The nat_traversal module provides support for handling far-end NAT traversal for SIP signaling. The module includes functionality to detect user agents behind NAT, to modify SIP headers to allow user agents to work transparently behind NAT and to send keepalive messages to user agents behind NAT in order to preserve their visibility in the network. The module can handle user agents behind multiple cascaded NAT boxes as easily as user agents behind a single level of NAT. The module is designed to work in complex environments where multiple SIP proxies may be involved in handling registration and routing and where the incoming and outgoing paths may not necessarily be the same, or where the routing path may even change between consecutive dialogs. The nat_traversal functionality is built primarily for IPv4 NAT handling and hasn't been adapted to support IPv6 session keepalives.
Copyright © 2008 Dan Pascu
