Delay in calls and phone pickup

Discussion in '3CX Phone System - General' started by mase2hot, Oct 9, 2010.

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  1. mase2hot

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    Hi,

    We have or PBX in Birmingham and an office in Manchester with about 15 extensions. The phones are configured wth the Briming PBX IP 81.... Working ok apart from sometimes if a phones are rining as ring all from a queue and somone picks up the phone the other phones carry on ringing for a bit. And if somoene else pics up the phone from that queue its then a conference call....

    Also there is a delay sometimes on calls...
     
  2. abc123

    abc123 Active Member

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    That is network latency and bandwidth problems.

    How are they connected? VPN? Dedicated connection? or over the public internet via the tunnel? Is your voip on a different network to your data? What is your bandwidth?

    This happens all the time with data, but you just dont notice it, packets are dropped and strangled (Sometimes your web pages take longer to load than others, especially when someone is downloading something). VOIP is real time audio and is less forgiving (think of those times when you watch youtube videos and they pause because your buffer caught up).

    Take a look at the network setup. Remember for G711 you need about 106K PER CALL. So that gets eaten up very quickly on a few calls plus data sharing.

    Also look at your QOS through the router and give SIP some top priority.

    It has been a long while since I left the UK and so dont know much about he ISPs there these days. For situations like yours we use MPLS systems in which inter office communication is given top priority through the isp. Do they have that in the UK yet? We do it with DSL and T1s.
     
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  3. RichardCrabb1

    RichardCrabb1 New Member

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    Hi,
    I agree with abc123it. In the UK you need to be sure that you use a good Internet provider, where contention is low.

    Sometimes it has to be said that you cannot do much about contention in BT exchanges, however if both ends for example are on 21CN connections then exchange contention will be good and the latency will be low, as long as you have a good provider. I recommend Voip-Unlimited for ADSL and as the SIP provider. With their service I use VPNs successfully. An advantage then is that there is only one provider to go to if there is a problem. They can supply conventional lines as well - ISDN and analogue.

    There are ways around highly contended exchanges, such as using MPLS, or even dedicated circuits.

    If you use the ADSL connection for VoIP and Internet, then you must configure QOS. Downloads otherwise tend to take all the bandwidth of the connection, leaving little for phone calls. Phone calls with then be broken up and have long delays.

    I hope that is of some help.
    Kind regards
    Richard Crabb
     
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  4. mase2hot

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    We have a seperate internet line for phones. Speeds are not that good though 8Mb Down and 550KB Up. Currently about 8 phones on this broadband in manchester with the PBX located in Brimingham. The remote extensions do not go via a vpn they each go directly to the PBX in Birmingham.

    The PBX has 20Mb Down and 1MB Up and has about 8 users connected to it locally.

    As for audio codec I have no idea what we are using how can I check? The grandstream phones show pcmu I think...
     
  5. abc123

    abc123 Active Member

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    You specify the codec in the provider setup page.

    550K means you MAY get 5 concurrent calls and the PBX MAY handle 10 concurrent calls with G711 but more like 4 and 9 respectively.

    Those are MAX speeds so given normal use and delays it would be more like 3 and 7 or 8 respectively. And then you dont say if the Birmingham users are using that same internet for data.

    You will get problems with this bandwidth and will get choppy audio very quickly.

    I also think you have your setup incorrect.

    You have put the PBX in the 8 office and get 15 people to remotely connect. Why not put them in the 15 office and get the 8 to remotely connect? Or better still why not put a pbx in Manchester and bridge the two?

    And finally I would suggest you use a digital assistant to control calls coming in and route them to Birmingham or Manchester as needed and not one big ring all group. Or use two groups and have the Birmingham one ring first and then if no answer have the Manchester one ring. Of course this is all only possible if your business model allows this.
     
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  6. RichardCrabb1

    RichardCrabb1 New Member

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    Hi Mase2hot,
    I missed the fact before that had 15 remote extensions in Manchester, with 8 in Birmingham - site of the 3CX. I think that you are far better off having a 3CX for each site, and use a bridge to link them for internal calls. The bandwidth requirement depends on the "calling rate" - ie how much each phone is used. It would easily be adequate if the maximum number of calls is say consistently below say 5 (probably unlikely?). You also need to remember that at the 3CX site (Birmingham), when an extension at Manchester makes an external call, two lots of bandwidth are needed 1) to the external extension in Manchester, and 2) to the SIP trunk provider. Therefore one call will take up 200+ K using G711. That way you use up bandwidth very quickly. One way around that is to have a separate broadband connection purely to link Manchester. I think overall though, you are better off having a separate 3CX at each site, each with it's own set of SIP trunks. Make sure that you use good quality ADSL. The importance of that is key to success.

    With regard to ring groups, I find that it is often best to try different combinations and see what works best for you. Don't forget queues are also effective.
    Kind regards
    Richard Crabb
     
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  7. mase2hot

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    Hi,

    reason pbx is in birmingham is because thats where the 3cx system first went live. Also in Birmingham the PBX upload speed is 1mb where in manchester it is only around 500kb.

    We have purchased the 24 concurrent package. Are we allowed to have 2 PBX's set up using the same licence as long as we dont go over 24 in both locations?

    I would prefer the 2 PBX setup as this seems to make more sence bandwith wise as mentioned we are using up bandwith by having these remote extensions.....

    Thanks
     
  8. RichardCrabb1

    RichardCrabb1 New Member

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    Hi Mase2hot,
    I think that you need to talk to 3CX sales. Surely they ought to come up with some arrangement?

    24 concurrent calls needs quite a lot of bandwidth. Are you assuming one call per extension? So far my experience is that the number of concurrent calls is usually much less, unless the application is for a call centre. Experience will tell you what this needs to be in practise. What is your view on the number that you need for each site?

    If you do need the bandwidth, SDSL is a better bet. The contention is lower as well.
    I hope that is helpful.

    Kind regards
    Richard Crabb
     
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