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網路電話 Session Initiation Protocol (SIP). Speaker: 王嘉裕 Date:2008/09/11. SIP - Session Initiation Protocol. 前身 - MMUSIC (Multiparty Multimedia Session Control), Sep. 1999 由 IETF 的 SIP Working Group 發展 開始於 1995 Proposed standard RFC2543, February 1999 - PowerPoint PPT Presentation
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網路電話Session Initiation Protocol (SIP)
Speaker: 王嘉裕Date:2008/09/11
SIP - Session Initiation Protocol
• 前身 - MMUSIC (Multiparty Multimedia Session Control), Sep. 1999
• 由 IETF 的 SIP Working Group 發展– 開始於 1995– Proposed standard RFC2543, February 1999– New Version of SIP - RFC 3261, June 2002
SIP
• A Signaling Protocol– Create, Modify, Terminate Multimedia Sessions
• 使用 IP• Client / Server 架構 • 相似於 HTTP, SMTP
– Uniform Resource Locator (URL)sip:bob@hit.edu.twsip:+886424961356@hit.edu.tw也可以是 tel:+886424961356
– Request and Response– 回應訊息
SIP 藉由現成的 IETF 協定來提供
• SIP 的訊息格式 (HTTP 1.1) – RFC 2616
• 描述媒體的連線– (SDP) RFC 2327
• 媒體 (RTP) – RFC 3550 and (RTSP) RFC 2326
• 定址方式 (URL) – RFC 1738 and (URI) RFC 2396
• 名稱解析和位置的移動性– (DHCP) RFC 2131 and (DNS) RFCs 1034&1035
• 資料編碼方式 (MIME) – RFC 2045
• 安全 (TLS) – RFC 2246– IPsec
• RFC 2401&2406
SIP 的封包格式
IHL Total Length
Identification Flags Fragment Offset
Header ChecksumProtocolTime to Live
Source Address
Destination Address
PaddingOptions
Version DSCP ECN
IPv4 的表頭
Source PortSource PortSource PortSource Port Destination PortDestination PortDestination PortDestination Port
ChecksumChecksumChecksumChecksumLengthLengthLengthLength
UDP 8 個 Bytes 的表頭 ( 這裡也可以是 TCP 或者 SCTP)
SIP 表頭以 US-ASCII 文字為基礎 , 變動長度
SIP 訊息主體也是變動長度 ,
視 Message-Type 的需要而存在可以是任何形式的資料
Protocol Zoo
Source: Henning Schulzrinne,http://www.cs.columbia.edu/~hgs/internet/
SIP 組成元件
User Agent
Proxy Server
Gateway
Proxy Server
Location Server
Redirect Server
Registrar Server
PSTNPSTN
PLMNPLMN
Gateway
SIP User Agents
• User Agent (UA)– 用戶端 User Agent Client (UAC)
• 送出 SIP 請求– 伺服器端 User Agent Server (UAS)
• 回應 SIP 請求 接受或拒絶– User Agent = UAC + UAS
UA 1 UA 2
LAN A
UA 3 UA 4
LAN B
SIP 訊息流程
Request
Response
Media SessionUser Agent
Proxy Server
Redirect Server Location Server
User Agent
Proxy Server
SIP Request methods
• RFC 3261– REGISTER– INVITE– ACK– BYE– OPTIONS– CANCEL
• 其它的 RFC…
SIP Request methods
– INFO (RFC 2976)– PRACK (RFC 3262)– SUBSCRIBE and NOTIFY (RFC 3265)– UPDATE (RFC 3311)– MESSAGE (RFC 3428)– REFER (RFC 3515)– PUBLISH (RFC 3903)
SIP Response 說明 範例
1xx Informational – 代表請求已收到
100 Trying 180 Ringing 181 Call is Being Forwarded 183 Session Progressing
2xx Success – 代表請求已被成功處理
200 OK 202 Acceptable
3xx Redirection – 代表重新導向
300 Multiple Choices 301 Moved Permanently 302 Moved Temporarily
4xx Client Error – 代表用互端錯誤
401 Unauthorized 406 Not Acceptable 407 Proxy Authentication Required 486 Busy Here 487 Request Terminated 488 Not Acceptable Here
5xx Server Error –代表伺服器端錯誤
502 Bad Gateway 503 Service Unavailable
6xx Global Failure – 代表整體網路環境錯誤 600 Busy Everywhere 603 Decline
SIP
INVITE
100 Trying INVITE
100 Trying
180 Ringing 180 Ringing
200 OK 200 OK
ACK ACK
BYE
100 TryingBYE
200 OK200 OK
Call Setup
Call Teardown
Media Session
UAC UASServer
• 連線過程– 建立連線– 通話– 斷線
SIP 訊息 – 範例
SIP
SDP
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
v=0o=Alice 2897654321 2897654321 IN IP4 10.0.0.1s=Phone Callc=IN IP4 192.168.0.1t=0 0m=audio 49170 RTP/AVP 0a=rtpmap:0 PCMU/8000
SIP Headers
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
SIP Headers
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
Method 即 命令 Request URI SIP 協定版本
SIP Headers
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
所有經過的 SIP 設備都會被列在這裡 ‘branch’ 用來識別不同的連線分支
在所有 SIP Requests 中都是必要的欄位
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
最多可以被幾個 Server 轉傳
SIP Headers
在所有 SIP Requests 之中除了 INFO 都是必要的欄位
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
目的地位址
SIP Headers
在所有 SIP Requests 中都是必要的欄位
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
來源位址 虛擬的隨機亂數 ( 當作是 ID 使用 )
SIP Headers
在所有 SIP Requests 中都是必要的欄位
James P
olk 20050503
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
在網域內獨一無二的識別碼
SIP Headers
在所有 SIP Requests 中都是必要的欄位
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
遞增的序號
SIP Headers
在所有 SIP Requests 中都是必要的欄位
James P
olk 20050503
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
直接可以路由到來源位址的完整網域名稱或 IP 位址
SIP Headers
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
用來描述附加的訊息主體格式 ( 如果有的話 )
SIP Headers
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
用來描述附加的訊息主體的內容長度 (Octets)
SIP Headers
INVITE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/UDP pc33.yyy.edu;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142
SIP Headers
Session Description Protocol (SDP)
• 描述多媒體連線的協定– RFC 2327
• 簡單,可以擴充的,以文字為基礎• SIP Offer/Answer Model
– RFC 3264
• 在每一行– 欄位 = 值 值 值 …
• 欄位是一個字元 ( 大小寫有差別 )
– 等號兩旁不可以有空格
• 分為 Session 和 Media 層次
SDP 的結構內容
• Session 層次 ( 從 v= 這一行開始 )– Session Name
– 主動發起的一端– 活動時間
• Media 層次 ( 從 m= 這一行開始 )– 媒體形式
• video, audio, …
– Port number
– 傳輸層協定• RTP/UDP/IP, H.320, ...
– 媒體格式• H.261 video, MPEG video, ...
SDP 的範例
SDP 的欄位
v= (protocol version)例如 : v=0
o= (owner/creator and session identifier)o=<username> <session id> <version> <network type> <address t
ype> <address>Username 不可以含有空格Session id 和 version 建議使用 Network Time Protocol (NTP) 的時
間戳記來確保值的唯一性 例如 : o=john 2887654326 2887654307 IN IP4 10.1.2.3
s= (session name string)例如 : s=SDP Seminar
t= (start time and stop time)例如 : t=2887654321 2887654310( 通常設為 0)
為必要欄位
SDP 的欄位
m= (media name and transport address)m=<media> <port> <transport> <format list>m=<media> <port>/<number of ports> <transport> <format list>例如 : m=video 49170/2 RTP/AVP 0 <media>
"audio", "video", "application", "data" and "control“<transport>
• RTP/AVP - the IETF's Realtime Transport Protocol using the Audio/Video profile carried over UDP
• UDP– RTP/AVP RFC 3551
• e= (email address)例如 : e=john@yyy.edu (John Doe) 或者 e=John Doe <john@yyy.edu>
• p= (phone number)例如 : p=+886-4-2496-1356 或者 p=+886 4 2496 1356
u-law PCM, single channel, audio sampled at 8KHz
SDP 的欄位
• c= (connection information)c=<network type> <address type> <connection address>
例如 : c=IN IP4 224.2.17.12/127
通常這個連線位址是一個 class D 的 IP 群播位址 , <base multicast address>/<ttl>/<number of addresses>
例如 : c=IN IP4 224.2.1.1/127/3 指的是多個 c=IN IP4 224.2.1.1/127, c=IN IP4 224.2.1.2/127, c=IN IP4 224.2.1.3/127
如果這一個會議連線不是群播 , 則它可以搭配額外的屬性欄位決定是完整網域位址或單一 IP 位址等等
SDP 的欄位
• i= (session information)
• u= (URI of description)
• b= (bandwidth information)
• z= (time zone adjustments)
• k= (encryption key)
• a= (zero or more session attribute lines)
• r= (zero or more repeat times)
SIP Methods: INVITE, ACK and BYEAlice Bob
INVITEINVITE sip:bob@192.168.10.20 SIP/2.0Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bK776asdhdsMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142 (Alice's SDP not shown)
SIP Methods: INVITE, ACK and BYE
INVITE
200 OK
Alice Bob
SIP/2.0 200 OKVia: SIP/2.0/TCP pc33.yyy.edu;branch=z9hG4bKnashds8 ;received=10.1.3.33To: Bob <sip:bob@zzz.edu>;tag=a6c85cfFrom: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 314159 INVITEContact: <sip:bob@192.168.10.20>Content-Type: application/sdpContent-Length: 131 (Bob's SDP not shown)
SIP Methods: INVITE, ACK and BYE
INVITE
200 OK
Alice Bob
ACKACK sip:bob@192.168.10.20 SIP/2.0Via: SIP/2.0/TCP pc33.yyy.edu;branch=z9hG4bKnashds8Max-Forwards: 70To: Bob <sip:bob@zzz.edu>;tag=a6c85cfFrom: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 314159 ACKContent-Length: 0
SIP Methods: INVITE, ACK and BYE
INVITE
200 OK
Session Established
Alice Bob
ACK
SIP Methods: INVITE, ACK and BYE
INVITE
200 OK
Session Established
Alice Bob
ACK
BYEBYE sip:alice@pc33.yyy.edu SIP/2.0Via: SIP/2.0/TCP 10.1.3.33;branch=z9hG4bKnashds8Max-Forwards: 70From: Bob <sip:bob@zzz.edu>;tag=a6c85cfTo: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 231 BYEContent-Length: 0
SIP Methods: INVITE, ACK and BYE
INVITE
200 OK
Session Established
Alice Bob
ACK
BYE
200 OKSIP/2.0 200 OKVia: SIP/2.0/TCP 192.168.10.20From: Alice <sip:alice@yyy.edu>;tag=1928301774To: Bob <sip:bob@zzz.edu>;tag=a6c85cf Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 231 BYEContent-Length: 0
Alice BobSIP Proxy “server.zzz.edu”
透過 Proxy Server
INVITE
INVITE sip:bob@zzz.edu/TCP SIP/2.0Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bK776asdhds ;received=10.1.3.33Max-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142 (Alice's SDP not shown)
INVITE INVITE
Alice Bob
透過 Proxy Server
SIP Proxy “server.zzz.edu”
INVITE sip:bob@192.168.10.20/TCP SIP/2.0Via: SIP/2.0/TCP server.zzz.edu ;branch=z9hG4bK4b43c2ff8.1 ;received=192.168.10.1Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bK776asdhds ;received=10.1.3.33Max-Forwards: 69To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 314159 INVITEContact: <sip:alice@pc33.yyy.edu>Content-Type: application/sdpContent-Length: 142 (Alice's SDP not shown)
Via Header for Alice’s phone
Via Header for zzz server
Max-Forwardsdecreases 1
James P
olk 20050503
INVITE INVITE
Alice Bob
透過 Proxy Server
SIP Proxy “server.zzz.edu”
200 OK
SIP/2.0 200 OKVia: SIP/2.0/TCP server.zzz.edu ;branch=z9hG4bK4b43c2ff8.1 ;received=192.168.10.1Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bKnashds8 ;received=10.1.3.33To: Bob <sip:bob@zzz.edu>;tag=a6c85cfFrom: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 314159 INVITEContact: <sip:bob@192.168.10.20>Content-Type: application/sdpContent-Length: 131 (Bob's SDP not shown)
Notice both Via headers
INVITE INVITE
200 OK
Alice Bob
透過 Proxy Server
SIP Proxy “server.zzz.edu”
200 OK
SIP/2.0 200 OKVia: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bKnashds8 ;received=10.1.3.33To: Bob <sip:bob@zzz.edu>;tag=a6c85cfFrom: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 314159 INVITEContact: <sip:bob@192.168.10.20>Content-Type: application/sdpContent-Length: 131 (Bob's SDP not shown)
Notice one Via header
INVITE INVITE
200 OK200 OK
Alice Bob
透過 Proxy Server
ACK
ACK sip:bob@192.168.10.20 SIP/2.0Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bKnashds8Max-Forwards: 70To: Bob <sip:bob@zzz.edu>;tag=a6c85cfFrom: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 314159 ACKContent-Length: 0
SIP Proxy “server.zzz.edu”
INVITE INVITE
200 OK200 OK
Session Established
Alice Bob
透過 Proxy Server
ACK
SIP Proxy “server.zzz.edu”
INVITE INVITE
200 OK200 OK
Session Established
Alice Bob
透過 Proxy Server
ACK
SIP Proxy “server.zzz.edu”
BYE sip:alice@pc33.yyy.edu SIP/2.0Via: SIP/2.0/TCP 10.1.3.33;branch=z9hG4bKnashds8Max-Forwards: 70From: Bob <sip:bob@zzz.edu>;tag=a6c85cfTo: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 231 BYEContent-Length: 0
BYE
INVITE INVITE
200 OK200 OK
Session Established
Alice Bob
透過 Proxy Server
ACK
BYE
SIP Proxy “server.zzz.edu”
200 OK
SIP/2.0 200 OKVia: SIP/2.0/TCP 192.168.10.20From: Alice <sip:alice@yyy.edu>;tag=1928301774To: Bob <sip:bob@zzz.edu>;tag=a6c85cf Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 231 BYEContent-Length: 0
Alice
SIP Methods: REGISTER
REGISTER – 註冊 • SIP URI 稱之為 Address
of Record (AOR)• 把一個 AOR 和現在可以連繫
得上的實際位址對應連接在一起
• 讓 UA 可以收到 SIP 的訊息• UAs 可以利用下列方法向伺
服器註冊– 手動設定– Address-of-Record
– Multicast [224.0.1.75]
REGISTER
REGISTER sip:server.yyy.edu SIP/2.0Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bk2l55n1To: Alice <sip:alice@yyy.edu>From: Alice <sip:alice@yyy.edu>;tag=283074Call-ID: a84b4g96te10@pc33.yyy.edu CSeq: 31862 REGISTERContact: <sip:alice@10.1.3.33>Expires: 21600Content-Length: 0
SIP Registrar Server
REGISTER
Alice
SIP Methods: REGISTER
SIP Registrar Server
200 OK
SIP/2.0 200 OKVia: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bk2l55n1; received=10.1.3.33To: Alice <sip:alice@yyy.edu>; tag=a6c85e3From: Alice <sip:alice@yyy.edu>;tag=283074Call-ID: a84b4g96te10@pc33.yyy.edu CSeq: 31862 REGISTERContact: <sip:alice@pc33.yyy.edu>Contact: <sip:alice@pda01.yyy.edu>Expires: 3600Contact-Length: 0
• 200 (OK) 回應包含一連串的 Contact
• Expires Header 告知 UA註冊的有效期限
REGISTER 通常是需要經過密碼認證的
Call Forking
INVITE
INVITE
Alice
INVITE
INVITE INVITE
yyy.edu zzz.edu
OfficeOfficePhonePhoneOfficeOfficePhonePhone
Bob’sBob’s
NotebookNotebookNotebookNotebookBob’s
Mobile phoneMobile phoneMobile phoneMobile phone
Bob’sBob’s
同時嚮,看哪一個先接!
Alice Bob
SIP Methods: MESSAGE (RFC3428)
• MESSAGE– 以 近乎 即時的方式傳送 – 存在在 MIME 的主體中– 不會啓始新的 dialogs
– 訊息之間沒有任何關聯– 不可以超過 1300 bytes
MESSAGE sip:bob@zzz.edu SIP/2.0Via: SIP/2.0/TCP pc33.yyy.edu ;branch=z9hG4bK776asegmaMax-Forwards: 70To: Bob <sip:bob@zzz.edu>From: Alice <sip:alice@yyy.edu>;tag=1928301774Call-ID: a84b4c76e66710@pc33.yyy.edu CSeq: 22756 MESSAGEContent-Type: text/plainContent-Disposition: renderContent-Length: 37 Isn’t this a great presentation, Bob?
MESSAGE
Alice Bob
SIP Methods: MESSAGE (RFC3428)
MESSAGE
200 OK
SIP/2.0 200 OKVia: SIP/2.0/TCP pc33.yyy.edu;branch=z9hG4bKnashds7; received=10.1.3.33To: sip: sip:bob@zzz.edu>; tag=a6c85e3From: alice@yyy.edu ;tag=1928301774 Call-ID: a84b4c76e66710@pc33.yyy.eduCSeq: 22756 MESSAGEContent-Length: 0
參考文獻• http://www.cs.columbia.edu/sip/
• “Carrier Grade Voice Over IP” – Daniel Collins
– 出版社 : McGraw-Hill
– ISBN 0071231552– http://catalogs.mhhe.com/mhhe/viewProductDetails.do?isbn=00
71406344
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