[求助]哪位高人知道SDH中回溯(crankback)功能的原理是怎样的，帮忙先容下吧，谢谢！

zgz2006

<p>如题，请高人赐教</p><p><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: 'times new roman'; mso-hansi-font-family: 'times new roman'; mso-bidi-font-family: 'times new roman'; mso-font-kerning: 1.0pt; mso-ansi-language: en-us; mso-fareast-language: zh-cn; mso-bidi-language: ar-sa;">“从提高连接建立成功概率，提高用户满意度的角度出发，测试网络是否具有<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: 'times new roman'; mso-bidi-font-size: 12.0pt; mso-font-kerning: 1.0pt; mso-ansi-language: en-us; mso-fareast-language: zh-cn; mso-bidi-language: ar-sa; mso-fareast-font-family: 宋体;">Crankback</span><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-size: 12.0pt; mso-ascii-font-family: 'times new roman'; mso-hansi-font-family: 'times new roman'; mso-bidi-font-family: 'times new roman'; mso-font-kerning: 1.0pt; mso-ansi-language: en-us; mso-fareast-language: zh-cn; mso-bidi-language: ar-sa;">能力，即回溯到源节点或中间节点（一般是域边界节点）进行重路由。</span>”这句话应该如何理解，比如A,B,C,D互联，有条A到D的业务，如果B,C间的链路出现问题，则重新建立一条啊A,X,C的链路（X为任何网元，也可能是B），是这样理解的吗？？？？？</span></p>