draft-ietf-httpbis-alt-svc-05.txt   draft-ietf-httpbis-alt-svc-06.txt 
HTTPbis Working Group M. Nottingham HTTPbis Working Group M. Nottingham
Internet-Draft Akamai Internet-Draft Akamai
Intended status: Standards Track P. McManus Intended status: Standards Track P. McManus
Expires: June 4, 2015 Mozilla Expires: August 9, 2015 Mozilla
J. Reschke J. Reschke
greenbytes greenbytes
December 1, 2014 February 5, 2015
HTTP Alternative Services HTTP Alternative Services
draft-ietf-httpbis-alt-svc-05 draft-ietf-httpbis-alt-svc-06
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)
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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 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 June 4, 2015. This Internet-Draft will expire on August 9, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 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
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 . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . 10
5. The Alt-Used HTTP Header Field . . . . . . . . . . . . . . . . 11 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 . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7.1. Header Field Registrations . . . . . . . . . . . . . . . . 12 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 . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9.1. Changing Ports . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Changing Ports . . . . . . . . . . . . . . . . . . . . . . 13
9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 14 9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 14
9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 14 9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 14
9.4. Tracking Clients Using Alternative Services . . . . . . . 15 9.4. Tracking Clients Using Alternative Services . . . . . . . 15
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . . 15 11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . . 16 11.2. 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) . . . . . . . . . . . . . . . . . . . . 16
A.1. Since draft-nottingham-httpbis-alt-svc-05 . . . . . . . . 16 A.1. Since draft-nottingham-httpbis-alt-svc-05 . . . . . . . . 16
A.2. Since draft-ietf-httpbis-alt-svc-00 . . . . . . . . . . . 16 A.2. Since draft-ietf-httpbis-alt-svc-00 . . . . . . . . . . . 16
A.3. Since draft-ietf-httpbis-alt-svc-01 . . . . . . . . . . . 16 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 . . . . . . . . . . . 17
A.7. Since draft-ietf-httpbis-alt-svc-05 . . . . . . . . . . . 18
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.
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security properties of the alternative service protocol are security properties of the alternative service protocol are
desirable, as compared to the existing connection. desirable, as compared to the existing connection.
If a client becomes aware of multiple alternative services, it MAY If a client becomes aware of multiple alternative services, it MAY
choose the most suitable according to its own criteria (again, choose the most suitable according to its own criteria (again,
keeping security properties in mind). For example, an origin might keeping security properties in mind). For example, an origin might
advertise multiple alternative services to notify clients of support advertise multiple alternative services to notify clients of support
for multiple versions of HTTP; or, an alternative service might for multiple versions of HTTP; or, an alternative service might
itself advertise an alternative. itself advertise an alternative.
When a client uses an alternate service, it MUST emit the Alt-Used When a client uses an alternative service for a request, it can
header field (Section 5) on every request using that alternate indicate this to the server using the Alt-Used header field
service. (Section 5).
The client does not need to block requests on any existing The client does not need to block requests on any existing
connection; it can be used until the alternative connection is connection; it can be used until the alternative connection is
established. However, if the security properties of the existing established. However, if the security properties of the existing
connection are weak (e.g. cleartext HTTP/1.1) then it might make connection are weak (e.g. cleartext HTTP/1.1) then it might make
sense to block until the new connection is fully available in order sense to block until the new connection is fully available in order
to avoid information leakage. to avoid information leakage.
Furthermore, if the connection to the alternative service fails or is Furthermore, if the connection to the alternative service fails or is
unresponsive, the client MAY fall back to using the origin or another unresponsive, the client MAY fall back to using the origin or another
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with the origin of that stream. 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).
The payload of an ALTSVC frame is identical to the payload of the +-------------------------------+-------------------------------+
Alt-Svc field value defined in Section 3 (ABNF production "Alt-Svc"). | Origin-Len (16) | Origin? (*) ...
+-------------------------------+-------------------------------+
| Alt-Svc-Field-Value (*) ...
+---------------------------------------------------------------+
ALTSVC Frame Payload
The ALTSVC frame contains the following fields:
Origin-Len: An unsigned, 16-bit integer indicating the length, in
octets, of the Origin field.
Origin: An OPTIONAL sequence of characters containing the ASCII
serialization of an origin ([RFC6454], Section 6.2) that the
alternative service is applicable to.
Alt-Svc-Field-Value: A sequence of octets (length determined by
subtracting the length of all preceding fields from the frame
length) containing a value identical to the Alt-Svc field value
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 a client-initiated stream containing non-empty
"Origin" information is invalid and MUST be ignored. Likewise, an "Origin" information is invalid and MUST be ignored. Likewise, an
ALTSVC frame on stream 0 with empty (length 0) "Origin" information ALTSVC frame on stream 0 with empty (length 0) "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 that an The Alt-Used header field is used in requests to indicate the
alternate service is in use. identity of the alternative service in use, just as the Host header
field (Section 5.4 of [RFC7230]) identifies the host and port of the
origin.
Alt-Used = use-flag *( OWS ";" OWS ext-param ) Alt-Used = uri-host [ ":" port ]
use-flag = "1" / "0"
ext-param = token "=" ( token / quoted-string )
Alt-Used is intended to allow alternate services to avoid sending Alt-Used is intended to allow alternative services to detect loops,
alternative service indications where there is a risk of generating a differentiate traffic for purposes of load balancing, and generally
loops. It also allows a service to identify requests for accounting to ensure that it is possible to identify the intended destination of
and load balancing purposes. traffic, since introducing this information after a protocol is in
use has proven to be problematic.
When using an alternative service, clients MUST include a Alt-Used When using an alternative service, clients SHOULD include a Alt-Used
header field in all requests. header field in all requests.
A flag value of "1" indicates that an alternate service was used, As the Alt-Used header field might be used by the server for tracking
while "0" means it was not. the client, a client MAY choose not to include it in its requests for
protecting its privacy (see Section 9.4).
For example: For example:
GET /thing HTTP/1.1 GET /thing HTTP/1.1
Host: origin.example.com Host: origin.example.com
Alt-Used: 1 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 [HTTP2] 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
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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 browser, 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 10. Acknowledgements
Thanks to Adam Langley, Eliot Lear, Erik Nygren, Guy Podjarny, Paul 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 Hoffman, Richard Barnes, Stephen Farrell, Stephen Ludin, and Will
Chan for their feedback and suggestions. Chan for their feedback and suggestions.
The Alt-Svc header field was influenced by the design of the The Alt-Svc header field was influenced by the design of the
Alternate-Protocol header field in SPDY. Alternate-Protocol header field in SPDY.
11. References 11. References
11.1. Normative References 11.1. Normative References
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Mention tracking by alt-svc host name in Security Considerations Mention tracking by alt-svc host name in Security Considerations
(<https://github.com/httpwg/http-extensions/issues/36>). (<https://github.com/httpwg/http-extensions/issues/36>).
"421 (Not Authoritative)" -> "421 (Misdirected Request)". "421 (Not Authoritative)" -> "421 (Misdirected Request)".
Allow the frame to carry multiple indicator and use the same payload Allow the frame to carry multiple indicator and use the same payload
formats for both formats for both
(<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
Go back to specifying the origin in Alt-Used, but make it a "SHOULD"
(<https://github.com/httpwg/http-extensions/issues/34>).
Restore Origin field in ALT-SVC frame
(<https://github.com/httpwg/http-extensions/issues/38>).
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
EMail: mcmanus@ducksong.com EMail: mcmanus@ducksong.com
URI: https://mozillians.org/u/pmcmanus/ URI: https://mozillians.org/u/pmcmanus/
Julian F. Reschke Julian F. Reschke
greenbytes GmbH greenbytes GmbH
EMail: julian.reschke@greenbytes.de EMail: julian.reschke@greenbytes.de
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