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基于p2p-sip架構(gòu)的認(rèn)證技術(shù)研究碩士學(xué)位論文(編輯修改稿)

2024-08-23 04:37 本頁(yè)面
 

【文章內(nèi)容簡(jiǎn)介】 From: UserA sip:UAA@。tag=589304To: UserB sip:UAB@CallID: 8204589102@CSeq: 1 INVITEContentLength: 0,User Agent B發(fā)送臨時(shí)消息(響鈴)給User Agent A,這樣它就不會(huì)超時(shí)和放棄。SIP/180 RingingFrom: UserA sip:UAA@。tag=589304To: UserB sip:UAB@。tag=314159CallID: 8204589102@CSeq: 1 INVITEContent Length: 0,User B決定接受呼叫。此時(shí),User Agent B發(fā)送一個(gè)OK響應(yīng)給User Agent A。在響應(yīng)的payload中,還有另一條SDP消息。它包含一組兩個(gè)用戶代理都支持的介質(zhì)編碼。此時(shí),雙方正式處于呼叫中。使用200類型的響應(yīng)可以接受所有類型的SIP請(qǐng)求。SIP/200 OKFrom: UserA sip:UAA@。tag=589304To: UserB sip:UAB@。tag=314159CallID: 8204589102@CSeq: 1 INVITEContact: sip:UserB@ContentType: application/sdpContentLength: 140v=0o=UserB 2890844527 2890844527 IN IP4 s=Session SDPc=IN IP4 t=3034423619 0m=audio 3456 RTP/AVP 0a=rtpmap:0 PCMU/80005. User Agent A最后使用一條ACK消息進(jìn)行確認(rèn)。對(duì)于這種請(qǐng)求類型來(lái)說(shuō),沒有重試和響應(yīng)消息,即使消息丟失。ACK只在INVITE消息中使用。ACKsip:UAB@ SIP/Via: SIP/:5060Route: sip:UserB@From: UserA sip:UAA@。tag=589304To: UserB sip:UAB@。tag=314159CallID: 8204589102@CSeq: 1 ACKContentLength: 06..兩個(gè)用戶代理現(xiàn)在使用最后一條SDP消息中選定的方法進(jìn)行連接。RTP使用PCMU/8000編碼對(duì)在端口49170 amp。 3456上雙向傳輸?shù)囊纛l數(shù)據(jù)進(jìn)行打包。,其中一個(gè)用戶掛斷。此時(shí),這個(gè)用戶的用戶代理發(fā)送一個(gè)新的請(qǐng)求BYE。這條消息可以由任一方發(fā)送。BYEsip:UAB@ SIP/Via: SIP/:5060To: UserB sip:UAB@。tag=314159From: UserA sip:UAA@。tag=589304CallID: 8204589102@CSeq: 1 BYEContentLength: 0,然后使用一條OK消息作為應(yīng)答。呼叫連接至此斷開。SIP/200 OKTo: UserB sip:UAB@。tag=314159From: UserA sip:UAA@。tag=589304CallID: 8204589102@CSeq: 1 BYEContentLength: 0 SIP應(yīng)用拓?fù)鋱D23 SIP應(yīng)用拓?fù)銼IP網(wǎng)絡(luò)的組成包括:-User Agent;-SIP Proxy ;-SIP Redirect; -SIP Registrar ;-SIP Location ;User Agent – 用戶代理 一個(gè)發(fā)起和終止會(huì)話的實(shí)體,包含兩個(gè)功能實(shí)體:?User Agent Clients (UAC) – 發(fā)起呼叫的功能實(shí)體. ?User Agent Server (UAS) – 接收呼叫的功能實(shí)體.SIP Proxy – 代理服務(wù)器?為其它的客戶機(jī)代理,進(jìn)行SIP消息的轉(zhuǎn)接和轉(zhuǎn)發(fā)的功能。消息機(jī)制與UAC和UAS相似。 ?對(duì)收到的請(qǐng)求消息進(jìn)行翻譯和處理后,傳遞給其他的服務(wù)器。SIP Redirect – 重定向服務(wù)器?接受SIP請(qǐng)求消息,進(jìn)行地址映射,將映射后的地址(零個(gè)或多個(gè))返回給客戶機(jī) ?與代理服務(wù)器proxy server不同的是, redirect server不會(huì)發(fā)起自己的呼叫。 ?與user agent server不同的是, redirect server不接受或主動(dòng)終止呼叫。 SIP Registrar 注冊(cè)服務(wù)器?接受REGISTER 請(qǐng)求的服務(wù)器。?可以支持鑒權(quán)的功能。?在典型應(yīng)用中,可與代理服務(wù)器proxy sever或重定向redirect server一起提供用戶定位服務(wù)。SIP Location – 位置服務(wù)器?為SIP 重定向Redirect Server或 代理proxy server 提供被叫用戶可能的位置信息。 SIP呼叫流程l 基本呼叫流程圖24 基本呼叫流程圖具體流程說(shuō)明如下:? INVITE is a Request and contains Tesla’s media information? 180 Ringing is an Informational response and is not required? 200 OK is a final Response and contains Marconi’s media information? ACK pletes threewayhandshake.? BYE tears down sessionl 代理呼叫流程圖25 代理呼叫流程圖具體流程說(shuō)明如下:? INVITE is sent to Proxy instead of to Heisenberg directly.? Proxy looks up address of Heisenberg and forwards INVITE to that IP Address. ? Responses to INVITE route back through the Proxy: 180 Ringing and 200 OK ? 200 OK contains a Contact header which allows the ACK and all future requests to go directly bypassing Proxy.l 重定向呼叫圖26 重定向呼叫流程圖具體流程說(shuō)明如下:? INVITE is sent to Redirect Server? Server looks up address of Heisenberg and returns that address in a Contact header in a 302 Moved Temporarily response ? The ACK pletes the transaction with the Server Schroedinger then resends the INVITE directly to Heisenbergl 注冊(cè)流程圖27 注冊(cè)流程圖具體流程說(shuō)明如下:? Heisenberg sends a REGISTER request to a Registrar Server. The request contains Contact headers listing the URLs for which Heisenberg wishes to receive ining SIP calls? Registrar Accepts registration and replies with 200 OK and echoes current Contact listl SIP到PSTN呼叫圖28 SIP到PSTN呼叫流程圖具體流程說(shuō)明如下:? RequestURI in the INVITE contains a Telephone Number which is sent to PSTN Gateway.? The Gateway maps the INVITE to a SS7 ISUP IAM (Initial Address Message)? 183 Session Progress establishes early media session so caller hears Ring Tone.? Two way Speech path is established after ANM (Answer Message) and 200 OKl PSTN到SIP呼叫圖29 PSTN到SIP呼叫流程圖具體流程說(shuō)明如下:? ISDN telephone call is routed to a PSTN/SIP Gateway? The Gateway maps the ISDN Setup message to a SIP INVITE message to a Proxy? Proxy consults Database and maps telephone number to SIP URL of the SIP Phone and proxies the INVITE? The 180 Ringing response is mapped to a ISDN Alerting message no ring tone is generatedl Proxy并行查找呼叫流程圖210 Proxy并行查找呼叫流程圖具體流程說(shuō)明如下:? Single INVITE request returns three Contact headers from Redirect Server.? Babbage tries each location in parallel? Each INVITE has same To, From, and CallID, but a unique branch tag which identifies each leg.? First two INVITEs fail, but third is successful and session is established.? Forking Proxy Servers also can perform this function.l SIP可靠性呼叫流程圖211 SIP可靠性呼叫流程圖具體流程說(shuō)明如下:? Unreliable UDP transport is assumed? OPTIONS message is lost between Proxy and UAS.? Stateful Proxy realizes message loss and retransmits message after timer T1 expires? 200 OK response is lost between Proxy and UAC.? UAC retransmits OPTIONS after timer T2 expires? Proxy realizes response loss and retransmits 200 OK response SDPSession Description Protocol(SDP)會(huì)話描述協(xié)議。最為一種會(huì)話參數(shù)屬性的描述協(xié)議,獨(dú)立于一般的傳輸協(xié)議,如包括會(huì)話通知協(xié)議 (SAP) 、會(huì)話初始協(xié)議(SIP)、實(shí)時(shí)流協(xié)議 (RTSP)、 MIME 擴(kuò)展協(xié)議的電子郵件以及超文本傳輸協(xié)議 (HTTP)。作為一種會(huì)話描述規(guī)范,其和其它傳輸協(xié)議共同完成網(wǎng)絡(luò)會(huì)話協(xié)商。SDP協(xié)議結(jié)構(gòu),SDP 信息是文本信息,采用 UTF8 編 碼中的 ISO 10646 字符集。 SDP 會(huì)話描述如下: ( 標(biāo)注 * 符號(hào)的表示可選字段 ) : v= (協(xié)議版本) o= (所有者/創(chuàng)建者和會(huì)話標(biāo)識(shí)符) s= (會(huì)話名稱) i=* (會(huì)話信息) u=* (URI 描述) e=* (Email 地址) p=* (電話號(hào)碼) c=* (連接信息 ― 如果包含在所有媒體中,則不需要該字段) b=* (帶寬信息)   一個(gè)或更多時(shí)間描述(如下所示): z=* (時(shí)間區(qū)域調(diào)整) k=* (加密密鑰) a=* (0 個(gè)或多個(gè)會(huì)話屬性行) 0個(gè)或多個(gè)媒體描述(如下所示)   時(shí)間描述 t= (會(huì)話活動(dòng)時(shí)間) r=* (0或多次重復(fù)次數(shù))   媒體描述 m= (媒體名稱和傳輸?shù)刂罚?i=* (媒體標(biāo)題) c=* (連接信息 — 如果包含在會(huì)話層則該字段可選) b=* (帶寬信息) k=* (加密密鑰) a=* (0 個(gè)或多個(gè)會(huì)話屬性行)SDP描述由許多文本行組成,文本行的格式為類型=值,類型是一個(gè)字母,值是結(jié)構(gòu)化的文本串,其格式依類型而定。 第三章 P2P技術(shù) P2P概述P2P網(wǎng)絡(luò)是一種具有較高擴(kuò)展性的分布式系統(tǒng)結(jié)構(gòu),其對(duì)等概念是指網(wǎng)絡(luò)中的物理節(jié)點(diǎn)在邏輯上具有相同的地位,而并非處理能力和信息負(fù)擔(dān)上完全的對(duì)等。P2P系統(tǒng)最大的特點(diǎn)就是用戶之間直接共享資源,其核心技術(shù)就是分布式對(duì)象的定位機(jī)制,這也是提高網(wǎng)絡(luò)可擴(kuò)展性、解決網(wǎng)絡(luò)帶寬被吞噬的關(guān)鍵所在。迄今為止,P2P網(wǎng)絡(luò)已經(jīng)歷了三代不同網(wǎng)絡(luò)模型,各種模型各有優(yōu)缺點(diǎn),有的還存在著本身難以克服的缺陷,因此在目前P2P技術(shù)還遠(yuǎn)未成熟的階段,各種網(wǎng)絡(luò)結(jié)構(gòu)依然能夠共存,甚至呈現(xiàn)相互借鑒的形式。P2P打破了傳統(tǒng)的Client/Server(C/S)模
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