📄 001_35.htm

📁 通讯类的标准。对要开发SS7的朋友有很大帮助的。（通讯协议）
💻 HTM
字号:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- saved from url=(0059)http://www.chinagk.org/technology/IPTech/001/css/001_35.htm -->
<HTML><HEAD><TITLE>001_35</TITLE>
<META http-equiv=Content-Type content="text/html; charset=gb2312">
<STYLE type=text/css>.pg {
	LEFT: 0px; WIDTH: 635px; POSITION: absolute; TOP: 0px; HEIGHT: 983px
}
BODY {
	FONT-SIZE: 13px; COLOR: #000000; FONT-FAMILY: ""; BACKGROUND-COLOR: #ffffff
}
A {
	TEXT-DECORATION: none
}
.ps0 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 102px
}
.ps1 {
	LEFT: 37px; WIDTH: 148px; POSITION: absolute; TOP: 123px
}
.ps2 {
	LEFT: 64px; WIDTH: 116px; POSITION: absolute; TOP: 145px
}
.ps3 {
	LEFT: 64px; WIDTH: 529px; POSITION: absolute; TOP: 164px
}
.ps4 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 185px
}
.ps5 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 206px
}
.ps6 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 226px
}
.ps7 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 247px
}
.ps8 {
	LEFT: 37px; WIDTH: 40px; POSITION: absolute; TOP: 268px
}
.ps9 {
	LEFT: 64px; WIDTH: 530px; POSITION: absolute; TOP: 290px
}
.ps10 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 309px
}
.ps11 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 330px
}
.ps12 {
	LEFT: 37px; WIDTH: 121px; POSITION: absolute; TOP: 350px
}
.ps13 {
	LEFT: 64px; WIDTH: 68px; POSITION: absolute; TOP: 372px
}
.ps14 {
	LEFT: 64px; WIDTH: 529px; POSITION: absolute; TOP: 392px
}
.ps15 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 412px
}
.ps16 {
	LEFT: 30px; WIDTH: 570px; POSITION: absolute; TOP: 433px
}
.ps17 {
	LEFT: 37px; WIDTH: 387px; POSITION: absolute; TOP: 454px
}
.ps18 {
	LEFT: 64px; WIDTH: 530px; POSITION: absolute; TOP: 476px
}
.ps19 {
	LEFT: 37px; WIDTH: 256px; POSITION: absolute; TOP: 495px
}
.ps20 {
	LEFT: 64px; WIDTH: 178px; POSITION: absolute; TOP: 517px
}
.ps21 {
	LEFT: 64px; WIDTH: 530px; POSITION: absolute; TOP: 536px
}
.ps22 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 557px
}
.ps23 {
	LEFT: 37px; WIDTH: 471px; POSITION: absolute; TOP: 578px
}
.ps24 {
	LEFT: 64px; WIDTH: 511px; POSITION: absolute; TOP: 598px
}
.ps25 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 620px
}
.ps26 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 640px
}
.ps27 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 660px
}
.ps28 {
	LEFT: 37px; WIDTH: 306px; POSITION: absolute; TOP: 681px
}
.ps29 {
	LEFT: 64px; WIDTH: 529px; POSITION: absolute; TOP: 702px
}
.ps30 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 722px
}
.ps31 {
	LEFT: 37px; WIDTH: 464px; POSITION: absolute; TOP: 743px
}
.ps32 {
	LEFT: 512px; WIDTH: 81px; POSITION: absolute; TOP: 744px
}
.ps33 {
	LEFT: 37px; WIDTH: 202px; POSITION: absolute; TOP: 764px
}
.ps34 {
	LEFT: 64px; WIDTH: 178px; POSITION: absolute; TOP: 786px
}
.ps35 {
	LEFT: 64px; WIDTH: 530px; POSITION: absolute; TOP: 805px
}
.ps36 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 826px
}
.ps37 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 846px
}
.ps38 {
	LEFT: 37px; WIDTH: 556px; POSITION: absolute; TOP: 867px
}
.ps39 {
	LEFT: 37px; WIDTH: 211px; POSITION: absolute; TOP: 888px
}
.ps40 {
	LEFT: 332px; WIDTH: 189px; POSITION: absolute; TOP: 54px
}
.ps41 {
	LEFT: 541px; WIDTH: 37px; POSITION: absolute; TOP: 31px
}
.ps42 {
	LEFT: 45px; WIDTH: 43px; POSITION: absolute; TOP: 64px
}
.ft1 {
	FONT-SIZE: 13px; FONT-FAMILY: "Times New Roman",Times,serif
}
.ft2 {
	FONT-STYLE: italic; FONT-FAMILY: ""
}
.ft3 {
	FONT-WEIGHT: bold; FONT-SIZE: 37px; FONT-STYLE: italic; FONT-FAMILY: "Times New Roman",Times,serif
}
.ft4 {
	FONT-SIZE: 21px; COLOR: #000000; FONT-STYLE: italic; FONT-FAMILY: ""
}
.em0 {
	FONT-SIZE: 13px; FONT-FAMILY: "Times New Roman",Times,serif
}
.em1 {
	FONT-SIZE: 13px; FONT-FAMILY: ""
}
.em2 {
	FONT-SIZE: 13px; FONT-STYLE: italic; FONT-FAMILY: ""
}
.em3 {
	FONT-SIZE: 10px; FONT-FAMILY: "Times New Roman",Times,serif
}
.em4 {
	FONT-SIZE: 13px; FONT-STYLE: italic; FONT-FAMILY: "Times New Roman",Times,serif
}
.im0 {
	LEFT: 35px; WIDTH: 561px; POSITION: absolute; TOP: 24px
}
</STYLE>

<META content="MSHTML 6.00.2600.0" name=GENERATOR></HEAD>
<BODY>
<DIV class=pg></DIV><!-- bitmap and vector images are written here -->
<DIV class=im0><IMG height=64 src="001_35.files/right.jpg" width=563 
border=0></DIV><!-- text starts here --><SPAN 
class=ps0><NOBR>交换。但是，当会议采用组播模式时，<SPAN class=em0>MCU</SPAN>使用<SPAN 
class=em0>H.245</SPAN>的<SPAN class=em0>communicationMode Command<SPAN 
class=em1>，</SPAN></SPAN>为</NOBR></SPAN> <SPAN 
class=ps1><NOBR>端点分配多点传送地址。</NOBR></SPAN> <SPAN class=ps2><NOBR><SPAN 
class=ft1>6. H.323 QoS-RSVP</SPAN></NOBR></SPAN> <SPAN 
class=ps3><NOBR>请求被关守接收的端点可以利用<SPAN class=em0>transportQoS</SPAN>域在<SPAN 
class=em0>ARQ RAS</SPAN>消息中指明其保留资源的能</NOBR></SPAN> <SPAN class=ps4><NOBR>力。<SPAN 
class=em0>H.323</SPAN>规定用<SPAN class=em0>RSVP</SPAN>协议作为提供呼叫服务质量的机制。第<SPAN 
class=em0>2</SPAN>章中将讨论<SPAN class=em0>RSVP<SPAN 
class=em1>，</SPAN></SPAN>但是必须</NOBR></SPAN> <SPAN class=ps5><NOBR>注意，<SPAN 
class=em0>RSVP</SPAN>保留只能通过直接在呼叫介质路径上的网络元件来实现。为了试图在呼叫建立过</NOBR></SPAN> <SPAN 
class=ps6><NOBR>程中控制介质流的路径，端点必须支持<SPAN class=em0>RSVP</SPAN>。<SPAN 
class=em0>RSVP</SPAN>不是普遍存在的，在离开<SPAN class=em0>H.323</SPAN>后，便</NOBR></SPAN> 
<SPAN class=ps7><NOBR>没有可靠的控制介质流质量的机制。这是新的<SPAN 
class=em0>VoIP</SPAN>呼叫信令协议的普遍问题，并非<SPAN class=em0>H.323</SPAN>所</NOBR></SPAN> 
<SPAN class=ps8><NOBR>特有。</NOBR></SPAN> <SPAN class=ps9><NOBR><SPAN 
class=ft1>QoS<SPAN class=em1>的监控是在</SPAN>RTCP<SPAN 
class=em1>的帮助下实现的，但是</SPAN>RTCP<SPAN 
class=em1>只在呼叫端点之间传送。因为有时分配</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps10><NOBR>给<SPAN class=em0>RTCP</SPAN>信令的带宽比较窄，因此使用<SPAN 
class=em0>RTCP</SPAN>数据判断<SPAN class=em0>QoS</SPAN>是不可靠的。在实际实现中，可以</NOBR></SPAN> 
<SPAN class=ps11><NOBR>通过其他途径，如<SPAN class=em0>SNMP<SPAN 
class=em1>，</SPAN></SPAN>来收集性能数据，并与<SPAN 
class=em0>RTCP</SPAN>相联系，从而得到网络性能和单个元</NOBR></SPAN> <SPAN 
class=ps12><NOBR>件性能的精确结论。</NOBR></SPAN> <SPAN class=ps13><NOBR><SPAN 
class=ft1>7. <SPAN class=em2>电话特性</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps14><NOBR>通常的电话特性包括可以从本地载波获得的服务，如呼叫发送、呼叫等待、三路呼叫和</NOBR></SPAN> <SPAN 
class=ps15><NOBR>呼叫跟踪等。当今的“笨”<SPAN 
class=em0>TDM</SPAN>网络中支持所有这些和更多的电话特性。但是这一领域内的</NOBR></SPAN> <SPAN 
class=ps16><NOBR>“聪明”的包信令协议和实现还十分落后。原因在于包电话技术起源于企业网和以后的因特网，</NOBR></SPAN> <SPAN 
class=ps17><NOBR>它们并没有优先考虑用户对<SPAN 
class=em0>5</SPAN>类服务和智能网络呼叫特性的要求。</NOBR></SPAN> <SPAN class=ps18><NOBR><SPAN 
class=ft1>H.323<SPAN class=em1>允许使用</SPAN>H.225.0<SPAN 
class=em1>的</SPAN>FACILITY<SPAN class=em1>消息和</SPAN>alternativeAddress<SPAN 
class=em1>域对呼叫重新定向。通过辅</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps19><NOBR>助服务的实现，能够提供更多的电话特性。</NOBR></SPAN> <SPAN class=ps20><NOBR><SPAN 
class=ft1>8. <SPAN class=em2>协议故障、健壮性和可靠性</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps21><NOBR>使用<SPAN class=em0>TCP</SPAN>传输<SPAN 
class=em0>H.245</SPAN>信令的重要意义就是可靠性。传输协议十分可靠，但是如果<SPAN 
class=em0>TCP</SPAN>连接</NOBR></SPAN> <SPAN 
class=ps22><NOBR>丢失，端点就会中断呼叫。这是一个有趣的问题，因为在通话期间，相互通信的端点之间没</NOBR></SPAN> <SPAN 
class=ps23><NOBR>有呼叫信令控制。所以和<SPAN 
class=em0>H.323</SPAN>的任何部分都无关的故障也可能导致呼叫中断。</NOBR></SPAN> <SPAN 
class=ps24><NOBR>在丢失<SPAN 
class=em3>T&nbsp;C&nbsp;P</SPAN>连接的情况下，呼叫中断的方法和任何一方有意断开呼叫的方法一样。</NOBR></SPAN> 
<SPAN class=ps25><NOBR><SPAN class=ft1>H.225.0<SPAN 
class=em1>也使用一个不同的</SPAN>TCP<SPAN 
class=em1>连接，当呼叫信令通道丢失而介质控制信道仍然有效时，会出</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps26><NOBR>现其他有趣的情况。如果<SPAN class=em0>GK</SPAN>能够检测到断开的<SPAN 
class=em0>TCP</SPAN>连接，其后的状态请求可以试图重建该连</NOBR></SPAN> <SPAN 
class=ps27><NOBR>接。如果一个端点检测到断开的<SPAN 
class=em0>TCP</SPAN>连接，根据它使用的是何种呼叫信令路由模型，它可以</NOBR></SPAN> <SPAN 
class=ps28><NOBR>选择中断该呼叫或者重建与<SPAN class=em0>GK</SPAN>或端点的呼叫信道。</NOBR></SPAN> 
<SPAN class=ps29><NOBR>实际上，<SPAN 
class=em0>TCP</SPAN>连接断开的原因是由于某些链路层故障或者设备故障造成的操作超时以及</NOBR></SPAN> <SPAN 
class=ps30><NOBR>无法交换保活消息。因为信令使用的两个<SPAN 
class=em0>TCP</SPAN>连接起源于相同的端点，所以更多的时候可能</NOBR></SPAN> <SPAN 
class=ps31><NOBR>是两个连接都会丢失，而不只是其中的一个。所以，可以设想，如果不能保证</NOBR></SPAN> <SPAN 
class=ps32><NOBR><SPAN class=ft1>TCP<SPAN 
class=em1>连接在可</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps33><NOBR>靠的方式下工作，呼叫将被中断。</NOBR></SPAN> <SPAN class=ps34><NOBR><SPAN 
class=ft1>9. <SPAN class=em2>性能问题、可升级性和比较</SPAN></SPAN></NOBR></SPAN> <SPAN 
class=ps35><NOBR>在声明呼叫完成之前，<SPAN 
class=em0>H.323</SPAN>中的呼叫建立并不试图保证有一个介质路径。在端点之间可</NOBR></SPAN> <SPAN 
class=ps36><NOBR>以有非常复杂的网络，即使在相同的区域和域中，甚至在企业中也是如此。因此，&nbsp;<SPAN 
class=em0>GK</SPAN>很容易</NOBR></SPAN> <SPAN class=ps37><NOBR>忽视呼叫中用户感受到的<SPAN 
class=em0>QoS</SPAN>问题。<SPAN class=em0>RTCP</SPAN>在端点之间传送<SPAN 
class=em0>QoS</SPAN>信息，但是并不存在一致的机</NOBR></SPAN> <SPAN 
class=ps38><NOBR>制来发送信令通知<SPAN 
class=em0>GK</SPAN>可能出现的问题。而且，呼叫信令模型可能是直接路由的，呼叫建立之</NOBR></SPAN> <SPAN 
class=ps39><NOBR>后，<SPAN class=em0>GK</SPAN>在呼叫期间并不了解情况。</NOBR></SPAN> <SPAN 
class=ps40><NOBR><SPAN class=ft2>第<SPAN class=em4>1</SPAN>章<SPAN 
class=em4>IP</SPAN>语音和交互应用的协议</SPAN></NOBR></SPAN> <SPAN class=ps41><NOBR><SPAN 
class=ft3>35</SPAN></NOBR></SPAN> <SPAN class=ps42><NOBR><SPAN 
class=ft4>文档</SPAN></NOBR></SPAN> </BODY></HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -