NAT devices not translating privileged ports

[Fernando Gont <fernando.gont () edgeuno com>]

Folks,

While discussing port randomization (in the context of 
https://www.ietf.org/archive/id/draft-ietf-ntp-port-randomization-06.txt
), it has been raised to us that some NAT devices do not translate the
source port if the source port is a privileged port (<1024).

Any clues/examples of this type of NATs?

Thanks!

Regards,
-- 
Fernando Gont
Director of Information Security
EdgeUno, Inc.
PGP Fingerprint: DFBD 63E3 B248 AE79 C598 AF23 EBAE DA03 0644 1531