[34720] in North American Network Operators' Group
Re: T3 Latency
daemon@ATHENA.MIT.EDU (Wayne Bouchard)
Sat Feb 17 10:43:48 2001
Date: Sat, 17 Feb 2001 08:41:03 -0700
From: Wayne Bouchard <web@typo.org>
To: Charles Scott <cscott@gaslightmedia.com>
Cc: "Matthew F. Ringel" <ringel@akamai.com>, nanog@merit.edu
Message-ID: <20010217084103.A29572@typo.org>
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In-Reply-To: <Pine.LNX.4.21.0102170930500.13454-100000@harbor.gaslightmedia.com>; from cscott@gaslightmedia.com on Sat, Feb 17, 2001 at 09:33:02AM -0500
Errors-To: owner-nanog-outgoing@merit.edu
Or, perhaps a more simplified and easily remembered figure...
RTT on a straight line run from sfo to dc would be ~63ms. (Seems to be
roughly 100 to 120 for most real circuits.)
We all know, however, that telcos rarely use straight lines. Still, I
would not expect more than 6 to 7ms. Perhaps your telcos equipment,
through some fluke, has you operating on the backup path?
On Sat, Feb 17, 2001 at 09:33:02AM -0500, Charles Scott wrote:
>
>
> Matthew:
> Appears to be a typo in your final number of 130 mi/sec, but I get where
> you're going with this. I'm just having a problem trying to figure out how
> I end up with a couple thousand fiber miles from Northern Michigan to
> Chicago. Should be interesting to sort this one out.
>
> Thanks,
>
> Chuck
>
>
> On Sat, 17 Feb 2001, Matthew F. Ringel wrote:
>
> >
> > The rule of thumb I use is that the speed of light in fiber-optic cable is
> > roughly 2x10^8 m/sec.
> >
> > 2x10^8 m/sec = 200,000,000 m/sec = 200,000 km/sec = 200 km/msec =~ 130 mi/sec
> >
> > I once worked with a customer whose first hop out was ~30ms, regardless of the
> > load on the line (a t3, iirc). Sure enough, he was on a very large SONET ring
> > that travelled the north-south length of the US roughly twice before his
> > traffic went elsewhere.
> >
> > ......Matthew
>
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Wayne Bouchard [Imagine Your ]
web@typo.org [Company Name Here]
Network Engineer
http://www.typo.org/~web/resume.html
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