VoIP stopping TCP traffic?
Hi List,
I am currently running a Knoppix-hd with 2.6 kernel. The machine is
connected to the internet through a 64k ISDN channel and to the LAN with
an ethernet realtek card. I also run asterisk on the box for my VoIP needs.
I usually have no issues _except_ when I place a VoIP phone calls. When
that happens, very quickly all non-voip traffic on the LAN crawls to a halt:
- I can't SSH from my laptop into the gateway
- I can't SSH from the gateway to my laptop
- Any existing open ssh connection freezes as soon as I issue a command
(ls, vim, whatever)
- Ping works fine
- Accessing the net from the gateway works fine
- Accessing the net from the LAN is completely broken
Phone call is perfect throughout though. Once the phone call is over,
traffic works again again (but I have to kill my SSH sessions, restart
any download, etc).
So it seems that when I place a phone call, all TCP traffic is killed
(SSH, FTP) for good while UDP works fine (VoIP, UDP).
Since I've been playing with traffic shaping, I thought this might be
the problem. Hence I do:
/etc/init.d/iptables clear
iptables -t nat -A POSTROUTING -o ippp0 -j MASQUERADE
tc qdisc del dev ippp0 root
tc qdisc del dev ippp0 ingress
tc qdisc del dev eth0 root
tc qdisc del dev eth0 ingress
In order to remove any firewall or traffic shaping issues - but the
behavior remains the same. Maybe there is some extra shaping I've done
without realising that is not cleared by those commands? I vaguely
remember playing with mtu through the 'ip' command.
Note that if I physically go on the gateway when a phone call is in
progress everything is fine: low load average, and I can download
anything I like from the net, but SSHing into any machine in the LAN is
impossible, although ping is.
Any idea of what's going on?
Cheers,
Jean-Michel.
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