Network Address Translation (NAT) Behavioral Requirements for Unicast UDP
RFC 4787
Document | Type |
RFC - Best Current Practice
(January 2007; No errata)
Also known as BCP 127
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Last updated | 2015-10-14 | ||
Replaces | draft-ietf-behave-nat | ||
Stream | IETF | ||
Formats | plain text pdf html bibtex | ||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4787 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Magnus Westerlund | ||
Send notices to | (None) |
Network Working Group F. Audet, Ed. Request for Comments: 4787 Nortel Networks BCP: 127 C. Jennings Category: Best Current Practice Cisco Systems January 2007 Network Address Translation (NAT) Behavioral Requirements for Unicast UDP Status of This Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document defines basic terminology for describing different types of Network Address Translation (NAT) behavior when handling Unicast UDP and also defines a set of requirements that would allow many applications, such as multimedia communications or online gaming, to work consistently. Developing NATs that meet this set of requirements will greatly increase the likelihood that these applications will function properly. Audet & Jennings Best Current Practice [Page 1] RFC 4787 NAT UDP Unicast Requirements January 2007 Table of Contents 1. Applicability Statement . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Network Address and Port Translation Behavior . . . . . . . . 5 4.1. Address and Port Mapping . . . . . . . . . . . . . . . . . 5 4.2. Port Assignment . . . . . . . . . . . . . . . . . . . . . 9 4.2.1. Port Assignment Behavior . . . . . . . . . . . . . . . 9 4.2.2. Port Parity . . . . . . . . . . . . . . . . . . . . . 11 4.2.3. Port Contiguity . . . . . . . . . . . . . . . . . . . 11 4.3. Mapping Refresh . . . . . . . . . . . . . . . . . . . . . 12 4.4. Conflicting Internal and External IP Address Spaces . . . 13 5. Filtering Behavior . . . . . . . . . . . . . . . . . . . . . . 15 6. Hairpinning Behavior . . . . . . . . . . . . . . . . . . . . . 16 7. Application Level Gateways . . . . . . . . . . . . . . . . . . 17 8. Deterministic Properties . . . . . . . . . . . . . . . . . . . 18 9. ICMP Destination Unreachable Behavior . . . . . . . . . . . . 19 10. Fragmentation of Outgoing Packets . . . . . . . . . . . . . . 20 11. Receiving Fragmented Packets . . . . . . . . . . . . . . . . . 20 12. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 21 13. Security Considerations . . . . . . . . . . . . . . . . . . . 24 14. IAB Considerations . . . . . . . . . . . . . . . . . . . . . . 25 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 16.1. Normative References . . . . . . . . . . . . . . . . . . . 26 16.2. Informative References . . . . . . . . . . . . . . . . . . 26 Audet & Jennings Best Current Practice [Page 2] RFC 4787 NAT UDP Unicast Requirements January 2007 1. Applicability Statement The purpose of this specification is to define a set of requirements for NATs that would allow many applications, such as multimedia communications or online gaming, to work consistently. Developing NATs that meet this set of requirements will greatly increase the likelihood that these applications will function properly. The requirements of this specification apply to Traditional NATs as described in [RFC2663]. This document is meant to cover NATs of any size, from small residential NATs to large Enterprise NATs. However, it should be understood that Enterprise NATs normally provide much more than just NAT capabilities; for example, they typically provide firewall functionalities. A comprehensive description of firewall behaviors and associated requirements is specifically out-of-scope for this specification. However, this specification does cover basic firewall aspects present in NATs (see Section 5). Approaches using directly signaled control of middle boxes are out of scope. UDP Relays (e.g., Traversal Using Relay NAT [TURN]) are out of scope. Application aspects are out of scope, as the focus here is strictly on the NAT itself. This document only covers aspects of NAT traversal related to Unicast UDP [RFC0768] over IP [RFC0791] and their dependencies on other protocols. 2. Introduction Network Address Translators (NATs) are well known to cause very significant problems with applications that carry IP addresses in the payload (see [RFC3027]). Applications that suffer from this problemShow full document text