e6cbe5aea9c8e88d359", opaque="", stale=FALSE, algorithm=MD5 Content-Length: 0

F3 ACK A -> Proxy 1 ACK sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=3flal12sf CSeq: 1 ACK Content-Length: 0

F4 INVITE A -> Proxy 1 INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com> Call-ID: 12345601@here.com CSeq: 2 INVITE Contact: <sip:UserA@100.101.102.103> Proxy-Authorization:Digest username="UserA", realm="wcom.com", nonce="wf84f1ceczx41ae6cbe5aea9c8e88d359", opaque="", uri="sip:UserB@there.com", response="42ce3cef44b22f50c6a6071bc8" Content-Type: application/sdp Content-Length: 147

F5 INVITE Proxy 1 -> Proxy 2 INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP ss1.wcom.com:5060 ;branch=z9hG4bK2d4790.1 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Max-Forwards: 69 Record-Route: <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com> Call-ID: 12345601@here.com CSeq: 2 INVITE Contact: <sip:UserA@100.101.102.103> Content-Type: application/sdp Content-Length: 147

F6 (100 Trying) Proxy 1 -> User A SIP/2.0 100 Trying Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com> Call-ID: 12345601@here.com CSeq: 2 INVITE Content-Length: 0

F7 INVITE Proxy 2 -> B INVITE sip:UserB@110.111.112.113 SIP/2.0 Via: SIP/2.0/UDP ss2.wcom.com:5060 ;branch=z9hG4bK721e418c4.1 Via: SIP/2.0/UDP ss1.wcom.com:5060 ;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Max-Forwards: 68 Record-Route: <sip:ss2.wcom.com;lr>,<sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com> Call-ID: 12345601@here.com ………

F8 (100 Trying) Proxy 2 -> Proxy 1

SIP/2.0 100 Trying Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com> Call-ID: 12345601@here.com CSeq: 2 INVITE Content-Length: 0

2004-2

SIP to SIP through two proxiesF9 180 Ringing B -> Proxy 2 SIP/2.0 180 Ringing Via: SIP/2.0/UDP ss2.wcom.com:5060;branch=z9hG4bK721e418c4.1 ;received=2.3.4.5 Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Record-Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com Contact: <sip:UserB@110.111.112.113> CSeq: 2 INVITE Content-Length: 0

F10 180 Ringing Proxy 2 -> Proxy 1 SIP/2.0 180 Ringing Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Record-Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com Contact: <sip:UserB@110.111.112.113> CSeq: 2 INVITE Content-Length: 0

F11 180 Ringing Proxy 1 -> A SIP/2.0 180 Ringing Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Record-Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com Contact: <sip:UserB@110.111.112.113> CSeq: 2 INVITE Content-Length: 0

F12 200 OK B -> Proxy 2 SIP/2.0 200 OK Via: SIP/2.0/UDP ss2.wcom.com:5060;branch=z9hG4bK721e418c4.1 ;received=2.3.4.5 Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Record-Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com CSeq: 2 INVITE Contact: <sip:UserB@110.111.112.113> Content-Type: application/sdp Content-Length: 147

F13 200 OK Proxy 2 -> Proxy 1 SIP/2.0 200 OK Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Record-Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com CSeq: 2 INVITE Contact: <sip:UserB@110.111.112.113> Content-Type: application/sdp Content-Length: 147

F14 200 OK Proxy 1 -> A SIP/2.0 200 OK Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Record-Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com CSeq: 2 INVITE Contact: <sip:UserB@110.111.112.113> Content-Type: application/sdp Content-Length: 147

F15 ACK A -> Proxy 1 ACK sip:UserB@110.111.112.113 SIP/2.0 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 Route: <sip:ss1.wcom.com;lr>, <sip:ss2.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com CSeq: 2 ACK Content-Length: 0

F16 ACK Proxy 1 -> Proxy 2 ACK sip:UserB@110.111.112.113 SIP/2.0 Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 Via: SIP/2.0/UDP here.com:5060;branch=z9hG4bK74bf9 ;received=100.101.102.103 Max-Forwards: 69 Route: <sip:ss2.wcom.com;lr> From: BigGuy <sip:UserA@here.com>;tag=9fxced76sl To: LittleGuy <sip:UserB@there.com>;tag=314159 Call-ID: 12345601@here.com CSeq: 2 ACK Content-Length: 0

2004-2

SIP to SIP through two proxiesF18 BYE User B -> Proxy 2 BYE sip:UserA@100.101.102.103 SIP/2.0 Via: SIP/2.0/UDP there.com:5060;branch=z9hG4bKnashds7 Max-Forwards: 70 Route: <sip:ss2.wcom.com;lr>, <sip:ss1.wcom.com;lr> From: LittleGuy <sip:UserB@there.com>;tag=314159 To: BigGuy <sip:UserA@here.com>;tag=9fxced76sl Call-ID: 12345601@here.com CSeq: 1 BYE Content-Length: 0

F19 BYE Proxy 2 -> Proxy 1 BYE sip:UserA@100.101.102.103 SIP/2.0 Via: SIP/2.0/UDP ss2.wcom.com:5060;branch=z9hG4bK721e418c4.1 Via: SIP/2.0/UDP there.com:5060;branch=z9hG4bKnashds7 ;received=110.111.112.113 Max-Forwards: 69 Route: <sip:ss1.wcom.com;lr> From: LittleGuy <sip:UserB@there.com>;tag=314159To: BigGuy <sip:UserA@here.com>;tag=9fxced76sl Call-ID: 12345601@here.com CSeq: 1 BYE Content-Length: 0

F20 BYE Proxy 1 -> User A BYE sip:UserA@100.101.102.103 SIP/2.0 Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 Via: SIP/2.0/UDP ss2.wcom.com:5060;branch=z9hG4bK721e418c4.1 ;received=2.3.4.5 Via: SIP/2.0/UDP there.com:5060;branch=z9hG4bKnashds7 ;received=110.111.112.113 Max-Forwards: 68 From: LittleGuy <sip:UserB@there.com>;tag=314159 To: BigGuy <sip:UserA@here.com>;tag=9fxced76sl Call-ID: 12345601@here.com CSeq: 1 BYE Content-Length: 0

F21 200 OK User A -> Proxy 1 SIP/2.0 200 OK Via: SIP/2.0/UDP ss1.wcom.com:5060;branch=z9hG4bK2d4790.1 ;received=1.2.3.4 Via: SIP/2.0/UDP ss2.wcom.com:5060;branch=z9hG4bK721e418c4.1 ;received=2.3.4.5 Via: SIP/2.0/UDP there.com:5060;branch=z9hG4bKnashds7 ;received=110.111.112.113 From: LittleGuy <sip:UserB@there.com>;tag=314159 To: BigGuy <sip:UserA@here.com>;tag=9fxced76sl Call-ID: 12345601@here.com CSeq: 1 BYE Content-Length: 0

F22 200 OK Proxy 1 -> Proxy 2 SIP/2.0 200 OK Via: SIP/2.0/UDP ss2.wcom.com:5060;branch=z9hG4bK721e418c4.1 ;received=2.3.4.5 Via: SIP/2.0/UDP there.com:5060;branch=z9hG4bKnashds7 ;received=100.101.102.103 From: LittleGuy <sip:UserB@there.com>;tag=314159 To: BigGuy <sip:UserA@here.com>;tag=9fxced76sl Call-ID: 12345601@here.com CSeq: 1 BYE Content-Length: 0

F23 200 OK Proxy 2 -> User B SIP/2.0 200 OK Via: SIP/2.0/UDP there.com:5060;branch=z9hG4bKnashds7 ;received=110.111.112.113 From: LittleGuy <sip:UserB@there.com>;tag=314159 To: BigGuy <sip:UserA@here.com>;tag=9fxced76sl Call-ID: 12345601@here.com CSeq: 1 BYE Content-Length: 0

2004-2

Header Fields

Max-Forwards 최대 Proxy 를 거쳐 갈 수 있는 수

Record-RouteProxy 에서 dialog 내의 request 를 받고자 할 때 추가

RouteRecord-Route Header 의 List 로 만들어 지며 , Request 가 거쳐 가야 할 Proxy 의 경로

Routing Header

2004-2

Header Fields

Authentication-Info

HTTP Digest 에서 mutual authentication을 지원하기 위해 사용

Authorization UA 의 authentication credentials 를 포함

Proxy-Authenticate

Proxy 에서 credential 을 만들기 위해 필요한 정보 포함

Security Header

Proxy-Authorization

UA 의 authentication information 를 포함하는 credentials 로 구성

WWW-Authorization

Authentication challenge 에 사용Key 를 만들 때 필요한 정보 포함

2004-2

Header Fields

Content-Disposition

Message body 가 UAC or UAS interpret 할지에 대한 내용

Content-Encoding

“media-type” 의 modifier 로 사용

Content-Language

사용 언어 표기

Content Processing

Content-Type Message-body 의 media type 을 나타냄

Content-Length Message-body 의 길이

MIME-Version MIME Version

2004-2

Header Fields

Accept사용 가능한 message format 을 나타낸다 .Accept Header 가 없는 경우 default 는 application/sdp

Accept-Encoding

사용 가능한 encoding 방법을 알려 줌

Accept-Language

Message 에 사용 가능한 언어를 알려 줌

Capability Information

Allow 처리 가능한 Method 를 알려줌

Proxy-Require Proxy 가 지원해야 하는 feature 를 알려줌

2004-2

Header Fields

RequireRequest 를 처리하기 위해서 지원해야 하는Extensions

Supported 지원하는 Extensions

Unsupported 지원 하지 않는 Extensions

Capability Information

2004-2

Header Fields

Call-IDIdentify a particular invitation or all registrations of a particular client

Call-Info Caller, Callee 의 부가적인 정보

ContactMethod, Request, Response 에 따라서 의미가 다름 INVITE Request 의 경우 Request 를 수신할 곳에 대한 정보

SIP Processing

CSeq Dialog 에서 transaction 의 순서로 사용

Date 날짜와 시간 정보를 포함

Error-Info error status 에 대한 부가 정보

2004-2

Header Fields

Expiresmessage 가 expire 될 상대적인 시간INVITE method 에서는 무시

From Initiator of the request

In-Reply-ToEnumerate the Call-IDs the this Call references or returns

SIP Processing

Min-Expires Soft-state 가 지원하는 최소 expire 시간 정보

OrganizationRequest 나 Response 보낸 Organization의 Name

Priority Indicate urgency

Reply-To, Retry-After, Server, Subject, Timestamp, To, User-Agent, Warning, Via

2004-2

Header Fields

Reply-To Logical return URI

Retry-After현재 Call 을 수락할 수 없을 때 , 얼마나 후에 처리가 가능한지 알려줌

Server UAS 가 사용하는 Software 정보

SIP Processing

Subject Summary the nature of call

Timestamp UAC 가 UAS 로 request 를 보낸 시점

To The logical recipient of the request

User-Agent, Warning, Via

2004-2

Header Fields

User-Agent Request 를 만든 UAC 에 대한 정보

WarningAdditional information about the status of response

Request 가 지나간 pathResponse 가 지나 가야 할 pathBranch value 는 Transaction identifier 로 사용 ,Loop detect 를 가능하게 함

SIP Processing

2004-2

Response Code

Informational = "100" ; Trying

| "180" ; Ringing

| "181" ; Call Is Being Forwarded

| "182" ; Queued (temporarily unavailable,

server has decided to queue the call)

| “183” ; Session Progress

Success = "200" ; OK

Redirection = "300" ; Multiple Choices

| "301" ; Moved Permanently

| "302" ; Moved Temporarily

| "303" ; See Other

| "305" ; Use Proxy

| "380" ; Alternative Service

2004-2

Response Code

| "420" ; Bad Extension

2004-2

Response Code

| "421" ; Extension Required

| "423" ; Interval Too Brief

| "480" ; Temporarily not available

| "481" ; Call Leg/Transaction Does Not Exist

| "482" ; Loop Detected

| "483" ; Too Many Hops

| "484" ; Address Incomplete

| "485" ; Ambiguous

| "486" ; Busy Here

| "487" ; Request Terminated

| "488" ; Not Acceptable Here

| "491" ; Request Pending

| "493" ; Undecipherable

2004-2

Response Code

Server-Error = "500" ; Internal Server Error

| "501" ; Not Implemented

| "502" ; Bad Gateway

| "503" ; Service Unavailable

| "504" ; Server Time-out

| "505" ; Version not supported

| "513" ; Message To Large

Global-Failure = "600" ; Busy Everywhere

| "603" ; Decline

| "604" ; Does not exist anywhere

| "606" ; Not Acceptable

sip (session initiation protocol) 순천향대학교 정보기술공학부 이상정

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