[OpenSIPS-Users] Filtering out RFC6263 traffic on Mediaproxy

[Andreas Sikkema]

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?

-- 
Andreas Sikkema