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Re: [gpsd-dev] Updated docs on NTP segment management
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-dev] Updated docs on NTP segment management |
Date: |
Thu, 26 Feb 2015 12:13:35 -0800 |
Yo Harlan!
On Thu, 26 Feb 2015 20:07:34 +0000
Harlan Stenn <address@hidden> wrote:
> "Gary E. Miller" writes:
> > The mode word can be used as a version.
>
> Yes, and folks who did not check for "unused bits must be zero" will
> lose, and that's OK in my book. I would have rather seen an explicit
> version field in the mode bits, and I'm game to add that now declaring
> the first (old) version bits are 0.
+1
> Adding to that, in my ACM article about NTP one of the first things I
> do is point folks at Dan Geer's Blackhat 2014 talk, which covers this
> point nicely.
Got a URL?
> One thing to think about is whether or not the SHMID should be
> different for each version where there is a change in size of shmTime.
That also works, but spawns complexity. I would rather avoid.
> I'm also wondering if the V2 SHM interface should include a preamble
> structure before the per-unit structures, as that seems to be a more
> efficient way to go. Duplicating data in the per-unit structures
> seems wasteful to me.
What is duplicated? And how to handle multiple senders?
> I also wonder if there is a good way (and a good reason) to support:
>
> - a mix of V1 and V2 SHM areas on the same shmid
Yes, but not at the same time. :-)
> - more than 4 units' data structures in an SHM segment
Absolutely. 207 supported now. With linuxptp and soon more senders
talking NTP SHM this could grow large in the lab.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
address@hidden Tel:+1(541)382-8588
- Re: [gpsd-dev] Updated docs on NTP segment management, (continued)
- Re: [gpsd-dev] Updated docs on NTP segment management, Miroslav Lichvar, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Miroslav Lichvar, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Hal Murray, 2015/02/27
- Re: [gpsd-dev] Updated docs on NTP segment management, Hal Murray, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Terje Mathisen, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management,
Gary E. Miller <=
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/25
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/25
- Re: [gpsd-dev] Updated docs on NTP segment management, Harlan Stenn, 2015/02/25
- Re: [gpsd-dev] Updated docs on NTP segment management, Eric S. Raymond, 2015/02/26
- Re: [gpsd-dev] Updated docs on NTP segment management, Hal Murray, 2015/02/28
- Re: [gpsd-dev] Updated docs on NTP segment management, Hal Murray, 2015/02/18
- Re: [gpsd-dev] Updated docs on NTP segment management, Gary E. Miller, 2015/02/18