MP的管理問題來自于會(huì)議系統(tǒng)自身的特點(diǎn)。會(huì)議是多點(diǎn)通信，這點(diǎn)和VoIP是有很大區(qū)別的，點(diǎn)對(duì)點(diǎn)通信時(shí)，媒體網(wǎng)關(guān)只負(fù)責(zé)就近接入用戶，接收相應(yīng)MGC的控制即可；但多點(diǎn)通信，一個(gè)MP可能需要同時(shí)處理處于多個(gè)會(huì)議的多個(gè)用戶，這多個(gè)會(huì)議有可能不在同一MC上進(jìn)行，這樣MP就需要接受多個(gè)MC的控制。這樣看起來問題似乎是有點(diǎn)大，因?yàn)榻邮芏喾娇刂仆ǔＲ馕吨靵y，但事實(shí)并非如此。當(dāng)一個(gè)MP需要同時(shí)支持多個(gè)不同MC召集的會(huì)議時(shí)，MP必須能夠支持以虛擬的MP接受多個(gè)MC控制，但MP 的主控權(quán)仍在它的默認(rèn)MC。其實(shí)H.248制定時(shí)就已考慮到這個(gè)問題，只是一直沒有給出具體應(yīng)用方式。實(shí)際應(yīng)用中，MP開機(jī)注冊(cè)時(shí)，仍然是向其默認(rèn)MC注冊(cè)，由MC將MP的信息上報(bào)給相應(yīng)的GK；如果需要MP參加在其他MC上的會(huì)議，則由其默認(rèn)MC通知以什么樣的能力和形式向其他MC注冊(cè)；會(huì)議結(jié)束后，再由其默認(rèn)MC要求MP從其他MC中退出。在H.248中的MG接受MGC的控制，使用mID（意指消息發(fā)起者）這樣一個(gè)參數(shù)，虛擬MP只需要將它的虛擬mID上報(bào)給的MC就可以了。
MP的安全問題
MP的安全問題其實(shí)是所有電信設(shè)備的公共問題，但之所以在這兒單獨(dú)提出來，是因?yàn)镸P是提出MCU分離概念后的一個(gè)新設(shè)備。不過既然MP 的位置和能力與MG如此相像，安全問題自然也是可以借鑒解決。其實(shí)一般來說安全問題都要提到使用H.235，但在H.235真正能使用之前，有很多加密算法被用作了媒體網(wǎng)關(guān)設(shè)備安全措施，這些措施借用到視訊系統(tǒng)來幾乎不需要改動(dòng)。
具體MP的管理和安全問題的解決都體現(xiàn)在注冊(cè)認(rèn)證過程中，只需要對(duì)ServiceChange的參數(shù)做相應(yīng)擴(kuò)充即可。
MP向MC發(fā)送ServiceChange進(jìn)行注冊(cè)，如果是開機(jī)注冊(cè)，ServcieChange 中的 TerminationId設(shè)置為Root，Method項(xiàng)為必選，設(shè)置為Restart，ServiceChang eReason 項(xiàng)為必選，version項(xiàng)為可選。命令中還應(yīng)該帶有四個(gè)用于認(rèn)證的X字段：一個(gè)用于數(shù)字簽名的數(shù)字串MGAUTH、算法ID和隨機(jī)數(shù)Rand；還帶有用于 DH交換的A；如果是虛擬MP向其他MC注冊(cè)，則mID為虛擬MP編號(hào)，命令中還應(yīng)該帶有三個(gè)用于虛擬注冊(cè)的X字段：指示MP將要受控的MC的地址，加入的會(huì)議號(hào)，要加入的會(huì)議需要的終結(jié)點(diǎn)數(shù)目，ServiceChangeMethod 增加一項(xiàng)，用來指示向其他域MC注冊(cè)或注銷。
從技術(shù)角度來看，MCU分離已經(jīng)是可以實(shí)現(xiàn)而且是大勢所趨。因?yàn)橐曈崢I(yè)務(wù)也勢必向下一代網(wǎng)過渡，MCU 的分離非常符合現(xiàn)在所提出的對(duì)下一代網(wǎng)信令和媒體分離的思想。但目前尚無實(shí)現(xiàn)的廠家，原因有很多，但主要原因是現(xiàn)在視訊會(huì)議的市場并不是很大。雖然美國的911和2003 年的SARS使得視訊通信的呼聲越來越高，但視訊業(yè)務(wù)真正的推廣卻有著很多阻礙。這有待于設(shè)備制造商，電信運(yùn)營商，內(nèi)容提供商等多方的共同努力。不過MCU分離的好處是顯而易見的，相信隨著視訊會(huì)議業(yè)務(wù)范圍的不斷擴(kuò)大，優(yōu)越性將會(huì)更明顯的表現(xiàn)出來。而隨著H.248協(xié)議的不斷完善和擴(kuò)充，它真正能夠被應(yīng)用到視訊會(huì)議設(shè)備中，會(huì)對(duì)視訊會(huì)議業(yè)務(wù)的推廣起重要作用。
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