draft-ietf-core-too-many-reqs-04.txt   draft-ietf-core-too-many-reqs-05.txt 
Network Working Group A. Keranen Network Working Group A. Keranen
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track July 24, 2018 Intended status: Standards Track October 22, 2018
Expires: January 25, 2019 Expires: April 25, 2019
Too Many Requests Response Code for the Constrained Application Protocol Too Many Requests Response Code for the Constrained Application Protocol
draft-ietf-core-too-many-reqs-04 draft-ietf-core-too-many-reqs-05
Abstract Abstract
A Constrained Application Protocol (CoAP) server can experience A Constrained Application Protocol (CoAP) server can experience
temporary overload because one or more clients are sending requests 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 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 to handle. This document defines a new CoAP Response Code for a
server to indicate that a client should reduce the rate of requests. server to indicate that a client should reduce the rate of requests.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 25, 2019. This Internet-Draft will expire on April 25, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. CoAP Server Behavior . . . . . . . . . . . . . . . . . . . . 3 3. CoAP Server Behavior . . . . . . . . . . . . . . . . . . . . 3
4. CoAP Client Behavior . . . . . . . . . . . . . . . . . . . . 3 4. CoAP Client Behavior . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4 8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . 4 8.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
The Constrained Application Protocol (CoAP) [RFC7252] Response Codes The Constrained Application Protocol (CoAP) [RFC7252] Response Codes
are used by a CoAP server to indicate the result of the attempt to are used by a CoAP server to indicate the result of the attempt to
understand and satisfy a request sent by a client. understand and satisfy a request sent by a client.
CoAP Response Codes are similar to the HTTP [RFC7230] Status Codes CoAP Response Codes are similar to the HTTP [RFC7230] Status Codes
and many codes are shared with similar semantics by both CoAP and and many codes are shared with similar semantics by both CoAP and
HTTP. HTTP has the code "429" registered for "Too Many Requests" HTTP. HTTP has the code "429" registered for "Too Many Requests"
[RFC6585]. This document registers a CoAP Response Code "4.29" for [RFC6585]. This document registers a CoAP Response Code "4.29" for
similar purpose and also defines use of the Max-Age option to similar purpose and also defines use of the Max-Age option (see
indicate a back-off period after which a client can try the request Section 5.10.5 of [RFC7252]) to indicate a back-off period after
again. which a client can try the request again.
While a server may not be able to respond to one kind of request, it 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 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 same client. Therefore the back-off period applies only to similar
requests. For the purpose of this response code, a request is 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 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 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 (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 be considered similar even if request URIs may be different. Because
request similarity is context-dependent, it is up to the application request similarity is context-dependent, it is up to the application
skipping to change at page 3, line 25 skipping to change at page 3, line 25
3. CoAP Server Behavior 3. CoAP Server Behavior
If a CoAP server is unable to serve a client that is sending CoAP 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 request messages more often than the server is capable or willing to
handle, the server SHOULD respond to the request(s) with the Response 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 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 indicate the number of seconds after which the server assumes it is
OK for the client to retry the request. OK for the client to retry the request.
An action result payload (see Section 5.5.1 in [RFC7252]) can be sent An action result payload (see Section 5.5.1 of [RFC7252]) can be sent
by the server to give more guidance to the client, e.g., about the by the server to give more guidance to the client, e.g., about the
details of the overload situation. details of the overload situation.
If a client repeats a request that was answered with 4.29 before Max-
Age time has passed, it is possible the client did not recognize the
error code and the server MAY respond with a more generic error code
(e.g., 5.03). Server MAY also limit how often it answers to a
client, e.g., to once every estimated RTT (if such estimate is
available). However, both of these methods add per-client state to
the server which may be counterproductive to reducing load.
4. CoAP Client Behavior 4. CoAP Client Behavior
If a client receives the 4.29 Response Code from a CoAP server to a 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 request, it SHOULD NOT send a similar request to the server before
the time indicated in the Max-Age option has passed. the time indicated in the Max-Age option has passed.
Note that a client may receive a 4.29 Response Code already on a 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 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 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 multiple clients aggregated by the proxy, or if a client has
restarted recently and does not remember its recent requests. restarted recently and does not remember its recent requests.
A client MUST NOT rely on a server being able to send the 4.29 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 Response Code in an overload situation because an overloaded server
may not be able to reply to all requests at all. may not be able to reply at all to some requests.
5. Security Considerations 5. Security Considerations
Replying to CoAP requests with a Response Code consumes resources Replying to CoAP requests with a Response Code consumes resources
from a server. For a server under attack it may be more appropriate from a server. For a server under attack it may be more appropriate
to simply drop requests without responding. to simply drop requests without responding at all. However, dropping
requests is likely to cause also well-behaving clients to simply
retry the requests.
If a CoAP reply with the Too Many Requests Response Code is not As with any other CoAP reply, a client should trust this Response
authenticated and integrity protected, an attacker can attempt to Code only to extent it trusts the underlying security mechanisms
spoof a reply and make the client wait for an extended period of time (e.g., DTLS [RFC6347]) for authentication and freshness. If a CoAP
before trying again. reply with the Too Many Requests Response Code is not authenticated
and integrity protected, an attacker can attempt to spoof a reply and
make the client wait for an extended period of time before trying
again.
If the Response Code is sent without encryption, it may leak
information about the server overload situation and client traffic
patterns.
6. IANA Considerations 6. IANA Considerations
IANA is requested to register the following Response Code in the IANA is requested to register the following Response Code in the
"CoRE Parameters Registry", "CoAP Response Codes" sub-registry: "CoRE Parameters Registry", "CoAP Response Codes" sub-registry:
o Response Code: 4.29 o Response Code: 4.29
o Description: Too Many Requests o Description: Too Many Requests
o Reference: [[This document]] o Reference: [[This document]]
7. Acknowledgements 7. Acknowledgements
This Response Code definition was originally part of the "Publish- This Response Code definition was originally part of the "Publish-
Subscribe Broker for CoAP" document [I-D.ietf-core-coap-pubsub]. Subscribe Broker for CoAP" document [I-D.ietf-core-coap-pubsub].
Author would like to thank Abhijan Bhattacharyya, Carsten Bormann, Author would like to thank Abhijan Bhattacharyya, Carsten Bormann,
Gyorgy Rethy, Jim Schaad, Klaus Hartke, and Sandor Katona for their Daniel Migault, Gyorgy Rethy, Jana Iyengar, Jim Schaad, Klaus Hartke,
contributions and reviews. Mohit Sethi, and Sandor Katona for their contributions and reviews.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, <https://www.rfc-editor.org/info/ DOI 10.17487/RFC2119, March 1997,
rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252, DOI 10.17487/ Application Protocol (CoAP)", RFC 7252,
RFC7252, June 2014, <https://www.rfc-editor.org/info/ DOI 10.17487/RFC7252, June 2014,
rfc7252>. <https://www.rfc-editor.org/info/rfc7252>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References 8.2. Informative References
[I-D.ietf-core-coap-pubsub] [I-D.ietf-core-coap-pubsub]
Koster, M., Keranen, A., and J. Jimenez, "Publish- Koster, M., Keranen, A., and J. Jimenez, "Publish-
Subscribe Broker for the Constrained Application Protocol Subscribe Broker for the Constrained Application Protocol
(CoAP)", draft-ietf-core-coap-pubsub-05 (work in (CoAP)", draft-ietf-core-coap-pubsub-05 (work in
progress), July 2018. progress), July 2018.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6585] Nottingham, M. and R. Fielding, "Additional HTTP Status [RFC6585] Nottingham, M. and R. Fielding, "Additional HTTP Status
Codes", RFC 6585, DOI 10.17487/RFC6585, April 2012, Codes", RFC 6585, DOI 10.17487/RFC6585, April 2012,
<https://www.rfc-editor.org/info/rfc6585>. <https://www.rfc-editor.org/info/rfc6585>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", RFC Protocol (HTTP/1.1): Message Syntax and Routing",
7230, DOI 10.17487/RFC7230, June 2014, <https://www.rfc- RFC 7230, DOI 10.17487/RFC7230, June 2014,
editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
Author's Address Author's Address
Ari Keranen Ari Keranen
Ericsson Ericsson
Email: ari.keranen@ericsson.com Email: ari.keranen@ericsson.com
 End of changes. 18 change blocks. 
29 lines changed or deleted 50 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/