TIPS Poor Quality (Lag) with new customer..

[Brandon Lucas]

Hi Guys-

I'm sure this question has been asked here 1000 times, but I can't seem to find the right way to search and find it! So, if someone could guide me in the right direction (without all the hating) I'd be very appreciative - as would my customer.

I've installed a PBX in a flash Virtual machine and it's working great - other than the fact that this is a very rural customer that is barely getting a 3 mb per second internet connection. Thus - they randomly get some static / lag in the line. Being's they are rural - this is the best we can do. They originally told me they had a 6 mb connection so I never even thought to check - BUT, now that the system is installed - I've got to support it. It's only 4 endpoints and doesn't happen very often - but is there a way to turn down the voice quality, turn up compression, etc? to help with the voice quality? I'm sure there is; however, I'm still fairly new!


thank you so much in advance!


Brandon Lucas

 

[atsak]

It's not likely the speed of the line but rather the quality. Make sure you have enable a jitter buffer and have QoS on the router/firewall to set aside enough space in case the line is busy.

I have a 1mbit customer; so we put two DSL circuits in. One for phone one for data. Works fine.

 

[krzykat]

3 meg ... up or download speed? Typically the bottleneck comes with the upload speed. You need to have 64 kb of upload (depending on codec). 4 Calls means 256Kb, which with DSL, is sometimes about as much as you get in rural. Are they using it for their computers as well? If so, then that can get in the way of your phone calls. You may want to invest in router with VoIP QOS, so that all VoIP traffic gets priority. Personally, I'm a big fan of pfSense.

 

[Brandon Lucas]

Fantastic. Thank you guys. Appreciate the info!

 

[briankelly63]

You need to work with the internet provider to check this thing end to end. Back at their end they should be able to see issues with the circuit. As noted speed is probably not the issue. People think of a digital circuit either working or its not but that's far from the truth. When you use a circuit like this for webpages and email you'd never notice all the issues that may be there.

 

[Chris Sweeney]

Recommend you look at using G729 as well to limit the amount of bandwidth you need.

 

[Hyksos]

Based on the insufficient info provided so far, using G729 could actually make it way worst for this type of scenario and not better.
Static and Lag are not the same thing and mean completely different thing to different people.

Not saying that's bad advice, just saying G729 is for specific scenario and Rural Crappy DSL might not be one of them, but yes, it depends what exactly, is crappy about this rural DSL link. The upstream speed? or the quality, or the round trip time?...

 

[psetti1]

Bandwidth isn't the problem here unless it's being overutilized. Technically 3mb would be enough for 48 calls using ulaw. The problem is latency. You need to use a jitterbuffer.

 

[Chris Sweeney]

Bandwidth isn't the problem here unless it's being overutilized. Technically 3mb would be enough for 48 calls using ulaw. The problem is latency. You need to use a jitterbuffer.

Assuming it is symmetric DSL yes, but assuming ADSL 4 phone calls is most likely using all the bandwidth here. You also have to account for the IP overhead not just the codec bandwidth of 64K, its actually about 87K per call for SIP. 48 calls would actually take about 4.1mb and leave nothing for web browsing or whatever else they are doing on the computers.

 

[hbonath]

QoS is imperative. I'm talking real-true priority egress queuing. Not bandwidth shaping, not home-grade router QoS.
This is most imperative if the data/voice are using the same internet connection.
I recommend a Cisco 1921 for a small connection. May be able to get away with an 800-series router as well if the site is small enough.
Now if the ISP is sketchy (you can test latency by doing an extended ping to your PBX with only a PC plugged into the router) then yes, jitterbuffers could be used to help with this.
QoS is key however in any successful VoIP deployment.