draft-ietf-httpbis-alt-svc-02.txt   draft-ietf-httpbis-alt-svc-03.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: January 5, 2015 Mozilla Expires: April 3, 2015 Mozilla
J. Reschke J. Reschke
greenbytes greenbytes
July 4, 2014 September 30, 2014
HTTP Alternative Services HTTP Alternative Services
draft-ietf-httpbis-alt-svc-02 draft-ietf-httpbis-alt-svc-03
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)
Discussion of this draft takes place on the HTTPBIS working group Discussion of this draft takes place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
<https://lists.w3.org/Archives/Public/ietf-http-wg/>. <https://lists.w3.org/Archives/Public/ietf-http-wg/>.
Working Group information can be found at Working Group information can be found at
<https://tools.ietf.org/wg/httpbis/> and <http://httpwg.github.io/>; <https://tools.ietf.org/wg/httpbis/> and <http://httpwg.github.io/>;
source code and issues list for tis draft can be found at source code and issues list for this draft can be found at
<https://github.com/httpwg/http-extensions>. <https://github.com/httpwg/http-extensions>.
The changes in this draft are summarized in Appendix A. The changes in this draft are summarized in Appendix A.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 January 5, 2015. This Internet-Draft will expire on April 3, 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
skipping to change at page 2, line 31 skipping to change at page 2, line 31
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 3 1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 3
2. Alternative Services Concepts . . . . . . . . . . . . . . . . 4 2. Alternative Services Concepts . . . . . . . . . . . . . . . . 4
2.1. Host Authentication . . . . . . . . . . . . . . . . . . . 5 2.1. Host Authentication . . . . . . . . . . . . . . . . . . . 5
2.2. Alternative Service Caching . . . . . . . . . . . . . . . 6 2.2. Alternative Service Caching . . . . . . . . . . . . . . . 6
2.3. Requiring Server Name Indication . . . . . . . . . . . . . 6 2.3. Requiring Server Name Indication . . . . . . . . . . . . . 6
2.4. Using Alternative Services . . . . . . . . . . . . . . . . 6 2.4. Using Alternative Services . . . . . . . . . . . . . . . . 6
3. The Alt-Svc HTTP Header Field . . . . . . . . . . . . . . . . 7 3. The Alt-Svc HTTP Header Field . . . . . . . . . . . . . . . . 7
3.1. Caching Alt-Svc Header Field Values . . . . . . . . . . . 9 3.1. Caching Alt-Svc Header Field Values . . . . . . . . . . . 9
4. The ALTSVC HTTP/2 Frame . . . . . . . . . . . . . . . . . . . 10 4. The ALTSVC HTTP/2 Frame . . . . . . . . . . . . . . . . . . . 9
5. The Alt-Svc-Used HTTP Header Field . . . . . . . . . . . . . . 11 5. The Alt-Svc-Used HTTP Header Field . . . . . . . . . . . . . . 11
6. The 421 Not Authoritative HTTP Status Code . . . . . . . . . . 12 6. The 421 Not Authoritative HTTP Status Code . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. Header Field Registrations . . . . . . . . . . . . . . . . 12 7.1. Header Field Registrations . . . . . . . . . . . . . . . . 12
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 . . . . . . . . . . . . . . . . . . . . . . 13 9.2. Changing Hosts . . . . . . . . . . . . . . . . . . . . . . 13
9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 14 9.3. Changing Protocols . . . . . . . . . . . . . . . . . . . . 14
9.4. Tracking Clients Using Alternative Services . . . . . . . 14 9.4. Tracking Clients Using Alternative Services . . . . . . . 14
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 . . . . . . . . . . . 16
A.4. Since draft-ietf-httpbis-alt-svc-02 . . . . . . . . . . . 16
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 these aspects; to be able In some cases, it is desirable to separate these aspects; to be able
to keep the same identifier for a resource, but interact with it to keep the same identifier for a resource, but interact with it
using a different location on the network. using a different location on the network.
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alternative. Likewise, the Host header field ([RFC7230], Section 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
[ALPN] [RFC7301]
o A host, as per [RFC3986], Section 3.2.2 o A host, as per [RFC3986], Section 3.2.2
o A port, as per [RFC3986], Section 3.2.3 o A port, as per [RFC3986], Section 3.2.3
Additionally, each alternative service MUST have: Additionally, each alternative service MUST have:
o A freshness lifetime, expressed in seconds; see Section 2.2 o A freshness lifetime, expressed in seconds; see Section 2.2
There are many ways that a client could discover the alternative There are many ways that a client could discover the alternative
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Clients MAY choose to use an alternative service instead of the Clients MAY choose to use an alternative service instead of the
origin at any time when it is considered fresh; see Section 2.4 for origin at any time when it is considered fresh; see Section 2.4 for
specific recommendations. specific recommendations.
Clients with existing connections to alternative services are not Clients with existing connections to alternative services are not
needed to fall back to the origin when its freshness lifetime ends; needed to fall back to the origin when its freshness lifetime ends;
i.e., the caching mechanism is intended for limiting how long an i.e., the caching mechanism is intended for limiting how long an
alternative service can be used for establishing new requests, not alternative service can be used for establishing new requests, not
limiting the use of existing ones. limiting the use of existing ones.
To mitigate risks associated with caching compromised values (see Clients ought to consider that changes in network configurations can
Section 9.2 for details), user agents SHOULD examine cached result in suboptimal or compromised cached alternative services.
alternative services when they detect a change in network
configuration, and remove any that could be compromised (for example,
those whose association with the trust root is questionable). UAs
that do not have a means of detecting network changes SHOULD place an
upper bound on their lifetime.
2.3. Requiring Server Name Indication 2.3. Requiring Server Name Indication
A client MUST only use a TLS-based alternative service if the client A client MUST only use a TLS-based alternative service if the client
also supports TLS Server Name Indication (SNI). This supports the also supports TLS Server Name Indication (SNI). This supports the
conservation of IP addresses on the alternative service host. conservation of IP addresses on the alternative service host.
2.4. Using Alternative Services 2.4. Using Alternative Services
By their nature, alternative services are OPTIONAL: clients do not By their nature, alternative services are OPTIONAL: clients do not
need to use them. However, it is advantageous for clients to behave need to use them. However, it is advantageous for clients to behave
in a predictable way when they are used by servers (e.g., for load in a predictable way when they are used by servers (e.g., for load
balancing). balancing).
Therefore, if a client becomes aware of an alternative service, the Therefore, if a client becomes aware of an alternative service, the
client SHOULD use that alternative service for all requests to the client SHOULD use that alternative service for all requests to the
associated origin as soon as it is available, provided that the associated origin as soon as it is available, provided that the
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
choose the most suitable according to its own criteria (again,
keeping security properties in mind). For example, an origin might
advertise multiple alternative services to notify clients of support
for multiple versions of HTTP; or, an alternative service might
itself advertise an alternative.
When a client uses an alternate service, it MUST emit the Alt-Svc- When a client uses an alternate service, it MUST emit the Alt-Svc-
Used header field (Section 5) on every request using that alternate Used header field (Section 5) on every request using that alternate
service. service.
The client does not need to block requests; the origin's connection The client does not need to block requests; the origin's connection
can be used until the alternative connection is established. can be used until the alternative connection is established.
However, if the security properties of the existing connection are However, if the security properties of the existing connection are
weak (e.g. cleartext HTTP/1.1) then it might make sense to block weak (e.g. cleartext HTTP/1.1) then it might make sense to block
until the new connection is fully available in order to avoid until the new connection is fully available in order to avoid
information leakage. information leakage.
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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 = token / quoted-string alt-authority = quoted-string ; containing [ uri-host ] ":" port
; containing [ uri-host ] ":" port
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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With these constraints, recipients can apply simple string comparison With these constraints, recipients can apply simple string comparison
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: http2=":8000" Alt-Svc: h2=":8000"
This indicates the "http2" protocol on the same host using the This indicates the "h2" protocol ([HTTP2]) on the same host using the
indicated port 8000. indicated port 8000.
An example involving a change of host: An example involving a change of host:
Alt-Svc: http2="new.example.org:80" Alt-Svc: h2="new.example.org:80"
This indicates the "http2" 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 when a host is specified in addition to a port (":" is not an used because ":" is not an allowed character in "token".
allowed character in "token").
Examples for protocol name escaping: Examples for protocol name escaping:
+--------------------+-------------+---------------------+ +--------------------+-------------+---------------------+
| ALPN protocol name | protocol-id | Note | | ALPN protocol name | protocol-id | Note |
+--------------------+-------------+---------------------+ +--------------------+-------------+---------------------+
| http2 | http2 | No escaping needed | | h2 | h2 | No escaping needed |
+--------------------+-------------+---------------------+ +--------------------+-------------+---------------------+
| w=x:y#z | w%3Dx%3Ay#z | "=" and ":" escaped | | w=x:y#z | w%3Dx%3Ay#z | "=" and ":" escaped |
+--------------------+-------------+---------------------+ +--------------------+-------------+---------------------+
| x%y | x%25y | "%" needs escaping | | x%y | x%25y | "%" needs escaping |
+--------------------+-------------+---------------------+ +--------------------+-------------+---------------------+
Alt-Svc MAY occur in any HTTP response message, regardless of the Alt-Svc MAY occur in any HTTP response message, regardless of the
status code. status code.
Alt-Svc does not allow advertisement of alternative services on other
hosts, to protect against various header-based attacks.
It can, however, have multiple values: It can, however, 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.
To reduce the ability of servers to track individual clients over To reduce the ability of servers to track individual clients over
time (see Section 9.4), an alternative service indication sent by a time (see Section 9.4), an alternative service indication sent by a
client SHOULD NOT include any alternative service information other client SHOULD NOT include any alternative service information other
than the protocol, host and port. than the protocol, host and port.
When using HTTP/2 ([HTTP2]), clients SHOULD instead send an ALTSVC When using HTTP/2 ([HTTP2]), servers SHOULD instead send an ALTSVC
frame. A single ALTSVC frame can be sent for a connection; a new frame (Section 4). A single ALTSVC frame can be sent for a
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;
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Host-Len: An unsigned, 8-bit integer indicating the length, in Host-Len: An unsigned, 8-bit integer indicating the length, in
octets, of the Host header field. octets, of the Host header field.
Host: A sequence of characters (length determined by "Host-Len") Host: A sequence of characters (length determined by "Host-Len")
containing an ASCII string indicating the host that the containing an ASCII string indicating the host that the
alternative service is available upon. alternative service is available upon.
Origin: An OPTIONAL sequence of characters (length determined by Origin: An OPTIONAL sequence of characters (length determined by
subtracting the length of all preceding fields from the frame subtracting the length of all preceding fields from the frame
length) containing the ASCII serialisation of an origin length) containing the ASCII serialization of an origin
([RFC6454], Section 6.2) that the alternate service is applicable ([RFC6454], Section 6.2) that the alternate service is applicable
to. 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.
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-Svc-Used HTTP Header Field 5. The Alt-Svc-Used HTTP Header Field
The Alt-Svc-Used HTTP header field is used in requests to indicate The Alt-Svc-Used HTTP header field is used in requests to indicate
that an alternate service is in use. that an alternate service is in use.
Alt-Svc-Used = ("1" / "0") *( OWS ";" OWS Alt-Svc-Used-Ext ) Alt-Svc-Used = use-flag *( OWS ";" OWS ext-param )
Alt-Svc-Used-Ext = token "=" ( token / quoted-string ) use-flag = "1" / "0"
ext-param = token "=" ( token / quoted-string )
Alt-Svc-Used is intended to allow alternate services to avoid sending Alt-Svc-Used is intended to allow alternate services to avoid sending
alternative service indications where there is a risk of generating a alternative service indications where there is a risk of generating a
loops. It also allows a service to identify requests for accounting loops. It also allows a service to identify requests for accounting
and load balancing purposes. and load balancing purposes.
When using an alternative service, clients MUST include a Alt-Svc- When using an alternative service, clients MUST include a Alt-Svc-
Used header field in all requests. Used header field in all requests.
A flag value of "1" indicates that an alternate service was used,
while "0" means it was not.
For example: For example:
GET /thing HTTP/1.1 GET /thing HTTP/1.1
Host: origin.example.com Host: origin.example.com
Alt-Svc-Used: 1 Alt-Svc-Used: 1
The extension parameters (Alt-Svc-Used-Ext) are reserved for future The extension parameters (ext-param) are reserved for future use;
use; specifications that want to define an extension will need to specifications that want to define an extension will need to update
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 Not Authoritative HTTP Status Code
The 421 (Not Authoritative) status code is defined in [HTTP2], The 421 (Not Authoritative) status code is defined in [HTTP2],
Section 9.1.2 to indicate that the current server instance is not Section 9.1.2 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 (Not Authoritative) from an alternative service
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known exploits to make an attacker's certificate appear as known exploits to make an attacker's certificate appear as
legitimate. legitimate.
Alternative services could be used to persist such an attack; for Alternative services could be used to persist such an attack; for
example, an intermediary could man-in-the-middle TLS-protected example, an intermediary could man-in-the-middle TLS-protected
communication to a target, and then direct all traffic to an communication to a target, and then direct all traffic to an
alternative service with a large freshness lifetime, so that the user alternative service with a large freshness lifetime, so that the user
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.
As a result, there is a requirement in Section 2.2 to examine cached
alternative services when a network change is detected.
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 had 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.
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Clients that do not wish to be tracked MAY choose to ignore Clients that do not wish to be tracked MAY choose to ignore
alternative service advertisements. 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 Eliot Lear, Stephen Farrell, Guy Podjarny, Stephen Ludin, Thanks to Adam Langley, Eliot Lear, Erik Nygren, Guy Podjarny, Paul
Erik Nygren, Paul Hoffman, Adam Langley, Will Chan and Richard Barnes Hoffman, Richard Barnes, Stephen Farrell, Stephen Ludin, and Will
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
[ALPN] Friedl, S., Popov, A., Langley, A., and S. Emile,
"Transport Layer Security (TLS) Application Layer Protocol
Negotiation Extension", draft-ietf-tls-applayerprotoneg-05
(work in progress), March 2014.
[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-http2-13 Transfer Protocol version 2", draft-ietf-httpbis-http2-14
(work in progress), June 2014. (work in progress), July 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 16, line 10 skipping to change at page 15, line 50
December 2011. December 2011.
[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.
[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.
[RFC7301] Friedl, S., Popov, A., Langley, A., and S. Emile,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, July 2014.
11.2. Informative References 11.2. 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.
[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.
Appendix A. Change Log (to be removed by RFC Editor before publication) Appendix A. Change Log (to be removed by RFC Editor before publication)
skipping to change at page 17, line 5 skipping to change at page 16, line 47
Note that ALTSVC frame is preferred to Alt-Svc header field Note that ALTSVC frame is preferred to Alt-Svc header field
(<https://github.com/http2/http2-spec/pull/503>). (<https://github.com/http2/http2-spec/pull/503>).
Incorporate ALTSRV frame Incorporate ALTSRV frame
(<https://github.com/http2/http2-spec/pull/507>). (<https://github.com/http2/http2-spec/pull/507>).
Moved definition of status code 421 to HTTP/2. Moved definition of status code 421 to HTTP/2.
Partly resolved <https://github.com/httpwg/http-extensions/issues/5>. Partly resolved <https://github.com/httpwg/http-extensions/issues/5>.
A.4. Since draft-ietf-httpbis-alt-svc-02
Updated ALPN reference.
Resolved <https://github.com/httpwg/http-extensions/issues/2>.
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
 End of changes. 29 change blocks. 
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