Hello,
I just found the great howto and started shaping my internet connection. The
howto's last update is a liitle in the past now so I have some questions
about how things are done the best way nowadays ;-)
To ensure a stable and low latency voip communication I added an HFSC qdisc to
device ppp0 (1 Mbit SDSL). There are two classes (by now): One for SIP and
RTP and one for the rest.
Question 1: I defined the voip qdisc as
tc class add dev ppp0 parent 1:1 classid 1:11 \
hfsc sc umax 1500b dmax 30ms rate 500kbit ul rate 900kbit
but "tc -s class show dev ppp0" shows
class hfsc 1:11 parent 1:1 sc m1 0bit d 6.0ms m2 500000bit \
ul m1 0bit d 0us m2 900000bit
Where does the "0bit d 6.0ms" come from, (what does the other stuff exactly
mean) and what would be a good setting for voip traffic?
This qdisc only affects outgoing traffic. But I also want to control incoming
packets and keep the isp's queue empty.
Question 2: What is the best solution for doing this: ingress qdisc, IMQ, ...
(thers's only one link to isp)?
Much traffic on this line is UDP traffic (OpenVPN).
Question 3: If I do policing on incoming traffic, do UDP transmissions care
about dropping and reduce transmit speed?
If I begin to control incoming traffic I only want to drop packets that are
non voip traffic.
Question 4: Is it possible to control what packets are dropped?
I always want to have enough bandwith for incoming voip traffic. But limiting
the other stuff to static 180 kbit only because voip packets could sometimes
reach a maximum of 800 kbit sounds not so good.
My idea: A script that periodically (or even better: triggered by asterisk)
controls the parameters for the ingress shaper (depending on the actual
upload traffic produced by voip which could easily be measured with tc).
Question 5: Is that possible? Is this necessary at all? Is there already a
solution?
Regards
Daniel
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