Internet Engineering Task Force E. Vyncke
Internet-Draft Cisco Systems
Intended status: Informational September 17, 2008
Expires: March 21, 2009
IPv6 Connectivity Check and Redirection by HTTP Servers
draft-vyncke-http-server-64aware-00
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
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.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on March 21, 2009.
Abstract
Rather than forcing the client to decide whether IPv4 or IPv6 is more
convenient to reach a web server; this document proposes to let the
web server check whether there is IPv6 connectivity to the client;
then the web server can do a HTTP redirect to the force the client to
use IPv6.
This is done easily by a script within the server HTML pages and does
not require any change in the client applications or configuration.
The client still can control whether he/she wants to enabled IPv6.
This draft could be discussed on the Applications Discuss mailing
list, https://www.ietf.org/mailman/listinfo/apps-discuss.
Vyncke Expires March 21, 2009 [Page 1]
Internet-Draft IPv6 Auto-Redirect September 2008
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. Verifying IPv6 Connectivity and Redirection . . . . . . . . . . 3
2.1. How can this be done? . . . . . . . . . . . . . . . . . . . 3
2.1.1. Example of HTML and Ecmascript Code . . . . . . . . . . 4
2.1.2. Proof of Concept . . . . . . . . . . . . . . . . . . . 5
2.2. Benefits of this Technique . . . . . . . . . . . . . . . . 5
3. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Improving the User's Experience . . . . . . . . . . . . . . 6
3.2. Extension to only measure the amount of IPv6 capable
client . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
Vyncke Expires March 21, 2009 [Page 2]
Internet-Draft IPv6 Auto-Redirect September 2008
1. Introduction
It is often claimed that web servers are not dual-stack because the
IPv6 has poor connectivity. Therefore, little to no web servers are
dual-stacks; it is common to find the same content on www.example.com
(for IPv4 access) and on ipv6.example.com (for IPv6 access).
The drawback of this setup is that once a user uses www.example.com,
then all his/her communication will be over IPv4. This document
proposes that the web server MAY run a dynamic and transparent check
for the IPv6 connectivity between the client and the server and if
there is IPv6 connectivity, then the client MAY be transparently
redirected to the IPv6 server, i.e. ipv6.example.com.
The check and the redirect can easily be done by a script within the
server HTML pages and MUST NOT require any change in the client
applications or configuration. The client still can control whether
he/she wants to enabled IPv6.
1.1. Requirements Language
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. Verifying IPv6 Connectivity and Redirection
2.1. How can this be done?
The procedure can be described as:
1. the IPv4 web server has a start page which includes a small
transparent image which is located on the ipv6.example.com web
server. Note: this kind of image is often used on web sites to
count access or as a spacer; it is usually a 1 by 1 pixel image.
2. the HTML SRC tag includes two events: onload() and onerror()
which are commonly implemented in browsers.
3. if the client has only access to IPv4: the image will fail to
load but the overall aspect of the web page will not be affected
as the size of the error is only 1 by 1 pixel. The onerror()
event is also triggered which could lead to change the web page
content (see the code example (Section 2.1.1)) or even replace
the 1x1 image by another 1x1 image reachable over IPv4.
Vyncke Expires March 21, 2009 [Page 3]
Internet-Draft IPv6 Auto-Redirect September 2008
4. if the client has also access to IPv6 (i.e. it has the IPv6
protocol installed and has a valid IPv6 connectivity), then the
image will load and the onload() event will be triggered. The
script code associated with the onload() can force an immediate
redirect of the client to the IPv6 web content.
All the above is only implemented in the HTTP server and does not
require any change in the client even if the actual script is done by
the client browser.
The redirect is also mostly transparent to the user.
The IPv6 connectivity works independently whether the client has
configured IPv4 or IPv6 as his/her preferred protocol. For instance,
it will work with Teredo [RFC4380] tunnels even if those are usually
configured as less preferrable than IPv4.
2.1.1. Example of HTML and Ecmascript Code
Here is an example in HTML [HTML] and in ECMAscript ECMA-262
[ECMA-262] (also known as Javascript). It demonstrates two things
which occur when IPv6 connectivity is detected (see the function
IPv6Image()):
1. the appearance of the web page is changed (a text about IPv6 is
displayed) and could now differ from the IPv4 only web page; this
step is optional;
2. a immediate redirection to http://ipv6.example.com is executed;
this is the core step.
Here is the HTML image tag which MUST include the onload() event and
MAY include the onerror() event. It MAY be followed by a HTML span
element which is used to display the result of the IPv6 connectivity
check.
Checking whether you have IPv6 access...
Vyncke Expires March 21, 2009 [Page 4]
Internet-Draft IPv6 Auto-Redirect September 2008
The example below implements the mandatory onload() event handler,
IPv6Image(), which redirects to the IPv6 version of the web site and
the optional onerror() event handler, NoIPv6Image(), which is
triggered when IPv6 connectivity does not exist (in this example, it
is used to display a message).
2.1.2. Proof of Concept
There is a very simple proof of concept of this technique. It is
hosted on a web server at the University of Liege in Belgium and can
be reached via the following URI:
http://sigma.hec.be/~evyncke/family/ip.php: the normal dual-stack
URI.
http://193.190.125.15/~evyncke/family/ip.php: if you would like to
check the technique as if your browser preferred IPv4.
http://[2001:6a8:2c80:1::15]/~evyncke/family/ip.php: if you would
like to check the technique as if your browser preferred IPv6.
2.2. Benefits of this Technique
The main benefit of this technique is that there is nothing to
install or to configure at the client side. Nevertheless, the client
has still the possibility to use only IPv4 by configuring his/her
protocol stacks.
Another benefit is that there is basically little connectivity risk
associated with this procedure, the client is redirect to the IPv6
version of the web server only if a HTTP transaction has been
Vyncke Expires March 21, 2009 [Page 5]
Internet-Draft IPv6 Auto-Redirect September 2008
completed successfully over IPv6. This transaction is a normal HTTP
transaction with full TCP handshake and HTTP protocol, so, it
includes several IPv6 datagrams of varying size. Therefore, if it is
successful then the IPv6 connectivity between the client and the
server has been proven.
Note: if Path MTU Discovery is a concern, the 1x1 pixel image could
changed to a larger one as long as it is kept transparent. As soon
as the larger image exceeds 1,500 bytes, Path MTU discovery will need
to be successful to display the image and to trigger the intrinsic
event 'onload()'.
3. Extensions
This section briefly describes potential extensions of this
technique.
3.1. Improving the User's Experience
By using another script associated to the onload() event, the user
experience could be improved:
The default page can dynamically be updated to reflect the
availability of IPv6 connectivity;
A pop-up window can be displayed asking the user whether he/she
wants to be redirect to the IPv6 version of the web server;
A HTTP [RFC2616] can be used by the web server to remember the
user's decision.
3.2. Extension to only measure the amount of IPv6 capable client
Rather then taking the drastic decision of redirecting its client to
its IPv6 content, the web server can simply log the result of the
connectivity check:
o IPv4 client with no IPv6 connectivity;
o IPv4 client with IPv6 connectivity.
This can be achieved by loading the 1x1 image over IPv6 but the image
source is no more a static image file but rather a server script
(PHP, Perl, etc.) which is called with the IPv4 address of the client
as an argument. Even if the server script execution (used to
generate the image) is initiated over IPv6, it can retrieve the
original IPv4 address from the HTTP query and log the association
Vyncke Expires March 21, 2009 [Page 6]
Internet-Draft IPv6 Auto-Redirect September 2008
between the IPv4 and IPv6 addresses.
The PHP [PHP] code fragment below shows how it can be done. This
fragment is run when the dual-stack client connects to
www.example.com; it collects the client IPv4 address with the help of
$_SERVER['REMOTE_ADDR'] and passes it as an argument to the
1x1pixel.php server script which is accessed over IPv6.
4. Acknowledgements
This I-D is based on some discussions with Chip Popoviciu.
5. IANA Considerations
This memo includes no request to IANA.
6. Security Considerations
No security issue has been identified.
Note: this technique requires to enable script execution on the
client browser; this setting is sometimes deemed less secure than
preventing the execution of any script by the browser.
7. Normative References
[ECMA-262]
ECMA, "ECMAScript Language Specification", 1999, .
[HTML] W3C, "HTML 4.01 Specification", 1999,
.
[PHP] The PHP Group, "PHP: Hypertext Preprocessor",
.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Vyncke Expires March 21, 2009 [Page 7]
Internet-Draft IPv6 Auto-Redirect September 2008
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380,
February 2006.
Author's Address
Eric Vyncke
Cisco Systems
De Kleetlaan, 6A
Diegem, B-1831
Belgium
Phone: +32 2 778 4677
Email: evyncke@cisco.com
Vyncke Expires March 21, 2009 [Page 8]
Internet-Draft IPv6 Auto-Redirect September 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Vyncke Expires March 21, 2009 [Page 9]