NTS not 'working', likely operator error

[Hal Murray]

> Using tools available (netcat), I've determined that UDP port 123 packets
> are being truncated at 1472 bytes. Rebooted router, timeserver, no change.  

The Ethernet MTU (max packet size) is 1500.  Round down for a couple of 
headers and you get 1472.  The Internet spec is 512.  (Or something like 
that.)  But (almost) everybody supports 1500.

NTP with NTS packets are a couple hundred bytes -- much biffer than 48, but 
well below 1500, even with 7 extra cookies.

There is a strange case that I don't think anybody has tracked down.  Some 
router (maybe many) drop NTP+NTS packets with 1, 2, or 3 extra cookies but 
work with 4.

I don't have a good story for why netcat work but ntp+nts doesn't.  Did you 
try both directions?  Or from port 123 to port 123?  [My head hurts trying to 
dance around NAT.]

-- 
These are my opinions.  I hate spam.