下列哪个子句实现对一个结果集进行分组和汇总？（）
A、HAVING
B、ORDERBY
C、WHERE
D、GROUPBY
支路单元组
Which type of traffic will cause Policed Discards errors on an interface on a JUNOS device?（）
A、Traffic that does not match any route in the forwarding table.
B、Traffic that exceeds the bandwidth of the interface.
C、Traffic of unsupported protocols on that interface.
D、Traffic arriving on unknown virtual-circuits on that interface.
关键信息基础设施的运营者采购网络产品和服务，应当按照规定与提供者签订（），明确安全和保密义务与责任。
How may L2TP tunnel destinations are allowed per domain?（）
A、1
B、11
C、21
D、31
Which two design goals describe the Junos OS design?（）
Aclean separation of security and routing policies
Bclean separation of control and forwarding planes
Cmodularization of multiple software processes
Da single hardware platform for all software applications