[LARTC] voip quality/bandwidth/latency techniques

[dale]

I have voip quality issues I would like to minimize.  I have a ~= 
3M/384k (Comcast) cable modem and a CentOS based Linux router (SME 7, 
2.6.9 kernel) with 5 NAT'd devices (3 PCs "DHCP", 2 Vonage adapters 
"static 10.10.2.10-11").  The quality problems are audio cutting out and 
popping.  I tried the following (see below) based on a Cookbook example, 
but I still have audio popping.  I have noticed popping corresponding 
with web browsing, etc.  Any suggestions that may improve voip quality? 
  Also, are there any network metric capture/graphing tools that are 
helpful to analyze these type of issues.  I'm thinking of a graph that 
shows various network metrics.  I could watch the graph while using the 
phone and correlate graph spikes with audio pops.  Thanks in advance for 
your help.

Dale



tc qdisc del root dev eth1
tc qdisc add dev eth1 root handle 1: htb default 12
tc class add dev eth1 parent 1:  classid 1:1  htb rate 300kbit ceil 300kbit
tc class add dev eth1 parent 1:1 classid 1:10 htb rate 200kbit ceil 
300kbit prio 0
tc class add dev eth1 parent 1:1 classid 1:11 htb rate  50kbit ceil 
300kbit prio 1
tc class add dev eth1 parent 1:1 classid 1:12 htb rate  30kbit ceil 
300kbit prio 2
tc filter add dev eth1 parent 1:0 protocol ip prio 1 handle 1 fw classid 
1:10
tc filter add dev eth1 parent 1:0 protocol ip prio 2 handle 2 fw classid 
1:11
tc filter add dev eth1 parent 1:0 protocol ip prio 3 handle 3 fw classid 
1:12
iptables -t mangle -A PREROUTING --src 10.10.2.10 -j MARK --set-mark 0x1
iptables -t mangle -A PREROUTING --src 10.10.2.10 -j RETURN
iptables -t mangle -A PREROUTING --src 10.10.2.11 -j MARK --set-mark 0x1
iptables -t mangle -A PREROUTING --src 10.10.2.11 -j RETURN
iptables -t mangle -A PREROUTING -j MARK --set-mark 0x3