Michael,

Personally I use "htb", seems to give me the best results.  I think the newer 
'hfsc' might work well for general mixed traffic, but I have found that 'hfsc' 
is too slow to adjust for VoIP to be its best.

Personally I set my Down/Up speed right at my advertised values (28 M / 4 M), 
if you want to knock them down by 5% that would be fine, a good starting point. 
 This will automatically leave about 20% of the up-link free for the highest 
priority class.  If you need more than 20% for your SIP traffic, then you can 
reduce you up-link speed value.

Regardless you should test by calling yourself via an 
inside-to-outside-to-inside call, place yourself on hold, listen to the hold 
music.  Then run a speed-test, the up-link test will show the worst case 
scenario.

#1 ) In this day and age much of the traffic will be classified by DSCP 
markings by default, which is honored, but be sure to set those in sip.conf:
--
tos_sip=cs3                     ; Sets TOS for SIP packets.
tos_audio=ef                    ; Sets TOS for RTP audio packets.
tos_video=af41                  ; Sets TOS for RTP video packets.
tos_text=af41                   ; Sets TOS for RTP text packets.
--
https://wiki.asterisk.org/wiki/display/AST/IP+Quality+of+Service

Setting the SIP RTP port range is still fine, and what we had to do in the 
Asterisk 1.2 days.

You can also do some tweaks here:

>From the Network tab -> Firewall Plugins: [ traffic-shaper ]

You can define/tweak some of the priorities, but the defaults should be good 
for the typical situation.  Should you have a NAS doing offsite backups or 
such, you may want to define SHAPER_P2P_HOSTS.


#2)  A 5% reduction is fine, you could start with no reduction and start from 
there.  Each ISP probably has it's own sweet spot. Be sure to test.


#3)  Downlink shaping is not as critical since the bottleneck is usually on the 
up-link, but it simply discards bursts of data higher than the limit.

It seems to me that getting quality voice connections is easier today than it 
was a few years ago.  Possibly the bigger pipes are the reason, possibly some 
traffic shaping is done by the ISP ?  I don't use IAX anymore. :-)  Also people 
are now so used to cell phones, crappy audio is tolerated more than it was in 
the past. :-)

Regardless enabling traffic shaping is good practice, if for nothing else to 
control buffer-bloat.

Bufferbloat
http://en.wikipedia.org/wiki/Bufferbloat

Lonnie

PS: We use 'tc' in the traffic shaper plugin to perform the shaping.


On Nov 17, 2012, at 3:53 PM, Michael Knill wrote:

> To the group
> 
> I realise that I don't completely understand how the traffic shaping works on 
> AstLinux and I really need to.
> I have set the following:
> 
> Type - I am using hfsc which I assume is the best
> Downlink speed - I am setting this to slightly less than than my DSL modems 
> reported speed e.g. 95%
> Uplink speed -  I am setting this to slightly less than than my DSL modems 
> reported speed e.g. 95%
> VoIP UDP Ports - 16384:16639. The same as I have set in rtp.conf
> 
> My questions are:
> 
> 1) Does the script only use the VoIP ports for queue classification. It 
> appears that even though I have the range set in rtp.conf, it only affects my 
> allocated port and not the destination port to my Service provider which is 
> not in this range? Wont this mean that I am not prioritising rtp on my 
> uplink? Can I force symmetrical RTP port allocation?
> 2) Is 95% ok for the reduction. Does anyone use a different formula
> 3) How does the Downlink traffic shaping work? Does it just restrict the 
> traffic flow of non VoIP traffic (e.g. not in the VoIP UDP Port Range) to fit 
> the Downlink traffic shaping envelope? 
> 
> What is everyone else doing?
> 
> Regards
> Michael Knill




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