Peer-to-Peer Communication Across Network Address Translators. Bryan FordMassachusetts Institute of Technologybaford (at) mit.edu Pyda SrisureshCaymas Systems, Inc.srisuresh (at) yahoo.com Dan Kegeldank (at) kegel.com J'fais des trous, des petits trous toujours des petits trous - S. Gainsbourg Abstract: Network Address Translation (NAT) causes well-known difficulties for peer-to-peer (P2P) communication, since the peers involved may not be reachable at any globally valid IP address.
The combined pressures of tremendous growth and massive security challenges have forced the Internet to evolve in ways that make life difficult for many applications. The Internet's new de facto address architecture is suitable for client/server communication in the typical case when the client is on a private network and the server is in the global address realm. One of the most effective methods of establishing peer-to-peer communication between hosts on different private networks is known as “hole punching.”
The rest of this paper is organized as follows. 2.2 Relaying . Upper/Lower Bounds On NAT Timer - FixUnix - Unix Linux Forum. Getting the IP address a SIP message was received from - mobicents-public. AG Projects: The SIP infrastructure experts - Best practices for SIP NAT traversal. Are You Behind NAT? STUN. STUN (Simple Traversal of UDP through NATs (Network Address Translation)) is a protocol for assisting devices behind a NAT firewall or router with their packet routing. RFC 5389 redefines the term STUN as 'Session Traversal Utilities for NAT'. Note: The STUN RFC states: This protocol is not a cure-all for the problems associated with NAT. STUN enables a device to find out its public IP address and the type of NAT service its sitting behind.
STUN operates on TCP and UDP port 3478. The problems with STUN are not design flaws in STUN. STUN RFC RFC 3489, now obsolete (Oct 2008)STUN RFC RFC 5389 (Current as per October 2008)STUN standard is currently has been rewritten with RFC 5389. STUN provides a work-around to this problem via XOR_MAPPED_ADDRESS. Unfortunately, not all STUN servers support XOR_MAPPED_ADDRESS. STUN sits along side a number of techniques to achieving NAT traversal, these include TURN, ICE UPnP and Session Border controllers. NAT, STUN, and RTP proxy.
Are You Behind NAT? NAT traversal for the SIP protocol | freshmeat.net. NAT stands for Network Address Translation. It's the technology which allows most people to have more than one computer in their home and still use a single IP address. Most of the time, a router with NAT support gets data packets from the internal network (with internal IP addresses) and sends them to Internet, changing the internal IP address of each packet to the external one. What's RTP? RTP stands for Real-Time Transport Protocol. What's SIP? SIP (Session Initiation Protocol) looks in syntax like HTTP, human readable text. SIP sends an INVITE packet with the caller IP address and port for RTP to the FWD server, and from there, FWD forwards the call to the intended destination. SIP + NAT, an unsolvable problem? The problem with SIP and NAT is not actually a SIP problem, but the RTP problem.
Even if a lot of SIP implementations and carriers are based on the fact that NAT will always try to allocate the same port, that assumption is false. Author's bio. AG Projects: The SIP infrastructure experts - Best practices for SIP NAT traversal.