Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension
RFC 6520

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Internet Engineering Task Force (IETF)                     R. Seggelmann
Request for Comments: 6520                                     M. Tuexen
Category: Standards Track               Muenster Univ. of Appl. Sciences
ISSN: 2070-1721                                              M. Williams
                                                   GWhiz Arts & Sciences
                                                           February 2012

                   Transport Layer Security (TLS) and
      Datagram Transport Layer Security (DTLS) Heartbeat Extension

Abstract

   This document describes the Heartbeat Extension for the Transport
   Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
   protocols.

   The Heartbeat Extension provides a new protocol for TLS/DTLS allowing
   the usage of keep-alive functionality without performing a
   renegotiation and a basis for path MTU (PMTU) discovery for DTLS.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6520.

Seggelmann, et al.           Standards Track                    [Page 1]
RFC 6520              TLS/DTLS Heartbeat Extension         February 2012

Copyright Notice

   Copyright (c) 2012 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
   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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Heartbeat Hello Extension . . . . . . . . . . . . . . . . . . . 3
   3.  Heartbeat Protocol  . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Heartbeat Request and Response Messages . . . . . . . . . . . . 5
   5.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.  Introduction

1.1.  Overview

   This document describes the Heartbeat Extension for the Transport
   Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
   protocols, as defined in [RFC5246] and [RFC6347] and their
   adaptations to specific transport protocols described in [RFC3436],
   [RFC5238], and [RFC6083].

   DTLS is designed to secure traffic running on top of unreliable
   transport protocols.  Usually, such protocols have no session
   management.  The only mechanism available at the DTLS layer to figure
   out if a peer is still alive is a costly renegotiation, particularly
   when the application uses unidirectional traffic.  Furthermore, DTLS
   needs to perform path MTU (PMTU) discovery but has no specific
   message type to realize it without affecting the transfer of user
   messages.

Seggelmann, et al.           Standards Track                    [Page 2]
RFC 6520              TLS/DTLS Heartbeat Extension         February 2012

   TLS is based on reliable protocols, but there is not necessarily a
   feature available to keep the connection alive without continuous
   data transfer.

   The Heartbeat Extension as described in this document overcomes these
   limitations.  The user can use the new HeartbeatRequest message,
   which has to be answered by the peer with a HeartbeartResponse
   immediately.  To perform PMTU discovery, HeartbeatRequest messages
   containing padding can be used as probe packets, as described in
   [RFC4821].

1.2.  Conventions

   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 [RFC2119].

2.  Heartbeat Hello Extension

   The support of Heartbeats is indicated with Hello Extensions.  A peer
   cannot only indicate that its implementation supports Heartbeats, it
   can also choose whether it is willing to receive HeartbeatRequest