端到端保护，可以在access link上用8031,中间用8032
XI.2 Layering ITU-T G.8031 protection over ITU-T G.8032
假定端到端保护用的是8031
XI.2.1 Basic guidelines for the layering of ITU-T G.8031 over ITU-T G.8032 Rule：
Working/protection每个路径Node2个，一进一出 ERP部分视为一条Link，具体路径由ERP决定 8031的hold off要设置足够大
Working/protection使用的vid要被ERP保护
XI.3 End-to-end service that traverses interconnected rings
规则类似单环
V2 neighbor, block RPL at both end It totally isolates RPL from the traffic channel