As you know there are (at least) two options to resolve the symmetric NAT traversal with SIP/RTP: 1. nathelper module and rtpproxy server 2. mediaproxy module and dispatcher/mediaproxy server However during our test we discovered that in terms of efficiency there is a big difference between these two approaches. Using mediaproxy and rtp generator tool (comes with mediaproxy server) on 1G RAM 3000 MHZ cpu machine, server was able to handle about 200 calls at the same time (rtpgenerator rate parameter set to 100). To be able to compare mediaproxy result to rtpproxy I made some modifications inside the rtpproxy server code and used the same rtpgenerator (there is different communication interface that I modified) and the result of the same test was quit different. Using the same environment I was able to generate 900 calls, I also made additional normal call (SER/mediaproxy/proxydispatcher/rtpproxy) thru this rtprpoxy to test quality of voice. So, my question is why there is not compatibility between these servers? There would be useful to implement these small changes into the rtp proxy code (I can send my version) and take all advantages of mediaproxy load balancing and rtpproxy efficiency. Darek