This forum includes tips for maintaining the best audio quality possible with the Ooma System. If your Ooma system is having issues with dropped calls, static audio or echo, look here for assistance.
#24790 by Zxel
Wed Oct 07, 2009 1:15 pm
The Question:
Is it possible to manipulate the DSCP value ooma uses?

Background:
I have a business class comcast internet account on a fixed IP at my house and have had it for many years. Before ooma I had comcast's IP phone service, and it worked great (one of the reasons I even considered ooma). When I first got ooma I was using my comcast IP phone service as the plugin line to ooma, my phone service was good and I was impressed how phone calls out of ooma still gave my comcast phone number, so I initiated the phone number transfer to ooma. After the number was transfered and my comcast IP phone service terminated my call quality over ooma crapped out (a technical term ;)).

Research and Testing: Did some investigating on why my service was fine and now for some reason after canceling my comcat IP phone callers can only hear me for a few seconds of a call and then cannot hear me at all (although I can hear them fine). Here is what I found out:
1. Comcast's IP phone service works on a seperate network then their internet services.
2. VOIP line quality testing (using websites that do such testing) shows that my upload packet loss is horrible.
3. Normal internet traffic has 0 packet loss, in fact my line quality is exceptional and my upload/download speed is fine (16mbps DOWN / 2mbps UP).
4. Using a program by Nestsoft called ping plotter I was able to manipulate the DSCP value of the packets (I used UDP packets) and discovered to my HORROR that packets with a VOIP priority actually get the LOWEST priority on the comcast network.

Conclusion:
I can only conclude that comcast is manipulating it's network to intentionally give a bad experience to people running their own VOIP as a way to promote comcasts IP phone service. I'm posting this here to see if there is someway the ooma router's DSCP value can be manipulated, in my case to change it to a different DSCP value ( Using ping plotter testing I found the DSCP value comcast is using to actually prioritize traffic on their network).

It pisses me off on how insidious comcast is being, hoping to find a solution.
#24811 by Groundhound
Wed Oct 07, 2009 1:59 pm
You're right about the separate network for Comcast Digital Voice. Like you, I'm ever suspicious of what Comcast might do given their history. So far for me though the tests I get at: http://www.whichvoip.com/voip/speed_test/ppspeed.html, are usually pretty good. Hopefully what you're seeing is not a trend of things to come.

Edit:
Here's a test on my Comcast line, which is typical:

VoIP test statistics
--------------------
Jitter: you --> server: 3.4 ms
Jitter: server --> you: 7.4 ms
Packet loss: you --> server: 0.0 %
Packet loss: server --> you: 0.0 %
Packet discards: 0.0 %
Packets out of order: 0.0 %
Estimated MOS score: 3.9

Speed test statistics
---------------------
Download speed: 3061024 bps
Upload speed: 5611184 bps
Download quality of service: 94 %
Upload quality of service: 92 %
Download test type: socket
Upload test type: socket
Maximum TCP delay: 80 ms
Average download pause: 6 ms
Minimum round trip time to server: 68 ms
Average round trip time to server: 69 ms
Estimated download bandwidth: 16000000bps
Route concurrency: 5.227009
Download TCP forced idle: 53 %
Maximum route speed: 7710000bps
#24818 by Zxel
Wed Oct 07, 2009 2:22 pm
Here is what I get on the VOIP side:

VoIP test statistics
--------------------
Jitter: you --> server: 0.7 ms
Jitter: server --> you: 1.0 ms
Packet loss: you --> server: 73.4 %
Packet loss: server --> you: 0.0 %
Packet discards: 0.0 %
Packets out of order: 0.0 %
Estimated MOS score: 3.5

As you can see the packet loss is horrible.

I wouldn't conclude that comcast as a whole is implementing a "trash VOIP traffic" as a policy, it could be just my local area that is effected. Many comcast facilities operate semi-independantly, this could be just a technician's (or sales) way of boosting comcast's IP phone service - duno.
#24825 by niknak
Wed Oct 07, 2009 2:42 pm
why do you need the VOIP Line?
Just plug the ooma into your router on the ISP circuit
#24835 by Dennis P
Wed Oct 07, 2009 3:02 pm
Zxel wrote:Conclusion:
I can only conclude that comcast is manipulating it's network to intentionally give a bad experience to people running their own VOIP as a way to promote comcasts IP phone service. I'm posting this here to see if there is someway the ooma router's DSCP value can be manipulated, in my case to change it to a different DSCP value ( Using ping plotter testing I found the DSCP value comcast is using to actually prioritize traffic on their network).


Fascinating. Unfortunately there is no way to change the DSCP value right now. We can look into allowing this on the Telo, but probably can't provide an immediate solution. You may be able to find a router that will allow you to re-map the DSCP bits, that would probably be the best short term solution.
#24846 by Zxel
Wed Oct 07, 2009 3:38 pm
niknak wrote:why do you need the VOIP Line?
Just plug the ooma into your router on the ISP circuit


Not sure what you mean, I think you're misunderstanding the problem.

Dennis P wrote:Fascinating. Unfortunately there is no way to change the DSCP value right now. We can look into allowing this on the Telo, but probably can't provide an immediate solution. You may be able to find a router that will allow you to re-map the DSCP bits, that would probably be the best short term solution.


I have a linksys RVS4000 (cisco product now) and it does have very sophisticated QoS and DSCP manipulation but I think what you're talking about would require a proxy server (which I could do - but what a pain in the arse). I hope that ooma would consider adding DSCP as an advanced option in their Telo (and maybe packet size too, both would be big helps in achieving good call quality).

If you have another idea I'd like to hear it (anyone?). Maybe I should post a request for this in the feature request forum?

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