ClearFoundation

I'm having an interesting problem with Qos and VOIP lines.

I'm using a clearbox with 2 ISP line:
a)One high lantecy, high Bandwith line ADSL (for Web)
b)One low lantency, lower bandwith Symetric line (For Voip and IPSec VPN connections)

The problem is with the Voip lines. The audio starts to break up and they become completely unusable. Sometimes the line doesn't even have dial-tone. It only last for a few minutes, and I can't reproduce the problem.

I've spoken with our provider several times in the past months and they say that the problem is on our side (since they can't see any issues with either the DSL modem or their infrastructure.

the SIP VOIP connections only requires around 20k/sec of bandwith. I've reserved 75k in both upload and download speeds but it doesn't seems to help. Latency between the source and destination is almost always below 10msec (mtr running for several hours reports an average of 7.9msec). The SIP client are connected directly in the Clearbox (eth2 and eth3).

The only other traffic on that link is VPN connections, (either PPTP or IPsec) with remote customer sites. I'm not sure how is that traffic handle by the QoS algorithm, but in all the "file-transfer over IPSec" tests that I did, the VOIP connections didn't seems to be affected.

At this point I'm looking for any clues as to way the line breaks. It sound like a latency problem (or packet drop) but I'm not 100% sure.

Any suggestions?

I think I may have found possible source of confusion that didn't help my case. The documentation states (www.clearcenter.com/support/documentatio...user_guide/bandwidth):

Reserve bandwidth to/from a VoIP/SIP Provider

If you have a SIP provider for your VoIP system, you will want to reserve bandwidth for this traffic. You will need to provide two bandwidth rules – one for traffic from your provider, and one for traffic to your provider.
Traffic from SIP Provider

Nickname: from_sip
IP Address - Source: 1.2.3.4
Direction - Download
Rate - 800 kbps

Traffic to SIP Provider

Nickname: to_sip
IP Address - Destination: 1.2.3.4
Direction - Upload
Rate - 800 kbps


But what I did was set these rules:
1) Source: 192.168.2.10, Download, 75k rate
2) Source: 192.168.2.10, Upload, 75k rate
3) Destination: 1.2.3.4, Download, 75k rate
4) Destination: 1.2.3.4, Upload, 75k rate

Should I change these rules these instead?
1) Source: 192.168.2.10, Download, 75k rate
2) Source: 192.168.2.10, Upload, 75k rate
3) Destination: 192.168.2.10, Download, 75k rate
4) Destination: 192.168.2.10, Upload, 75k rate