Re: [LARTC] Random Early Detection

[Jason Bath <jbath@ckua.org>]

Oops.  I was referring to changing the sfq to red or gred, not pfifo.

Jason Bath
Network Administrator
CKUA Radio Network
780.428.2017


Jason Bath wrote:
> I'm streaming audio over a WAN that is 1.5Mbit/s.  The audio has to go 
> both ways and can be over tcp or udp.  The manufacturers recommend udp 
> as it has less overhead but has a higher chance of dropping out. The 
> audio requires 130-200kbit/s in each direction for a combined 
> 260-400kbit/s.  I have two transparent bridges on either side of the WAN 
> to do traffic control.  I split it so that each bridge is capped at half 
> of the total bandwidth allowed with some leeway for performance since 
> most network traffic is one-sided in the exchange.  ie: client at co-lo 
> makes http request which is small but then receives a huge amount of 
> data respectively to that http request.
> 
> My problem at this point is that this WAN handles all traffic from our 
> co-location - web, mail, ftp, smb and the audio.  I find I get packet 
> loss on the audio when I'm doing smb file transfers (usually in the 
> handshake portion of the transaction) and almost everytime the co-lo 
> uses the web.  I'd make a separate rule for the web but it doesn't fix 
> the general problem.
> 
> I'm wondering if my problem is global synchronization and if RED would 
> help quell my problem.  Or else I'm  handling the bursty traffic 
> improperly and need to tweak my current config.  I tested a line or two 
> with red but I found the man page a bit misleading in regards to the 
> burst.  My original line was:
> 
> tc qdisc add dev $DEV0 parent 1:20 handle 11: red limit 400kbit min 3000 
> max 6000 avpkt 1000 burst 40000
> 
> Yes, the 40000 is really high and the computer warned me about it - then 
> the network dropped to nothing until I reverted to the old pfifo line. 
> The man page recommended burst = (min + min + max) / (3 * avpkt).  I 
> understand that should be in bytes, but the command calls for number of 
> packets.
> 
> Any tips or hints?
> 
> This is my script at the moment.  I've applied all the rules on both 
> interfaces in the case that someone fiddles with ethernet cables at the 
> co-lo and can't remember which interface to put them into (Yes, my bad 
> for not labeling but if something goes wrong with the co-lo, I'm 300km 
> away)
> 
> 
> #!/bin/bash
> DEV0=eth0
> DEV1=eth1
> tc qdisc del root dev $DEV0 2> /dev/null
> tc qdisc del root dev $DEV1 2> /dev/null
> sleep 2
> 
> tc qdisc add dev $DEV0 root handle 1: htb default 20
> tc qdisc add dev $DEV1 root handle 2: htb default 20
> 
> tc class add dev $DEV0 parent 1: classid 1:1 htb rate 900kbit ceil 900kbit
> tc class add dev $DEV1 parent 2: classid 2:1 htb rate 900kbit ceil 900kbit
> 
> # audio
> tc class add dev $DEV0 parent 1:1 classid 1:10 htb prio 0 rate 200kbit
> tc class add dev $DEV1 parent 2:1 classid 2:10 htb prio 0 rate 200kbit
> # everything else
> tc class add dev $DEV0 parent 1:1 classid 1:20 htb prio 2 rate 400kbit 
> ceil 400kbit
> tc class add dev $DEV1 parent 2:1 classid 2:20 htb prio 2 rate 400kbit 
> ceil 400kbit
> 
> # audio ports tcp
> tc filter add dev $DEV0 protocol ip parent 1:0 u32 match ip dport 2001 
> 0xffff flowid 1:10
> tc filter add dev $DEV1 protocol ip parent 2:0 u32 match ip dport 2001 
> 0xffff flowid 2:10
> tc filter add dev $DEV0 protocol ip parent 1:0 u32 match ip sport 2001 
> 0xffff flowid 1:10
> tc filter add dev $DEV1 protocol ip parent 2:0 u32 match ip sport 2001 
> 0xffff flowid 2:10
> # audio ports udp
> tc filter add dev $DEV0 protocol ip parent 1:0 u32 match ip dport 2002 
> 0xffff flowid 1:10
> tc filter add dev $DEV1 protocol ip parent 2:0 u32 match ip dport 2002 
> 0xffff flowid 2:10
> tc filter add dev $DEV0 protocol ip parent 1:0 u32 match ip sport 2002 
> 0xffff flowid 1:10
> tc filter add dev $DEV1 protocol ip parent 2:0 u32 match ip sport 2002 
> 0xffff flowid 2:10
> 
> 
> tc qdisc add dev $DEV0 parent 1:10 handle 10: pfifo
> tc qdisc add dev $DEV0 parent 1:20 handle 11: sfq perturb 10
> tc qdisc add dev $DEV1 parent 2:10 handle 10: pfifo
> tc qdisc add dev $DEV1 parent 2:20 handle 11: sfq perturb 10
> 
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