From: Bill Stewart <stewarts@ix.netcom.com>
Date: Sat, 11 May 1996 02:25:57 +0800
To: nyap@mailhub.garban.com (Noel Yap)
Subject: Re: time services on the Net
Message-ID: <199605100039.RAA00738@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


At 11:11 AM 5/7/96 -0400, you wrote:
>I'm in need of a time service available over the Internet.
>Time-stamping is a plus, but the actual time (GMT, local, ...)
>is more important.  Does anyone have, or know of where I
>can find, a list of these services?

Check out http://www.clock.org/clock.org.html and
http://tycho.usno.navy.mil/ for more information.

There are some standard TCP/IP protocols for time.
You can check the RFCs for more information on them,
and look in whatever your operating system calls the "services" file.

There's a simple "daytime" protocol which gives the time in
hours:minutes:seconds at 1-second resolution, in ASCII or
binary, over TCP or UDP.  It's dumb, but it works fine
if that's enough resolution for you, and there are programs
to set your system clock based on it, such as rdate for Suns
and wsntime for Winsock.  

There's a far fancier protocol called NTP, the Network Time Protocol,
which is a multi-tiered time protocol with servers and clients
and mutual agreement and adjustment for round-trip delay and such.
Depending on the quality of your network connections, it can
be accurate to very fine time resolutions.

It's good form for ISPs to support NTP, both to keep their
clocks synchronized and to feed time to their clients,
but not all of them do that.  It's also good form for ISPs to
keep _all_ their machines in sync, not just most of them,
as occasionally happens at (ahem) some large well-known ISPs,
especially if they're going to bill for prime/nonprime time...
Another motivation is so that tycho.usno.navy.mil and its
friends tick and tock.usno.navy.mil only get hit by a few
thousand ISPs instead of potentially millions of individuals.

Ask your ISP's administrators what they do about clock sync,
unless of course you _are_ the administrator, or your ISP
takes three weeks to respond to tech support questions like
the (ahem) large well-known ISP not named above.
I currently use wsntime to sync off cesium.clock.org because
my ISP has reconfigured their time service and takes
weeks to respond to tech support quetions, but I was using
the ISP directly for a while.
#					Thanks;  Bill
# Bill Stewart, stewarts@ix.netcom.com, +1-415-442-2215
# goodtimes signature virus innoculation