Which two statements about the anti-replay feature are true? (Choose two)

A.
By default, the receiver uses a single 64-packet sliding window.

B.
The replay error counter is incremented only when a packet is dropped.

C.
The receiver performs a hash of each packet in the window to detect replays.

D.
The sender assigns two unique sequence numbers to each encrypted packet.

E.
The sender assigns two unique sequence numbers to each clear-text packet.

F.
By default, the sender uses a single 1024-packet sliding window.

Explanation:
IPSec provides anti-replay protection against an attacker who duplicates encrypted
packets with the assignment of a monotonically increasing sequence number to each
encrypted packet. The receiving IPSec endpoint keeps track of which packets it has already processed on the basis of these numbers with the use of a sliding window of all
acceptable sequence numbers. Currently, the default anti-replay window size in Cisco
IOS® implementation is 64 packets. This is illustrated in this figure:
If the sequence number falls within the window and was previously received, the packet
is dropped, and the replay counter is incremented.
http://www.cisco.com/c/en/us/support/docs/ip/internet-key-exchange-ike/116858-
problem-replay-00.html