Which two functions can be provided by an Integrated Services Router （ISR） in a VoIP network？（）

• A、 ISR can perform the functions of a multipoint control unit to facilitate voice conferencing.
• B、 ISR can perform the function of a call agent in the event of loss of communication with a CallManager.
• C、 ISR can provide XML applications to the phones.
• D、 ISR can provide all of the functionality of a CallManager in the event of loss ofcommunication to the CallManager.
• E、 ISR can act as a voice gateway to the PSTN.