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 ---------- M. F. Ringel Network Engineer Akamai Technologies, Inc. ringel@akamai.com On Sat, Feb 17, 2001 at 07:37:48AM +0000, Walter Prue wrote:
Chuck,
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.
Walt