[Ntp] NTP speed of synchronization question

[Toerless Eckert <[e-mail]>]

Dear NTP WG

I have a few quick ops question against NTP which would take me a lot longer to investigate
on actual devices. This is for reviewing draft-ietf-bess-evpn-fast-df-recovery which wants
to utilize clock synchronization between routers.

Assuming typical high-end routers and their implementation of NTP:

1. Is there any reasonw why we should NOT be able to achieve synchronization of less than 5 msec ?

2. Assuming synchronization only across some WAN connection, how long would it typically
   take for a restarting router to synchronize against a peer to that level of accuracy or better ?

3. Would synchronization to a local peer be faster ? If so, how fast could it be ?

4. Am i correct to remember that the accuracy of synchronization should be accessible to
   user of NTP (such as the aforementioned drafts mechanism) through some diagnostics interface ?
   ( think to remmeber that to be the case from typical NTP implementation CLI).

Thanks so much!
    Toerless