002_32.htm
来自「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 代码 · 共 224 行
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class=ps0><NOBR>现在网络中某处会导致潜在失序包的存在，解压缩器必须对它们进行处理，而这种处理太过</NOBR></SPAN> <SPAN
class=ps1><NOBR>冒险，可以获得的好处也很小。</NOBR></SPAN> <SPAN class=ps2><NOBR><SPAN
class=ft1>11. RTP<SPAN class=em3>有效载荷多路复用</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps3><NOBR><SPAN class=ft1>RTP<SPAN
class=em0>有效载荷多路复用会增加网关之间的带宽利用效率。图</SPAN>2-19<SPAN
class=em0>中是包括来自两个信源的</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps4><NOBR>有效载荷的多路复用<SPAN class=em1>RTP</SPAN>包格式。</NOBR></SPAN> <SPAN
class=ps5><NOBR><SPAN class=ft2>图<SPAN class=em4>2-19
RTP</SPAN>用户数据多路复用</SPAN></NOBR></SPAN> <SPAN
class=ps6><NOBR>信道<SPAN class=em1>ID<SPAN class=em0>（</SPAN>Channel ID<SPAN
class=em0>，</SPAN>CID<SPAN class=em0>）</SPAN></SPAN>是信道编号，长度指示用来为<SPAN
class=em1>CID</SPAN>确定有效载荷的最后一个</NOBR></SPAN> <SPAN class=ps7><NOBR>字节。<SPAN
class=em1>T</SPAN>是传输比特位，用于协商对所包含包的处理类型， <SPAN
class=em1>R</SPAN>是保留比特位。<SPAN class=em1>CID</SPAN>在概念上和</NOBR></SPAN> <SPAN
class=ps8><NOBR><SPAN class=ft1>AAL2<SPAN class=em0>中的</SPAN>CID<SPAN
class=em0>类似，希望通过带外信令分配。</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps9><NOBR>多路复用包也可以使用<SPAN class=em1>RTP</SPAN>的标准压缩算法进行压缩，但是它们强调来自主<SPAN
class=em1>RTP</SPAN>报头中那</NOBR></SPAN> <SPAN class=ps10><NOBR>个<SPAN
class=em1>SSRC</SPAN>的包。只有在有效载荷的解多路复用的端点处，信道标识重要性才有意义。</NOBR></SPAN> <SPAN
class=ps11><NOBR><SPAN class=ft3>2.1.4 <SPAN
class=em5>小结和技术展望</SPAN></SPAN></NOBR></SPAN> <SPAN class=ps12><NOBR><SPAN
class=ft1>RTP<SPAN
class=em0>是能够为我们带来集成多媒体和基本电话服务的传输机制。在本节中，我们讨论了</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps13><NOBR><SPAN class=ft1>RTP<SPAN class=em0>和它的伴随协议</SPAN>RTCP<SPAN
class=em0>，</SPAN><SPAN class=em0>它们被</SPAN>H.323<SPAN
class=em0>、</SPAN>S/MGCP<SPAN class=em0>和</SPAN>SIP<SPAN
class=em0>所接受，但是</SPAN>H.323<SPAN class=em0>已经允许有效载</SPAN></SPAN></NOBR></SPAN>
<SPAN class=ps14><NOBR>荷报头定义，特别是对于视频传输，它们在跨越相同的网桥时会把其他的信令协议带进网络。</NOBR></SPAN>
<SPAN class=ps15><NOBR>在使用包电话技术的网络中存在大量的未知因素，但是一旦做出应用的重大决定，相信技术</NOBR></SPAN>
<SPAN class=ps16><NOBR>问题的解决将是<SPAN
class=em1>VoIP</SPAN>发展过程的一部分。任何重大技术应用有时都会有讨厌的小故障，但是</NOBR></SPAN> <SPAN
class=ps17><NOBR>新网络增加的价值有望同时减轻任何少数用户的麻烦。</NOBR></SPAN> <SPAN
class=ps18><NOBR><SPAN class=ft1>IP<SPAN
class=em0>上的语音是所有主要载波中第一个大规模应用的服务，主要供应商关心的是增值服务。</SPAN></SPAN></NOBR></SPAN>
<SPAN class=ps19><NOBR>同样地，与我们在有线线路<SPAN
class=em1>PSTN</SPAN>上的两方电话呼叫的感受尽可能匹配，这也是重心之所在。</NOBR></SPAN> <SPAN
class=ps20><NOBR><SPAN class=ft1>VoIP<SPAN
class=em0>能够接近这种感受，其代价是简单</SPAN>PCM<SPAN
class=em0>呼叫使用高带宽，以及对不同介质类型的网络重</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps21><NOBR>叠，随着时间的推移，为集成服务接入的压缩<SPAN
class=em1>IP</SPAN>语音将成为现实，至少也将是一种服务选择。</NOBR></SPAN> <SPAN
class=ps22><NOBR>其动力可能是因为家庭和小型办公室可以获得数据应用的高带宽，并分享接入连接的窄带宽。</NOBR></SPAN> <SPAN
class=ps23><NOBR>只有时间才会知道，在使用新服务时会出现多少新的商业动力，其中一些甚至现在还没有人</NOBR></SPAN> <SPAN
class=ps24><NOBR><SPAN class=ft4>88 <SPAN class=em2>IP </SPAN><SPAN
class=em6>电话技术：稳定的</SPAN><SPAN class=em2>VoIP</SPAN><SPAN
class=em6>服务集成</SPAN></SPAN></NOBR></SPAN> <SPAN class=ps25><NOBR><SPAN
class=ft5>文档</SPAN></NOBR></SPAN> <SPAN class=ps26><NOBR><SPAN class=ft6>报头<SPAN
class=em7>(40</SPAN>字节<SPAN class=em7>)</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps27><NOBR><SPAN class=ft6>小报头<SPAN
class=em7>1</SPAN></SPAN></NOBR></SPAN> <SPAN class=ps28><NOBR><SPAN
class=ft6>小报头<SPAN class=em7>2</SPAN></SPAN></NOBR></SPAN> <SPAN
class=ps29><NOBR><SPAN class=ft7>RTP<SPAN
class=em8>语音包</SPAN>1</SPAN></NOBR></SPAN> <SPAN class=ps30><NOBR><SPAN
class=ft7>RTP<SPAN class=em8>语音包</SPAN>2</SPAN></NOBR></SPAN> </BODY></HTML>
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