> From: asterisk-biz-bounces@lists.digium.com [mailto:asterisk-biz-
> bounces@lists.digium.com] On Behalf Of Alex Balashov
> Sent: Monday, October 05, 2009 2:25 PM
>
> The proper approach to this problem is to have the CPE set a DiffServ
> codepoint bit (e.g. EF) on RTP packets, rather like the 'tosaudio'
> parameter in sip.conf in Asterisk. This bit can then be matched on
> and prioritised (and propogated upstream if need be).
>
> I am under the impression this is something most CPE can do.
Certainly would agree, however, do upstream providers strip or modify
DSCP?
We use Comcast and I'm reasonably sure that they're rewriting DSCP to
0x20/cs1 on anything above 0x00. My initial plan for QoS was to use DSCP
but it seems various traffic (including, but not all, VoIP) was tagged
the same 0x20 from them so it was pointless for us.
In a simple router situation I can see QoS being easier with IAX as you
simply prioritize udp/4569. We're using PIX/ASA so we do SIP inspect,
prioritize the RTP and rate limit all other traffic to below 80% of our
purchased service. It's not DSCP but we're unable to use a true DSCP
method due to our upstream.
So far so good, it works well for us on a small scale.
sl
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