FEC指（）
在MPLS中，FEC的角色是什么？（）A、FEC决定IP数据包在LSP中如何转发B、FEC决定如何建立LSP路径C、FEC决定LSP如何与组对应D、FEC决定标签如何存储
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What is the role of Forwarding Equivalence Class （FEC） in MPLS？（）A、FEC determines how IP packets are forwarded in MPLS LSP.B、FEC determines how to establish an LSP path.C、FEC determines how a group of IP packets are mapped to an LSP.D、FEC determines how MPLS labels are stacked in LSP.E、None of above.
通常情况下，NBDP遇险通信采用（）工作模式。A、只有FECB、只有ARQC、同时采用FEC和ARQD、FEC或者ARQ
FEC
Which two statements about forwarding equivalence class （FEC） are true？（）A、FEC might correspond to a destination IP subnet， but it might also correspond to any traffic class that the edge LSR considers significant.B、FEC is a group of IP packets that is forwarded over a different path， but with the same forwarding treatment.C、FEC is a group of IP packets that is forwarded over the same path， and with the same forwarding treatment.D、FEC is a group of IP packets that is forwarded over a different path， but with the different forwarding treatment.E、FEC is a group of IP packets that is forwarded over the same path， but with a different forwarding treatment
某LSR运行在DU的标签分配模式、有序的标签控制模式下，下列说法正确的是（）。A、该LSR收到了上游LSR针对某FEC的标签分配请求，且该LSR是该FEC的最下游设备时才可以为该FEC分配标签B、该LSR收到了下游设备针对某FEC的label mapping消息时就可以为该FEC分配标签，无需等待上游的标签分配请求C、该LSR是某FEC的最下游设备就可以为该FEC分配标签，无需等待上游的标签分配请求D、该LSR只要收到上游设备针对某FEC的标签分配请求就可以为该FEC分配标签
编码增益是衡量前向纠错编码（FEC）纠错能力的参数。关于编码增益，以下说法错误的是（）。A、在保持误码率恒定条件下，采用纠错编码所节省的信噪比称为编码增益；B、编码增益越大，说明FEC纠错能力越强；C、带内FEC的编码增益比带外FEC的编码增益大；D、AFEC的编码增益比FEC的编码增益大。
