多项选择题
Which of the following are functions that are often provided by an ITSP but are not typically provided by the PSTN？（）
A. QoS B. call setup and teardown C. call routing D. call supervision E. audio signal compression
单项选择题 WhichofthefollowingisnotinformationprovidedfromanIPphonetoaCatalystswitchusingCDP？（）
单项选择题 WhichofthefollowingwillgenerateanRSTPtopologychangenotification？（）
单项选择题 WhichofthefollowingHSRProuterstatesdoesanactiverouterenterwhenitispreemptedbyahigherpriorityrouter？（）
