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From: resnick@cogsci.uiuc.edu (Pete Resnick)
Newsgroups: comp.protocols.appletalk
Subject: Re: NTP on the Mac
Message-ID: <1990Oct11.235244.6595@ux1.cso.uiuc.edu>
Date: 11 Oct 90 23:52:44 GMT
References: <20907.655667380@GNOME.CS.CMU.EDU>
Sender: news@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 38

Ravinder.Chandhok@CS.CMU.EDU (Rob Chandhok) writes:

>About using other time protocols (like UDP time and whatever) that ntp is
>much more robust and accurate.  In fact, ntp is somewhat overkill for the
>1/60th second resolution of the mac clock.  

You mean a mac does not need 200 picosecond precision?? :-)

>I understand some AppleTalk based protocol should be used so MAc's don't
>have to depend on IP hosts for time information, but the fact of the matter
>is that there is an already existing extremely accurate hierarchy of time
>servers on the internet.  Also, you could easily make a Mac into an ntp
>server, and just use DDP instead of UDP.

Personally, I am trying to make my Mac MORE dependent on IP hosts. I mean
heck, I got MacTCP for a reason.

>Regarding the statement (from Pete Resnick?) that "the math is too hard for
>ntp", if anyone would like to implement a better form of ntp for the mac
>(cdev or init) then please take my sources! John Pane and I figured out how
>to convert from Mac time to ntp's notion of time.  The rest of it is just
>getting and sending packets.

Let me re-phrase: I took a look at the NTP RFC. The math is very complex
and requires repeated packet sends and re-adjustment. My figuring was
that I would not want to bog down my poor little SE with so many
calculations and IP transmissions to set my clock when I don't need the
200 picosecond precision. Anywhere between 2 and 10 second precision
was fine with me, so I used the UDP Time RFC. Wasting more than a couple
of ticks just to get my clock set "reasonably" seemed absurd.

pr
--
Pete Resnick             (...so what is a mojo, and why would one be rising?)
Graduate assistant - Philosophy Department, Gregory Hall, UIUC
System manager - Cognitive Science Group, Beckman Institute, UIUC
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