Internet DRAFT - draft-polli-retry-scope
draft-polli-retry-scope
Network Working Group R. Polli
Internet-Draft Team Digitale, Italian Government
Intended status: Standards Track 9 March 2020
Expires: 10 September 2020
Retry-Scope header field
draft-polli-retry-scope-00
Abstract
This document defines the Retry-Scope header field for HTTP thus
allowing a server to communicate the scope of the returned Retry-
After header field.
Note to Readers
_RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/
(https://lists.w3.org/Archives/Public/ietf-http-wg/).
The source code and issues list for this draft can be found at
https://github.com/ioggstream/draft-polli-Retry-Scope
(https://github.com/ioggstream/draft-polli-Retry-Scope).
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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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 10 September 2020.
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Copyright Notice
Copyright (c) 2020 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/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Header Specifications . . . . . . . . . . . . . . . . . . . . 3
2.1. Retry-Scope . . . . . . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
3.1. Role of intermediaries . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. Retry-Scope Header Field Registration . . . . . . . . . . 4
5. Normative References . . . . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Retry-After header defined in Section 7.1.3 of [SEMANTICS] allows
a server to indicate how long the user agent ought to wait before
making a follow-up request.
While Retry-After applies to the issued request, it may be useful for
the server to communicate to the user agent that the conditions that
lead to returning Retry-After are broader in scope than a single
request.
This proposal allows a server to convey that scope in the Retry-Scope
response header field, and ask the client to temporarily refrain from
making other requests to the same resource, or even to all resources
on the same server.
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1.1. Notational Conventions
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. These words may also appear in this
document in lower case as plain English words, absent their normative
meanings.
This document uses the Augmented BNF defined in [RFC5234] and updated
by [RFC7405] along with the "#rule" extension defined in Section 7 of
[MESSAGING] and the URI-reference rule defined in Section 2.7 of
[MESSAGING].
The terms "intermediaries" and "target URI" are to be interpreted as
described in [MESSAGING].
2. Header Specifications
The following header is defined
2.1. Retry-Scope
The Retry-Scope response header field indicates that the conditions
that lead to returning Retry-After are broader in scope than a single
request.
Retry-Scope = URI-reference
Two examples of Retry-Scope:
Retry-Scope: /books
Retry-Scope: https://api.example/
A user agent receiving the Retry-Scope header field in conjunction
with a Retry-After header field ought to wait before making further
request to the resource identified by the Retry-Scope field value.
This header MUST NOT be repeated; if a user agent receives multiple
Retry-Scope header fields, then it SHOULD ignore them.
Intermediaries aware of the Retry-Scope semantics (eg. reverse
proxies) MAY modify the Retry-Scope in order to help the user agent
to correctly identify the scope and ensure that the field value
matches the target URI, like they would have done for the Location
header field defined in Section 7.1.2 of [SEMANTICS].
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3. Security Considerations
3.1. Role of intermediaries
An intermediary, by chance or purpose, might alter the scope of the
Retry-Scope thus causing the user agent to refrain contacting other
server resource.
When the server originating the Retry-Scope is behind one or more
intermediaries it is possible that the field value is not consistent
with the target URI.
4. IANA Considerations
4.1. Retry-Scope Header Field Registration
This section registers the "Retry-Scope" header field in the
"Permanent Message Header Field Names" registry ([RFC3864]).
Header field name: "Retry-Scope"
Applicable protocol: http
Status: standard
Author/Change controller: IETF
Specification document(s): Section 2.1 of this document
5. Normative References
[MESSAGING]
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>.
[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>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
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[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/info/rfc7405>.
[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>.
[SEMANTICS]
Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
Appendix A. Acknowledgements
This specification was born from a thread created by Martin Thomson,
and the subsequent discussion.
FAQ
Q: Why not using link relations? This solution is simpler and was
previously discussed here (https://github.com/httpwg/http-core/
pull/317#issuecomment-585868767).
Change Log
RFC EDITOR PLEASE DELETE THIS SECTION.
Author's Address
Roberto Polli
Team Digitale, Italian Government
Email: robipolli@gmail.com
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