[KUDU-2937] built-in NTP client: implement 'iburst'

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: ntp-client
• Labels: clock ntp
• Assignee: Unassigned
• Reporter: Alexey Serbin
• Created: 14/Sep/19 05:47
• Updated: 03/Feb/20 20:06

Description

For fast initial synchronisation with NTP sources it's necessary to implement iburst-like behavior.

From RFC5905 :

   If the BURST flag is lit and the server is reachable and a valid
   source of synchronization is available, the client sends a burst of
   BCOUNT (8) packets at each poll interval.  The interval between
   packets in the burst is two seconds.  This is useful to accurately
   measure jitter with long poll intervals.  If the IBURST flag is lit
   and this is the first packet sent when the server has been
   unreachable, the client sends a burst.  This is useful to quickly
   reduce the synchronization distance below the distance threshold and
   synchronize the clock.