Too Many Requests Response Code for the Constrained Application Protocol
The information below is for an old version of the document.
This is an older version of an Internet-Draft that was ultimately published as RFC 8516.
|Last updated||2018-10-12 (Latest revision 2018-07-24)|
|RFC stream||Internet Engineering Task Force (IETF)|
TSVART Last Call review by Jana Iyengar Ready w/nits
|Additional resources||Mailing list discussion|
|Stream||WG state||Submitted to IESG for Publication|
|Document shepherd||Carsten Bormann|
|Shepherd write-up||Show Last changed 2018-08-15|
|IESG||IESG state||IESG Evaluation|
Needs a YES. Needs 9 more YES or NO OBJECTION positions to pass.
|Responsible AD||Alexey Melnikov|
|Send notices to||Carsten Bormann <email@example.com>|
|IANA||IANA review state||IANA OK - Actions Needed|
Network Working Group A. Keranen Internet-Draft Ericsson Intended status: Standards Track July 24, 2018 Expires: January 25, 2019 Too Many Requests Response Code for the Constrained Application Protocol draft-ietf-core-too-many-reqs-04 Abstract A Constrained Application Protocol (CoAP) server can experience temporary overload because one or more clients are sending requests to the server at a higher rate than the server is capable or willing to handle. This document defines a new CoAP Response Code for a server to indicate that a client should reduce the rate of requests. 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 25, 2019. Copyright Notice Copyright (c) 2018 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. Keranen Expires January 25, 2019 [Page 1] Internet-Draft Too Many Requests Response Code for CoAP July 2018 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. CoAP Server Behavior . . . . . . . . . . . . . . . . . . . . 3 4. CoAP Client Behavior . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 8.1. Normative References . . . . . . . . . . . . . . . . . . 4 8.2. Informative References . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction The Constrained Application Protocol (CoAP) [RFC7252] Response Codes are used by a CoAP server to indicate the result of the attempt to understand and satisfy a request sent by a client. CoAP Response Codes are similar to the HTTP [RFC7230] Status Codes and many codes are shared with similar semantics by both CoAP and HTTP. HTTP has the code "429" registered for "Too Many Requests" [RFC6585]. This document registers a CoAP Response Code "4.29" for similar purpose and also defines use of the Max-Age option to indicate a back-off period after which a client can try the request again. While a server may not be able to respond to one kind of request, it may be able to respond to a request of different kind, even from the same client. Therefore the back-off period applies only to similar requests. For the purpose of this response code, a request is similar if it has the same method and Request-URI. Also if a client is sending a sequence of requests that are part of the same series (e.g., a set of measurements to be processed by the server) they can be considered similar even if request URIs may be different. Because request similarity is context-dependent, it is up to the application logic to decide how the similarity of the requests should be evaluated. The 4.29 code is similar to the 5.03 "Service Unavailable" [RFC7252] code in a way that the 5.03 code can also be used by a server to signal an overload situation. However the 4.29 code indicates that the too frequent requests from the requesting client are the reason for the overload. Keranen Expires January 25, 2019 [Page 2] Internet-Draft Too Many Requests Response Code for CoAP July 2018 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Readers should also be familiar with the terms and concepts discussed in [RFC7252]. 3. CoAP Server Behavior If a CoAP server is unable to serve a client that is sending CoAP request messages more often than the server is capable or willing to handle, the server SHOULD respond to the request(s) with the Response Code 4.29, "Too Many Requests". The Max-Age option is used to indicate the number of seconds after which the server assumes it is OK for the client to retry the request. An action result payload (see Section 5.5.1 in [RFC7252]) can be sent by the server to give more guidance to the client, e.g., about the details of the overload situation. 4. CoAP Client Behavior If a client receives the 4.29 Response Code from a CoAP server to a request, it SHOULD NOT send a similar request to the server before the time indicated in the Max-Age option has passed. Note that a client may receive a 4.29 Response Code already on a first request to a server. This can happen, for example, if there is a proxy on the path and the server replies based on the load from multiple clients aggregated by the proxy, or if a client has restarted recently and does not remember its recent requests. A client MUST NOT rely on a server being able to send the 4.29 Response Code in an overload situation because an overloaded server may not be able to reply to all requests at all. 5. Security Considerations Replying to CoAP requests with a Response Code consumes resources from a server. For a server under attack it may be more appropriate to simply drop requests without responding. If a CoAP reply with the Too Many Requests Response Code is not authenticated and integrity protected, an attacker can attempt to Keranen Expires January 25, 2019 [Page 3] Internet-Draft Too Many Requests Response Code for CoAP July 2018 spoof a reply and make the client wait for an extended period of time before trying again. 6. IANA Considerations IANA is requested to register the following Response Code in the "CoRE Parameters Registry", "CoAP Response Codes" sub-registry: o Response Code: 4.29 o Description: Too Many Requests o Reference: [[This document]] 7. Acknowledgements This Response Code definition was originally part of the "Publish- Subscribe Broker for CoAP" document [I-D.ietf-core-coap-pubsub]. Author would like to thank Abhijan Bhattacharyya, Carsten Bormann, Gyorgy Rethy, Jim Schaad, Klaus Hartke, and Sandor Katona for their contributions and reviews. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ RFC2119, March 1997, <https://www.rfc-editor.org/info/ rfc2119>. [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/ RFC7252, June 2014, <https://www.rfc-editor.org/info/ rfc7252>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. 8.2. Informative References [I-D.ietf-core-coap-pubsub] Koster, M., Keranen, A., and J. Jimenez, "Publish- Subscribe Broker for the Constrained Application Protocol (CoAP)", draft-ietf-core-coap-pubsub-05 (work in progress), July 2018. Keranen Expires January 25, 2019 [Page 4] Internet-Draft Too Many Requests Response Code for CoAP July 2018 [RFC6585] Nottingham, M. and R. Fielding, "Additional HTTP Status Codes", RFC 6585, DOI 10.17487/RFC6585, April 2012, <https://www.rfc-editor.org/info/rfc6585>. [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014, <https://www.rfc- editor.org/info/rfc7230>. Author's Address Ari Keranen Ericsson Email: firstname.lastname@example.org Keranen Expires January 25, 2019 [Page 5]