多项选择题
Which two implementations are standard Virtual Private LAN Service （VPLS） implementations that aresupported by the IETF？（）
A.VPLS uses LDP for signaling. B.VPLS uses BGP for autodiscovery and signaling. C.VPLS uses extended IS-IS for signaling D.VPLS uses OSPF version 3 for auto discovery and signaling E.VPLS uses spanning tree for signaling
单项选择题 IntheIS-ISDesignatedIntermediateSystem（DIS）electionprocess，whichcriteriaisusedforDIS selection？（）
单项选择题 WhichstatementaboutRemotelyTriggeredBlackHole（RTBH）istrue？（）
单项选择题 WhatisoneoftheprimaryoverheadfieldsassociatedwiththeOpticalPayloadUnit（OPU）？（）
