[分享]分组传送网（PTN）概况

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<p><span lang="ZH-CN" style="font-family: SimSun;">分组传送网（</span><span lang="EN-US">TN</span><span lang="ZH-CN" style="font-family: SimSun;">）概况</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">众所周知，</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">技术是针对窄带</span><span lang="EN-US">TDM</span><span lang="ZH-CN" style="font-family: SimSun;">业务开发的，缺乏对宽带业务、数据业务的支撑，为用户提供多种类带宽存在着瓶颈，带宽利用率低，自身能够对外提供的标准接口种类有限，难以高效的承载速率丰富的各种宽带业务。</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">尽管这些年，为了提高</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">技术传送数据业务的能力，提出了</span><span lang="EN-US">VC</span><span lang="ZH-CN" style="font-family: SimSun;">虚级联、链路容量调整方案（</span><span lang="EN-US">LCAS</span><span lang="ZH-CN" style="font-family: SimSun;">）、通用成帧规程（</span><span lang="EN-US">GFP</span><span lang="ZH-CN" style="font-family: SimSun;">）、弹性分组环技术</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">（</span><span lang="EN-US">RPR</span><span lang="ZH-CN" style="font-family: SimSun;">）和</span><span lang="EN-US">MartiniMPLS</span><span lang="ZH-CN" style="font-family: SimSun;">等技术，形成了多业务传送平台（</span><span lang="EN-US">MSTP</span><span lang="ZH-CN" style="font-family: SimSun;">）设备，但所改善的只是设备的接口和传送能力，而设备的核心结构仍然为时隙交</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">换，不能有效地利用分组技术的统计复用的优点。</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">为了解决这一问题，</span><span lang="EN-US">TN</span><span lang="ZH-CN" style="font-family: SimSun;">技术应运而生，它支撑多种基于分组交换业务的双向点对点连接通道，具有适合各种粗细颗粒业务、端到端的组网能力，提供了更</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">加适合于</span><span lang="EN-US">IP</span><span lang="ZH-CN" style="font-family: SimSun;">业务特性的“柔性”传输管道；点对点连接通道的保护切换可以在</span><span lang="EN-US">50</span><span lang="ZH-CN" style="font-family: SimSun;">毫秒内完成，可以实现传输级别的业务保护和恢复；继承了</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">技术的操作、</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">管理和维护机制，具有点对点连接的完整</span><span lang="EN-US">OAM</span><span lang="ZH-CN" style="font-family: SimSun;">，保证网络具备保护切换、错误检测和通道监控能力；完成了与</span><span lang="EN-US">IP/MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">多种方式的互连互通，无缝承载核心</span><span lang="ZH-CN">
                </span><span lang="EN-US">IP</span><span lang="ZH-CN" style="font-family: SimSun;">业务；网管系统可以控制连接信道的建立和设置，实现了业务</span><span lang="EN-US">QoS</span><span lang="ZH-CN" style="font-family: SimSun;">的区分和保证，灵活提供</span><span lang="EN-US">SLA</span><span lang="ZH-CN" style="font-family: SimSun;">等优点。</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">另外，它可利用各种底层传输通道（如</span><span lang="EN-US">SDH/Ethernet/OTN</span><span lang="ZH-CN" style="font-family: SimSun;">）。总之，它具有完善的</span><span lang="EN-US">OAM</span><span lang="ZH-CN" style="font-family: SimSun;">机制，精确地故障定位和严格的业务隔离功能，最大限度地管理和利用光纤资源，保证了业务安全性，在结合</span><span lang="EN-US">GMPLS</span><span lang="ZH-CN" style="font-family: SimSun;">后，可实现资源的自动配置及网状网的高生存性。</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">目前，</span><span lang="EN-US">TN</span><span lang="ZH-CN" style="font-family: SimSun;">技术主要有三个，即</span><span lang="EN-US">W/VPLS</span><span lang="ZH-CN" style="font-family: SimSun;">、</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">和</span><span lang="EN-US">BT</span><span lang="ZH-CN" style="font-family: SimSun;">，这三种技术的比较详见表</span><span lang="EN-US">1</span><span lang="ZH-CN" style="font-family: SimSun;">。</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">表</span><span lang="EN-US">1 
PTN</span><span lang="ZH-CN" style="font-family: SimSun;">三种关键技术的比较</span></p><img src="http://bbs.cnttr.com/attachments/day_080430/20080430_8c2c94516592a9975fa8EShyn9vTVaw2.jpg" alt=""/><br/><p><img alt="" src="C:/DOCUME%7E1/ADMINI%7E1/LOCALS%7E1/Temp/moz-screenshot.jpg"/></p>



<p><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">经由阿尔卡特朗讯、爱立信、富士通、HUAWEI和泰乐等众多支撑者提议，于</span><span lang="EN-US">2006</span><span lang="ZH-CN" style="font-family: SimSun;">年</span><span lang="EN-US">2</span><span lang="ZH-CN" style="font-family: SimSun;">月由</span><span lang="EN-US">ITU-T</span><span lang="ZH-CN" style="font-family: SimSun;">实现了技术的标准化，是</span><span lang="EN-US">PTN</span><span lang="ZH-CN" style="font-family: SimSun;">的首次尝</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">试。它基于</span><span lang="EN-US">ITU-TG.805</span><span lang="ZH-CN" style="font-family: SimSun;">传输网络结构，由</span><span lang="EN-US">ITU</span><span lang="ZH-CN" style="font-family: SimSun;">完成标准化（</span><span lang="EN-US">G.8110.1</span><span lang="ZH-CN" style="font-family: SimSun;">，</span><span lang="EN-US">G.8112</span><span lang="ZH-CN" style="font-family: SimSun;">，</span><span lang="EN-US">G.8121</span><span lang="ZH-CN" style="font-family: SimSun;">），其主要改进包括通过消除</span><span lang="EN-US">IP</span><span lang="ZH-CN" style="font-family: SimSun;">控制层</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">简化</span><span lang="EN-US">MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">以及增加传输网络需要的</span><span lang="EN-US">OAM</span><span lang="ZH-CN" style="font-family: SimSun;">和管理功能。</span></p>

<p><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">则由北电予以支撑，它源自</span><span lang="EN-US">IEEE802.1ah</span><span lang="ZH-CN" style="font-family: SimSun;">定义的“</span><span lang="EN-US">PBB-TE</span><span lang="ZH-CN" style="font-family: SimSun;">”（运营商骨干网桥接传输技术），并希翼</span><span lang="EN-US">2007</span><span lang="ZH-CN" style="font-family: SimSun;">年能够开始技术的标准</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">化。</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">着眼于解决以太网的缺点，</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">着眼于解决</span><span lang="EN-US">IP/MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">的复杂性。它们都为从现有的</span><span lang="EN-US">SONET/SDH</span><span lang="ZH-CN" style="font-family: SimSun;">向完全分组交换网络的转变提供了</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">平滑过渡的方法。从标准化的程度上看，</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">更成熟，</span><span lang="EN-US">ITU-T</span><span lang="ZH-CN" style="font-family: SimSun;">已经完成了大部分标准化工作，正在修订部分标准并与</span><span lang="EN-US">IETF</span><span lang="ZH-CN" style="font-family: SimSun;">合作；</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">则处于标准</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">发展的早期，</span><span lang="EN-US">2007</span><span lang="ZH-CN" style="font-family: SimSun;">年</span><span lang="EN-US">3</span><span lang="ZH-CN" style="font-family: SimSun;">月在</span><span lang="EN-US">IEEE</span><span lang="ZH-CN" style="font-family: SimSun;">批准立项，标准化过程需持续</span><span lang="EN-US">2</span><span lang="ZH-CN" style="font-family: SimSun;">～</span><span lang="EN-US">3</span><span lang="ZH-CN" style="font-family: SimSun;">年，</span><span lang="EN-US">IETF</span><span lang="ZH-CN" style="font-family: SimSun;">的</span><span lang="EN-US">GELS</span><span lang="ZH-CN" style="font-family: SimSun;">工作组预备成立，提交了</span><span lang="EN-US">2</span><span lang="ZH-CN" style="font-family: SimSun;">个</span><span lang="EN-US">IETFdraft</span><span lang="ZH-CN" style="font-family: SimSun;">，并且，</span><span lang="EN-US"> 802.1agCFM</span><span lang="ZH-CN" style="font-family: SimSun;">本身尚未批准。</span></p>

<p><span lang="ZH-CN" style="font-family: SimSun;">总之，全</span><span lang="EN-US">IP</span><span lang="ZH-CN" style="font-family: SimSun;">时代已经离大家越来越近了，每个电信运营商必须做好充分的准备，以在激烈的竞争中保持不败。</span></p><p><span lang="ZH-CN" style="font-family: SimSun;">手上有一些关于PTN的简报资料,无奈却无法上传</span></p>