An FTP Application Layer Gateway (ALG) for IPv4-to-IPv6 Translation
draft-tsou-behave-ftp46-01
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
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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.
Tsou, et al. Expires March 20, 2014 [Page 1]
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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
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