draft-ietf-httpbis-alt-svc-06.txt   draft-ietf-httpbis-alt-svc-07.txt 
HTTPbis Working Group M. Nottingham HTTP Working Group M. Nottingham
Internet-Draft Akamai Internet-Draft Akamai
Intended status: Standards Track P. McManus Intended status: Standards Track P. McManus
Expires: August 9, 2015 Mozilla Expires: November 16, 2015 Mozilla
J. Reschke J. Reschke
greenbytes greenbytes
February 5, 2015 May 15, 2015
HTTP Alternative Services HTTP Alternative Services
draft-ietf-httpbis-alt-svc-06 draft-ietf-httpbis-alt-svc-07
Abstract Abstract
This document specifies "alternative services" for HTTP, which allow This document specifies "alternative services" for HTTP, which allow
an origin's resources to be authoritatively available at a separate an origin's resources to be authoritatively available at a separate
network location, possibly accessed with a different protocol network location, possibly accessed with a different protocol
configuration. configuration.
Editorial Note (To be removed by RFC Editor) Editorial Note (To be removed by RFC Editor)
skipping to change at page 1, line 49 skipping to change at page 1, line 49
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 http://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 August 9, 2015. This Internet-Draft will expire on November 16, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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 (http://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
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 4 1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 4
2. Alternative Services Concepts . . . . . . . . . . . . . . . . 5 2. Alternative Services Concepts . . . . . . . . . . . . . . . . 5
2.1. Host Authentication . . . . . . . . . . . . . . . . . . . 6 2.1. Host Authentication . . . . . . . . . . . . . . . . . . . 6
2.2. Alternative Service Caching . . . . . . . . . . . . . . . 7 2.2. Alternative Service Caching . . . . . . . . . . . . . . . 7
2.3. Requiring Server Name Indication . . . . . . . . . . . . . 7 2.3. Requiring Server Name Indication . . . . . . . . . . . . . 7
2.4. Using Alternative Services . . . . . . . . . . . . . . . . 7 2.4. Using Alternative Services . . . . . . . . . . . . . . . . 7
3. The Alt-Svc HTTP Header Field . . . . . . . . . . . . . . . . 8 3. The Alt-Svc HTTP Header Field . . . . . . . . . . . . . . . . 8
3.1. Caching Alt-Svc Header Field Values . . . . . . . . . . . 10 3.1. Caching Alt-Svc Header Field Values . . . . . . . . . . . 10
4. The ALTSVC HTTP/2 Frame . . . . . . . . . . . . . . . . . . . 10 4. The ALTSVC HTTP/2 Frame . . . . . . . . . . . . . . . . . . . 11
5. The Alt-Used HTTP Header Field . . . . . . . . . . . . . . . . 12 5. The Alt-Used HTTP Header Field . . . . . . . . . . . . . . . . 12
6. The 421 Misdirected Request HTTP Status Code . . . . . . . . . 12 6. The 421 Misdirected Request HTTP Status Code . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7.1. Header Field Registrations . . . . . . . . . . . . . . . . 13 7.1. Header Field Registrations . . . . . . . . . . . . . . . . 13
7.2. The ALTSVC HTTP/2 Frame Type . . . . . . . . . . . . . . . 13 7.2. The ALTSVC HTTP/2 Frame Type . . . . . . . . . . . . . . . 13
8. Internationalization Considerations . . . . . . . . . . . . . 13 8. Internationalization Considerations . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9.1. Changing Ports . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Changing Ports . . . . . . . . . . . . . . . . . . . . . . 14
9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 14 9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 14
9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 14 9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 15
9.4. Tracking Clients Using Alternative Services . . . . . . . 15 9.4. Tracking Clients Using Alternative Services . . . . . . . 15
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 9.5. Confusion Regarding Request Scheme . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Change Log (to be removed by RFC Editor before Appendix A. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 16 publication) . . . . . . . . . . . . . . . . . . . . 17
A.1. Since draft-nottingham-httpbis-alt-svc-05 . . . . . . . . 16 A.1. Since draft-nottingham-httpbis-alt-svc-05 . . . . . . . . 17
A.2. Since draft-ietf-httpbis-alt-svc-00 . . . . . . . . . . . 16 A.2. Since draft-ietf-httpbis-alt-svc-00 . . . . . . . . . . . 17
A.3. Since draft-ietf-httpbis-alt-svc-01 . . . . . . . . . . . 17 A.3. Since draft-ietf-httpbis-alt-svc-01 . . . . . . . . . . . 17
A.4. Since draft-ietf-httpbis-alt-svc-02 . . . . . . . . . . . 17 A.4. Since draft-ietf-httpbis-alt-svc-02 . . . . . . . . . . . 17
A.5. Since draft-ietf-httpbis-alt-svc-03 . . . . . . . . . . . 17 A.5. Since draft-ietf-httpbis-alt-svc-03 . . . . . . . . . . . 17
A.6. Since draft-ietf-httpbis-alt-svc-04 . . . . . . . . . . . 17 A.6. Since draft-ietf-httpbis-alt-svc-04 . . . . . . . . . . . 18
A.7. Since draft-ietf-httpbis-alt-svc-05 . . . . . . . . . . . 18 A.7. Since draft-ietf-httpbis-alt-svc-05 . . . . . . . . . . . 18
A.8. Since draft-ietf-httpbis-alt-svc-06 . . . . . . . . . . . 18
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
HTTP [RFC7230] conflates the identification of resources with their HTTP [RFC7230] conflates the identification of resources with their
location. In other words, "http://" (and "https://") URLs are used location. In other words, "http://" (and "https://") URLs are used
to both name and find things to interact with. to both name and find things to interact with.
In some cases, it is desirable to separate identification and In some cases, it is desirable to separate identification and
location in HTTP; keeping the same identifier for a resource, but location in HTTP; keeping the same identifier for a resource, but
interacting with it at a different location on the network. interacting with it at a different location on the network.
For example: For example:
o An origin server might wish to redirect a client to a different o An origin server might wish to redirect a client to a different
server when it needs to go down for maintenance, or it has found a server when it needs to go down for maintenance, or it has found a
server in a location that is more local to the client. server in a location that is more local to the client.
o An origin server might wish to offer access to its resources using o An origin server might wish to offer access to its resources using
a new protocol (such as HTTP/2, see [HTTP2]) or one using improved a new protocol (such as HTTP/2, see [RFC7540]) or one using
security (such as Transport Layer Security (TLS), see [RFC5246]). improved security (such as Transport Layer Security (TLS), see
[RFC5246]).
o An origin server might wish to segment its clients into groups of o An origin server might wish to segment its clients into groups of
capabilities, such as those supporting Server Name Indication capabilities, such as those supporting Server Name Indication
(SNI, see Section 3 of [RFC6066]) and those not supporting it, for (SNI, see Section 3 of [RFC6066]) and those not supporting it, for
operational purposes. operational purposes.
This specification defines a new concept in HTTP, "Alternative This specification defines a new concept in HTTP, "Alternative
Services", that allows an origin server to nominate additional means Services", that allows an origin server to nominate additional means
of interacting with it on the network. It defines a general of interacting with it on the network. It defines a general
framework for this in Section 2, along with specific mechanisms for framework for this in Section 2, along with specific mechanisms for
advertising their existence using HTTP header fields (Section 3) or advertising their existence using HTTP header fields (Section 3) or
an HTTP/2 frame type (Section 4). HTTP/2 frames (Section 4), plus a way to indicate that an alternative
service was used (Section 5).
It also introduces a new status code in Section 6, so that origin It also introduces a new status code in Section 6, so that origin
servers (or their nominated alternatives) can indicate that they are servers (or their nominated alternatives) can indicate that they are
not authoritative for a given origin, in cases where the wrong not authoritative for a given origin, in cases where the wrong
location is used. location is used.
1.1. Notational Conventions 1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
This document uses the Augmented BNF defined in [RFC5234] along with This document uses the Augmented BNF defined in [RFC5234] along with
the "OWS", "delta-seconds", "parameter", "port", "quoted-string", the "#rule" extension defined in Section 7 of [RFC7230]. The rules
"token", and "uri-host" rules from [RFC7230], and uses the "#rule" below are defined in [RFC7230] and [RFC7234]:
extension defined in Section 7 of that document.
OWS = <OWS, see [RFC7230], Section 3.2.3>
delta-seconds = <delta-seconds; see [RFC7234], Section 1.2.1>
port = <port, see [RFC7230], Section 2.7>
quoted-string = <quoted-string, see [RFC7230], Section 3.2.6>
token = <token, see [RFC7230], Section 3.2.6>
uri-host = <uri-host, see [RFC7230], Section 2.7>
2. Alternative Services Concepts 2. Alternative Services Concepts
This specification defines a new concept in HTTP, the "alternative This specification defines a new concept in HTTP, the "alternative
service". When an origin (see [RFC6454]) has resources that are service". When an origin (see [RFC6454]) has resources that are
accessible through a different protocol / host / port combination, it accessible through a different protocol / host / port combination, it
is said to have an alternative service available. is said to have an alternative service available.
An alternative service can be used to interact with the resources on An alternative service can be used to interact with the resources on
an origin server at a separate location on the network, possibly an origin server at a separate location on the network, possibly
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options for that protocol. options for that protocol.
This means that clients using an alternative service can change the This means that clients using an alternative service can change the
host, port and protocol that they are using to fetch resources, but host, port and protocol that they are using to fetch resources, but
these changes MUST NOT be propagated to the application that is using these changes MUST NOT be propagated to the application that is using
HTTP; from that standpoint, the URI being accessed and all HTTP; from that standpoint, the URI being accessed and all
information derived from it (scheme, host, port) are the same as information derived from it (scheme, host, port) are the same as
before. before.
Importantly, this includes its security context; in particular, when Importantly, this includes its security context; in particular, when
TLS [RFC5246] is in use, the alternative service will need to present TLS [RFC5246] is used to authenticate, the alternative service will
a certificate for the origin's host name, not that of the need to present a certificate for the origin's host name, not that of
alternative. Likewise, the Host header field ([RFC7230], Section the alternative. Likewise, the Host header field ([RFC7230], Section
5.4) is still derived from the origin, not the alternative service 5.4) is still derived from the origin, not the alternative service
(just as it would if a CNAME were being used). (just as it would if a CNAME were being used).
The changes MAY, however, be made visible in debugging tools, The changes MAY, however, be made visible in debugging tools,
consoles, etc. consoles, etc.
Formally, an alternative service is identified by the combination of: Formally, an alternative service is identified by the combination of:
o An Application Layer Protocol Negotiation (ALPN) protocol, as per o An Application Layer Protocol Negotiation (ALPN) protocol, as per
[RFC7301] [RFC7301]
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3. The Alt-Svc HTTP Header Field 3. The Alt-Svc HTTP Header Field
An HTTP(S) origin server can advertise the availability of An HTTP(S) origin server can advertise the availability of
alternative services to clients by adding an Alt-Svc header field to alternative services to clients by adding an Alt-Svc header field to
responses. responses.
Alt-Svc = 1#( alternative *( OWS ";" OWS parameter ) ) Alt-Svc = 1#( alternative *( OWS ";" OWS parameter ) )
alternative = protocol-id "=" alt-authority alternative = protocol-id "=" alt-authority
protocol-id = token ; percent-encoded ALPN protocol identifier protocol-id = token ; percent-encoded ALPN protocol identifier
alt-authority = quoted-string ; containing [ uri-host ] ":" port alt-authority = quoted-string ; containing [ uri-host ] ":" port
parameter = token "=" ( token / quoted-string )
ALPN protocol names are octet sequences with no additional ALPN protocol names are octet sequences with no additional
constraints on format. Octets not allowed in tokens ([RFC7230], constraints on format. Octets not allowed in tokens ([RFC7230],
Section 3.2.6) MUST be percent-encoded as per Section 2.1 of Section 3.2.6) MUST be percent-encoded as per Section 2.1 of
[RFC3986]. Consequently, the octet representing the percent [RFC3986]. Consequently, the octet representing the percent
character "%" (hex 25) MUST be percent-encoded as well. character "%" (hex 25) MUST be percent-encoded as well.
In order to have precisely one way to represent any ALPN protocol In order to have precisely one way to represent any ALPN protocol
name, the following additional constraints apply: name, the following additional constraints apply:
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to match protocol identifiers. to match protocol identifiers.
The "alt-authority" component consists of an OPTIONAL uri-host The "alt-authority" component consists of an OPTIONAL uri-host
("host" in Section 3.2.2 of [RFC3986]), a colon (":"), and a port ("host" in Section 3.2.2 of [RFC3986]), a colon (":"), and a port
number. number.
For example: For example:
Alt-Svc: h2=":8000" Alt-Svc: h2=":8000"
This indicates the "h2" protocol ([HTTP2]) on the same host using the This indicates the "h2" protocol ([RFC7540]) on the same host using
indicated port 8000. the indicated port 8000.
An example involving a change of host: An example involving a change of host:
Alt-Svc: h2="new.example.org:80" Alt-Svc: h2="new.example.org:80"
This indicates the "h2" protocol on the host "new.example.org", This indicates the "h2" protocol on the host "new.example.org",
running on port 80. Note that the "quoted-string" syntax needs to be running on port 80. Note that the "quoted-string" syntax needs to be
used because ":" is not an allowed character in "token". used because ":" is not an allowed character in "token".
Examples for protocol name escaping: Examples for protocol name escaping:
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status code. status code.
The Alt-Svc field value can have multiple values: The Alt-Svc field value can have multiple values:
Alt-Svc: h2c=":8000", h2=":443" Alt-Svc: h2c=":8000", h2=":443"
The value(s) advertised by Alt-Svc can be used by clients to open a The value(s) advertised by Alt-Svc can be used by clients to open a
new connection to one or more alternative services immediately, or new connection to one or more alternative services immediately, or
simultaneously with subsequent requests on the same connection. simultaneously with subsequent requests on the same connection.
When using HTTP/2 ([HTTP2]), servers SHOULD instead send an ALTSVC When using HTTP/2 ([RFC7540]), servers SHOULD instead send an ALTSVC
frame (Section 4). A single ALTSVC frame can be sent for a frame (Section 4). A single ALTSVC frame can be sent for a
connection; a new frame is not needed for every request. connection; a new frame is not needed for every request.
Note that all field elements that allow "quoted-string" syntax MUST Note that all field elements that allow "quoted-string" syntax MUST
be processed as per Section 3.2.6 of [RFC7230]. be processed as per Section 3.2.6 of [RFC7230].
3.1. Caching Alt-Svc Header Field Values 3.1. Caching Alt-Svc Header Field Values
When an alternative service is advertised using Alt-Svc, it is When an alternative service is advertised using Alt-Svc, it is
considered fresh for 24 hours from generation of the message. This considered fresh for 24 hours from generation of the message. This
can be modified with the 'ma' (max-age) parameter; can be modified with the 'ma' (max-age) parameter:
Alt-Svc: h2=":443"; ma=3600 Alt-Svc: h2=":443"; ma=3600
which indicates the number of seconds since the response was which indicates the number of seconds since the response was
generated the alternative service is considered fresh for. generated the alternative service is considered fresh for.
ma = delta-seconds ma = delta-seconds
See Section 4.2.3 of [RFC7234] for details of determining response See Section 4.2.3 of [RFC7234] for details of determining response
age. age.
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When an Alt-Svc response header field is received from an origin, its When an Alt-Svc response header field is received from an origin, its
value invalidates and replaces all cached alternative services for value invalidates and replaces all cached alternative services for
that origin. that origin.
See Section 2.2 for general requirements on caching alternative See Section 2.2 for general requirements on caching alternative
services. services.
4. The ALTSVC HTTP/2 Frame 4. The ALTSVC HTTP/2 Frame
The ALTSVC HTTP/2 frame ([HTTP2], Section 4) advertises the The ALTSVC HTTP/2 frame ([RFC7540], Section 4) advertises the
availability of an alternative service to an HTTP/2 client. availability of an alternative service to an HTTP/2 client.
The ALTSVC frame is a non-critical extension to HTTP/2. Endpoints The ALTSVC frame is a non-critical extension to HTTP/2. Endpoints
that do not support this frame can safely ignore it. that do not support this frame can safely ignore it.
An ALTSVC frame from a server to a client on a client-initiated An ALTSVC frame from a server to a client on a stream other than
stream indicates that the conveyed alternative service is associated stream 0 indicates that the conveyed alternative service is
with the origin of that stream. associated with the origin of that stream.
An ALTSVC frame from a server to a client on stream 0 indicates that An ALTSVC frame from a server to a client on stream 0 indicates that
the conveyed alternative service is associated with the origin the conveyed alternative service is associated with the origin
contained in the Origin field of the frame. An association with an contained in the Origin field of the frame. An association with an
origin that the client does not consider authoritative for the origin that the client does not consider authoritative for the
current connection MUST be ignored. current connection MUST be ignored.
The ALTSVC frame type is 0xa (decimal 10). The ALTSVC frame type is 0xa (decimal 10).
+-------------------------------+-------------------------------+ +-------------------------------+-------------------------------+
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subtracting the length of all preceding fields from the frame subtracting the length of all preceding fields from the frame
length) containing a value identical to the Alt-Svc field value length) containing a value identical to the Alt-Svc field value
defined in Section 3 (ABNF production "Alt-Svc"). defined in Section 3 (ABNF production "Alt-Svc").
The ALTSVC frame does not define any flags. The ALTSVC frame does not define any flags.
The ALTSVC frame is intended for receipt by clients; a server that The ALTSVC frame is intended for receipt by clients; a server that
receives an ALTSVC frame MUST treat it as a connection error of type receives an ALTSVC frame MUST treat it as a connection error of type
PROTOCOL_ERROR. PROTOCOL_ERROR.
An ALTSVC frame on a client-initiated stream containing non-empty An ALTSVC frame on stream 0 with empty (length 0) "Origin"
"Origin" information is invalid and MUST be ignored. Likewise, an information is invalid and MUST be ignored. An ALTSVC frame on a
ALTSVC frame on stream 0 with empty (length 0) "Origin" information stream other than stream 0 containing non-empty "Origin" information
is invalid and MUST be ignored. is invalid and MUST be ignored.
The ALTSVC frame is processed hop-by-hop. An intermediary MUST NOT The ALTSVC frame is processed hop-by-hop. An intermediary MUST NOT
forward ALTSVC frames, though it can use the information contained in forward ALTSVC frames, though it can use the information contained in
ALTSVC frames in forming new ALTSVC frames to send to its own ALTSVC frames in forming new ALTSVC frames to send to its own
clients. clients.
5. The Alt-Used HTTP Header Field 5. The Alt-Used HTTP Header Field
The Alt-Used header field is used in requests to indicate the The Alt-Used header field is used in requests to indicate the
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Host: origin.example.com Host: origin.example.com
Alt-Used: alternate.example.net Alt-Used: alternate.example.net
The extension parameters (ext-param) are reserved for future use; The extension parameters (ext-param) are reserved for future use;
specifications that want to define an extension will need to update specifications that want to define an extension will need to update
this document (and ought to introduce an extension registry). this document (and ought to introduce an extension registry).
6. The 421 Misdirected Request HTTP Status Code 6. The 421 Misdirected Request HTTP Status Code
The 421 (Misdirected Request) status code is defined in Section 9.1.2 The 421 (Misdirected Request) status code is defined in Section 9.1.2
of [HTTP2] to indicate that the current server instance is not of [RFC7540] to indicate that the current server instance is not
authoritative for the requested resource. This can be used to authoritative for the requested resource. This can be used to
indicate that an alternative service is not authoritative; see indicate that an alternative service is not authoritative; see
Section 2). Section 2).
Clients receiving 421 (Misdirected Request) from an alternative Clients receiving 421 (Misdirected Request) from an alternative
service MUST remove the corresponding entry from its alternative service MUST remove the corresponding entry from its alternative
service cache (see Section 2.2) for that origin. Regardless of the service cache (see Section 2.2) for that origin. Regardless of the
idempotency of the request method, they MAY retry the request, either idempotency of the request method, they MAY retry the request, either
at another alternative server, or at the origin. at another alternative server, or at the origin.
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| Alt-Svc | http | standard | Section 3 | | Alt-Svc | http | standard | Section 3 |
| Alt-Used | http | standard | Section 5 | | Alt-Used | http | standard | Section 5 |
+-------------------+----------+----------+-----------+ +-------------------+----------+----------+-----------+
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
7.2. The ALTSVC HTTP/2 Frame Type 7.2. The ALTSVC HTTP/2 Frame Type
This document registers the ALTSVC frame type in the HTTP/2 Frame This document registers the ALTSVC frame type in the HTTP/2 Frame
Types registry ([HTTP2], Section 11.2). Types registry ([RFC7540], Section 11.2).
Frame Type: ALTSVC Frame Type: ALTSVC
Code: 0xa Code: 0xa
Specification: Section 4 of this document Specification: Section 4 of this document
8. Internationalization Considerations 8. Internationalization Considerations
An internationalized domain name that appears in either the header An internationalized domain name that appears in either the header
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agent still directs traffic to the attacker even when not using the agent still directs traffic to the attacker even when not using the
intermediary. intermediary.
9.3. Changing Protocols 9.3. Changing Protocols
When the ALPN protocol is changed due to the use of an alternative When the ALPN protocol is changed due to the use of an alternative
service, the security properties of the new connection to the origin service, the security properties of the new connection to the origin
can be different from that of the "normal" connection to the origin, can be different from that of the "normal" connection to the origin,
because the protocol identifier itself implies this. because the protocol identifier itself implies this.
For example, if a "https://" URI had a protocol advertised that does For example, if a "https://" URI has a protocol advertised that does
not use some form of end-to-end encryption (most likely, TLS), it not use some form of end-to-end encryption (most likely, TLS), it
violates the expectations for security that the URI scheme implies. violates the expectations for security that the URI scheme implies.
Therefore, clients cannot blindly use alternative services, but Therefore, clients cannot blindly use alternative services, but
instead evaluate the option(s) presented to assure that security instead evaluate the option(s) presented to assure that security
requirements and expectations (of specifications, implementations and requirements and expectations (of specifications, implementations and
end users) are met. end users) are met.
9.4. Tracking Clients Using Alternative Services 9.4. Tracking Clients Using Alternative Services
Choosing an alternative service implies connecting to a new, server- Choosing an alternative service implies connecting to a new, server-
supplied host name. By using many different (potentially unique) supplied host name. By using many different (potentially unique)
host names, servers could conceivably track client requests. host names, servers could conceivably track client requests.
Clients concerned by the additional fingerprinting can choose to Clients concerned by the additional fingerprinting can choose to
ignore alternative service advertisements. ignore alternative service advertisements.
In a browser, any alternative service information MUST be removed In a user agent, any alternative service information MUST be removed
when origin-specific data is cleared (for instance, when cookies are when origin-specific data is cleared (for instance, when cookies are
cleared). cleared).
10. Acknowledgements 9.5. Confusion Regarding Request Scheme
Thanks to Adam Langley, Bence Beky, Eliot Lear, Erik Nygren, Guy
Podjarny, Herve Ruellan, Martin Thomson, Matthew Kerwin, Paul
Hoffman, Richard Barnes, Stephen Farrell, Stephen Ludin, and Will
Chan for their feedback and suggestions.
The Alt-Svc header field was influenced by the design of the
Alternate-Protocol header field in SPDY.
11. References Alternative Services MUST NOT be advertised for a protocol that is
not designed to carry the scheme. In particular, HTTP/1.1 over TLS
cannot carry safely requests for http resources.
11.1. Normative References 10. References
[HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext 10.1. Normative References
Transfer Protocol version 2", draft-ietf-httpbis-http2-16
(work in progress), November 2014.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5890] Klensin, J., "Internationalized Domain Names for [RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework", Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010. RFC 5890, August 2010,
<http://www.rfc-editor.org/info/rfc5890>.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions: [RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011. Extension Definitions", RFC 6066, January 2011,
<http://www.rfc-editor.org/info/rfc6066>.
[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
December 2011. December 2011, <http://www.rfc-editor.org/info/rfc6454>.
[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", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, June 2014. RFC 7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, June 2014. RFC 7234, June 2014,
<http://www.rfc-editor.org/info/rfc7234>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and S. Emile, [RFC7301] Friedl, S., Popov, A., Langley, A., and S. Emile,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, July 2014. Negotiation Extension", RFC 7301, July 2014,
<http://www.rfc-editor.org/info/rfc7301>.
11.2. Informative References [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol version 2", RFC 7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.
10.2. Informative References
[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864, Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004. September 2004, <http://www.rfc-editor.org/info/rfc3864>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
Appendix A. Change Log (to be removed by RFC Editor before publication) Appendix A. Change Log (to be removed by RFC Editor before publication)
A.1. Since draft-nottingham-httpbis-alt-svc-05 A.1. Since draft-nottingham-httpbis-alt-svc-05
This is the first version after adoption of This is the first version after adoption of
draft-nottingham-httpbis-alt-svc-05 as Working Group work item. It draft-nottingham-httpbis-alt-svc-05 as Working Group work item. It
only contains editorial changes. only contains editorial changes.
A.2. Since draft-ietf-httpbis-alt-svc-00 A.2. Since draft-ietf-httpbis-alt-svc-00
skipping to change at page 18, line 13 skipping to change at page 18, line 30
(<https://github.com/httpwg/http-extensions/issues/37>). (<https://github.com/httpwg/http-extensions/issues/37>).
A.7. Since draft-ietf-httpbis-alt-svc-05 A.7. Since draft-ietf-httpbis-alt-svc-05
Go back to specifying the origin in Alt-Used, but make it a "SHOULD" Go back to specifying the origin in Alt-Used, but make it a "SHOULD"
(<https://github.com/httpwg/http-extensions/issues/34>). (<https://github.com/httpwg/http-extensions/issues/34>).
Restore Origin field in ALT-SVC frame Restore Origin field in ALT-SVC frame
(<https://github.com/httpwg/http-extensions/issues/38>). (<https://github.com/httpwg/http-extensions/issues/38>).
A.8. Since draft-ietf-httpbis-alt-svc-06
Disallow use of alternative services when the protocol might not
carry the scheme
(<https://github.com/httpwg/http-extensions/issues/12>).
Align opp-sec and alt-svc
(<https://github.com/httpwg/http-extensions/issues/33>).
alt svc frame on pushed (even and non-0) frame
(<https://github.com/httpwg/http-extensions/issues/44>).
"browser" -> "user agent"
(<https://github.com/httpwg/http-extensions/pull/61>).
ABNF for "parameter"
(<https://github.com/httpwg/http-extensions/issues/65>).
Updated HTTP/2 reference.
Appendix B. Acknowledgements
Thanks to Adam Langley, Bence Beky, Eliot Lear, Erik Nygren, Guy
Podjarny, Herve Ruellan, Martin Thomson, Matthew Kerwin, Paul
Hoffman, Richard Barnes, Stephen Farrell, Stephen Ludin, and Will
Chan for their feedback and suggestions.
The Alt-Svc header field was influenced by the design of the
Alternate-Protocol header field in SPDY.
Authors' Addresses Authors' Addresses
Mark Nottingham Mark Nottingham
Akamai Akamai
EMail: mnot@mnot.net EMail: mnot@mnot.net
URI: https://www.mnot.net/ URI: https://www.mnot.net/
Patrick McManus Patrick McManus
Mozilla Mozilla
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