What can I do about Latency?

[richard]

Hi

I have a question on the cause of latency and also would like to know if there is anything I can do with it.

Basically the problem is that when I use Voxalot I often get alot of latency in the call. Sometimes 3 to 4 seconds of delay :-( When I change to using vBuzzer or VoipBuster directly the latency is not noticable. Usually less than one second. I don't remember ever having a problem with Latency on vBuzzer or VoipBuster but quite frequently on Voxlot.

Can anyone tell me what factors cause latency and if there is anything I can do about it. Also, where this is an issue with Voxalot and not the other two ITSP I use.

My environement is:

Sipura SPA3000 & SPA 841
5Mbps Internet Connection
US Robotics Router

I connect via us.voxalot.com and I use stun stun01.sipphone.com:3478.

Any help would be greatly appreciated.


Richard

[ctylor]

It is a bad sign, it sounds like the voice data is going through Voxalot's servers on the way to you, wasting valuable time when it should be going directly between you and your provider. I am not sure of any quick fixes, just making sure your Sipura settings are good, the STUN and NAT support settings properly set for your connection, opening up ports in your router to your Sipuras, and perhaps setting "Enable symmetric NAT handling (if unsure, set to "Yes")" to "No". Beyond that, if it persists, you might not be a good candidate for using Voxalot. I don't believe I suffer your problem--as far as I can tell, utilizing Voxalot adds no delay for me--so for some people it does work without any extra delays.

[skandymicky]

If you are not from the US... did you try to use the european server eu.voxalot.com?

[richard]

I'm in Canada so the us.voxalot.com would be the best server.

I still haven't got any insight in the factors that contribute to latency? Could it be codec choices? Internet Speeds? I'm curious what could be causing this.

Richard

[martin]

Originally Posted by richard

I'm in Canada so the us.voxalot.com would be the best server.

I still haven't got any insight in the factors that contribute to latency? Could it be codec choices? Internet Speeds? I'm curious what could be causing this.

Richard

On the 16th when the new web-site is released, there will be a couple of new options that allow members to explicitly control RTP proxing.

This new web interface will allow you to manually setup which providers you do or do not want proxied.

At the moment, the system automatically makes that decision for you.
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[richard]

Hi Martin

Ah, so this is what CTaylor was saying when he said "it sounds like the voice data is going through Voxalot's servers on the way to you". I didn't realize that these VoIP calls would actually go through a third party proxy. It thought except for the call setup, everything would be peer-to-peer.

As a bit of education for me, why would the system think going through a proxy is better?

Also, what difference does enabling symmetric NAT handling make?

I'm trying to understand what causes latency.

Thanks for helping me understand :-)

Richard

[martin]

Originally Posted by richard

Also, what difference does enabling symmetric NAT handling make?

Setting symmetric NAT handling to No turns off Voxalot's NAT handling/detection logic and essentially leaves the responsibility of NAT handling to the client.

This is only half the picture though. When calls go via one of the embedded providers there is still the possibility that the voice streams are bridged.

Our observations are that this happens quite a lot, hence the reason we are introducing a new setting (made available to all members free and premium) to allow members to control RTP Proxy settings down at the provider level.

Once we release the new site on the 16th hopefully things will be a bit more clear.
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