[问答题] what is the purpose of frame-relay LMI？

防腐 Multi Protocol Label Switching （MPLS） is a data-carrying mechanism that belongs to the family of packet-switched networks. For an MPLS label，if the stack bit is set to1，which option is true？（） ["The stack bit will only be used when LDP is the label distribution protocol","The label is the last entry in the label stack.","The stack bit is for Cisco implementations exclusively and will only be used when TDP is the label distribution protocol.","The stack bit is reserved for future use."] In an L2TP voluntary tunneling scenario， the VPDN tunnel is terminated between：（） [" The client and the NAS."," The NAS andthe LNS."," The NAS and the LAC."," The client and the LNS."] 吸收衰减特点。 凡在公共场所直接为旅客、顾客服务的人员，从业前必须经过健康检查，并取得卫生防疫站核发的（）。 ["卫生合格证","卫生许可证","健康合格证"] what is the purpose of frame-relay LMI？