Ip Alarm Signalling

[jimcarter]

I got that Jeff. In our GPRS/PSTN solution we are using GPRS as the primary path, and GPRS is IP. But you don't need a fixed IP address to "talk" to the unit or the panel for UDL. Infact, what James is saying is correct.

As soon as you add in a fixed IP address on a GPRS SIM card you open yourself to a number of attack senarios..the ones that those who dont like IP solutions continually harp on about, such as Denial of Service. So the BEST way in a GPRS/PSTN (or GPRS only) is to have a Dynamic Addressed SIM (bog standard), infact that goes for all IP based solutions.

Not to say we have not looked at Fixed Addressing on our SIMs, or that we may still use it, but it has to be in a very controlled manner.

So to confirm, agree that IP over GPRS is fine, as that is what it is...and that a fixed IP address is not needed and from our point of view we do not need a fixed net facing address on IP or GPRS to carry out UDL or communicate with the SPT.

Do give me a call sometime Jeff, especially if my emails are not clear.

Jim

[james.wilson]

single path then Jef?

GPRS is packet based so is in effect IP anyway, but i wouldnt trust it single path on any sort of risk. Id like to see poll stats at 60 seconds i reakon it would be down a lot.

GPRS is poor on my phone. It says its there all the time it has signal, but often when i want to use its not there and i have to re-register the gprs. That has been the same on all of my phones, windows phone, nokias, android and blackberry. However the BB does seem to handle it better.

[jb-eye]

single path then Jef?

GPRS is packet based so is in effect IP anyway, but i wouldnt trust it single path on any sort of risk. Id like to see poll stats at 60 seconds i reakon it would be down a lot.

GPRS is poor on my phone. It says its there all the time it has signal, but often when i want to use its not there and i have to re-register the gprs. That has been the same on all of my phones, windows phone, nokias, android and blackberry. However the BB does seem to handle it better.

Agreed James. But im comparing the like for like product such as the redsecure and dualcom and of course the cost comparison. Your post that caused so much interest was based on polling times IIRC. I had less concern (risk evident) with polling with more emphasis on reporting. IP over GPRS (thx Jim for the dynamic/fixed explanation) gives the faster polling you so strenuously highlighted

[james.wilson]

not so much based on polling times, more on time to report a failure.

I tested GPRS availability through my phone. I wrote a small app and made it ping google every minute.

Youd expect that every ping would be successful wouldnt you?

Well it wasnt. Ill rerun it and do some stats if anyone is interested

[jb-eye]

not so much based on polling times, more on time to report a failure.

and the diffrence being?

[james.wilson]

polling times are in the background. Ie a G2 dualpath unit could poll every second, hour, or day. As long as it reports a failure within 24 hours.

the faster the polling times then in theory the faster the reporting time 'can' be.

ie on those tests i did i found that the gprs side of that grade 3 dualcom was polling every 10 minutes. But it/the system didnt report a failure to the arc for 5 hours.

Also the less often you poll the better your link appears to be. All you can prove without polling is the network seems to be available. Until you use it you dont know. ie 50v on a tel line dont mean the line is available and will connect a call. As such GPRS regestration doesnt mean that a signal will get through if sent.

If you poll say every minute then some polls will fail but the system will know it has an issue and can restart the comms unit, log off and back on etc. If it does this every hour then it could of been down for 59 mins couldnt it. if it polls every 4 hours it could of been down for 3hours 59mins etc etc.

You would be suprised if you tested your phone continously for data you would be suprised how poor it was.

I know you hate radio so im suprised your that interested in single path GPRS only signalling

[jb-eye]

polling times are in the background. Ie a G2 dualpath unit could poll every second, hour, or day. As long as it reports a failure within 24 hours.

the faster the polling times then in theory the faster the reporting time 'can' be.

You would be suprised if you tested your phone continously for data you would be suprised how poor it was.

I know you hate radio so im suprised your that interested in single path GPRS only signalling

But it dosent poll that often.

Yes i hate wireless and often use the wired line v the wireless analogy to exspose wireless as second rate medium. i think we all agree that redcare and IP/WAN are the best carriers but to avail the best carrier for a Price v Risk is what we are now discussing.

[jimcarter]

Another couple of factors here. Every time you poll from end to end you use bandwidth. GPRS traiffs are based on bandwidth. The more Bandwidth you use, the more expensive the tariff. QED...the more you poll, the more Bandwidth you use and the higher the tariff.

That means, to get to say a Grade 4 solution on GPRS only, you need to be polling as a minimum every 90 seconds. Because you cant simply report a failure on the loss of a single poll.

Whats more, you are more likely to pick up a short line break of some sort and you cant rely on signal or interface checking as there is no alternative path to send the fail. As James says, the less you poll the better your link appears, the more you poll, the better the stats you get.

Having said that, in general I have to disagree with James (and we have debated this before) that actually GPRS is pretty reliable..BUT..I would always advocate it as a solution coupled with an alternative (and different technology) signalling method. Its fine as a backup, but too prone to failures due to influences that none of us can overcome.

Oh..and let not forget..its IP..so we cant possibly use it for alarm signalling..tongue firmly in cheek!

I couldnt possibly comment on your last post Jeff....

[jb-eye]

Having said that, in general I have to disagree with James (and we have debated this before) that actually GPRS is pretty reliable..BUT..I would always advocate it as a solution coupled with an alternative (and different technology) signalling method. Its fine as a backup, but too prone to failures due to influences that none of us can overcome.

James is prone to changing his mind faced with a desent argument or the chance of proffit

[james.wilson]

Jeff I'd agree its a decision based on the risk assesement, I can see that a gprs only comm is similar to a digi re risk, slightly better but not much. But as I have said before when I explain to my customers what the worse case timings are I have only had one so far not opt for G4 signalling. These are police systems mind.