draft-ietf-httpbis-bcp56bis-08.txt   draft-ietf-httpbis-bcp56bis-latest.txt 
HTTP Working Group M. Nottingham HTTP Working Group M. Nottingham
Internet-Draft November 9, 2018 Internet-Draft May 16, 2019
Obsoletes: 3205 (if approved) Obsoletes: 3205 (if approved)
Intended status: Best Current Practice Intended status: Best Current Practice
Expires: May 13, 2019 Expires: November 17, 2019
Building Protocols with HTTP Building Protocols with HTTP
draft-ietf-httpbis-bcp56bis-08 draft-ietf-httpbis-bcp56bis-latest
Abstract Abstract
HTTP is often used as a substrate for other application protocols HTTP is often used as a substrate for other application protocols
(a.k.a. HTTP-based APIs). This document specifies best practices (a.k.a. HTTP-based APIs). This document specifies best practices
for such protocols' use of HTTP when they are defined for diverse for such protocols' use of HTTP when they are defined for diverse
implementation and broad deployment (e.g., in standards efforts). implementation and broad deployment (e.g., in standards efforts).
Note to Readers Note to Readers
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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 https://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 May 13, 2019. This Internet-Draft will expire on November 17, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 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
(https://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
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Is HTTP Being Used? . . . . . . . . . . . . . . . . . . . . . 4 2. Is HTTP Being Used? . . . . . . . . . . . . . . . . . . . . . 4
3. What's Important About HTTP . . . . . . . . . . . . . . . . . 5 3. What's Important About HTTP . . . . . . . . . . . . . . . . . 5
3.1. Generic Semantics . . . . . . . . . . . . . . . . . . . . 5 3.1. Generic Semantics . . . . . . . . . . . . . . . . . . . . 5
3.2. Links . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Links . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Rich Functionality . . . . . . . . . . . . . . . . . . . 7 3.3. Rich Functionality . . . . . . . . . . . . . . . . . . . 7
4. Best Practices for Using HTTP . . . . . . . . . . . . . . . . 8 4. Best Practices for Using HTTP . . . . . . . . . . . . . . . . 8
4.1. Specifying the Use of HTTP . . . . . . . . . . . . . . . 8 4.1. Specifying the Use of HTTP . . . . . . . . . . . . . . . 8
4.2. Defining HTTP Resources . . . . . . . . . . . . . . . . . 9 4.2. Defining HTTP Resources . . . . . . . . . . . . . . . . . 9
4.3. Specifying Client Behaviours . . . . . . . . . . . . . . 9 4.3. Specifying Client Behaviours . . . . . . . . . . . . . . 10
4.4. HTTP URLs . . . . . . . . . . . . . . . . . . . . . . . . 10 4.4. HTTP URLs . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4.1. Initial URL Discovery . . . . . . . . . . . . . . . . 11 4.4.1. Initial URL Discovery . . . . . . . . . . . . . . . . 11
4.4.2. URL Schemes . . . . . . . . . . . . . . . . . . . . . 11 4.4.2. URI Schemes . . . . . . . . . . . . . . . . . . . . . 11
4.4.3. Transport Ports . . . . . . . . . . . . . . . . . . . 12 4.4.3. Transport Ports . . . . . . . . . . . . . . . . . . . 12
4.5. HTTP Methods . . . . . . . . . . . . . . . . . . . . . . 13 4.5. HTTP Methods . . . . . . . . . . . . . . . . . . . . . . 13
4.5.1. GET . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.5.1. GET . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.5.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . 14 4.5.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . 14
4.6. HTTP Status Codes . . . . . . . . . . . . . . . . . . . . 15 4.6. HTTP Status Codes . . . . . . . . . . . . . . . . . . . . 15
4.6.1. Redirection . . . . . . . . . . . . . . . . . . . . . 16 4.6.1. Redirection . . . . . . . . . . . . . . . . . . . . . 16
4.7. HTTP Header Fields . . . . . . . . . . . . . . . . . . . 17 4.7. HTTP Header Fields . . . . . . . . . . . . . . . . . . . 17
4.8. Defining Message Payloads . . . . . . . . . . . . . . . . 18 4.8. Defining Message Payloads . . . . . . . . . . . . . . . . 18
4.9. HTTP Caching . . . . . . . . . . . . . . . . . . . . . . 18 4.9. HTTP Caching . . . . . . . . . . . . . . . . . . . . . . 18
4.10. Application State . . . . . . . . . . . . . . . . . . . . 20 4.10. Application State . . . . . . . . . . . . . . . . . . . . 20
4.11. Client Authentication . . . . . . . . . . . . . . . . . . 21 4.11. Client Authentication . . . . . . . . . . . . . . . . . . 21
4.12. Co-Existing with Web Browsing . . . . . . . . . . . . . . 21 4.12. Co-Existing with Web Browsing . . . . . . . . . . . . . . 21
4.13. Application Boundaries . . . . . . . . . . . . . . . . . 23 4.13. Application Boundaries . . . . . . . . . . . . . . . . . 23
4.14. Server Push . . . . . . . . . . . . . . . . . . . . . . . 23 4.14. Server Push . . . . . . . . . . . . . . . . . . . . . . . 24
4.15. Versioning and Evolution . . . . . . . . . . . . . . . . 24 4.15. Versioning and Evolution . . . . . . . . . . . . . . . . 24
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
6. Security Considerations . . . . . . . . . . . . . . . . . . . 25 6. Security Considerations . . . . . . . . . . . . . . . . . . . 25
6.1. Privacy Considerations . . . . . . . . . . . . . . . . . 25 6.1. Privacy Considerations . . . . . . . . . . . . . . . . . 25
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.1. Normative References . . . . . . . . . . . . . . . . . . 26 7.1. Normative References . . . . . . . . . . . . . . . . . . 26
7.2. Informative References . . . . . . . . . . . . . . . . . 27 7.2. Informative References . . . . . . . . . . . . . . . . . 28
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 30 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Appendix A. Changes from RFC 3205 . . . . . . . . . . . . . . . 30 Appendix A. Changes from RFC 3205 . . . . . . . . . . . . . . . 31
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 30 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
HTTP [I-D.ietf-httpbis-semantics] is often used as a substrate for HTTP [I-D.ietf-httpbis-semantics] is often used as a substrate for
applications other than Web browsing; this is sometimes referred to applications other than Web browsing; this is sometimes referred to
as creating "HTTP-based APIs", or just "HTTP APIs". This is done for as creating "HTTP-based APIs", or just "HTTP APIs". This is done for
a variety of reasons, including: a variety of reasons, including:
o familiarity by implementers, specifiers, administrators, o familiarity by implementers, specifiers, administrators,
developers and users, developers and users,
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This is largely because implementations (both client and server) will This is largely because implementations (both client and server) will
implement and evolve at different paces. As a result, such an HTTP- implement and evolve at different paces. As a result, such an HTTP-
based API will need to more carefully consider how extensibility of based API will need to more carefully consider how extensibility of
the service will be handled and how different deployment requirements the service will be handled and how different deployment requirements
will be accommodated. will be accommodated.
More generally, application protocols using HTTP face a number of More generally, application protocols using HTTP face a number of
design decisions, including: design decisions, including:
o Should it define a new URL scheme? Use new ports? o Should it define a new URI scheme? Use new ports?
o Should it use standard HTTP methods and status codes, or define o Should it use standard HTTP methods and status codes, or define
new ones? new ones?
o How can the maximum value be extracted from the use of HTTP? o How can the maximum value be extracted from the use of HTTP?
o How does it coexist with other uses of HTTP - especially Web o How does it coexist with other uses of HTTP - especially Web
browsing? browsing?
o How can interoperability problems and "protocol dead ends" be o How can interoperability problems and "protocol dead ends" be
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"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Is HTTP Being Used? 2. Is HTTP Being Used?
Different applications have different goals when using HTTP. The Different applications have different goals when using HTTP. The
requirements in this document apply when any of the following requirements in this document apply when any of the following
conditions are true: conditions are true:
o The transport port in use is 80 or 443, o the transport port in use is 80 or 443,
o The URL scheme "http" or "https" is used, o the URI scheme "http" or "https" is used,
o The ALPN protocol ID [RFC7301] generically identifies HTTP (e.g., o the ALPN protocol ID [RFC7301] generically identifies HTTP (e.g.,
"http/1.1", "h2", "h2c"), or "http/1.1", "h2", "h2c"), or
o The IANA registries defined for HTTP are updated or modified. o the IANA registries defined for HTTP are updated or modified.
When an application is using HTTP, all of the requirements of the When an application is using HTTP, all of the requirements of the
HTTP protocol suite are in force (including but not limited to HTTP protocol suite are in force (including but not limited to
[I-D.ietf-httpbis-semantics], [I-D.ietf-httpbis-cache], [I-D.ietf-httpbis-semantics], [I-D.ietf-httpbis-cache],
[I-D.ietf-httpbis-messaging], and [RFC7540]). [I-D.ietf-httpbis-messaging], and [RFC7540]).
An application might not use HTTP according to this definition and An application might not use HTTP according to this definition and
still rely upon the HTTP specifications in some manner. For example, still rely upon the HTTP specifications in some manner. For example,
an application might wish to avoid re-specifying parts of the message an application might wish to avoid re-specifying parts of the message
format, but change others; or, it might want to use a different set format, but change others; or, it might want to use a different set
of methods. of methods.
Such applications are referred to as "protocols based upon HTTP" in Such applications are referred to as "protocols based upon HTTP" in
this document. These have more freedom to modify protocol this document. These have more freedom to modify protocol
operations, but are also likely to lose at least a portion of the operations, but are also likely to lose at least a portion of the
benefits outlined above, as most HTTP implementations won't be easily benefits outlined above, as most HTTP implementations won't be easily
adaptable to these changes, and as the protocol diverges from HTTP, adaptable to these changes, and as the protocol diverges from HTTP,
the benefit of mindshare will be lost. the benefit of mindshare will be lost.
Protocols that are based upon HTTP MUST NOT reuse HTTP's URL schemes, Protocols that are based upon HTTP MUST NOT reuse HTTP's URI schemes,
transport ports, ALPN protocol IDs or IANA registries; rather, they transport ports, ALPN protocol IDs or IANA registries; rather, they
are encouraged to establish their own. are encouraged to establish their own.
3. What's Important About HTTP 3. What's Important About HTTP
Applications using HTTP are defined and deployed in many ways; Applications using HTTP are defined and deployed in many ways;
sometimes they are brought to the IETF for standardisation. What sometimes they are brought to the IETF for standardisation. What
might be workable for deployment in a limited fashion isn't might be workable for deployment in a limited fashion isn't
appropriate for standardisation and the corresponding broader appropriate for standardisation and the corresponding broader
deployment. deployment.
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(or a portion thereof) is exclusively for the use of a single (or a portion thereof) is exclusively for the use of a single
application. This effectively overlays special, application-specific application. This effectively overlays special, application-specific
semantics onto that space, precludes other applications from using semantics onto that space, precludes other applications from using
it. it.
As explained in [RFC7320], such "squatting" on a part of the URL As explained in [RFC7320], such "squatting" on a part of the URL
space by a standard usurps the server's authority over its own space by a standard usurps the server's authority over its own
resources, can cause deployment issues, and is therefore bad practice resources, can cause deployment issues, and is therefore bad practice
in standards. in standards.
Instead of statically defining URL components like paths, it is Instead of statically defining URI components like paths, it is
RECOMMENDED that applications using HTTP define links in payloads, to RECOMMENDED that applications using HTTP define links in payloads, to
allow flexibility in deployment. allow flexibility in deployment.
Using runtime links in this fashion has a number of other benefits - Using runtime links in this fashion has a number of other benefits -
especially when an application is to have multiple implementations especially when an application is to have multiple implementations
and/or deployments (as is often the case for those that are and/or deployments (as is often the case for those that are
standardised). standardised).
For example, navigating with a link allows a request to be routed to For example, navigating with a link allows a request to be routed to
a different server without the overhead of a redirection, thereby a different server without the overhead of a redirection, thereby
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Content-Length: 500 Content-Length: 500
Server: Bar/2.2 Server: Bar/2.2
[payload here] [payload here]
4.2. Defining HTTP Resources 4.2. Defining HTTP Resources
Applications that use HTTP should focus on defining the following Applications that use HTTP should focus on defining the following
application-specific protocol elements: application-specific protocol elements:
o Media types [RFC6838], often based upon a format convention such o media types [RFC6838], often based upon a format convention such
as JSON [RFC8259], as JSON [RFC8259],
o HTTP header fields, as per Section 4.7, and o HTTP header fields, as per Section 4.7, and
o The behaviour of resources, as identified by link relations o the behaviour of resources, as identified by link relations
[RFC8288]. [RFC8288].
By composing these protocol elements, an application can define a set By composing these protocol elements, an application can define a set
of resources, identified by link relations, that implement specified of resources, identified by link relations, that implement specified
behaviours, including: behaviours, including:
o Retrieval of their state using GET, in one or more formats o retrieval of their state using GET, in one or more formats
identified by media type; identified by media type;
o Resource creation or update using POST or PUT, with an o resource creation or update using POST or PUT, with an
appropriately identified request body format; appropriately identified request body format;
o Data processing using POST and identified request and response o data processing using POST and identified request and response
body format(s); and body format(s); and
o Resource deletion using DELETE. o Resource deletion using DELETE.
For example, an application might specify: For example, an application might specify:
Resources linked to with the "example-widget" link relation type are Resources linked to with the "example-widget" link relation type are
Widgets. The state of a Widget can be fetched in the Widgets. The state of a Widget can be fetched in the
"application/example-widget+json" format, and can be updated by PUT "application/example-widget+json" format, and can be updated by PUT
to the same link. Widget resources can be deleted. to the same link. Widget resources can be deleted.
The "Example-Count" response header field on Widget representations The "Example-Count" response header field on Widget representations
indicates how many Widgets are held by the sender. indicates how many Widgets are held by the sender.
The "application/example-widget+json" format is a JSON [RFC8259] The "application/example-widget+json" format is a JSON [RFC8259]
format representing the state of a Widget. It contains links to format representing the state of a Widget. It contains links to
related information in the link indicated by the Link header field related information in the link indicated by the Link header field
value with the "example-other-info" link relation type. value with the "example-other-info" link relation type.
Applications can also specify the use of URI Templates [RFC6570] to
allow clients to generate URLs based upon runtime data.
4.3. Specifying Client Behaviours 4.3. Specifying Client Behaviours
Some behaviours (e.g., automatic redirect handling) and extensions Some behaviours (e.g., automatic redirect handling) and extensions
(e.g., Cookies) are not required by HTTP, but nevertheless have (e.g., Cookies) are not required by HTTP, but nevertheless have
become very common, possibly because they are supported by Web become very common, possibly because they are supported by Web
browsers. If their use is not explicitly specified by applications browsers. If their use is not explicitly specified by applications
using HTTP, there may be confusion and interoperability problems. using HTTP, there may be confusion and interoperability problems.
This section recommends default handling for these mechanisms. This section recommends default handling for these mechanisms.
o Redirect handling - Applications need to specify how redirects are o Redirect handling - Applications need to specify how redirects are
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If an application using HTTP has browser compatibility as a goal, If an application using HTTP has browser compatibility as a goal,
client interaction ought to be defined in terms of [FETCH], since client interaction ought to be defined in terms of [FETCH], since
that is the abstraction that browsers use for HTTP; it enforces many that is the abstraction that browsers use for HTTP; it enforces many
of these best practices. of these best practices.
Applications using HTTP MUST NOT require HTTP features that are Applications using HTTP MUST NOT require HTTP features that are
usually negotiated to be supported by clients. For example, usually negotiated to be supported by clients. For example,
requiring that clients support responses with a certain content- requiring that clients support responses with a certain content-
coding ([I-D.ietf-httpbis-semantics], Section 6.2.2) instead of coding ([I-D.ietf-httpbis-semantics], Section 6.2.2) instead of
negotiating for it ({{?I-D.ietf-httpbis-semantics, Section 8.4.4) negotiating for it ([I-D.ietf-httpbis-semantics], Section 8.4.4)
means that otherwise conformant clients cannot interoperate with the means that otherwise conformant clients cannot interoperate with the
application. Applications MAY encourage the implementation of such application. Applications MAY encourage the implementation of such
features, though. features, though.
4.4. HTTP URLs 4.4. HTTP URLs
In HTTP, URLs are opaque identifiers under the control of the server. In HTTP, URLs are opaque identifiers under the control of the server.
As outlined in [RFC7320], standards cannot usurp this space, since it As outlined in [RFC7320], standards cannot usurp this space, since it
might conflict with existing resources, and constrain implementation might conflict with existing resources, and constrain implementation
and deployment. and deployment.
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URL) with the capabilities that resource supports, bringing about URL) with the capabilities that resource supports, bringing about
many of the same interoperability problems that [RFC4367] warns of. many of the same interoperability problems that [RFC4367] warns of.
For example, specifying that a "GET to the URL /foo retrieves a bar For example, specifying that a "GET to the URL /foo retrieves a bar
document" is bad practice. Likewise, specifying "The widget API is document" is bad practice. Likewise, specifying "The widget API is
at the path /bar" violates [RFC7320]. at the path /bar" violates [RFC7320].
Instead, applications are encouraged to ensure that URLs are Instead, applications are encouraged to ensure that URLs are
discovered at runtime, allowing HTTP-based services to describe their discovered at runtime, allowing HTTP-based services to describe their
own capabilities. One way to do this is to use typed links [RFC8288] own capabilities. One way to do this is to use typed links [RFC8288]
to convey the URIs that are in use, as well as the semantics of the to convey the URLs that are in use, as well as the semantics of the
resources that they identify. See Section 4.2 for details. resources that they identify. See Section 4.2 for details.
4.4.1. Initial URL Discovery 4.4.1. Initial URL Discovery
Generally, a client will begin interacting with a given application Generally, a client will begin interacting with a given application
server by requesting an initial document that contains information server by requesting an initial document that contains information
about that particular deployment, potentially including links to about that particular deployment, potentially including links to
other relevant resources. other relevant resources.
Applications are encouraged to allow an arbitrary URL to be used as Applications are encouraged to allow an arbitrary URL to be used as
that entry point. For example, rather than specifying "the initial that entry point. For example, rather than specifying "the initial
document is at "/foo/v1", they should allow a deployment to use any document is at "/foo/v1", they should allow a deployment to use any
URL as the entry point for the application. URL as the entry point for the application.
In cases where doing so is impractical (e.g., it is not possible to In cases where doing so is impractical (e.g., it is not possible to
convey a whole URL, but only a hostname) applications can request a convey a whole URL, but only a hostname) applications can request a
well-known URL [I-D.nottingham-rfc5785bis] as an entry point. well-known URI [I-D.nottingham-rfc5785bis] as an entry point.
4.4.2. URL Schemes 4.4.2. URI Schemes
Applications that use HTTP will typically employ the "http" and/or Applications that use HTTP will typically employ the "http" and/or
"https" URL schemes. "https" is RECOMMENDED to provide "https" URI schemes. "https" is RECOMMENDED to provide
authentication, integrity and confidentiality, as well as mitigate authentication, integrity and confidentiality, as well as mitigate
pervasive monitoring attacks [RFC7258]. pervasive monitoring attacks [RFC7258].
However, application-specific schemes can also be defined. When However, application-specific schemes can also be defined. When
defining an URL scheme for an application using HTTP, there are a defining an URI scheme for an application using HTTP, there are a
number of tradeoffs and caveats to keep in mind: number of tradeoffs and caveats to keep in mind:
o Unmodified Web browsers will not support the new scheme. While it o Unmodified Web browsers will not support the new scheme. While it
is possible to register new URL schemes with Web browsers (e.g. is possible to register new URI schemes with Web browsers (e.g.
registerProtocolHandler() in [HTML5], as well as several registerProtocolHandler() in [HTML5], as well as several
proprietary approaches), support for these mechanisms is not proprietary approaches), support for these mechanisms is not
shared by all browsers, and their capabilities vary. shared by all browsers, and their capabilities vary.
o Existing non-browser clients, intermediaries, servers and o Existing non-browser clients, intermediaries, servers and
associated software will not recognise the new scheme. For associated software will not recognise the new scheme. For
example, a client library might fail to dispatch the request; a example, a client library might fail to dispatch the request; a
cache might refuse to store the response, and a proxy might fail cache might refuse to store the response, and a proxy might fail
to forward the request. to forward the request.
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[I-D.ietf-httpbis-rfc6265bis], authentication [I-D.ietf-httpbis-rfc6265bis], authentication
[I-D.ietf-httpbis-semantics], caching [I-D.ietf-httpbis-cache], [I-D.ietf-httpbis-semantics], caching [I-D.ietf-httpbis-cache],
HSTS [RFC6797], and CORS [FETCH] might or might not work HSTS [RFC6797], and CORS [FETCH] might or might not work
correctly, depending on how they are defined and implemented. correctly, depending on how they are defined and implemented.
Generally, they are designed and implemented with an assumption Generally, they are designed and implemented with an assumption
that the URL will always be "http" or "https". that the URL will always be "http" or "https".
o Web features that require a secure context [SECCTXT] will likely o Web features that require a secure context [SECCTXT] will likely
treat a new scheme as insecure. treat a new scheme as insecure.
See [RFC7595] for more information about minting new URL schemes. See [RFC7595] for more information about minting new URI schemes.
4.4.3. Transport Ports 4.4.3. Transport Ports
Applications can use the applicable default port (80 for HTTP, 443 Applications can use the applicable default port (80 for HTTP, 443
for HTTPS), or they can be deployed upon other ports. This decision for HTTPS), or they can be deployed upon other ports. This decision
can be made at deployment time, or might be encouraged by the can be made at deployment time, or might be encouraged by the
application's specification (e.g., by registering a port for that application's specification (e.g., by registering a port for that
application). application).
If a non-default port is used, it needs to be reflected in the If a non-default port is used, it needs to be reflected in the
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While historically some applications (e.g., [RFC4791]) have defined While historically some applications (e.g., [RFC4791]) have defined
non-generic methods, [I-D.ietf-httpbis-semantics] now forbids this. non-generic methods, [I-D.ietf-httpbis-semantics] now forbids this.
When authors believe that a new method is required, they are When authors believe that a new method is required, they are
encouraged to engage with the HTTP community early, and document encouraged to engage with the HTTP community early, and document
their proposal as a separate HTTP extension, rather than as part of their proposal as a separate HTTP extension, rather than as part of
an application's specification. an application's specification.
4.5.1. GET 4.5.1. GET
GET is one of the most common and useful HTTP methods; its retrieval GET is the most common and useful HTTP method; its retrieval
semantics allow caching, side-effect free linking and underlies many semantics allow caching, side-effect free linking and underlies many
of the benefits of using HTTP. of the benefits of using HTTP.
A common use of GET is to perform queries, often using the query A common use of GET is to perform queries, often using the query
component of the URL; this is a familiar pattern from Web browsing, component of the URL; this is a familiar pattern from Web browsing,
and the results can be cached, improving efficiency of an often and the results can be cached, improving efficiency of an often
expensive process. expensive process.
In some cases, however, GET might be unwieldy for expressing queries, In some cases, however, GET might be unwieldy for expressing queries,
because of the limited syntax of the URL; in particular, if binary because of the limited syntax of the URI; in particular, if binary
data forms part of the query terms, it needs to be encoded to conform data forms part of the query terms, it needs to be encoded to conform
to URL syntax. to URI syntax.
While this is not an issue for short queries, it can become one for While this is not an issue for short queries, it can become one for
larger query terms, or ones which need to sustain a high rate of larger query terms, or ones which need to sustain a high rate of
requests. Additionally, some HTTP implementations limit the size of requests. Additionally, some HTTP implementations limit the size of
URLs they support - although modern HTTP software has much more URLs they support - although modern HTTP software has much more
generous limits than previously (typically, considerably more than generous limits than previously (typically, considerably more than
8000 octets, as required by [I-D.ietf-httpbis-semantics]. 8000 octets, as required by [I-D.ietf-httpbis-semantics].
In these cases, an application using HTTP might consider using POST In these cases, an application using HTTP might consider using POST
to express queries in the request body; doing so avoids encoding to express queries in the request body; doing so avoids encoding
overhead and URL length limits in implementations. However, in doing overhead and URL length limits in implementations. However, in doing
so it should be noted that the benefits of GET such as caching and so it should be noted that the benefits of GET such as caching and
linking to query results are lost. Therefore, applications using linking to query results are lost. Therefore, applications using
HTTP that feel a need to allow POST queries ought consider allowing HTTP that feel a need to allow POST queries ought consider allowing
both methods. both methods.
Applications SHOULD NOT define GET requests to have side effects, Applications should not change their state or have other side effects
since implementations can and do retry HTTP GET requests that fail. that might be significant to the client, since implementations can
and do retry HTTP GET requests that fail. Note that this does not
include logging and similar functions; see
[I-D.ietf-httpbis-semantics], Section 7.2.1.
Finally, note that while HTTP allows GET requests to have a body Finally, note that while HTTP allows GET requests to have a body
syntactically, this is done only to allow parsers to be generic; as syntactically, this is done only to allow parsers to be generic; as
per [I-D.ietf-httpbis-semantics], Section 7.3.1, a body on a GET has per [I-D.ietf-httpbis-semantics], Section 7.3.1, a body on a GET has
no meaning, and will be either ignored or rejected by generic HTTP no meaning, and will be either ignored or rejected by generic HTTP
software. software.
4.5.2. OPTIONS 4.5.2. OPTIONS
The OPTIONS method was defined for metadata retrieval, and is used The OPTIONS method was defined for metadata retrieval, and is used
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o For metadata about a specific resource, create a separate resource o For metadata about a specific resource, create a separate resource
and link to it using a Link response header or a link serialised and link to it using a Link response header or a link serialised
into the representation's body. See [RFC8288]. Note that the into the representation's body. See [RFC8288]. Note that the
Link header is available on HEAD responses, which is useful if the Link header is available on HEAD responses, which is useful if the
client wants to discover a resource's capabilities before they client wants to discover a resource's capabilities before they
interact with it. interact with it.
4.6. HTTP Status Codes 4.6. HTTP Status Codes
The primary function of a HTTP status code is to convey semantics for HTTP status codes convey semantics both for the benefit of generic
the benefit of generic HTTP software, not to convey application- HTTP components - such as caches, intermediaries, and clients - and
specific semantics. applications themselves. However, applications can encounter a
number of pitfalls in their use.
Status codes are often generated or overwritten by intermediaries, as First, status codes are often generated by intermediaries, as well as
well as server and client implementations. This can happen, for server and client implementations. This can happen, for example,
example, when network errors are encountered, a captive portal is when network errors are encountered, a captive portal is present,
present, when an implementation is overloaded, or it thinks it is when an implementation is overloaded, or it thinks it is under
under attack. As a result, the status code that a server-side attack. As a result, if an application assigns specific semantics to
application generates and the one that the client software receives one of these status codes, a client can be misled about its state,
often differ. because the status code was generated by a generic component, not the
application itself.
This means that status codes are not a reliable way to carry Furthermore, mapping application errors to individual HTTP status
application-specific signals. Specifying that a particular status codes one-to-one often leads to a situation where the finite space of
code has a specific meaning in the context of an application can have applicable HTTP status codes is exhausted. This, in turn, leads to a
unintended side effects; if that status code is generated by a number of bad practices - including minting new, application-specific
generic HTTP component can lead clients to believe that the status codes, or using existing status codes even though the link
application is in a state that wasn't intended. between their semantics and the application's is tenuous at best.
Instead, applications using HTTP should specify the implications of Instead, applications using HTTP should define their errors to use
general classes of responses (e.g., "successful response" for 2xx; the most applicable status code, making generous use of the general
"client error" for 4xx and "server error" for 5xx), conveying any status codes (200, 400 and 500) when in doubt. Importantly, they
application-specific information in the message body and/or HTTP SHOULD NOT specify a one-to-one relationship between status codes and
header fields, not the status code. [RFC7807] provides one way for application errors, thereby avoiding the exhaustion issue outlined
applications using HTTP to do so for error conditions. above.
There are limited exceptions to this; for example, applications might To distinguish between multiple error conditions that are mapped to
use 201 (Created) or 404 (Not Found) to convey application semantics the same status code, and to avoid the misattribution issue outlined
that are compatible with the generic HTTP semantics of those status above, applications using HTTP SHOULD convey finer-grained error
codes. In general, though, applications should resist the temptation information in the response's message body and/or header fields.
to map their semantics into fine-grained status codes. [RFC7807] provides one way to do so.
Because the set of registered HTTP status codes can expand, Because the set of registered HTTP status codes can expand,
applications using HTTP should explicitly point out that clients applications using HTTP SHOULD explicitly point out that clients
ought to be able to handle all applicable status codes gracefully ought to be able to handle all applicable status codes gracefully
(i.e., falling back to the generic "n00" semantics of a given status (i.e., falling back to the generic "n00" semantics of a given status
code; e.g., "499" can be safely handled as "400" by clients that code; e.g., "499" can be safely handled as "400" by clients that
don't recognise it). This is preferable to creating a "laundry list" don't recognise it). This is preferable to creating a "laundry list"
of potential status codes, since such a list is never complete. of potential status codes, since such a list won't be complete in the
foreseeable future.
Applications using HTTP MUST NOT re-specify the semantics of HTTP Applications using HTTP MUST NOT re-specify the semantics of HTTP
status codes, even if it is only by copying their definition. They status codes, even if it is only by copying their definition. They
MUST NOT require specific reason phrases to be used; the reason MUST NOT require specific reason phrases to be used; the reason
phrase has no function in HTTP, is not guaranteed to be preserved by phrase has no function in HTTP, is not guaranteed to be preserved by
implementations, and the reason phrase is not carried at all in the implementations, and is not carried at all in the HTTP/2 [RFC7540]
HTTP/2 [RFC7540] message format. message format.
Applications MUST only use registered HTTP status codes. As with Applications MUST only use registered HTTP status codes. As with
methods, new HTTP status codes are rare, and required (by methods, new HTTP status codes are rare, and required (by
[I-D.ietf-httpbis-semantics]) to be registered with IETF Review. [I-D.ietf-httpbis-semantics]) to be registered with IETF Review.
Similarly, HTTP status codes are generic; they are required (by Similarly, HTTP status codes are generic; they are required (by
[I-D.ietf-httpbis-semantics]) to be potentially applicable to all [I-D.ietf-httpbis-semantics]) to be potentially applicable to all
resources, not just to those of one application. resources, not just to those of one application.
When authors believe that a new status code is required, they are When authors believe that a new status code is required, they are
encouraged to engage with the HTTP community early, and document encouraged to engage with the HTTP community early, and document
their proposal as a separate HTTP extension, rather than as part of their proposal as a separate HTTP extension, rather than as part of
an application's specification. an application's specification.
4.6.1. Redirection 4.6.1. Redirection
The 3xx series of status codes specified in The 3xx series of status codes specified in Section 9.4
[I-D.ietf-httpbis-semantics], Section 9.4 direct the user agent to [I-D.ietf-httpbis-semantics] direct the user agent to another
another resource to satisfy the request. The most common of these resource to satisfy the request. The most common of these are 301,
are 301, 302, 307 and 308 ([RFC7538]), all of which use the Location 302, 307 and 308, all of which use the Location response header field
response header field to indicate where the client should send the to indicate where the client should send the request to.
request to.
There are two ways that this group of status codes differ: There are two ways that this group of status codes differ:
o Whether they are permanent or temporary. Permanent redirects can o Whether they are permanent or temporary. Permanent redirects can
be used to update links stored in the client (e.g., bookmarks), be used to update links stored in the client (e.g., bookmarks),
whereas temporary ones can not. Note that this has no effect on whereas temporary ones can not. Note that this has no effect on
HTTP caching; it is completely separate. HTTP caching; it is completely separate.
o Whether they allow the redirected request to change the request o Whether they allow the redirected request to change the request
method from POST to GET. Web browsers generally do change POST to method from POST to GET. Web browsers generally do change POST to
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This table summarises their relationships: This table summarises their relationships:
+-------------------------------------------+-----------+-----------+ +-------------------------------------------+-----------+-----------+
| | Permanent | Temporary | | | Permanent | Temporary |
+-------------------------------------------+-----------+-----------+ +-------------------------------------------+-----------+-----------+
| Allows changing the request method from | 301 | 302 | | Allows changing the request method from | 301 | 302 |
| POST to GET | | | | POST to GET | | |
| Does not allow changing the request | 308 | 307 | | Does not allow changing the request | 308 | 307 |
| method | | | | method | | |
+-------------------------------------------+-----------+-----------+ +-------------------------------------------+-----------+-----------+
As noted in [I-D.ietf-httpbis-semantics], a user agent is allowed to As noted in [I-D.ietf-httpbis-semantics], a user agent is allowed to
automatically follow a 3xx redirect that has a Location response automatically follow a 3xx redirect that has a Location response
header field, even if they don't understand the semantics of the header field, even if they don't understand the semantics of the
specific status code. However, they aren't required to do so; specific status code. However, they aren't required to do so;
therefore, if an application using HTTP desires redirects to be therefore, if an application using HTTP desires redirects to be
automatically followed, it needs to explicitly specify the automatically followed, it needs to explicitly specify the
circumstances when this is required. circumstances when this is required.
Applications using HTTP SHOULD specify that 301 and 302 responses Applications using HTTP SHOULD specify that 301 and 302 responses
change the subsequent request method from POST (but no other method) change the subsequent request method from POST (but no other method)
to GET, to be compatible with browsers. to GET, to be compatible with browsers.
Generally, when a redirected request is made, its header fields are Generally, when a redirected request is made, its header fields are
copied from the original request's. However, they can be modified by copied from the original request's. However, they can be modified by
various mechanisms; e.g., sent Authorization various mechanisms; e.g., sent Authorization
([I-D.ietf-httpbis-semantics]) and Cookie ([I-D.ietf-httpbis-semantics]) and Cookie
([I-D.ietf-httpbis-rfc6265bis]) headers will change if the origin ([I-D.ietf-httpbis-rfc6265bis]) headers will change if the origin
(and sometimes path) of the request changes. Applications using HTTP (and sometimes path) of the request changes. An application using
SHOULD specify if any request headers need to be modified or removed HTTP SHOULD specify if any request headers that it defines need to be
upon a redirect; however, this behaviour cannot be relied upon, since modified or removed upon a redirect; however, this behaviour cannot
a generic client (like a browser) will be unaware of such be relied upon, since a generic client (like a browser) will be
requirements. unaware of such requirements.
4.7. HTTP Header Fields 4.7. HTTP Header Fields
Applications MAY define new HTTP header fields. Typically, using Applications MAY define new HTTP header fields. Typically, using
HTTP header fields is appropriate in a few different situations: HTTP header fields is appropriate in a few different situations:
o Their content is useful to intermediaries (who often wish to avoid o Their content is useful to intermediaries (who often wish to avoid
parsing the body), and/or parsing the body), and/or
o Their content is useful to generic HTTP software (e.g., clients, o Their content is useful to generic HTTP software (e.g., clients,
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4.10. Application State 4.10. Application State
Applications MAY use stateful cookies [I-D.ietf-httpbis-rfc6265bis] Applications MAY use stateful cookies [I-D.ietf-httpbis-rfc6265bis]
to identify a client and/or store client-specific data to to identify a client and/or store client-specific data to
contextualise requests. contextualise requests.
When used, it is important to carefully specify the scoping and use When used, it is important to carefully specify the scoping and use
of cookies; if the application exposes sensitive data or capabilities of cookies; if the application exposes sensitive data or capabilities
(e.g., by acting as an ambient authority), exploits are possible. (e.g., by acting as an ambient authority), exploits are possible.
Mitigations include using a request-specific token to assure the Mitigations include using a request-specific token to assure the
intent of the client. intent of the client.
Applications MUST NOT make assumptions about the relationship between Applications MUST NOT make assumptions about the relationship between
separate requests on a single transport connection; doing so breaks separate requests on a single transport connection; doing so breaks
many of the assumptions of HTTP as a stateless protocol, and will many of the assumptions of HTTP as a stateless protocol, and will
cause problems in interoperability, security, operability and cause problems in interoperability, security, operability and
evolution. evolution.
4.11. Client Authentication 4.11. Client Authentication
Applications MAY use HTTP authentication [I-D.ietf-httpbis-semantics] Applications MAY use HTTP authentication [I-D.ietf-httpbis-semantics]
to identify clients. The Basic authentication scheme [RFC7617] MUST to identify clients. The Basic authentication scheme [RFC7617] MUST
NOT be used unless the underlying transport is authenticated, NOT be used unless the underlying transport is authenticated,
integrity-protected and confidential (e.g., as provided the "HTTPS" integrity-protected and confidential (e.g., as provided the "HTTPS"
URL scheme, or another using TLS). The Digest scheme [RFC7616] MUST URI scheme, or another using TLS). The Digest scheme [RFC7616] MUST
NOT be used unless the underlying transport is similarly secure, or NOT be used unless the underlying transport is similarly secure, or
the chosen hash algorithm is not "MD5". the chosen hash algorithm is not "MD5".
With HTTPS, clients might also be authenticated using certificates With HTTPS, clients might also be authenticated using certificates
[RFC5246]. [RFC5246].
When used, it is important to carefully specify the scoping and use When used, it is important to carefully specify the scoping and use
of authentication; if the application exposes sensitive data or of authentication; if the application exposes sensitive data or
capabilities (e.g., by acting as an ambient authority), exploits are capabilities (e.g., by acting as an ambient authority), exploits are
possible. Mitigations include using a request-specific token to possible. Mitigations include using a request-specific token to
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This is only a small sample of the kinds of issues that applications This is only a small sample of the kinds of issues that applications
using HTTP must consider. Generally, the best approach is to using HTTP must consider. Generally, the best approach is to
consider the application actually as a Web application, and to follow consider the application actually as a Web application, and to follow
best practices for their secure development. best practices for their secure development.
A complete enumeration of such practices is out of scope for this A complete enumeration of such practices is out of scope for this
document, but some considerations include: document, but some considerations include:
o Using an application-specific media type in the Content-Type o Using an application-specific media type in the Content-Type
header, and requiring clients to fail if it is not used header, and requiring clients to fail if it is not used.
o Using X-Content-Type-Options: nosniff [FETCH] to assure that o Using X-Content-Type-Options: nosniff [FETCH] to assure that
content under attacker control can't be coaxed into a form that is content under attacker control can't be coaxed into a form that is
interpreted as active content by a Web browser interpreted as active content by a Web browser.
o Using Content-Security-Policy [CSP] to constrain the capabilities o Using Content-Security-Policy [CSP] to constrain the capabilities
of active content (such as HTML [HTML5]), thereby mitigating of active content (such as HTML [HTML5]), thereby mitigating
Cross-Site Scripting attacks Cross-Site Scripting attacks.
o Using Referrer-Policy [REFERRER-POLICY] to prevent sensitive data o Using Referrer-Policy [REFERRER-POLICY] to prevent sensitive data
in URLs from being leaked in the Referer request header in URLs from being leaked in the Referer request header.
o Using the 'HttpOnly' flag on Cookies to assure that cookies are o Using the 'HttpOnly' flag on Cookies to assure that cookies are
not exposed to browser scripting languages not exposed to browser scripting languages
[I-D.ietf-httpbis-rfc6265bis] [I-D.ietf-httpbis-rfc6265bis].
o Avoiding use of compression on any sensitive information (e.g., o Avoiding use of compression on any sensitive information (e.g.,
authentication tokens, passwords), as the scripting environment authentication tokens, passwords), as the scripting environment
offered by Web browsers allows an attacker to repeatedly probe the offered by Web browsers allows an attacker to repeatedly probe the
compression space; if the attacker has access to the path of the compression space; if the attacker has access to the path of the
communication, they can use this capability to recover that communication, they can use this capability to recover that
information information.
Depending on how they are intended to be deployed, specifications for Depending on how they are intended to be deployed, specifications for
applications using HTTP might require the use of these mechanisms in applications using HTTP might require the use of these mechanisms in
specific ways, or might merely point them out in Security specific ways, or might merely point them out in Security
Considerations. Considerations.
An example of a HTTP response from an application that does not An example of a HTTP response from an application that does not
intend for its content to be treated as active by browsers might look intend for its content to be treated as active by browsers might look
like this: like this:
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4.15. Versioning and Evolution 4.15. Versioning and Evolution
It's often necessary to introduce new features into application It's often necessary to introduce new features into application
protocols, and change existing ones. protocols, and change existing ones.
In HTTP, backwards-incompatible changes are possible using a number In HTTP, backwards-incompatible changes are possible using a number
of mechanisms: of mechanisms:
o Using a distinct link relation type [RFC8288] to identify a URL o Using a distinct link relation type [RFC8288] to identify a URL
for a resource that implements the new functionality for a resource that implements the new functionality.
o Using a distinct media type [RFC6838] to identify formats that o Using a distinct media type [RFC6838] to identify formats that
enable the new functionality enable the new functionality.
o Using a distinct HTTP header field to implement new functionality o Using a distinct HTTP header field to implement new functionality
outside the message body outside the message body.
5. IANA Considerations 5. IANA Considerations
This document has no requirements for IANA. This document has no requirements for IANA.
6. Security Considerations 6. Security Considerations
Section 4.10 discusses the impact of using stateful mechanisms in the Section 4.10 discusses the impact of using stateful mechanisms in the
protocol as ambient authority, and suggests a mitigation. protocol as ambient authority, and suggests a mitigation.
skipping to change at page 25, line 28 skipping to change at page 25, line 37
Section 4.12 highlights the implications of Web browsers' Section 4.12 highlights the implications of Web browsers'
capabilities on applications that use HTTP. capabilities on applications that use HTTP.
Section 4.13 discusses the issues that arise when applications are Section 4.13 discusses the issues that arise when applications are
deployed on the same origin as Web sites (and other applications). deployed on the same origin as Web sites (and other applications).
Section 4.14 highlights risks of using HTTP/2 server push in a manner Section 4.14 highlights risks of using HTTP/2 server push in a manner
other than specified. other than specified.
Applications that use HTTP in a manner that involves modification of Applications that use HTTP in a manner that involves modification of
implementations - for example, requiring support for a new URL implementations - for example, requiring support for a new URI
scheme, or a non-standard method - risk having those implementations scheme, or a non-standard method - risk having those implementations
"fork" from their parent HTTP implementations, with the possible "fork" from their parent HTTP implementations, with the possible
result that they do not benefit from patches and other security result that they do not benefit from patches and other security
improvements incorporated upstream. improvements incorporated upstream.
6.1. Privacy Considerations 6.1. Privacy Considerations
HTTP clients can expose a variety of information to servers. Besides HTTP clients can expose a variety of information to servers. Besides
information that's explicitly sent as part of an application's information that's explicitly sent as part of an application's
operation (for example, names and other user-entered data), and "on operation (for example, names and other user-entered data), and "on
skipping to change at page 26, line 21 skipping to change at page 26, line 32
control over its data. As a result, applications are advised to control over its data. As a result, applications are advised to
specify that clients should only emit the information they need to specify that clients should only emit the information they need to
function in requests. function in requests.
Finally, if an application exposes the ability to run mobile code, Finally, if an application exposes the ability to run mobile code,
great care needs to be taken, since any ability to observe its great care needs to be taken, since any ability to observe its
environment can be used as an opportunity to both fingerprint the environment can be used as an opportunity to both fingerprint the
client and to obtain and manipulate private data (including session client and to obtain and manipulate private data (including session
information). For example, access to high-resolution timers (even information). For example, access to high-resolution timers (even
indirectly) can be used to profile the underlying hardware, creating indirectly) can be used to profile the underlying hardware, creating
a unique identifier for the system. Applications are advised avoid a unique identifier for the system. Applications are advised to
allowing the use of mobile code where possible; when it cannot be avoid allowing the use of mobile code where possible; when it cannot
avoided, the resulting system's security properties need be carefully be avoided, the resulting system's security properties need be
scrutinised. carefully scrutinised.
7. References 7. References
7.1. Normative References 7.1. Normative References
[I-D.ietf-httpbis-cache] [I-D.ietf-httpbis-cache]
Fielding, R., Nottingham, M., and J. Reschke, "HTTP Fielding, R., Nottingham, M., and J. Reschke, "HTTP
Caching", draft-ietf-httpbis-cache-03 (work in progress), Caching", draft-ietf-httpbis-cache-03 (work in progress),
October 2018. October 2018.
skipping to change at page 28, line 7 skipping to change at page 28, line 23
<https://www.w3.org/TR/2016/WD-CSP3-20160913>. <https://www.w3.org/TR/2016/WD-CSP3-20160913>.
[FETCH] WHATWG, "Fetch - Living Standard", n.d., [FETCH] WHATWG, "Fetch - Living Standard", n.d.,
<https://fetch.spec.whatwg.org>. <https://fetch.spec.whatwg.org>.
[HTML5] WHATWG, "HTML - Living Standard", n.d., [HTML5] WHATWG, "HTML - Living Standard", n.d.,
<https://html.spec.whatwg.org>. <https://html.spec.whatwg.org>.
[I-D.ietf-httpbis-header-structure] [I-D.ietf-httpbis-header-structure]
Nottingham, M. and P. Kamp, "Structured Headers for HTTP", Nottingham, M. and P. Kamp, "Structured Headers for HTTP",
draft-ietf-httpbis-header-structure-08 (work in progress), draft-ietf-httpbis-header-structure-09 (work in progress),
October 2018. December 2018.
[I-D.ietf-httpbis-rfc6265bis] [I-D.ietf-httpbis-rfc6265bis]
Barth, A. and M. West, "Cookies: HTTP State Management Barth, A. and M. West, "Cookies: HTTP State Management
Mechanism", draft-ietf-httpbis-rfc6265bis-02 (work in Mechanism", draft-ietf-httpbis-rfc6265bis-02 (work in
progress), August 2017. progress), August 2017.
[I-D.nottingham-rfc5785bis] [I-D.nottingham-rfc5785bis]
Nottingham, M., "Well-Known Uniform Resource Identifiers Nottingham, M., "Well-Known Uniform Resource Identifiers
(URIs)", draft-nottingham-rfc5785bis-08 (work in (URIs)", draft-nottingham-rfc5785bis-08 (work in
progress), October 2018. progress), October 2018.
skipping to change at page 29, line 9 skipping to change at page 29, line 28
<https://www.rfc-editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC5861] Nottingham, M., "HTTP Cache-Control Extensions for Stale [RFC5861] Nottingham, M., "HTTP Cache-Control Extensions for Stale
Content", RFC 5861, DOI 10.17487/RFC5861, May 2010, Content", RFC 5861, DOI 10.17487/RFC5861, May 2010,
<https://www.rfc-editor.org/info/rfc5861>. <https://www.rfc-editor.org/info/rfc5861>.
[RFC6415] Hammer-Lahav, E., Ed. and B. Cook, "Web Host Metadata", [RFC6415] Hammer-Lahav, E., Ed. and B. Cook, "Web Host Metadata",
RFC 6415, DOI 10.17487/RFC6415, October 2011, RFC 6415, DOI 10.17487/RFC6415, October 2011,
<https://www.rfc-editor.org/info/rfc6415>. <https://www.rfc-editor.org/info/rfc6415>.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012,
<https://www.rfc-editor.org/info/rfc6570>.
[RFC6797] Hodges, J., Jackson, C., and A. Barth, "HTTP Strict [RFC6797] Hodges, J., Jackson, C., and A. Barth, "HTTP Strict
Transport Security (HSTS)", RFC 6797, Transport Security (HSTS)", RFC 6797,
DOI 10.17487/RFC6797, November 2012, DOI 10.17487/RFC6797, November 2012,
<https://www.rfc-editor.org/info/rfc6797>. <https://www.rfc-editor.org/info/rfc6797>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>. October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>. 2014, <https://www.rfc-editor.org/info/rfc7258>.
[RFC7538] Reschke, J., "The Hypertext Transfer Protocol Status Code
308 (Permanent Redirect)", RFC 7538, DOI 10.17487/RFC7538,
April 2015, <https://www.rfc-editor.org/info/rfc7538>.
[RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines [RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
and Registration Procedures for URI Schemes", BCP 35, and Registration Procedures for URI Schemes", BCP 35,
RFC 7595, DOI 10.17487/RFC7595, June 2015, RFC 7595, DOI 10.17487/RFC7595, June 2015,
<https://www.rfc-editor.org/info/rfc7595>. <https://www.rfc-editor.org/info/rfc7595>.
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport [RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605, Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <https://www.rfc-editor.org/info/rfc7605>. August 2015, <https://www.rfc-editor.org/info/rfc7605>.
[RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP [RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
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