3CX call usage

[Zenithpeople]

Hi

We had the 3cx system installed in january this year but have continually had issues with it, mainly because of the Broadband in our area. We moved to a new business park but the dl/ul speeds are very poor, best we can get is 1.5mb dl and 800kb ul.

We have gotten around slow speeds for our data usage by buying some bandwidth from another local company who have direct fibre into their building (not an option for us as it's costly. The problem is they can't put a quality of service on for the 3cx system so using that is not an option as it keeps dropping calls.

Before I look into this any further, would someone be able to tell me how much bandwidth in terms of ul/dl speed is needed per call?

Apparently Cisco systems require 400kb per call.

Please let me know
Cheers

David

 

[markshehan]

For G711 the rule of thumb is 100k each way.

For G729 it is about 60k from memory.

We have customers who are in a similar situation to you and so we put a second DSL in there just for the phones.

 

[Zenithpeople]

Not sure which system we have (how do I know), I think it's phone system 10. We also use GXP1450 handsets (not sure if that makes a difference)

At the moment we have an ADSL line which solely has our phone system on, however to stabilise it the speed has been reduced quite significantly. Don't particularly want to put a 2nd line in to do this if it's only going to push us to 2.5 - 3 MB and still have problems.

Does the system use more dl/ul when first making the call before reducing once the calls has been initiated?

 

[markshehan]

Not sure which system we have (how do I know), I think it's phone system 10. We also use GXP1450 handsets (not sure if that makes a difference)

At the moment we have an ADSL line which solely has our phone system on, however to stabilise it the speed has been reduced quite significantly. Don't particularly want to put a 2nd line in to do this if it's only going to push us to 2.5 - 3 MB and still have problems.

Does the system use more dl/ul when first making the call before reducing once the calls has been initiated?

It isnt the phone system so much as your voip provider.

Under the settings for the provider you can specify which codecs to use and in which order of priority. They will tell you which they can support. Bear in mind that G729 is a licensed codec and you only get a few licenses with the paid version of 3cx (will tell you in your license area how many G729).

The set up and tear down of a call is tiny (about 1k) as it really is a simple "text" message. It is the voice that carries all the bandwidth.

If you have 1.5M down and 768k up then in theory you can make 7 concurrent calls with nothing else on that dsl. But no one gets 768 up - more like 650, so do a speed test. But you should still have 5 or 6 concurrent calls with no data loss.

Are you sure no one is using the dsl for data too? If they plugged a pc into the ports of the 1450 then they are on your dsl network and not the data one. How are you routing data over the two networks?

I have seen offices use systems like this with no problems with 4 or 5 concurrent calls on a dedicated dsl line.

Would need more information of your setup for better trouble shooting

 

[Zenithpeople]

Not sure which system we have (how do I know), I think it's phone system 10. We also use GXP1450 handsets (not sure if that makes a difference)

At the moment we have an ADSL line which solely has our phone system on, however to stabilise it the speed has been reduced quite significantly. Don't particularly want to put a 2nd line in to do this if it's only going to push us to 2.5 - 3 MB and still have problems.

Does the system use more dl/ul when first making the call before reducing once the calls has been initiated?

It isnt the phone system so much as your voip provider.

Under the settings for the provider you can specify which codecs to use and in which order of priority. They will tell you which they can support. Bear in mind that G729 is a licensed codec and you only get a few licenses with the paid version of 3cx (will tell you in your license area how many G729).

The set up and tear down of a call is tiny (about 1k) as it really is a simple "text" message. It is the voice that carries all the bandwidth.

If you have 1.5M down and 768k up then in theory you can make 7 concurrent calls with nothing else on that dsl. But no one gets 768 up - more like 650, so do a speed test. But you should still have 5 or 6 concurrent calls with no data loss.

Are you sure no one is using the dsl for data too? If they plugged a pc into the ports of the 1450 then they are on your dsl network and not the data one. How are you routing data over the two networks?

I have seen offices use systems like this with no problems with 4 or 5 concurrent calls on a dedicated dsl line.

Would need more information of your setup for better trouble shooting

I'm certain there's no one else using the data. We basically have fibre over a satellite network, which has a contention of 1 : 5 (or is it 5:1) which means we share the connection with four other businesses (this is pinched from another IT company who has a 1000mb line in their building). Tried to use 3cx over this but it is simply too unstable for voip as calls would keep dropping (it's fine for our data, in terms of emails browsing etc).

So we have a dedicated pstn line for the phone system and use plusnet broadband for . We even have the phone system running on it's own server to keep it separate from the main business server.

When we done a speed test yesterday we have download speeds of 1.6mb and upload of just below 800kb

At present we have 12 phones, however unlikely all will be used at the same time, more likely to be around 6 - 8 phones being used at once when we are busy. With things winding down for Xmas we've still been getting crackling lines on calls but that is generally what we hear, the other end hears us just fine.

Just had a look at the licences and we get 4 G720 channels

 

[markshehan]

So it looks like you are running the 8ccs version of 3cx.

You say that you are running the 3cx on its own server and that they can hear you but you have a problem with the line hearing them.

So your upload is fine but download and voice translation (from digital to audio) is a problem.

Which sounds like someone is downloading something on your dsl. Could be other problems (such as handset or 3cx server).

If you have them all on the same wired network, how do the phones and 3cx know not to go out through the other internet gateway and vice versa?

Or is someone doing a lot on the internal network and you have a switch/hub bottleneck?

I would do a wireshark in promiscuous mode and see what is on the network.

 

[Zenithpeople]

So it looks like you are running the 8ccs version of 3cx.

You say that you are running the 3cx on its own server and that they can hear you but you have a problem with the line hearing them.

So your upload is fine but download and voice translation (from digital to audio) is a problem.

Which sounds like someone is downloading something on your dsl. Could be other problems (such as handset or 3cx server).

If you have them all on the same wired network, how do the phones and 3cx know not to go out through the other internet gateway and vice versa?

Or is someone doing a lot on the internal network and you have a switch/hub bottleneck?

I would do a wireshark in promiscuous mode and see what is on the network.

Basically yes, our old server was converted into a server for the phones (Our IT chap didn't trust the chap who was installing it).

Both connections run through a draytek router then split. The fibre controls all data, emails etc, and the adsl is soley for the voip. We've also got a quality of service put on for the phone system so it gets priority. Had a lot of problems with the adsl line because of the distance to the exchange. the latest thing they did to stabilise the line was pin the SNR which reduced the line speed and got rid of the errors we were getting down the line.

So do you think the connection we have is enough for the 3cx system or do you still think we need more bandwidth

 

[markshehan]

In theory you have just enough bandwidth as it is dedicated. In practice you should have enough for 5 or 6 concurrent external calls on that DSL.

You complain of crackling on your end, meaning download not upload and your download is higher than upload.

So either something is also downloading or you have an audio problem on 3cx or the handsets.

Wireshark is going to help you.

 

[Zenithpeople]

I'll get a wireshark done and post back

 

[dlazure]

Why dont you get a sip trink provider who gives you a modem for a separate internet access ?