shuford@cs.utk.edu (Richard Shuford) (02/03/91)
martinea@ireq.hydro.qc.ca (Alain Martineau of Hydro Quebec, Centre de Conduite du Reseau) writes: > ...trying to write the specifications for a new national control center. > ...So we try to incorporate in our specs as many standards as possible, > we really need an OPEN system; > we don't want to repeat this 70 million dollars purchase every ten years. Historically, the ISO committees have been more concerned to create standards with maximum generality than to design implementations that perform at high speed or withstand real-world stresses. Since you seem to have significant real-time performance concerns, the lengthy negotiation phase that most OSI protocols go through to establish a connection are a bottleneck that could become a pain in the neck. If you were to use your own physical media, your choice of protocols could reflect more closely the requirements of the problem than if you have to use whatever is available on somebody else's network. Therefore, instead of using X.25 links or any other shared-resource network, have you thought about getting your transmission people to install fiber-optic ground wire (FOGW) along your high-voltage transmission corridors? This puts the circuits right where you need data, and you can install fiber-optic transmitters and receivers (and other active hardware) of your own choosing. The bandwidth is typically limited by the electronics, not by the fiber, so future upgrades in capacity would not require stringing new cables. Such a design would give you complete control over the physical media for your data collection, giving a margin of confidence that you cannot have when your time-critical data are sharing a wire with somebody else's traffic. Of course, if you absolutely must have constant data flowing at a constant rate, you would be well advised to arrange for back-up circuits, which could be dial-up links on the switched network. Or perhaps you have non-co-routed redundant paths in your power- distribution network so that the FOGW links could also be routed for failsafe operation. -- ....Richard S. Shuford | These opinions here are held neither by the ....shuford@cs.utk.edu | University of Tennessee nor by the National ....BIX: richard | Football League.