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Voice delay for PSTN lines

Discussion in '3CX Phone System - General' started by jparaujo, Jul 20, 2009.

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  1. jparaujo

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    Hello,

    I'm using 4 PSTN lines connected to a Grandstream GXW-4104 and I have some Grandstream BT-201 as extensions connected to the 3CX. When people call to those PSTN lines, there's a delay during the conversation. All those equipments are connected via local network, so I think there should be minimal delay, when actually there's a delay of 1 second or so, much higher than extension to extension calls, when one extension is remote. Any tips on this?

    Thank you.
     
  2. jharrell

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    We are using a GXW-4104 with no noticeable delay with our Polycom phones.

    Do you have "PBX delivers audio" turned on in the advanced gateway config? If so I believe that could add significant delay as all audio is sent to 3cx then to gateway from the phone and perhaps even transcoded from say g.729 to g.711 by 3cx depending on how it negotiates codecs adding even more delay.
     
  3. jparaujo

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    Hi, thanks for the reply.

    I checked and "PBX delivers audio" is not enabled for any extension. Also, I'm using the phones with primary codec set to PCMU, so I think there's no transcoding.

    One funny thing is that the delay is happening randomly. Sometimes the calls are perfect, while sometimes there's that huge delay.

    Other ideas?

    Thank you!
     
  4. jharrell

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    Random delay could be a symptom of packet loss or congestion on the network between the phone and the gateway, as it might cause retry's and buffering that contribute to latency, also it could be just buggy firmware in the phone or gateway.

    I know the Polycoms had noticably less delay phone to phone then the grandstream phones we tried.
     
  5. leejor

    leejor Well-Known Member

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    You could try running the 3CX and a couple of sets on a different switch, one less busy or a different make of switch, perhaps the one you are using has issues.
     
  6. mbaltus

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    Delay and poor call quality are some of the most common problems in VOIP environments, mostly caused by network congestion and other (less important) traffic taking up the bandwidth.

    Do you use a manageable switch that allows setting QoS? Then I suggest that configuring QoS is most likely beneficial. If you don't have one, that may be a good solution. There are very affordable manageable switches available and depending on speed, etc. you could look into HP ProCurve 1700 or 1800 serie, 3Com's or Linksys.

    This all assuming that the 3CX server is not having any CPU/memory utilization problems.
     
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  7. jparaujo

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    Hi,

    right now for example I'm using my Grandstream without any noticeable delay, just like a PSTN to PSTN call.

    But anyway, I'm using a Linksys WRT310N with the VoIP DD-WRT firmware, v. 24 sp1. I configured the QoS for WAN and LAN, with premium priority for the OpenVPN service, at 1194 and for the 3CX server and the GXW-4104. I have a VPN configured too, for the remote extensions. So this router is a VPN server, with 3 client routers connected to it. And our system, hosted here, is accessed via Internet through it too. However there's low use of bandwidth for the system. We have like 10 or more people working simutaneously, but they just run some queries, not at the same time and very randomly. I could check that with bandwidth usage on the router, and I really think it's not causing the problem. The average CPU usage on the router is 10% and memory seems to be ok at 49% free. But I gotta check those values when the delays start happening. As for the Windows 2003 Server where 3CX runs, it's a dual Xeon with 4 GB of memory, running just the 3CX and with plenty of resources free. Other than that the switches are used just for the phones.

    Well, that's pretty much it.
     
  8. jharrell

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    *Deleted because I didn't want to clutter this thread.
     
  9. dbergsma

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    I had grandstream 4104 - had same problem.
    flashed device to current rev. same issue.
    Needed pbx supply audio - total decode time 1 way was +/- 70=100ms which both ways was .2sec, which was very noticable and very disconcerting to other callers.
    gave up.

    Phoned grandstream - no response.
    Tried web - nothing.

    spent days on this.

    Bought patton 4 port. Pain the butt to configure, but absolutely no problems after that (Do not throw out the serial dongle thingy -- you will need it eventually). Nothing in the environment changed.
    No problems. Happy customer now.

    Anyone want to buy a spare grandstream 4104 out of Canada?
    cheap.

    Dean.
     
  10. jparaujo

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