Packet Loss cause of VOIP choppiness?

Hi there,
We have been using a voice over IP line for our business in Mexico via a 1Mb cable modem connection. Recently the calls have been choppy. I have tested the bandwidth and the latency (100 ms to Yahoo server in US) and they seem fine.  However, I have been running a trace and there is packet loss of 10-50% on almost every hop (17 hops on average) to Yahoo's US server.  We are connected via a netware 24-port 10/100 switch which is connected into a Vonage VOIP appliance which is connected into a motorola cable modem.  I have a similar setup at my home in Mexico and experience great call quality and minimal packet loss.  The only other relevant information is they recently put a filter on our cable modem, with the hopes of improving the quality, it does not seem to have worked I guess.

If anyone could help map out what I should do to test and find the source of this packet loss problem, that would be great.

Thanks,
Jaeson
jaesonrosenfeldAsked:
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JonShCommented:
Hmm....one of the first things I would do is run the Brix test for VOIP:
http://www.testmyvoip.com/

But that packet loss you describe is incredible....if I read you right, you lose a percentage on every hop?  if I send 100 packets on a 17 hop journey, and I lose 10% on each hop, I get 17/100 packets throughput.  Um, that's got to be an ISP problem.  How did you show the loss at each hop?  I'm questioning your numbers cause they seem that bad....

Do you experience any loss in your own network? Another thought....you say it works fine from home?  So swap the cable modems and see if the problem follows the modem...

Also test the latency/packet loss to some other sites.  How about Cisco, Ibm, Microsoft, Ebay.  Do you get the same packet loss?



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jaesonrosenfeldAuthor Commented:
I have not been able to swap the modems yet, but I did run the Brix report that you pointed to. I paste it below.  It appears from the report that packet loss is indeed the problem, but only on the return (which explains the terrible voice quality that we hear, but the good voice quality on the other end that they are hearing).  Anyways, here is the detailed report from Brix below, let me know if this sheds any light.

Best,
Jaeson

 Test Details
The information below explains why your call quality score (MOS) was less than perfect.

Find the results that you want more quickly...
 Jump to:     Media Quality     Signaling Quality     VoIP Traceroute  
 
MOS Analysis from You TO Boston
 
 Media Quality MOS   4.2 / 5.0
(Best with G.711 is 4.4)  
 

 
Degradation Sources
  Codec 0.57 76.7%
  Latency 0.05 6.5%
  Packet Discards 0.12 16.5%
  Packet Loss 0.00 0.0%
 
Codec G.711 (PCM at 64kbps,
 20ms RTP payload,
 80kbps IP BW)
Round-Trip
Latency 210 ms
Packet Discards 0.5%  
Packet Loss 0.0%  
Loss Periods Min: 20 ms
Avg: 20 ms
Max: 20 ms
Random Loss
 
Jitter Min: 0 ms
Avg: 5 ms
Max: 38 ms
 
 Signaling Quality Post-Dial Delay 160 ms
Call Setup Time 180 ms
Media Delay 380 ms
   MOS Analysis FROM Boston To You
 
 Media Quality MOS   1.3 / 5.0
(Best with G.711 is 4.4)  
 

 
Degradation Sources
  Codec 0.58 15.6%
  Latency 0.09 2.3%
  Packet Discards 0.06 1.5%
  Packet Loss 2.98 80.6%
 
Codec G.711 (PCM at 64kbps,
 20ms RTP payload,
 80kbps IP BW)
Round-Trip
Latency 210 ms
Packet Discards 0.3%  
Packet Loss 14.5%  
Loss Periods Min: 20 ms
Avg: 20 ms
Max: 80 ms
Burst Loss
 
Jitter Min: 0 ms
Avg: 1 ms
Max: 30 ms
 
 Signaling Quality Post-Pickup Delay 203 ms
Call Setup Time 212 ms
Media Delay 233 ms
 
 
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JonShCommented:
Hmm...You should see this in other things (packet loss to you), like generically downloads of all kinds, etceteras.  My next stop would be to take the Brix Report over to my ISP's office and say excuse me but we seem to have a problem here.  Maybe they set up QoS on their routers/switches and weighted the traffic backwards?
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jaesonrosenfeldAuthor Commented:
OK, one last question before I assign the points to you.  What do you mean by this statement: Maybe they set up QoS on their routers/switches and weighted the traffic backwards?

Just for my own information really.

Best,
Jaeson
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JonShCommented:
QoS stands for QualityofService, and it's any number of ways of deciding which packets are supposed to have prededence over others....for instance, VoIP traffic should be identifiable based on call setup, let's let those packets have the greatest priority so we preserve voice quality at the expense of say a file transfer going on.......

That's how QoS is supposed to work.  Now suppose they identify the right packets and mistakenly give them the lowest precedence instead of the highest? :)

voila.....!
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