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Re: T3 Latency
- From: Matthew F. Ringel
- Date: Sat Feb 17 07:55:10 2001
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.
M. F. Ringel
Akamai Technologies, Inc.
On Sat, Feb 17, 2001 at 07:37:48AM +0000, Walter Prue wrote:
> The question posed by Chris, "how long is your access line"?, is a rather
> important data point before answering your question. I have a T3 that is
> about 15 miles long. It runs between two 7500 routers. Its minimum ping
> round trip time with 100 byte pings is 2 ms. It is not very heavily loaded
> with peaks of about 10 Mb/s today and the max round trip time was 21 ms.
> So that should give you some minimal bounds of what you might expect. As
> the saying goes your mileage may vary. Speed of light does play in here,
> if the circuit is longer. Also intervening electronics such as a frame cloud
> or telco muxes also add latency.