An FTP Application Layer Gateway (ALG) for IPv4-to-IPv6 Translation
draft-tsou-behave-ftp46-01

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Internet Engineering Task Force                             T. Tsou, Ed.
Internet-Draft                                 Huawei Technologies (USA)
Intended status: Informational                              S. Perreault
Expires: March 20, 2014                                         Viagenie
                                                                J. Huang
                                                     Huawei Technologies
                                                      September 16, 2013

  An FTP Application Layer Gateway (ALG) for IPv4-to-IPv6 Translation
                       draft-tsou-behave-ftp46-01

Abstract

   An FTP ALG for NAT64 was defined in RFC 6384.  Its scope was limited
   to an IPv6 client connecting to an IPv4 server.  This memo supports
   the case of an IPv4 client connecting to an IPv6 server.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on March 20, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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
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   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.

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  PASV to EPSV  . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  EPSV (IPv4) to EPSV (IPv6)  . . . . . . . . . . . . . . . . .   4
   6.  Command to disable FTP ALG  . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Overview

   During the transition from IPv4 to IPv6, some operators need to
   deploy NAT in their network.  Some subscribers have the need to run
   IPv4 based FTP servers at home, and some of the FTP [RFC0959] control
   messages carry IP address and port number in the payload, which will
   cause a NAT traversal problem.

   [RFC6384] defines FTP ALG for NAT64, but only for the case where the
   FTP client is on the inside of the NAT64.  The case where an FTP
   server is on the inside of the NAT64 is not covered.

   When the FTP server is behind NAT, it can publish its service address
   via a HTTP redirect server and a DDNS system which needs to support
   both IP address and port rather than IP address only, or other
   possible methods.  The FTP server can listen on any possible ports,
   not just port 21; FTP server can get it external IP address and port
   via some technology like UPnP, and then publish the acquired IP
   address and port as its URI, ftp://203.0.113.1:1200, port 1200 is
   allocated by NAT.

1.1.  Requirements Language

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   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Terminology

3.  Scenarios

   There can be several scenarios if NAT is involved in the network.

   a) In this scenario, the FTP client is behind NAT, FTP ALG needs to
   handle the EPRT / PORT command in FTP active mode, translating the IP