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Re: T3 Latency

  • From: Wayne Bouchard
  • Date: Sat Feb 17 10:45:31 2001

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
> 

----------------------------------------------------------------------
Wayne Bouchard                                    [Imagine Your     ]
web@typo.org                                      [Company Name Here]
Network Engineer
http://www.typo.org/~web/resume.html
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