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Strategies & Market Trends : DAYTRADING Fundamentals -- Ignore unavailable to you. Want to Upgrade?

To: Eric P who wrote (347)	6/9/1999 7:18:00 AM
From: Wes Stevens	Read Replies (1) \| Respond to of 18137

I have a number of satellite links to south america at the office. A round trip ping usually takes about 800 to 900 mili seconds. Your 1/2 second estimate is in the ball park. Remember that satellite is 23k miles up.

To: Eric P who wrote (347)	6/9/1999 12:18:00 PM
From: -	Respond to of 18137

<may main concern is 0.5sec delay due to satellite prop time...> Eric, I threw that # into an early post as an upper-bound for Satellite links... actually I believe the nominal time for a dish link is about 0.2secs (200 millisec). The potentially bigger, variable component of the delay is from the network that delivers the dish... in otherwords the router backbone. Most of these satellite data-delivery networks are dedicated in nature (private networks), so you don't have as much competing traffic, making them somewhat faster than the internet. As far as satellite feeds, I've had them all - BMI, DBC, Comstock, etc. For the past year, I've used an S&P Comstock Feed (Dish on the roof) as my main price-quote source... I get internet quotes from 3 other sources, but the satellite feed is the best. BMI and DBC are OK too, but their customer service is legendarily poor, and their network latency goes up noticably during busy market periods. Comstock is pricey, but their service is excellent (coincedentally, one of their techs is up on my roof now, realigning my dish -- that would NEVER happen with BMI; you're on your own). Even with great stock quotes coming in over the net, which is nice, I find it hard to do without a good satellite link, which is ALWAYS reliable! But, you have to accept that when the market gets really busy, everyone is going to get their quotes a little slower. It's not the network so much that backs up, it's the hosts that are delivering the price data. If you're trading S&P Futures, you can circumvent this problem by getting a "sqwak box" audio link right into the pit. However, when the market gets "fast", they're STILL going to nail you - chalk it up to "slippage". Problem with the NASDAQ is, there is no "pit"! Except for those mainframes up in Connecticut... and all the wires (data networks) that lead to them... Good trading, -Steve

To: Eric P who wrote (347)	6/9/1999 12:45:00 PM
From: Raymond Duray	Read Replies (1) \| Respond to of 18137

Hi Eric, My main concern with the satellite feed is from a recent comment of a possible ~0.5 seconds latentcy for getting the data from satellite (the satellite is located over the equator, south of Houston). Can anyone confirm this for certain? Your data is traveling at the speed of light or very close thereto. Since that is 186,000 mi./sec., the uplink and downlink theoretically require [(2 x 22,700 + 130) /186,000)= .245 seconds or 245 milliseconds. Where 22,700 is the height of the bird above the equator and 130 is the calculated hypotenuse of a triangulation from 29 Deg. N, 95 Deg. W to 0 Deg., 95 Deg. W. In other words, from Houston to the spot on the Equator directly under the bird. For video signals this is perfectly acceptable. For the transmission of your data it is not quite as bad as the 15 minute delay some of us find acceptable. (Hey, no twitch instinct here!) For full duplex (two way) voice communication this 240 ms. delay is anathema in that the human ear can detect latency greater than ~150milliseconds. The PSTN (Publicly Switched Telephone Network) is set up so the average latency when you are in converastion on a long distance call is ~75 milliseconds. So geostationary satellites will nver be useful for replacing the existing PSTN. One of the bugaboos of trying to establish VoIP is the latency issue. This should be satisfactorily resolved by mid 2000. Back to your PC quote issue. The only way to reduce the latency inherent in the use of GEO birds is to stick to a land line solution today. And possibly make use of a LEO solution when it become available (Both Skybridge and Teledesic are in the planning stages right now.) HTH, Ry