Congestion

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Postby Barry » Tue Aug 12, 2008 8:59 am

streaker69 wrote:Or, like in our case, we're talking covering about 60 square miles across 40 different stations. While Wifi is not a good solution for that, we haven't found a decent one in any other band either. Problem with our situation is, all of our assets are in the low ground, so getting wireless anything to be reliable is tough.


Can't you guys lease copper? That's how we connected to our remote schools.
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Postby streaker69 » Tue Aug 12, 2008 10:15 am

Barry wrote:Can't you guys lease copper? That's how we connected to our remote schools.


Not that's cost effective. I got a quote for an MPLS setup, was going to cost us over $9000/month for 56k connections to all the stations.
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Postby Barry » Tue Aug 12, 2008 12:33 pm

streaker69 wrote:Not that's cost effective. I got a quote for an MPLS setup, was going to cost us over $9000/month for 56k connections to all the stations.


I don't think we were paying near that much, though we owned all the equipment. Basically they were "alarm" circuits.
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Postby streaker69 » Tue Aug 12, 2008 12:37 pm

Barry wrote:I don't think we were paying near that much, though we owned all the equipment. Basically they were "alarm" circuits.


We actually want to pass data over them. 'Alarm' Circuit or "Dry Pairs' work ok if you're gonna use HDSL equipment, but you'd still need to be with in 13,000 wirefeet of the other end point, without passing through any LEN's.
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Postby Barry » Tue Aug 12, 2008 3:31 pm

streaker69 wrote:We actually want to pass data over them. 'Alarm' Circuit or "Dry Pairs' work ok if you're gonna use HDSL equipment, but you'd still need to be with in 13,000 wirefeet of the other end point, without passing through any LEN's.


Oh, yea, forgot about that part...
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SCADA radios

Postby Airstreamer » Tue Aug 12, 2008 4:57 pm

We use licensed channels in the 900 mHz band, master/slave 45mHz split, so each site can run full duplex data during the time slot that the SCADA master polls them.

The MDS system is a digital radio where the master has it's carrier in an 'always on' state, (in our system anyway,) and does time division access to each of remote radios. We have them setup 'transparently' so the actual SCADA system doesn't even know that the radio link exists. The actual RTUs "don't speak unless spoken to," so the com data part of the radio channel is idle except for the traffic between the SCADA master and one RTU at a time. However, there is a maintenance channel that is running between the radio master and all the slave remotes full time, but its data is not passed out of the master on the normal data port but shows up on a separate connector. If you hook to that maintenance port of the master, you can get to any radio on the system IF you know its radio address. (There are some discovery tools, but I've not had good luck with them.)

Signal levels, equipment temperatures, programming, etc can be viewed if needed, and if enabled, you can re-configure the radio just as if you had the programming cable plugged directly in. All "over the air" data is encrypted.


We can get 19.2k or even 38.4k if we push it, but mostly we run 9600. They're good for more than 40-50 miles line-of-sight with the right antennas.
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Postby beakmyn » Tue Aug 12, 2008 5:22 pm

Airstreamer wrote:We use licensed channels in the 900 mHz band, master/slave 45mHz split, so each site can run full duplex data during the time slot that the SCADA master polls them.

The MDS system is a digital radio where the master has it's carrier in an 'always on' state, (in our system anyway,) and does time division access to each of remote radios. We have them setup 'transparently' so the actual SCADA system doesn't even know that the radio link exists. The actual RTUs "don't speak unless spoken to," so the com data part of the radio channel is idle except for the traffic between the SCADA master and one RTU at a time. However, there is a maintenance channel that is running between the radio master and all the slave remotes full time, but its data is not passed out of the master on the normal data port but shows up on a separate connector. If you hook to that maintenance port of the master, you can get to any radio on the system IF you know its radio address. (There are some discovery tools, but I've not had good luck with them.)

Signal levels, equipment temperatures, programming, etc can be viewed if needed, and if enabled, you can re-configure the radio just as if you had the programming cable plugged directly in. All "over the air" data is encrypted.


We can get 19.2k or even 38.4k if we push it, but mostly we run 9600. They're good for more than 40-50 miles line-of-sight with the right antennas.


This is what I'm seeing. SCADA is still pretty muched a wired environment. I am starting to see more manufacturer's come out with wifi however most of it is not 2.4 GHz. We just had a vendor come through with a bunch of propoganda about wireless and they were touting that their devices are bluetooth. That's the last thing I need to put into a critical system.
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Postby Airstreamer » Tue Aug 12, 2008 10:25 pm

beakmyn wrote:This is what I'm seeing. SCADA is still pretty muched a wired environment. I am starting to see more manufacturer's come out with wifi however most of it is not 2.4 GHz. We just had a vendor come through with a bunch of propoganda about wireless and they were touting that their devices are bluetooth. That's the last thing I need to put into a critical system.



We are going to be implementing a 915mHz spread spectrum data collection system (data loggers,) that will have about 6 remote nodes that will have to loop through a repeater node, and about 6 more sites that will report directly to the "main" base unit. The longest hop is about 2600 feet, and has good RF properties. We've already setup a test radio and measured levels at each of the sites in turn to make sure it's going to work, at least as far as the RF hops are concerned.

The units can speak something called PakBus and can store and forward packets between units to make up a small mesh/repeater network. A contractor is putting it all together, including the solar panels and other gear.

Should be kind of fun, actually!

Equipment from Campbell Scientific:
CR206: Datalogger with 915 MHz Spread Spectrum Radio and RF401: 900 MHz Spread Spectrum Radio
(If anybody is interested..)

Hope it works. At least it won't be blamed on me if it doesn't! :rolleyes:
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Postby Paxton » Wed Aug 13, 2008 1:38 am

It seems as though everyone is placing the blame for the congestion squarely on the shoulders of the residential users who are streaming video, file swapping, etc.

You're not going to be able to change all those home routers now, so where would you put the Industrial, Scientific & Medical users now? Up at 5GHz?
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Postby streaker69 » Wed Aug 13, 2008 4:06 am

Paxton wrote:It seems as though everyone is placing the blame for the congestion squarely on the shoulders of the residential users who are streaming video, file swapping, etc.

You're not going to be able to change all those home routers now, so where would you put the Industrial, Scientific & Medical users now? Up at 5GHz?


No, the frequency doesn't need to change, just more channels need to be allocated above channel 12 specifically for business/industrial use.

I think we're correct in blaming residential users, most commercial networks are properly setup, whereas most residential are not.
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Should ordinary people go back to wired?

Postby Paxton » Wed Aug 13, 2008 4:57 am

streaker69 wrote:I completely agree with this. I think a dedicated Wifi system for SCADA would be great.

I think one of the issues is that many people can't see outside of their own little world and don't realize that there's other people out there that NEED to use it instead of wanting to use it.

I can't tell you the number of people that I've talked that have no need for wireless in their homes, but still have it. People with a desktop machine sitting 5 feet from an AP with a USB dongle sticking out of the front. Damnit, just plug the CAT5 cable in.




It seems that a lot of people are buying broadband packages and get given a WiFi router, so they will naturally connect wirelessly to that rather than over ethernet. If they had to pay extra for the WiFi router then many might be happy with a wired connection. You could even put a tax on WiFi usage in urban areas.
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Postby streaker69 » Wed Aug 13, 2008 10:47 am

Paxton wrote:It seems that a lot of people are buying broadband packages and get given a WiFi router, so they will naturally connect wirelessly to that rather than over ethernet. If they had to pay extra for the WiFi router then many might be happy with a wired connection. You could even put a tax on WiFi usage in urban areas.


Oh, more taxes, I'm sure that will go over big, are you in England?

Previously you alluded to that it would be good to get the Government involved at all in regulating the band and now you're talking about taxing citizens for using an unregulated band.

Kind of nonsensical isn't it?
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Postby brwrdrvr » Wed Aug 13, 2008 3:22 pm

SOHO wireless is just too cheap and too prevalent for many of the things that you would think about to "fix" the "congestion". I liked the idea of some type of fuzzy logic program (Just for the novelty of it)built into the residential wifi routers that would do a scan of the area and then choose an appropriate channel to operate on. It would have to then be like a wasp protecting the nest and calling that channel it's own and not change or rescan unless power were lost. The next router to be plugged in would scan the area and choose another channel. I guess the criteria would be if the router finds other routers close by they could not use a channel already being used if the signal strength is above 20-30. Not really able to set a criteria for a link quality as you would have to have routers connecting to other routers to find out that percentage. That would be quite a mess.

For the technology we have now, adding more channels to the band would be a great start.

You could always do like I did. Move away from the urban jungle and out to the sticks. Make sure your neighbors are all retired people and they don't spend the $$ on the neat little gadgets with wifi built into them. I have 2 APs near my house. Both with insignificant signals. So it's all good. :D
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Postby streaker69 » Wed Aug 13, 2008 4:05 pm

brwrdrvr wrote:SOHO wireless is just too cheap and too prevalent for many of the things that you would think about to "fix" the "congestion". I liked the idea of some type of fuzzy logic program (Just for the novelty of it)built into the residential wifi routers that would do a scan of the area and then choose an appropriate channel to operate on. It would have to then be like a wasp protecting the nest and calling that channel it's own and not change or rescan unless power were lost. The next router to be plugged in would scan the area and choose another channel. I guess the criteria would be if the router finds other routers close by they could not use a channel already being used if the signal strength is above 20-30. Not really able to set a criteria for a link quality as you would have to have routers connecting to other routers to find out that percentage. That would be quite a mess.

For the technology we have now, adding more channels to the band would be a great start.

You could always do like I did. Move away from the urban jungle and out to the sticks. Make sure your neighbors are all retired people and they don't spend the $$ on the neat little gadgets with wifi built into them. I have 2 APs near my house. Both with insignificant signals. So it's all good. :D


Clearing congestion is very easy. Just write a script to auto-deauth all other AP's other than your own, every few seconds.
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Postby MikeP928 » Wed Aug 13, 2008 5:29 pm

streaker69 wrote:Clearing congestion is very easy. Just write a script to auto-deauth all other AP's other than your own, every few seconds.


Just get the good stuff. We brought up a network last friday using the new Enterasys (Trapeze) gear. We had set the Rogue detection mode to the aggressive range. Within 2 seconds of deploying the code from the switch controllers to the thin APs, every other AP in the building went away, including the customer's legacy network. We looked around and said "damn, that was cool. Let's do it again." So we deploy the rogue detection only and everything comes back. Push the changes back out again and boom, we own the world. It must be a similar feeling to what Streak has every time he props up on that big valve.

I will implement it for a different customer tomorrow in a rolling fashion. Or maybe a circular pattern around the building. Or alternating floors, or just random. It may be a good thing I am bailing out of Canada for God's country Saturday.

I hope NorthWorst has the scotch well stocked in first class. I love the new charges from the airlines. Everything applies to the back of the bus, so it makes it easier to justify first. Hell, it figures up to about $125. per hop just to take the golf sticks along.

Canada would be a nice country if it were not for being filled up with Canadians. (OK, the obligatory shit stirring comment is out of the way, so I will crawl back in my hole before Beak staggers over to his pc.)

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