Cellular networks often use Internet standard technologies to handle
synchronization. This document defines an extension based on WESP.
Usually, several traffic flows are carried in one IPsec tunnel, for
some applications, such as, 1588 or NTP, the packets need to be
identified after IPsec encryption to handle specially. In order to
achieve high scalability in implement, a separate IPsec tunnel will
not be established for some special traffic. This document analyses
the need for security methods for synchronization messages
distributed over the Internet. This document also gives a solution
on how to mark the synchronization message when IPSec is implemented
in end to end frequency synchronization."