什么是SIP PnP? 原理和協(xié)議流程

SIP PnPn (Plug & Play)?即插即用是簡捷SIP電話終端（IP電話機/網(wǎng)關）支持的一種國際標準常用“自動配置”（Auto Provisioning）的方法。默認情況下，SIP電話機會向多播地址（常用IP地址是：224.0.1.75）發(fā)送 SIP SUBSCRIBE 消息（通常譯作訂閱消息）。任何理解該訂閱消息的 SIP 服務器都可以通過包含自動配置服務器 URL地址（設置服務器 URL）的 SIP Notify消息（通常譯作通知消息）進行回復，電話機收到這個回復后，就知道可以從該 URL 地址獲得其配置文件。

PnP配置是出廠默認啟用的，用戶無需配置。

SIP PnP原理

SIP協(xié)議流程

IP電話機上電啟動聯(lián)網(wǎng)之后，會周期性的向多播地址224.0.1.75:5060發(fā)送 SIP SUBSCRIBE 消息: 在該消息的“Event”頭字段中，應包含 SIP終端的?商，型號，版本等基本信息。

Sent to udp:224.0.1.75:5060?at?24/12/2023?00:00:19:248?(448?bytes): SUBSCRIBE sip:MAC%3a00135E874B49@192.168.3.99 SIP/2.0 Via: SIP/2.0/UDP?192.168.3.67:5060;rport From: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=658512961 To: <sip:MAC%3a00135E874B49@192.168.3.99> Call-ID:?1930770594@192.168.3.67 CSeq:?1?SUBSCRIBE Event: ua-profile;profile-type="device";vendor="OEM";model="OEM";version="7.1.19" Expires:?0 Accept: application/url Contact: <sip:192.168.3.67:5060> Content-Length:?0

局域網(wǎng)內(nèi)的SIP服務器收到這個消息后，會發(fā)送一個確認消息，格式如下：

Received from udp:192.168.3.99:5060?at?24/12/2024?00:00:19:287?(480?bytes): SIP/2.0?200?OK Via: SIP/2.0/UDP?192.168.3.67:5060;rport=5060 Record-Route: <sip:127.0.0.1;lr;transport=tcp;route-id=fb4fb92b7775c2a7> Record-Route: <sip:192.168.3.99;lr;transport=UDP;route-id=fb4fb92b7775c2a7> Contact: <sip:192.168.3.99;transport=UDP;handler=dum> To: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=91955270 From: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=658512961 Call-ID:?1930770594@192.168.3.67 CSeq:?1?SUBSCRIBE Expires:?0 Content-Length:?0

由包含自動配置URL的SIP NOTIFY消息推送 “http://192.168.3.99/sipphone/sipphoneconfig.php?mac={mac}”:

Received from udp:192.168.3.99:5060?at?24/12/2024?00:00:19:293?(868?bytes): NOTIFY sip:192.168.3.67:5060?SIP/2.0 Via: SIP/2.0/UDP?192.168.3.99:5060;branch=z9hG4bK-d8754z-c3ea5f0e74462613-1---d8754z-;rport Via: SIP/2.0/TCP?127.0.0.1:5060;branch=z9hG4bK-d8754z-7ca96c30144f3e04-1---d8754z-;rport=40916 Max-Forwards:?20 Record-Route: <sip:192.168.3.99;lr;route-id=e3470eb400e9c0a4> Record-Route: <sip:127.0.0.1;lr;transport=TCP;route-id=e3470eb400e9c0a4> Contact: <sip:192.168.3.99;transport=TCP;handler=dum> To: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=658512961 From: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=91955270 Call-ID:?1930770594@192.168.3.67 CSeq:?3?NOTIFY Content-Type: application/urlSubscription-State: terminated;reason=timeout Event: ua-profile;profile-type="device";vendor="OEM";model="OEM";version="7.1.19" Content-Length:?57 http://192.168.3.99/sipphone/sipphoneconfig.php?mac={mac}

IP電話機收到這條消息并且確認:

Sent to udp:192.168.3.99:5060?at?24/12/2024?00:00:19:315?(542?bytes): SIP/2.0?200?Ok Via: SIP/2.0/UDP?192.168.3.99:5060;branch=z9hG4bK-d8754z-c3ea5f0e74462613-1---d8754z-;rport=5060 Via: SIP/2.0/TCP?127.0.0.1:5060;branch=z9hG4bK-d8754z-7ca96c30144f3e04-1---d8754z-;rport=40916 Record-Route: <sip:192.168.3.99;lr;route-id=e3470eb400e9c0a4> Record-Route: <sip:127.0.0.1;lr;transport=TCP;route-id=e3470eb400e9c0a4> From: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=91955270 To: <sip:MAC%3a00135E874B49@192.168.3.99>;tag=658512961 Call-ID:?1930770594@192.168.3.67 CSeq:?3?NOTIFY Content-Length:?0

在采用了PnP 自動配置后，電話機會把收到這個URL保存下來。

常見的設置界面如下：