On Wed, 20 Dec 1995 01:11:30 -0700 (MST) you said:
Time for me to jump on the bandwagon.
We're a Sprint Customer. Right now we have a 256K fractional T1 line to the net. We're tied to Stockton-7. "Our End" of the line is in Helena Montana.
For months now, I've been asking them why our ping times look like: Sending 100, 32-byte ICMP Echos to 144.228.47.21, timeout is 1 seconds: !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Success rate is 100 percent (100/100), round-trip min/avg/max = 100/104/204 ms
Note the 100 ms. I have NEVER seen it below 100 ms EVER. No matter what the traffic, time of day, etc. Well, maybe I've seen it at 98 or 99 once or twice.
In theory, a round trip time should be two times the single direction distance, which should be composed of the following two items:
1) 256K maximum bitrate (amount of time to clock the bits out) - 32 bytes * 8 bit bytes = 256 bit times 256 bit times * (1/256,000) (one bit time) ~= 1 ms 2) Speed of Light Limit (The Rest) In vacuum, light can travel 186 miles per millisecond. Not sure how much it differs in fibre, but I figure that even if you assume that its 150 miles per millisecond, you can travel roughly 7000 miles in the remaining time (59ish ms).
So, that puts my link 7000 miles away. Now I'm curious as to how they have my line routed over 7000 miles. So I call up their INSC and ask who I can talk to about this. I end up opening a trouble ticket, and eventually the engineer I talk to say's that it is in the acceptable limits for the distance of circuit, which they tell me goes from Helena to Seattle and then to Stockton California in more or less of a straight line between the points. According to my calculation there's about 1200 miles of fiber there. Still 5800 miles short.
I backed off after reading some papers on ping times versus maxumum flow. That is until I had an outage last week caused by a Fiber Cut in Texas. Now I'm mad. I supposedly have a line from Helena to Seattle to California which somehow goes through Texas. After finally yelling loud enough about either this cut not being my problem or my line isn't routed where I was told it was, I finally got a manager or VP who was kind enough to tell me that my line is routed through Arizona, and Texas, and a couple of other places in what I call the "mideast", and then to the Dakotas, through montana to the spokane (eastern washington) area, and then back to Montana. Adding up the miles, I get about 4-5,000 miles. I can believe that, with some switch latency.
Here are some tests I have done at 256kb: Line From-to Medium 8000 octet 1000 octet 32 octet speed ping ping ping in seconds in seconds in seconds ----- ------------- ---------- ---------- ---------- ---------- 256kb Israel-Israel fiber .524 .068 .008 256kb Israel-Israel FR, CIR=0 .628 .144 .016 256kb Israel-USA satellite 1.096 .640 .572 256kb Israel-Europe fiber .576 .116 .052 For 32 octets and 100ms - that is twice the rate we get with a fiber link from Tel-Aviv to Geneva - a few thousand miles. Hank