Common Requirements for Carrier-Grade NATs (CGNs)
RFC 6888
Document | Type |
RFC - Best Current Practice
(April 2013; No errata)
Updates RFC 4787
|
|
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Authors | Simon Perreault , Ikuhei Yamagata , Shin Miyakawa , Akira Nakagawa , Hiroyuki Ashida | ||
Last updated | 2015-10-14 | ||
Replaces | draft-nishitani-cgn | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6888 (Best Current Practice) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Martin Stiemerling | ||
IESG note | Dan Wing (dwing@cisco.com) is the document shepherd. | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) S. Perreault, Ed. Request for Comments: 6888 Viagenie BCP: 127 I. Yamagata Updates: 4787 S. Miyakawa Category: Best Current Practice NTT Communications ISSN: 2070-1721 A. Nakagawa Japan Internet Exchange (JPIX) H. Ashida Cisco Systems April 2013 Common Requirements for Carrier-Grade NATs (CGNs) Abstract This document defines common requirements for Carrier-Grade NATs (CGNs). It updates RFC 4787. Status of This Memo This memo documents an Internet Best Current Practice. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6888. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Perreault, et al. Best Current Practice [Page 1] RFC 6888 CGN Requirements April 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements for CGNs . . . . . . . . . . . . . . . . . . . 4 4. Logging . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5. Port Allocation Scheme . . . . . . . . . . . . . . . . . . . 11 6. Deployment Considerations . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . 12 9.2. Informative Reference . . . . . . . . . . . . . . . . . 13 1. Introduction With the shortage of IPv4 addresses, it is expected that more Internet Service Providers (ISPs) may want to provide a service where a public IPv4 address would be shared by many subscribers. Each subscriber is assigned a private address, and a Network Address Translator (NAT) [RFC2663] situated in the ISP's network translates the traffic between private and public addresses. When a second IPv4 NAT is located at the customer edge, this results in two layers of NAT. This service can conceivably be offered alongside others, such as IPv6 services or regular IPv4 service assigning public addresses to subscribers. Some ISPs started offering such a service long before there was a shortage of IPv4 addresses, showing that there are driving forces other than the shortage of IPv4 addresses. One approach to CGN deployment is described in [RFC6264]. This document describes behavior that is required of those multi- subscriber NATs for interoperability. It is not an IETF endorsement of CGNs or a real specification for CGNs; rather, it is just a minimal set of requirements that will increase the likelihood of applications working across CGNs. Because subscribers do not receive unique IPv4 addresses, Carrier- Grade NATs introduce substantial limitations in communications between subscribers and with the rest of the Internet. In particular, it is considerably more involved to establish proxy functionality at the border between internal and external realms. Some applications may require substantial enhancements, while some others may not function at all in such an environment. Please see "Issues with IP Address Sharing" [RFC6269] for details. Perreault, et al. Best Current Practice [Page 2] RFC 6888 CGN Requirements April 2013Show full document text