Hi Saul,
On 11/26/2011 04:53 AM, Saul Ibarra Corretge wrote:
Hi Andreas,
On Nov 25, 2011, at 5:35 PM, Andreas Sikkema wrote:
Guys,
I'm currently routing some calls from one VoIP platform to another
OpenSIPS based platform using two ISDN to SIP gateways that are
connected back to back. This setup is quite recource heavy, expensive
and has a limited capacity. So I'm thinking of connecting both
platforms using a (well protected) SIP interconnection. That part is
easy, we've done that before.
The problem is in the RTP some phones, connected to the old platform,
are sending out. Every 30 seconds or so they send out 0 length RTP
messages that some SIP UAs really don't like. Some hardware will
hangup a call when it receives 0 length UDP frames in an RTP stream,
others will stop handling the incoming RTP traffic allthogether
resulting in one way audio. The 0 length UDP messages appear to
conform to RFC6263 (http://tools.ietf.org/html/rfc6263) which is
really new...
I've tried talking to the manufacturer of the phones, talked to the
supplier of the VoIP platform, talked to everyone and their neighbour
and all say it's not their problem. I've identified two places where
*I* can solve it.
- In our core routers
- At every mediaproxy machine
The first option is sub-optimal, I don't want all our routers having a
drop-this-packet "firewall" line for various reasons. The second
option I've started to like more and more. There's two ways to resolve
this:
- I just make sure I add an iptables call somewhere in the startup script, or
- I/We add an RFC6263 configuration option to Mediaproxy that does
more or less the same
The iptables call would drop all 0 length UDP messages sent to the
mediaproxy ports.
Am I wrong in my thinking?
Once the call is up (a single RTP packet was received from each endpoint)
MediaProxy will setup a conntrack rule, and the Linux kernel will do the
relaying. This means that MediaProxy itself cannot inspect the RTP packets at
that point, because they are not traversing user-space code anymore.
As far as understood, what Andreas wants to do is to drop such packages
from iptables rule, not necessarily from media relay software.
Regards,
Bogdan
--
Bogdan-Andrei Iancu
OpenSIPS Founder and Developer
OpenSIPS solutions and "know-how"
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