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Versions: 00 01

Network Working Group                                         W. Tarreau
Internet-Draft                                                Exceliance
Expires: July 20, 2013                                        E. Stephan
                                                                  Orange
                                                           G. Montenegro
                                                               Microsoft
                                                        January 16, 2013


                          HTTP 2.0 Negotiation
             draft-montenegro-httpbis-http2-negotiation-01

Abstract

   This document describes an Upgrade-based protocol negotiation
   proposal for HTTP 2.0.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 20, 2013.

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
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   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Optimizing the Handshake  . . . . . . . . . . . . . . . . . . . 5
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Appendix  . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9








































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1.  Introduction

   User agents interact with numerous servers from different domains
   using different versions of HTTP.  In particular, the co-existence of
   HTTP/1.x and HTTP/2.x requires a protocol negotiation mechanism
   transparent to the user agents.  This document specifies an Upgrade-
   based HTTP 2.0 connection negotiation.

   HTTP/2.0 will have the capability (but not the requirement) to use
   the same ports as HTTP/1.X, typically, but not limited to, 80 (in the
   clear) and 443 (when over TLS/SSL).  Of course, it is possible for a
   client to somehow acquire knowledge that a server implements HTTP/2.0
   at a given port.  In such a case, the client can immediately begin
   sending HTTP/2.0 binary frames to the server, and the server can
   immediately respond with the corresponding HTTP/2.0 frames.  How that
   knowledge is acquired is not the subject of this note.  It could be
   acquired by some out-of-band means such as using the DNS, or by some
   configuration prior to the HTTP/2.0 exchange.  Or it could have been
   aquired earlier in-band in a previous exchange using, for example,
   the Upgrade-based mechanism specified in this document.  It could
   have also been acquired at an earlier phase of this same exchange,
   for example, at a lower protocol layer that precedes the overall HTTP
   sequence, such as in the TLS handshake (if using TLS).

   Nevertheless, there may be some situations, in which the client can
   only assume that a server speaks HTTP/1.X. In such cases, a
   connection upgrade mechanism to opportunistically attempt switching
   to HTTP/2.0 is essential.  Otherwise, the exchange will remain at
   HTTP/1.X despite both client and server being willing to speak
   HTTP/2.0.

   This document specifies such a connection upgrade for HTTP/2.0.  This
   handshake does not incur any extra delay in obtaining a response in
   HTTP/2.0, as the protocol switch is immediate and effective within
   the first round trip.  There is no delay either if there is no
   protocol switch, as the server is capable to respond via HTTP/1.1
   also within the first initial round trip.

   This handshake uses the Upgrade header defined in HTTP/1.1
   [I-D.ietf-httpbis-p1-messaging].  This Upgrade header is also in wide
   use by the WebSocket protocol for similar purposes [RFC6455].

   The goal of this document is to propose additional text to the
   HTTP/2.0 specification.  The starting point for HTTP/2.0, the initial
   version of [I-D.ietf-httpbis-http2], has no language with respect to
   a connection upgrade procedure.  Hence, the text below could be
   incorporated as a new section or sections within the HTTP/2.0
   document.



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2.  Negotiation

   If a client has no knowledge about a server's support for HTTP/2.0,
   it starts with HTTP/1.1 and attempt an upgrade to HTTP/2.0 as
   follows:

        GET /default.htm HTTP/1.1
        Host: server.example.com
        Connection: Upgrade
        Upgrade: HTTP/2.0

   If the server does not support the new protocol, it will simply
   respond to the client using HTTP/1.1:

        HTTP/1.1 200 OK
        Content-length: 243
        Content-type: text/html
        ...

   If the server switches to the new protocol, it will signal so via a
   101 response.  The server switches to HTTP/2.0 immediately after the
   empty line which terminates the 101 response
   [I-D.ietf-httpbis-p2-semantics].

        HTTP/1.1 101 Switching Protocols
        Connection: Upgrade
        Upgrade: HTTP/2.0

        [ HTTP/2.0 frame ]

   In the above, the string "HTTP/2.0" represents the final version of
   the protocol defined in [I-D.ietf-httpbis-http2].  However, per
   guidance in that document, preliminary revisions of that document
   (either draft or experimental) are denoted by adding the
   corresponding version or revision number.  For example, if the above
   handshake were negotiating the use of the 03 version of the draft
   (draft-ietf-httpbis-http2-03), then, instead of using "HTTP/2.0"
   above, the handshake would use "HTTP-03/2.0" instead.













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3.  Optimizing the Handshake

   This handshake may be further optimized by the definition of HTTP
   headers of the form "HTTP2-header_name".  These "HTTP2" headers would
   be meant to be interpreted exclusively by HTTP/2.0 servers and
   applied upon a successful Upgrade to further optimize or proactively
   configure the subsequent HTTP/2.0 exchanges.  These headers would be
   ignored by HTTP/1.1 servers.  The HTTP2 headers are for future
   revisions of this document.










































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4.  Acknowledgements

   This document incorporates material from
   [I-D.tarreau-httpbis-network-friendly] and
   [I-D.montenegro-httpbis-speed-mobility].

   This document was produced using the xml2rfc tool [RFC2629].












































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5.  Appendix

   This Upgrade-based handshake may have issues with certain proxies and
   intermediaries, particularly those that are not aware of its use and
   don't obey its semantics.  Some heuristics that have been observed to
   help in this respect is to turn off caching by adding the following
   to the client request:

        Pragma: no-cache
        Cache-Control: no-cache









































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6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

   [I-D.ietf-httpbis-p1-messaging]
              Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Message Syntax and Routing",
              draft-ietf-httpbis-p1-messaging-21 (work in progress),
              October 2012.

   [I-D.ietf-httpbis-p2-semantics]
              Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Semantics and Content",
              draft-ietf-httpbis-p2-semantics-21 (work in progress),
              October 2012.

6.2.  Informative References

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

   [RFC6455]  Fette, I. and A. Melnikov, "The WebSocket Protocol",
              RFC 6455, December 2011.

   [I-D.ietf-httpbis-http2]
              Belshe, M., Peon, R., Thomson, M., and A. Melnikov, "SPDY
              Protocol", draft-ietf-httpbis-http2-00 (work in progress),
              November 2012.

   [I-D.montenegro-httpbis-speed-mobility]
              Trace, R., Foresti, A., Singhal, S., Mazahir, O., Nielsen,
              H., Raymor, B., Rao, R., and G. Montenegro, "HTTP Speed+
              Mobility", draft-montenegro-httpbis-speed-mobility-02
              (work in progress), June 2012.

   [I-D.tarreau-httpbis-network-friendly]
              Tarreau, W., Jeffries, A., and A. Croy, "Proposal for a
              Network-Friendly HTTP Upgrade",
              draft-tarreau-httpbis-network-friendly-00 (work in
              progress), March 2012.




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Authors' Addresses

   Willy Tarreau
   Exceliance

   Email: w@1wt.eu


   Emile Stephan
   Orange

   Email: emile.stephan@orange.com


   Gabriel Montenegro
   Microsoft

   Email: Gabriel.Montenegro@microsoft.com

































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