[Cerowrt-devel] debugging sip udp weirdness in 3.3.[68]

Dave Taht dave.taht at gmail.com
Fri Aug 10 14:06:48 EDT 2012

On Thu, Aug 9, 2012 at 6:07 PM, Michael Mee <mm2001 at pobox.com> wrote:
> [Hoping to help with feedback, but not sure if this is the right place.
> Apologies and please redirect me if so!]
> When I run the stock Android Jelly Bean SIP client (part of the dialer)
> over my Netgear WNDR3800 on 2.4g (CEROwrt) with 3.3.8 (and also 3.3.6
> prior), the conversations are poor. It sounds like packets are being
> dropped all over the place. This is despite plenty of bandwidth
> available (ADSL2 at 15 x 1.5Mbps, IPv4). Other (generic, non-CEROwrt)
> wireless networks I've tried work well, as does the 4G or 3G service
> from my phone. I'm running the GSM codec which consumes about 30kbps.
> This is a vanilla SIP connection, using UDP. It doesn't happen all the
> time - about 50% (+/- 25%!) of calls.

Yes, this is interesting.

Are you using QoS on the outgoing link at all?

One bug that cropped up in releases prior to 3.3.8-11 was that the VI and BK
portions of the wireless spectrum were being "interestingly" stomped
on by the ath9k driver.

http://www.bufferbloat.net/issues/402 and 401

As cerowrt is now doing extensive diffserv classification on wifi this
could possibly affect voip significantly. (the problem was generic to
the ath9k driver however)

I'm not ready with a new release of cerowrt yet, however.

Also we were using some settings for codel that were suboptimal. In
fact it's increasingly likely that no setting on the current fq_codel
is optimal in the spot on the wifi driver stack it's at.

> If this is interesting to anyone and I can help debug it by providing
> more information, I'm happy to. Or, feel free to say "Doh, of course it
> doesn't work, this is beta software at best. Go away!"

Oh, no, making sure wifi voip works well is very high on our priority list.

tcpdump a test stream (I can provide detailed syntax) and we can look
at the drop pattern.

> thanks, Michael
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel

Dave Täht
http://www.bufferbloat.net/projects/cerowrt/wiki - "3.3.8-6 is out
with fq_codel!"

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