QoS and VoIP

sebelk · 12-10-2009, 09:46 AM

Hi,

I work on a organization that have a little office near to main building. That office has only 3 PC's and 3 telephone. Phones are "connected" to an asterisk server.

The problem is that ISP service is not simmetric. ISP provides 1 bit for download and hopefully 256k for upload. PC's are connected to a hub that is connected to a Linksys WRT54GL router with OpenWRT which in turn is connected to ISP modem.

I'd wonder if I can tweak in some way qos on OpenWRT in order to avoid "jerky" voice when someone make a phone call.

The following is my script, please could you help me to improve it?

Thanks in advance

Code:

UPVOIPSVR=X.X.X.X                                      
MYORGNET=X.X.X.Y/24                                           
IFWAN=eth0.1                                                    
PHYSICALBW_MBPS=10 # mbps                                       
let PHYSICALBW=$PHYSICALBW_MBPS*1000000 # bps                   
CONTRACTBW_MBPS=1  # mbps 
let CONTRACTBW=$CONTRACTBW_MBPS*1000000  # bps                               
CODEC=g711                                                                   
CALLBW_KBPS=87 # kbps                                                        
let CALLBW=$CALLBW_KBPS*1000 # bps                                           
FRAMEINTERVAL_MS=20 # in miliseconds                                         
CALLS=3                                                                      
let VOIPBW=$CALLS*$CALLBW                                                    
let VOIPBW_KPBS=$VOIPBW/1000                                                 
let NONVOIPBW=$CONTRACTBW-$VOIPBW                                            
let NONVOIPBW_KPBS=$NONVOIPBW/1000                                           
let NONVOIPBWUP=$NONVOIPBW/4
let NONVOIPBWUP_KBPS=$NONVOIPBWUP/1000
UPVOIPSVR=200.69.213.172                                        
UPNET=200.69.213.0/24                                           
IFWAN=eth0.1                                                    
PHYSICALBW_MBPS=10 # mbps                                       
let PHYSICALBW=$PHYSICALBW_MBPS*1000000 # bps                   
CONTRACTBW_MBPS=1  # mbps 
let CONTRACTBW=$CONTRACTBW_MBPS*1000000  # bps                               
CODEC=g711                                                                   
CALLBW_KBPS=87 # kbps                                                        
let CALLBW=$CALLBW_KBPS*1000 # bps                                           
FRAMEINTERVAL_MS=20 # in miliseconds                                         
CALLS=3                                                                      
let VOIPBW=$CALLS*$CALLBW                                                    
let VOIPBW_KPBS=$VOIPBW/1000                                                 
let NONVOIPBW=$CONTRACTBW-$VOIPBW                                            
let NONVOIPBW_KPBS=$NONVOIPBW/1000                                           
let NONVOIPBWUP=$NONVOIPBW/4
let NONVOIPBWUP_KBPS=$NONVOIPBWUP/1000

let INTERVALCAPACITY=$CONTRACTBW*$FRAMEINTERVAL_MS/1000/8 # bytes
let INTERVALVOIPUSAGE=$CALLS*$CALLBW*$FRAMEINTERVAL_MS/1000/8 #bytes
let NONVOIPBURST=$INTERVALCAPACITY-$INTERVALVOIPUSAGE

tc qdisc add dev $IFWAN ingress handle ffff:
tc filter add dev $IFWAN parent ffff: protocol ip prio 1 u32 \
    match ip src $UPVOIPSVR \
    flowid ffff:1
tc filter add dev $IFWAN parent ffff: protocol ip prio 2 u32 \
    match ip src 0.0.0.0/0 \
    police rate $NONVOIPBW burst 100kb drop \
    flowid ffff:2
tc qdisc add dev $IFWAN root handle 1:0 prio
tc filter add dev $IFWAN parent 1:0 protocol ip prio 1 u32 \
    match ip dst $UPVOIPSVR \
    police rate $VOIPBW burst 100kb continue \
    flowid 1:1
tc filter add dev $IFWAN parent 1:0 protocol ip prio 2 u32 \
    match ip dst 0.0.0.0/0 \
    flowid 1:2
tc qdisc add dev $IFWAN parent 1:2 handle 12: tbf \
        rate $NONVOIPBWUP burst $NONVOIPBURST limit 100kb

let INTERVALCAPACITY=$CONTRACTBW*$FRAMEINTERVAL_MS/1000/8 # bytes
let INTERVALVOIPUSAGE=$CALLS*$CALLBW*$FRAMEINTERVAL_MS/1000/8 #bytes
let NONVOIPBURST=$INTERVALCAPACITY-$INTERVALVOIPUSAGE

tc qdisc add dev $IFWAN ingress handle ffff:
tc filter add dev $IFWAN parent ffff: protocol ip prio 1 u32 \
    match ip src $UPVOIPSVR \
    flowid ffff:1
tc filter add dev $IFWAN parent ffff: protocol ip prio 2 u32 \
    match ip src 0.0.0.0/0 \
    police rate $NONVOIPBW burst 100kb drop \
    flowid ffff:2
tc qdisc add dev $IFWAN root handle 1:0 prio
tc filter add dev $IFWAN parent 1:0 protocol ip prio 1 u32 \
    match ip dst $UPVOIPSVR \
    police rate $VOIPBW burst 100kb continue \
    flowid 1:1
tc filter add dev $IFWAN parent 1:0 protocol ip prio 2 u32 \
    match ip dst 0.0.0.0/0 \
    flowid 1:2
tc qdisc add dev $IFWAN parent 1:2 handle 12: tbf \
        rate $NONVOIPBWUP burst $NONVOIPBURST limit 100kb

nimnull22 · 12-10-2009, 09:54 AM

Before doing any changes, make some experiment - change HUB to (not cheap) SWITCH, then disconnect any computers from switch, and try to call from ALL phones at the same time.

Why I suggest it to you, because these problems could be outside of your network.