Which two statements are true about the application of QoS in a converged network？（）

• A、end-to-end network delay times that exceed 50 ms for real-time traffic are considered unacceptable
• B、end-to-end network delay times that exceed 250 ms for real-time traffic are considered unacceptable
• C、end-to-end network delay is not a factor as long as the  delay is consistent
• D、some packet loss can be corrected by codec algorithms
• E、RSVP handles voice packet retransmission
• F、fragmentation is a result of packet loss