poor sound quality on receiving side

[kostlandinc]

We have a in-house VOIP server, 3cx. Everything is fine except the sound quality of the receiving side is cutting-in and -out, very choppy. The sound quality of extensions in the office are fine. For example, if a customer calls, people who are in office can hear the conversation clearly, but the customer can't get clear voice, it cuts in and out, and breaking up. Do you have any suggestions?

Our setup is

Time Warner Cable: Business class 12MB/1.5MB --> Arris DOCSIS 3.0 modem --> Linksys EA6500 Router --> 3cx on VMware esxi v5.5 (Intel Intel i5, 3cx runs 2 v-core, 6GB memory, Windows 2008 R2 SP1) Wired connection.

There are only 2 people in the offices using phones. Office also hosts a web server (IIS) and sql server, external people can access the web server.
Linksys EA6500 --> Linksys LGS116P (unmanaged) --> voip phone and HP Poliant 380 G6 (VMware esxi v5.5 , web and sql servers)

Please advise. Thanks.

-Tony

 

[intellegens]

Use this link to run a VOIP test and simulate 6 lines.
http://voiptest.8x8.com/

Depending on number of users and type of traffic, bandwidth may be an issue.
Do you have bandwidth management or QoS in place which prioritizes VOIP traffic?

 

[intellegens]

Please post VOIP test results here

 

[lneblett]

You are experiencing jitter and likely for one of several reasons:

Intellingens is likely correct in that there is not enough upstream bandwidth to support all the various demands. The upstream is the 1.5 and why the external caller is having the audio issue. Running a web server for external use is likely putting a strain on things as well as the every day browsing and internet use by those in the office. You likely do not have enough "pipe" to handle all the demands, much less peak demands. QOS may help some, but only marginally so or perhaps not at all if the web server is under heavy load. This also explains why inside calls have no issue as you have plenty of bandwidth.

Also, while not an absolute, 3CX does not recommend running SQLServer (or Exchange server) on the same box. I am not suggesting this as a cause as I have no way to know if on the same box or even how busy the server really is. My guess is that if on the same and as long as the SQL aspect is not really taking up most of the resources, you are likely OK, but given the nature of how databases are combined with the randomness with which data transactions and phone calls occur it could conceivably cause problems that might also contribute to the issue.

If the web server is on its own box perhaps you can bandwidth throttle same thereby giving the voice a better shot of sharing what you have. You might also look into a different router such that you can associate and reserve a bandwidth for the voice side of things. The latter might be a little wasteful as it reserves regardless of other demands, but it may still help.

Of course, getting more will be a better option, but not sure that what you can get from Time Warner will do it given the web server. In our area, the most they will provide in a standard cable modem configuration is 5Mb in the upstream. They have other offerings, but then these get rather expensive and negate what most small businesses hoped to save in the first place.

 

[kostlandinc]

intellegens, thanks for replying. Here is the result of voiptest.8x8.com test

Speed test statistics
------------------------
Download speed: 12347 kbps
Upload speed: 1497 kbps
Download consistency of service: 75%
Upload consistency of service: 75%
Download test type: socket
Upload test type: socket
Maximum TCP delay: 81 ms
Average download pause: 1 ms
Minimum round trip time to server: 41 ms
Average round trip time to server: 70 ms
Estimated download bandwidth: 13089 kbps
Route concurrency: 1.0600376
Download TCP forced idel: 42%
Maximum route speed: 12787 kbps

VOIP test statistics
-----------------------
Jitter: you --> server: 14.1 ms
Jitter: server --> you: 5.4 ms
Packet loss: you --> server: 0.0%
Packet loss: server --> you: 0.0%
Packet discards: 0.4%
Packets out of order: 0.0%
Estimated MOS score: 3.9

General information
------------------------
IP address: xxx.xxx.xxx.xxx
Local time: Jun 30, 2014 11:24:20 PM
Test server: http://voiptest.8x8.com:82/

Please advise. Thanks.

-Tony

 

[kostlandinc]

intellegens, thanks for replying. Here is the result of voiptest.8x8.com test

Speed test statistics
------------------------
Download speed: 12347 kbps
Upload speed: 1497 kbps
Download consistency of service: 75%
Upload consistency of service: 75%
Download test type: socket
Upload test type: socket
Maximum TCP delay: 81 ms
Average download pause: 1 ms
Minimum round trip time to server: 41 ms
Average round trip time to server: 70 ms
Estimated download bandwidth: 13089 kbps
Route concurrency: 1.0600376
Download TCP forced idel: 42%
Maximum route speed: 12787 kbps

VOIP test statistics
-----------------------
Jitter: you --> server: 14.1 ms
Jitter: server --> you: 5.4 ms
Packet loss: you --> server: 0.0%
Packet loss: server --> you: 0.0%
Packet discards: 0.4%
Packets out of order: 0.0%
Estimated MOS score: 3.9

General information
------------------------
IP address: xxx.xxx.xxx.xxx
Local time: Jun 30, 2014 11:24:20 PM
Test server: http://voiptest.8x8.com:82/

Please advise. Thanks.

-Tony

 

[kostlandinc]

lneblett, thanks for the lengthy analysis.

One thing I want to point out is that our sql server and web server are not running on the same server of 3cx. They are running on a different box, although everything is on the same subnet. The usage of web server is very light. Only our accounting people, who sit in a different office, accessing the site via internet. Given, does this change your assessment?

-Tony

 

[bardissi]

Get a 2nd time warner modem for just the voice traffic.

 

[lneblett]

Thanks for the added info.

No, my assessment has not changed. The testing you did is marginal based upon a 3.9 MOS score. Would I be correct in assuming that the accounting people in the other office also make use of the 3CX system? You already indicated that they do use the Internet to access the main.

The bottom line is that it is not the system, but the carrier (TWC). In your case, you may need to do several tests over a period of time to get a feel for how good a connection you really have. The internet is pretty dynamic as to congestion and routing. One test is merely a snapshot and it behooves you to do others and particularly so at times when you are absolutely positive that there is virtually no traffic coming to/from your site. Adding bandwidth will likely provide some relief, but if the carrier is not reliable, then bandwidth alone may not solve the problem.

Bardissi's suggestion is essentially the same thing as adding bandwidth and at the same time segregating the traffic so voice and data do not compete. To do this, you would still need a router that allows for protocol binding or IP grouping so that you can do the separation.

 

[intellegens]

How many extensions is the PBX supporting?
Are the SQL and web server supporting queries/access from the Internet?
A typical T1 circuit (which is effectively your up speed) supports roughly 13 calls using G.711 codec or 37 calls with G.729 codec - provided bandwidth is not being consumed by any applications.
In your case, It appears that VOIP traffic is competing with inbound web traffic to the SQL/Web server so it is likely that the number of concurrent VOIP calls that can be supported - without noticeable loss of quality - is somewhere in the low single digits at any given time - at best. Also, since you don't seem to have any QoS implemented, there is no throttling of application bandwidth usage therefore call quality cannot be guaranteed for even a limited number of calls

 

[intellegens]

Get a high speed data line from Comcast if it is available and with cost of decent switches pretty low, I would recommend keeping voice and data traffic completely separate in your case - that way you do not have to worry about QoS

 

[bardissi]

If he is in a time Warner area chances are he can't get comcast (yet)