Nathan Stratton wrote:
On Thu, 11 Sep 1997, Vadim Antonov wrote:
Quote from Jim Steinhardt's <jsteinha@cisco.com> personal message:
a) light is slower in dense media
The index of refraction of glass is 1.5 vs 1.0 for a vacuum. Hence, the speed of light in glass is 2 * 10 **8 m/s.
That gives 60 ms RTT on 4000 mile line.
Case closed.
Yep, but you also need to add a few ms for electronics in that 4000 mile line.
My original point. (Concerning latency)
We tend to see around 64 - 65 ms delay between our DCA and PAL routers.
rt1.DCA.netrail.net# ping rt1.PAL ICMP ECHO rt1.PAL.netrail.net (205.215.45.33): 56 data bytes 64 bytes from 205.215.45.33: icmp_seq=0 ttl=255 time=65.764 ms 64 bytes from 205.215.45.33: icmp_seq=1 ttl=255 time=64.851 ms 64 bytes from 205.215.45.33: icmp_seq=2 ttl=255 time=65.053 ms 64 bytes from 205.215.45.33: icmp_seq=3 ttl=255 time=64.994 ms ^C
How may hops is that ping ? I am curious, this is interesting. (Even if I did get mail bombed by responses...... ;) You realize we need to be comparing a *series* of routers, vs a *series* of ATM switches. (this is the real world, and we are modelling delivery to anywhere, not just 1 hop across the continent.) It would be interesting to see someone set up a performance test. Latency/Variability with no hops, Latency/Variability with 1 router vs 1 switch Latency/Variability with 2 routers vs 2 switches Up to about 10. I wonder what that curve would look like ? Media would have to be consistent in size (ie DS3, all the way through) Interesting , no ?
--- rt1.PAL.netrail.net ICMP ECHO statistics --- 4 packets transmitted, 4 packets received, 0% packet loss round-trip min/avg/max = 64.851/65.160/65.764 ms rt1.DCA.netrail.net#
Nathan Stratton President, CTO, NetRail,Inc. ------------------------------------------------------------------------ Phone (888)NetRail NetRail, Inc. Fax (404)522-1939 230 Peachtree Suite 500 WWW http://www.netrail.net/ Atlanta, GA 30303 ------------------------------------------------------------------------ "No king is saved by the size of his army; no warrior escapes by his great strength. - Psalm 33:16
Richard