Network Working Group                               N. Mavrogiannopoulos
Internet-Draft                                                   Red Hat
Intended status: Informational                              D. Woodhouse
Expires: March 25, 2017                                            Intel
                                                      September 21, 2016

                 A TLS application-specific identifier


   This memo proposes an application-specific identifier for use with
   the TLS and DTLS protocols.  It defines a TLS extension to allow an
   arbitrary identifier to be specified in the Client Hello, which can
   be used for application-specific routing purposes.

Status of This Memo

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   This Internet-Draft will expire on March 25, 2017.

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1.  Introduction

   In certain applications, a TLS or DTLS session follows-up a
   previously established communication channel which has already
   assigned the user to a particular server from a pool or a particular
   system process.  In these cases it is desirable for the follow-up
   sessions to be forwarded by a routing process or system to the
   initial handler, early, prior to any TLS negotiation.

   That can be implemented with an application-specific identifier which
   will be included by the client on its initial Client Hello message.
   The routing processor will utilize that identifier to forward the
   session to the appropriate handler.  This document describes a way
   for applications to attach application-specific identifiers to the
   Client Hello message.

2.  Terminology

   This document uses the same notation and terminology used in the TLS
   and DTLS protocol specifications [RFC5246][RFC6347].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  TLS Extension: Application-specific identifier

   The TLS application-specific identifier is an arbitrary byte sequence
   encoded in the Client Hello as an extension.  It is applicable to
   both the TLS and DTLS protocols [RFC5246][RFC6347].

3.1.  Extension Negotiation

   In order to specify the identifier, clients include an extension of
   type "application_specific_identifier" to the extended client hello
   message.  The "application_specific_identifier" TLS extension is
   assigned the value of TDB-BY-IANA from the TLS ExtensionType
   registry.  This value is used as the extension number for the
   extensions in the client hello message.  The server MUST NOT include
   a corresponding value to the Server Hello for this extension.  The
   hello extension mechanism is described in [RFC5246].

   This extension data have the following format.

           opaque ApplicationID<1..2^8-1>;

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   The contents and size of ApplicationID are application-specific.
   Examples are, a 32-bit identifier, an 128-bit UUID [RFC4122], or a
   value defined by the application profile or policy.

4.  Security Considerations

   Applications and application profiles must ensure that they do not
   reveal sensitive data, or data that could compromise the TLS
   protocol's properties through the ApplicationID value.

5.  IANA Considerations

   This document defines a new TLS extension,
   "application_specific_identifier", assigned a value of TBD-BY-IANA
   (the value 48018 is suggested) from the TLS ExtensionType registry
   defined in [RFC5246].  This value is used as the extension number for
   the extensions in the client hello message.

6.  References

6.1.  Normative References

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

6.2.  Informative References

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,

Appendix A.  Acknowledgements

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Authors' Addresses

   Nikos Mavrogiannopoulos
   Red Hat, Inc.
   Czech Republic


   David Woodhouse


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