[ntpwg] Documents, slides, etc. from WG meeting

[M. Warner Losh]

In message: <p06240801c344a38ce792@[10.240.20.124]>
            Brad Knowles <brad at shub-internet.org> writes:
: On 10/23/07, Danny Mayer wrote:
: 
: >>  A long discussion at end of meeting discussing the future of
: >>  timekeeping here in the IETF.  Is the future 1588 over IP?
: >>  NTP over IP?  No consensus was reached.
: >
: >  Could some explain exactly what that means? Is this a question of
: >  certain protocols (DNS and Kerberos come immediately to mind) that
: >  require that two interacting servers keep their clocks within X minutes
: >  of each other in order for various security requirements to work
: >  correctly or ro be assumed to be valid? Is it something else?
: 
: Well, NTP is inherently an IP protocol.  From reading the IEEE 1588 
: page, it's not clear whether this works over IP or not, although it 
: does seem to work over Ethernet (and maybe others?).

IEEE 1588 uses multicast IP addresses.

: But IEEE 1588 
: seems to focus on ultra-high resolution, like sub-microsecond or even 
: sub-nanosecond.

Well, sub-microsecond is easy and comes from the timestamping of
packets in hardware.  If NTP had extensions to do that, it could get
sub-microsecond time.  Sub-nanosecond time is possible, but it takes
very specialized hardware.  Most commercial 1588 solutions use a "low"
resolution clock to timestamp things.  Low here means something like
the PCI bus clock.

Warner