Peer-to-Peer (P2P) communication across middleboxes

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Status of this Memo

   This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026.  Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups.  Note that other groups may also distribute working documents as Internet-Drafts.

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Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This memo documents the methods used by the current peer-to-peer(P2P) applications to communicate in the presence of middleboxes such as firewalls and network address translators (NAT). In addition, the memo suggests guidelines to application designers and middlebox implementers on the measures they could take to enable immediate, wide deployment of P2P applications with or without requiring the use of special proxy, relay or midcom protocols. 

Table of Contents

   1.  Introduction .................................................
   2.  Terminology ..................................................
   3.  Techniques for P2P communication over middleboxes ............
       3.1.  Relaying ...............................................
       3.2.  Connection reversal ....................................
       3.3.  UDP Hole Punching ......................................
             3.3.1.  Peers behind different NATs ..................
             3.3.2.  Peers behind the same NAT ....................
             3.3.3.  Peers separated by multiple NATs ...............
             3.3.4.  Consistent port bindings .......................
       3.4.  UDP Port number prediction .............................
       3.5.  Simultaneous TCP open ..................................
   4.  Application design guidelines ................................
       4.1. What works with P2P middleboxes .........................
       4.2. Applications behind the same NAT ........................
       4.3. Peer discovery ..........................................
       4.4. TCP P2P applications ....................................
       4.5. Use of midcom protocol ..................................
   5.  NAT design guidelines ........................................
       5.1. Deprecate the use of symmetric NATs .....................
       5.2. Add incremental Cone-NAT support to symmetric NAT devices
       5.3. Maintaining consistent port bindings for UDP ports .....
             5.3.1.  Preserving Port Numbers ........................
       5.4. Maintaining consistent port bindings for TCP ports .....
       5.5. Large timeout for P2P applications ......................
   6.  Security considerations ......................................