draft-ietf-httpbis-alt-svc-04.txt   draft-ietf-httpbis-alt-svc-05.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: April 30, 2015 Mozilla Expires: June 4, 2015 Mozilla
J. Reschke J. Reschke
greenbytes greenbytes
October 27, 2014 December 1, 2014
HTTP Alternative Services HTTP Alternative Services
draft-ietf-httpbis-alt-svc-04 draft-ietf-httpbis-alt-svc-05
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 April 30, 2015. This Internet-Draft will expire on June 4, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . 10
5. The Alt-Used HTTP Header Field . . . . . . . . . . . . . . . . 12 5. The Alt-Used HTTP Header Field . . . . . . . . . . . . . . . . 11
6. The 421 Not Authoritative HTTP Status Code . . . . . . . . . . 13 6. The 421 Misdirected Request HTTP Status Code . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. Header Field Registrations . . . . . . . . . . . . . . . . 13 7.1. Header Field Registrations . . . . . . . . . . . . . . . . 12
7.2. The ALTSVC HTTP/2 Frame Type . . . . . . . . . . . . . . . 14 7.2. The ALTSVC HTTP/2 Frame Type . . . . . . . . . . . . . . . 13
8. Internationalization Considerations . . . . . . . . . . . . . 14 8. Internationalization Considerations . . . . . . . . . . . . . 13
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9.1. Changing Ports . . . . . . . . . . . . . . . . . . . . . . 14 9.1. Changing Ports . . . . . . . . . . . . . . . . . . . . . . 13
9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 14 9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 14
9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 15 9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 14
9.4. Tracking Clients Using Alternative Services . . . . . . . 15 9.4. Tracking Clients Using Alternative Services . . . . . . . 15
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . . 16 11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . . 17 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) . . . . . . . . . . . . . . . . . . . . 17 publication) . . . . . . . . . . . . . . . . . . . . 16
A.1. Since draft-nottingham-httpbis-alt-svc-05 . . . . . . . . 17 A.1. Since draft-nottingham-httpbis-alt-svc-05 . . . . . . . . 16
A.2. Since draft-ietf-httpbis-alt-svc-00 . . . . . . . . . . . 17 A.2. Since draft-ietf-httpbis-alt-svc-00 . . . . . . . . . . . 16
A.3. Since draft-ietf-httpbis-alt-svc-01 . . . . . . . . . . . 17 A.3. Since draft-ietf-httpbis-alt-svc-01 . . . . . . . . . . . 16
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 . . . . . . . . . . . 18 A.5. Since draft-ietf-httpbis-alt-svc-03 . . . . . . . . . . . 17
A.6. Since draft-ietf-httpbis-alt-svc-04 . . . . . . . . . . . 17
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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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).
0 1 2 3 The payload of an ALTSVC frame is identical to the payload of the
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Alt-Svc field value defined in Section 3 (ABNF production "Alt-Svc").
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max-Age (32) |
+-------------------------------+---------------+---------------+
| Port (16) | Proto-Len (8) |
+-------------------------------+---------------+---------------+
| Protocol-ID (*) |
+---------------+-----------------------------------------------+
| Host-Len (8) | Host (*) ...
+---------------+-----------------------------------------------+
| Origin? (*) ...
+---------------------------------------------------------------+
ALTSVC Frame Payload
The ALTSVC frame contains the following fields:
Max-Age: An unsigned, 32-bit integer indicating the freshness
lifetime of the alternative service association, as per
Section 2.2.
Port: An unsigned, 16-bit integer indicating the port that the
alternative service is available upon.
Proto-Len: An unsigned, 8-bit integer indicating the length, in
octets, of the Protocol-ID field.
Protocol-ID: A sequence of bytes (length determined by "Proto-Len")
containing the ALPN protocol identifier of the alternative
service.
Host-Len: An unsigned, 8-bit integer indicating the length, in
octets, of the Host header field.
Host: A sequence of characters (length determined by "Host-Len")
containing an ASCII string indicating the host that the
alternative service is available upon.
Origin: An OPTIONAL sequence of characters (length determined by
subtracting the length of all preceding fields from the frame
length) containing the ASCII serialization of an origin
([RFC6454], Section 6.2) that the alternate service is applicable
to.
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
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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: 1
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 Not Authoritative HTTP Status Code 6. The 421 Misdirected Request HTTP Status Code
The 421 (Not Authoritative) status code is defined in [HTTP2], The 421 (Misdirected Request) status code is defined in Section 9.1.2
Section 9.1.2 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
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 (Not Authoritative) from an alternative service Clients receiving 421 (Misdirected Request) from an alternative
MUST remove the corresponding entry from its alternative service service MUST remove the corresponding entry from its alternative
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.
A 421 (Not Authoritative) response MAY carry an Alt-Svc header field. A 421 (Misdirected Request) response MAY carry an Alt-Svc header
field.
7. IANA Considerations 7. IANA Considerations
7.1. Header Field Registrations 7.1. Header Field Registrations
HTTP header fields are registered within the "Message Headers" HTTP header fields are registered within the "Message Headers"
registry maintained at registry maintained at
<https://www.iana.org/assignments/message-headers/>. <https://www.iana.org/assignments/message-headers/>.
This document defines the following HTTP header fields, so their This document defines the following HTTP header fields, so their
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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
The Alt-Used header field (Section 5) provides a server with one Choosing an alternative service implies connecting to a new, server-
additional bit of information that can be used to correlate requests. supplied host name. By using many different (potentially unique)
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 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
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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
[HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol version 2", draft-ietf-httpbis-http2-14 Transfer Protocol version 2", draft-ietf-httpbis-http2-16
(work in progress), July 2014. (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.
[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.
[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.
skipping to change at page 18, line 16 skipping to change at page 17, line 29
Renamed "Alt-Svc-Used" to "Alt-Used" Renamed "Alt-Svc-Used" to "Alt-Used"
(<https://github.com/httpwg/http-extensions/issues/17>). (<https://github.com/httpwg/http-extensions/issues/17>).
Clarify ALTSVC Origin information requirements Clarify ALTSVC Origin information requirements
(<https://github.com/httpwg/http-extensions/issues/19>). (<https://github.com/httpwg/http-extensions/issues/19>).
Remove/tune language with respect to tracking risks (see Remove/tune language with respect to tracking risks (see
<https://github.com/httpwg/http-extensions/issues/34>). <https://github.com/httpwg/http-extensions/issues/34>).
A.6. Since draft-ietf-httpbis-alt-svc-04
Mention tracking by alt-svc host name in Security Considerations
(<https://github.com/httpwg/http-extensions/issues/36>).
"421 (Not Authoritative)" -> "421 (Misdirected Request)".
Allow the frame to carry multiple indicator and use the same payload
formats for both
(<https://github.com/httpwg/http-extensions/issues/37>).
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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