draft-ietf-httpbis-origin-frame-03.txt		draft-ietf-httpbis-origin-frame-04.txt
	HTTP Working Group M. Nottingham		HTTP Working Group M. Nottingham
	Internet-Draft		Internet-Draft
	Intended status: Standards Track E. Nygren		Intended status: Standards Track E. Nygren
	Expires: October 22, 2017 Akamai		Expires: February 24, 2018 Akamai
	April 20, 2017		August 23, 2017
	The ORIGIN HTTP/2 Frame		The ORIGIN HTTP/2 Frame
	draft-ietf-httpbis-origin-frame-03		draft-ietf-httpbis-origin-frame-04
	Abstract		Abstract
	This document specifies the ORIGIN frame for HTTP/2, to indicate what		This document specifies the ORIGIN frame for HTTP/2, to indicate what
	origins are available on a given connection.		origins are available on a given connection.
	Note to Readers		Note to Readers
	Discussion of this draft takes place on the HTTP working group		Discussion of this draft takes place on the HTTP 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 http://httpwg.github.io/ ;		Working Group information can be found at http://httpwg.github.io/;
	source code and issues list for this draft can be found at		source code and issues list for this draft can be found at
	https://github.com/httpwg/http-extensions/labels/origin-frame .		https://github.com/httpwg/http-extensions/labels/origin-frame.
	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 October 22, 2017.		This Internet-Draft will expire on February 24, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2017 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 26 ¶		skipping to change at page 2, line 26 ¶
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3		1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
	2. The ORIGIN HTTP/2 Frame . . . . . . . . . . . . . . . . . . . 3		2. The ORIGIN HTTP/2 Frame . . . . . . . . . . . . . . . . . . . 3
	2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3		2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2.2. Processing ORIGIN Frames . . . . . . . . . . . . . . . . 3		2.2. Processing ORIGIN Frames . . . . . . . . . . . . . . . . 3
	2.3. The Origin Set . . . . . . . . . . . . . . . . . . . . . 4		2.3. The Origin Set . . . . . . . . . . . . . . . . . . . . . 4
	2.4. Authority, Push and Coalescing with ORIGIN . . . . . . . 5		2.4. Authority, Push and Coalescing with ORIGIN . . . . . . . 5
	3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 6		4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	5.1. Normative References . . . . . . . . . . . . . . . . . . 6		5.1. Normative References . . . . . . . . . . . . . . . . . . 7
	5.2. Informative References . . . . . . . . . . . . . . . . . 7		5.2. Informative References . . . . . . . . . . . . . . . . . 8
	Appendix A. Non-Normative Processing Algorithm . . . . . . . . . 7		Appendix A. Non-Normative Processing Algorithm . . . . . . . . . 8
	Appendix B. Operational Considerations for Servers . . . . . . . 8		Appendix B. Operational Considerations for Servers . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
	1. Introduction		1. Introduction
	HTTP/2 [RFC7540] allows clients to coalesce different origins		HTTP/2 [RFC7540] allows clients to coalesce different origins
	[RFC6454] onto the same connection when certain conditions are met.		[RFC6454] onto the same connection when certain conditions are met.
	However, in certain cases, a connection is is not usable for a		However, in certain cases, a connection is not usable for a coalesced
	coalesced origin, so the 421 (Misdirected Request) status code		origin, so the 421 (Misdirected Request) status code ([RFC7540],
	([RFC7540], Section 9.1.2) was defined.		Section 9.1.2) was defined.
	Using a status code in this manner allows clients to recover from		Using a status code in this manner allows clients to recover from
	misdirected requests, but at the penalty of adding latency. To		misdirected requests, but at the penalty of adding latency. To
	address that, this specification defines a new HTTP/2 frame type,		address that, this specification defines a new HTTP/2 frame type,
	"ORIGIN", to allow servers to indicate what origins a connection is		"ORIGIN", to allow servers to indicate what origins a connection is
	usable for.		usable for.
	Additionally, experience has shown that HTTP/2's requirement to		Additionally, experience has shown that HTTP/2's requirement to
	establish server authority using both DNS and the server's		establish server authority using both DNS and the server's
	certificate is onerous. This specification relaxes the requirement		certificate is onerous. This specification relaxes the requirement
	to check DNS when the ORIGIN frame is in use. Doing so has		to check DNS when the ORIGIN frame is in use. Doing so has
	additional benefits, such as removing the latency associated with		additional benefits, such as removing the latency associated with
	some DNS lookups, and improving DNS privacy.		some DNS lookups.
	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].
	2. The ORIGIN HTTP/2 Frame		2. The ORIGIN HTTP/2 Frame
	The ORIGIN HTTP/2 frame ([RFC7540], Section 4) allows a server to		The ORIGIN HTTP/2 frame ([RFC7540], Section 4) allows a server to
	indicate what origin(s) [RFC6454] the server would like the client to		indicate what origin(s) [RFC6454] the server would like the client to
	consider as members of the Origin Set (Section 2.3) for the		consider as members of the Origin Set (Section 2.3) for the
	connection it occurs within.		connection it occurs within.
	2.1. Syntax		2.1. Syntax
	The ORIGIN frame type is 0xc (decimal 12).		The ORIGIN frame type is 0xc (decimal 12), and contains zero to many
			Origin-Entry.
	+-------------------------------+-------------------------------+		+-------------------------------+-------------------------------+
	| Origin-Len (16) | ASCII-Origin? (*) ...		| Origin-Entry (*) ...
	+-------------------------------+-------------------------------+		+-------------------------------+-------------------------------+
	The ORIGIN frame's payload contains the following fields, sets of		An Origin-Entry is a length-delimited string:
	which may be repeated within the frame to indicate multiple origins:
			+-------------------------------+-------------------------------+
			| Origin-Len (16) | ASCII-Origin? ...
			+-------------------------------+-------------------------------+
			Specifically:
	Origin-Len: An unsigned, 16-bit integer indicating the length, in		Origin-Len: An unsigned, 16-bit integer indicating the length, in
	octets, of the ASCII-Origin field.		octets, of the ASCII-Origin field.
	Origin: An optional sequence of characters containing the ASCII		Origin: An OPTIONAL sequence of characters containing the ASCII
	serialization of an origin ([RFC6454], Section 6.2) that the		serialization of an origin ([RFC6454], Section 6.2) that the
	sender believes this connection is or could be authoritative for.		sender believes this connection is or could be authoritative for.
	The ORIGIN frame does not define any flags. However, future updates		The ORIGIN frame does not define any flags. However, future updates
	to this specification MAY define flags. See Section 2.2.		to this specification MAY define flags. See Section 2.2.
	2.2. Processing ORIGIN Frames		2.2. Processing ORIGIN Frames
	The ORIGIN frame is a non-critical extension to HTTP/2. Endpoints		The ORIGIN frame is a non-critical extension to HTTP/2. Endpoints
	that do not support this frame can safely ignore it upon receipt.		that do not support this frame can safely ignore it upon receipt.
	skipping to change at page 4, line 33 ¶		skipping to change at page 4, line 39 ¶
	parsing fails, the field MUST be ignored.		parsing fails, the field MUST be ignored.
	See Appendix A for an illustrative algorithm for processing ORIGIN		See Appendix A for an illustrative algorithm for processing ORIGIN
	frames.		frames.
	2.3. The Origin Set		2.3. The Origin Set
	The set of origins (as per [RFC6454]) that a given connection might		The set of origins (as per [RFC6454]) that a given connection might
	be used for is known in this specification as the Origin Set.		be used for is known in this specification as the Origin Set.
	By default, a connections's Origin Set is uninitialised. When an		By default, the Origin Set for a connection is uninitialised. When
	ORIGIN frame is first received and successfully processed by a		an ORIGIN frame is first received and successfully processed by a
	client, the connection's Origin Set is defined to contain a single		client, the connection's Origin Set is defined to contain an initial
	origin, composed from:		origin. The initial origin is composed from:
	o Scheme: "https"		o Scheme: "https"
	o Host: the value sent in Server Name Indication ([RFC6066]		o Host: the value sent in Server Name Indication (SNI, [RFC6066]
	Section 3), converted to lower case		Section 3), converted to lower case
	o Port: the remote port of the connection (i.e., the server's port)		o Port: the remote port of the connection (i.e., the server's port)
	The contents of that ORIGIN frame (and subsequent ones) allows the		The contents of that ORIGIN frame (and subsequent ones) allows the
	server to incrementally add new origins to the Origin Set, as		server to incrementally add new origins to the Origin Set, as
	described in Section 2.2.		described in Section 2.2.
	The Origin Set is also affected by the 421 (Misdirected Request)		The Origin Set is also affected by the 421 (Misdirected Request)
	response status code, defined in [RFC7540] Section 9.1.2. Upon		response status code, defined in [RFC7540] Section 9.1.2. Upon
	receipt of a response with this status code, implementing clients		receipt of a response with this status code, implementing clients
	MUST create the ASCII serialisation of the corresponding request's		MUST create the ASCII serialisation of the corresponding request's
	origin (as per [RFC6454], Section 6.2) and remove it from the		origin (as per [RFC6454], Section 6.2) and remove it from the
	connection's Origin Set, if present.		connection's Origin Set, if present.
	skipping to change at page 5, line 8 ¶		skipping to change at page 5, line 15 ¶
	server to incrementally add new origins to the Origin Set, as		server to incrementally add new origins to the Origin Set, as
	described in Section 2.2.		described in Section 2.2.
	The Origin Set is also affected by the 421 (Misdirected Request)		The Origin Set is also affected by the 421 (Misdirected Request)
	response status code, defined in [RFC7540] Section 9.1.2. Upon		response status code, defined in [RFC7540] Section 9.1.2. Upon
	receipt of a response with this status code, implementing clients		receipt of a response with this status code, implementing clients
	MUST create the ASCII serialisation of the corresponding request's		MUST create the ASCII serialisation of the corresponding request's
	origin (as per [RFC6454], Section 6.2) and remove it from the		origin (as per [RFC6454], Section 6.2) and remove it from the
	connection's Origin Set, if present.		connection's Origin Set, if present.
			Note: When sending an ORIGIN frame to a connection that is
			initialised as an Alternative Service [RFC7838], the initial
			origin set Section 2.3 will contain an origin with the appropriate
			scheme and hostname (since Alternative Services specifies that the
			origin's hostname be sent in SNI). However, it is possible that
			the port will be different than that of the intended origin, since
			the initial origin set is calculated using the actual port in use,
			which can be different for the alternative service. In this case,
			the intended origin needs to be sent in the ORIGIN frame
			explicitly.
			For example, a client making requests for "https://example.com" is
			directed to an alternative service at ("h2", "x.example.net",
			"8443"). If this alternative service sends an ORIGIN frame, the
			initial origin will be "https://example.com:8443". The client
			will not be able to use the alternative service to make requests
			for "https://example.com" unless that origin is explicitly
			included in the ORIGIN frame.
	2.4. Authority, Push and Coalescing with ORIGIN		2.4. Authority, Push and Coalescing with ORIGIN
	[RFC7540], Section 10.1 uses both DNS and the presented TLS		[RFC7540], Section 10.1 uses both DNS and the presented TLS
	certificate to establish the origin server(s) that a connection is		certificate to establish the origin server(s) that a connection is
	authoritative for, just as HTTP/1.1 does in [RFC7230]. Furthermore,		authoritative for, just as HTTP/1.1 does in [RFC7230].
	[RFC7540] Section 9.1.1 explicitly allows a connection to be used for
	more than one origin server, if it is authoritative. This affects
	what requests can be sent on the connection, both in HEADERS frame by
	the client and as PUSH_PROMISE frames from the server.
	Once an Origin Set has been initialised for a connection, clients
	that implement this specification change these behaviors in the
	following ways:
	o Clients MUST NOT consult DNS to establish the connection's		Furthermore, [RFC7540] Section 9.1.1 explicitly allows a connection
	authority for new requests. The TLS certificate MUST stil be used		to be used for more than one origin server, if it is authoritative.
	to do so, as described in [RFC7540] Section 9.1.1.		This affects what requests can be sent on the connection, both in
			HEADERS frame by the client and as PUSH_PROMISE frames from the
			server ([RFC7540], Section 8.2.2).
	o Clients sending a new request SHOULD use an existing connection if		Once an Origin Set has been initialised for a connection, clients
	the request's origin is in that connection's Origin Set, unless		that implement this specification use it to help determine what the
	there are operational reasons for creating a new connection.		connection is authoritative for. Specifically, such clients MUST NOT
			consider a connection to be authoritative for an origin not present
			in the Origin Set, and SHOULD use the connection for all requests to
			origins in the Origin Set for which the connection is authoritative,
			unless there are operational reasons for opening a new connection.
	o Clients MUST use the Origin Set to determine whether a received		Note that for a connection to be considered authoritative for a given
	PUSH_PROMISE is authoritative, as described in [RFC7540],		origin, the client is still required to obtain a certificate that
	Section 8.2.2.		passes suitable checks; see [RFC7540] Section 9.1.1 for more
			information. This includes verifying that the host matches a
			"dNSName" value from the certificate "subjectAltName" field (using
			the wildcard rules defined in [RFC2818]; see also [RFC5280]
			Section 4.2.1.6).
	Note that clients are still required to perform checks on the		Additionally, clients MAY avoid consulting DNS to establish the
	certificate presented by the server for each origin that a connection		connection's authority for new requests; however, those that do so
	is used for; see [RFC7540] Section 9.1.1 for more information. This		face new risks, as explained in Section 4
	includes verifying that the host matches a "dNSName" value from the
	certificate "subjectAltName" field (using the wildcard rules defined
	in [RFC2818]; see also [RFC5280] Section 4.2.1.6).
	Because ORIGIN can change the set of origins a connection is used for		Because ORIGIN can change the set of origins a connection is used for
	over time, it is possible that a client might have more than one		over time, it is possible that a client might have more than one
	viable connection to an origin open at any time. When this occurs,		viable connection to an origin open at any time. When this occurs,
	clients SHOULD not emit new requests on any connection whose Origin		clients SHOULD not emit new requests on any connection whose Origin
	Set is a subset of another connection's Origin Set, and SHOULD close		Set is a proper subset of another connection's Origin Set, and SHOULD
	it once all outstanding requests are satisfied.		close it once all outstanding requests are satisfied.
			The Origin Set is unaffected by any alternative services [RFC7838]
			advertisements made by the server. Advertising an alternative
			service does not affect whether a server is authoritative.
	3. IANA Considerations		3. IANA Considerations
	This specification adds an entry to the "HTTP/2 Frame Type" registry.		This specification adds an entry to the "HTTP/2 Frame Type" registry.
	o Frame Type: ORIGIN		o Frame Type: ORIGIN
	o Code: 0xc		o Code: 0xc
	o Specification: [this document]		o Specification: [this document]
	skipping to change at page 6, line 25 ¶		skipping to change at page 6, line 50 ¶
	4. Security Considerations		4. Security Considerations
	Clients that blindly trust the ORIGIN frame's contents will be		Clients that blindly trust the ORIGIN frame's contents will be
	vulnerable to a large number of attacks. See Section 2.4 for		vulnerable to a large number of attacks. See Section 2.4 for
	mitigations.		mitigations.
	Relaxing the requirement to consult DNS when determining authority		Relaxing the requirement to consult DNS when determining authority
	for an origin means that an attacker who possesses a valid		for an origin means that an attacker who possesses a valid
	certificate no longer needs to be on-path to redirect traffic to		certificate no longer needs to be on-path to redirect traffic to
	them; instead of modifying DNS, they need only convince the user to		them; instead of modifying DNS, they need only convince the user to
	visit another Web site, in order to coalesce connections to the		visit another Web site in order to coalesce connections to the target
	target onto their existing connection.		onto their existing connection.
			As a result, clients opting not to consult DNS ought to employ some
			alternative means to increase confidence that the certificate is
			legitimate. Examples of mechanisms that can give additional
			confidence in a certificate include checking for a Signed Certificate
			Timestamp [RFC6929] and performing certificate revocation checks.
			Clients opting not to consult DNS ought to do so only if they have a
			high degree of confidence that the certificate is legitimate. For
			instance, clients might skip consulting DNS only if they receive
			proof of inclusion in a Certificate Transparency log [RFC6929] or
			they have a recent OCSP response [RFC6960] (possibly using the
			"status_request" TLS extension [RFC6066]) showing that the
			certificate was not revoked.
			The Origin Set's size is unbounded by this specification, and thus
			could be used by attackers to exhaust client resources. To mitigate
			this risk, clients can monitor their state commitment and close the
			connection if it is too high.
	5. References		5. References
	5.1. Normative References		5.1. Normative References
	[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,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
	<http://www.rfc-editor.org/info/rfc2119>.		editor.org/info/rfc2119>.
	[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,		[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
	DOI 10.17487/RFC2818, May 2000,		DOI 10.17487/RFC2818, May 2000, <https://www.rfc-
	<http://www.rfc-editor.org/info/rfc2818>.		editor.org/info/rfc2818>.
	[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,		[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
	Housley, R., and W. Polk, "Internet X.509 Public Key		Housley, R., and W. Polk, "Internet X.509 Public Key
	Infrastructure Certificate and Certificate Revocation List		Infrastructure Certificate and Certificate Revocation List
	(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,		(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
	<http://www.rfc-editor.org/info/rfc5280>.		<https://www.rfc-editor.org/info/rfc5280>.
	[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)		[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
	Extensions: Extension Definitions", RFC 6066,		Extensions: Extension Definitions", RFC 6066,
	DOI 10.17487/RFC6066, January 2011,		DOI 10.17487/RFC6066, January 2011, <https://www.rfc-
	<http://www.rfc-editor.org/info/rfc6066>.		editor.org/info/rfc6066>.
	[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,		[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
	DOI 10.17487/RFC6454, December 2011,		DOI 10.17487/RFC6454, December 2011, <https://www.rfc-
	<http://www.rfc-editor.org/info/rfc6454>.		editor.org/info/rfc6454>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext		[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,		Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,		DOI 10.17487/RFC7540, May 2015, <https://www.rfc-
	<http://www.rfc-editor.org/info/rfc7540>.		editor.org/info/rfc7540>.
	5.2. Informative References		5.2. Informative References
	[RFC5988] Nottingham, M., "Web Linking", RFC 5988,		[RFC5988] Nottingham, M., "Web Linking", RFC 5988,
	DOI 10.17487/RFC5988, October 2010,		DOI 10.17487/RFC5988, October 2010, <https://www.rfc-
	<http://www.rfc-editor.org/info/rfc5988>.		editor.org/info/rfc5988>.
			[RFC6929] DeKok, A. and A. Lior, "Remote Authentication Dial In User
			Service (RADIUS) Protocol Extensions", RFC 6929,
			DOI 10.17487/RFC6929, April 2013, <https://www.rfc-
			editor.org/info/rfc6929>.
			[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
			Galperin, S., and C. Adams, "X.509 Internet Public Key
			Infrastructure Online Certificate Status Protocol - OCSP",
			RFC 6960, DOI 10.17487/RFC6960, June 2013,
			<https://www.rfc-editor.org/info/rfc6960>.
	[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, DOI 10.17487/RFC7230, June 2014,		RFC 7230, DOI 10.17487/RFC7230, June 2014,
	<http://www.rfc-editor.org/info/rfc7230>.		<https://www.rfc-editor.org/info/rfc7230>.
	[RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP		[RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP
	Alternative Services", RFC 7838, DOI 10.17487/RFC7838,		Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
	April 2016, <http://www.rfc-editor.org/info/rfc7838>.		April 2016, <https://www.rfc-editor.org/info/rfc7838>.
	Appendix A. Non-Normative Processing Algorithm		Appendix A. Non-Normative Processing Algorithm
	The following algorithm illustrates how a client could handle		The following algorithm illustrates how a client could handle
	received ORIGIN frames:		received ORIGIN frames:
	1. If the client is configured to use a proxy for the connection,		1. If the client is configured to use a proxy for the connection,
	ignore the frame and stop processing.		ignore the frame and stop processing.
	2. If the connection is not identified with the "h2" protocol		2. If the connection is not identified with the "h2" protocol
	skipping to change at page 7, line 50 ¶		skipping to change at page 9, line 8 ¶
	3. If the frame occurs upon any stream except stream 0, ignore the		3. If the frame occurs upon any stream except stream 0, ignore the
	frame and stop processing.		frame and stop processing.
	4. If any of the flags 0x1, 0x2, 0x4 or 0x8 are set, ignore the		4. If any of the flags 0x1, 0x2, 0x4 or 0x8 are set, ignore the
	frame and stop processing.		frame and stop processing.
	5. If no previous ORIGIN frame on the connection has reached this		5. If no previous ORIGIN frame on the connection has reached this
	step, initialise the Origin Set as per Section 2.3.		step, initialise the Origin Set as per Section 2.3.
	6. For each Origin field "origin_raw" in the frame payload:		6. For each "Origin-Entry" in the frame payload:
	1. Parse "origin_raw" as an ASCII serialization of an origin		1. Parse "ASCII-Origin" as an ASCII serialization of an origin
	([RFC6454], Section 6.2) and let the result be		([RFC6454], Section 6.2) and let the result be
	"parsed_origin". If parsing fails, skip to the next		"parsed_origin". If parsing fails, skip to the next "Origin-
	"origin_raw".		Entry".
	2. Add "parsed_origin" to the Origin Set.		2. Add "parsed_origin" to the Origin Set.
	Appendix B. Operational Considerations for Servers		Appendix B. Operational Considerations for Servers
	The ORIGIN frame allows a server to indicate for which origins a		The ORIGIN frame allows a server to indicate for which origins a
	given connection ought be used.		given connection ought be used. The set of origins advertised using
			this mechanism is under control of the server; servers are not
			obligated to use it, or to advertise all origins which they might be
			able to answer a request for.
	For example, it can be used to inform the client that the connection		For example, it can be used to inform the client that the connection
	is to only be used for the SNI-based origin, by sending an empty		is to only be used for the SNI-based origin, by sending an empty
	ORIGIN frame. Or, a larger number of origins can be indicated by		ORIGIN frame. Or, a larger number of origins can be indicated by
	including a payload.		including a payload.
	Generally, this information is most useful to send before sending any		Generally, this information is most useful to send before sending any
	part of a response that might initiate a new connection; for example,		part of a response that might initiate a new connection; for example,
	"Link" headers [RFC5988] in a response HEADERS, or links in the		"Link" headers [RFC5988] in a response HEADERS, or links in the
	response body.		response body.
End of changes. 37 change blocks.
	76 lines changed or deleted		136 lines changed or added
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