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. Regards, -- Saúl Ibarra Corretgé AG Projects _______________________________________________ Users mailing list [email protected] http://lists.opensips.org/cgi-bin/mailman/listinfo/users
