Within the Encrypted Security Payload (ESP) extension header, which of the following ensures
that messages end on a 64-bit boundary?

A.
Sequence Number.

B.
Payload Type.

C.
Padding.

D.
Security Parameters Index (SPI).

Explanation:
Padding is used to control the size and alignment of the message. The Pad Length indicates the
number of 8-bit passing bytes to be added after the data.
Incorrect Answers:
A: The sequence number is a 32-bit unsigned number used to provide anti-replay abilities.
B: The ESP header does not have a field called the payload type. There is payload data and
payload length, for the length of the payload. The type of payload is actually stored in the next
header field.
D: By combining the SPI with the destination address and the Security Protocol (ESP) identifies
the security association of the packet. The SPI is an unsigned 32-bit integer.