Constrained Application Protocol (CoAP) Hop-Limit Option
draft-ietf-core-hop-limit-07

Document Type Active Internet-Draft (core WG)
Last updated 2019-12-02 (latest revision 2019-10-17)
Replaces draft-boucadair-core-hop-limit
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CORE                                                        M. Boucadair
Internet-Draft                                                    Orange
Intended status: Standards Track                                T. Reddy
Expires: April 19, 2020                                           McAfee
                                                              J. Shallow
                                                        October 17, 2019

        Constrained Application Protocol (CoAP) Hop-Limit Option
                      draft-ietf-core-hop-limit-07

Abstract

   The presence of Constrained Application Protocol (CoAP) proxies may
   lead to infinite forwarding loops, which is undesirable.  To prevent
   and detect such loops, this document specifies the Hop-Limit CoAP
   option.

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 19, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://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
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   include Simplified BSD License text as described in Section 4.e of

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Intended Usage  . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Hop-Limit Option  . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Debugging & Troubleshooting . . . . . . . . . . . . . . . . .   5
   5.  HTTP-Mapping Considerations . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  CoAP Response Code  . . . . . . . . . . . . . . . . . . .   6
     6.2.  CoAP Option Number  . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   More and more applications are using the Constrained Application
   Protocol (CoAP) [RFC7252] as a communication protocol between
   application agents.  For example, [I-D.ietf-dots-signal-channel]
   specifies how CoAP is used as a signaling protocol between domains
   under distributed denial-of-service (DDoS) attacks and DDoS
   mitigation providers.  In such contexts, a CoAP client can
   communicate directly with a server or indirectly via proxies.

   When multiple proxies are involved, infinite forwarding loops may be
   experienced (e.g., routing misconfiguration, policy conflicts).  To
   prevent such loops, this document defines a new CoAP option, called
   Hop-Limit (Section 3).  Also, the document defines a new CoAP
   Response Code (Section 6.1) to report loops together with relevant
   diagnostic information to ease troubleshooting (Section 4).

1.1.  Intended Usage

   The Hop-Limit option was originally designed for a specific use case
   [I-D.ietf-dots-signal-channel].  However, its intended usage is
   general:

      New CoAP proxies MUST implement this option and have it enabled by
      default.

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   Note that this means that a server that receives requests both via
   proxies and directly from clients may see otherwise identical
   requests with and without the Hop-Limit option included; servers with
   internal caching will therefore also want to implement this option,
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