Path-coupled signaling for NAT/firewall traversal

Many complex protocols negotiate secondary flows on the application layer. Examples of such protocols include many peer-to-peer applications, SIP, H.323, etc. In general, this prevents firewalls from allowing them and through NATs public/private address space mapping from routing them. In this paper, we describe the requirements and design of an end-application triggered, path-coupled signaling protocol for NAT/firewall traversal. Finally, we show a prototypical implementation and discuss preliminary performance evaluation.