< draft-wkumari-dhc-capport-12.txt		draft-wkumari-dhc-capport-13.txt >
	Network Working Group W. Kumari		Network Working Group W. Kumari
	Internet-Draft Google		Internet-Draft Google
	Intended status: Standards Track O. Gudmundsson		Intended status: Standards Track O. Gudmundsson
	Expires: September 5, 2015 CloudFlare		Expires: December 20, 2015 CloudFlare
	P. Ebersman		P. Ebersman
	Comcast		Comcast
	S. Sheng		S. Sheng
	ICANN		ICANN
	March 04, 2015		June 18, 2015
	Captive-Portal identification in DHCP / RA		Captive-Portal Identification in DHCP / RA
	draft-wkumari-dhc-capport-12		draft-wkumari-dhc-capport-13
	Abstract		Abstract
	In many environments offering short-term or temporary Internet access		In many environments offering short-term or temporary Internet access
	(such as coffee shops), it is common to start new connections in a		(such as coffee shops), it is common to start new connections in a
	captive portal mode. This highly restricts what the customer can do		captive portal mode. This highly restricts what the customer can do
	until the customer has authenticated.		until the customer has authenticated.
	This document describes a DHCP option (and a RA extension) to inform		This document describes a DHCP option (and a RA extension) to inform
	clients that they are behind some sort of captive portal device, and		clients that they are behind some sort of captive portal device, and
	that they will need to authenticate to get Internet Access.		that they will need to authenticate to get Internet Access. It is
			not a full solution to address all of the issues that clients may
			have with captive portals; it is designed to be used in larger
			solutions.
			[ Ed note (remove): This document is being developed in github:
			https://github.com/wkumari/draft-wkumari-dhc-capport . ]
	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 September 5, 2015.		This Internet-Draft will expire on December 20, 2015.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	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
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	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3		1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3
	2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. The Captive-Portal Option . . . . . . . . . . . . . . . . . . 3
	2.1. DNS Redirection . . . . . . . . . . . . . . . . . . . . . 4		2.1. IPv4 DHCP Option . . . . . . . . . . . . . . . . . . . . 3
	2.2. HTTP Redirection . . . . . . . . . . . . . . . . . . . . 4		2.2. IPv6 DHCP Option . . . . . . . . . . . . . . . . . . . . 4
	2.3. IP Hijacking . . . . . . . . . . . . . . . . . . . . . . 4		3. The Captive-Portal IPv6 RA Option . . . . . . . . . . . . . . 4
	3. The Captive-Portal Option . . . . . . . . . . . . . . . . . . 5		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	3.1. IPv4 DHCP Option . . . . . . . . . . . . . . . . . . . . 5		5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	3.2. IPv6 DHCP Option . . . . . . . . . . . . . . . . . . . . 6		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
	4. The Captive-Portal IPv6 RA Option . . . . . . . . . . . . . . 6		7. Normative References . . . . . . . . . . . . . . . . . . . . 6
	5. Use of the Captive-Portal Option . . . . . . . . . . . . . . 7		Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 6
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
	9. Normative References . . . . . . . . . . . . . . . . . . . . 9
	Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 10
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	In many environments, users need to connect to a captive portal		In many environments, users need to connect to a captive portal
	device and agree to an acceptable use policy and / or provide billing		device and agree to an acceptable use policy (AUP) and / or provide
	information before they can access the Internet.		billing information before they can access the Internet. It is
			anticipated that the IETF will work on a more fully featured protocol
	Many devices perform DNS, HTTP, and / or IP hijacks in order to		at some point, to ease interaction with Captive Portals. Regardless
	present the user with the captive portal web page. These workarounds		of how that protocol operates, it is expected that this document will
	and techniques resemble attacks that DNSSEC and TLS are intended to		provide needed functionality because the client will need to know
	protect against. This document describe a DHCP ([RFC2131]) option		when it is behind a CP and how to contact it.
	(Captive Portal) and an IPv6 Router Advertisement (RA) ([RFC4861])
	extension that informs clients that they are behind a captive portal
	device and how to contact it.
	This document neither condones nor condemns the use of captive		In order to present users with the payment or AUP pages, the captive
	portals; instead, it recognises that their apparent necessity, and		portal device has to intercept the user's connections and redirect
	attempts to improve the user experience.		the user to the captive portal, using methods that are very similar
			to man-in-the-middle (MITM) attacks. As increasing focus is placed
			on security, and end nodes adopt a more secure stance, these
			interception techniques will become less effective and / or more
			intrusive.
	[ Ed note: This solution is somewhat similar / complements 802.11u /		This document describe a DHCP ([RFC2131]) option (Captive Portal) and
	WiFi Passpoint Online Sign-up, but is much simpler, easier to deploy,		an IPv6 Router Advertisement (RA) ([RFC4861]) extension that informs
	and works on wired as well ]		clients that they are behind a captive portal device and how to
			contact it.
	1.1. Requirements notation		1.1. Requirements notation
	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. Background		2. The Captive-Portal Option
	Some ISPs implement a captive portal (CP) - a system that intercepts
	user requests and redirects them to an interstitial login page - in
	order to require the user accept an Acceptable Use Policy (AUP),
	provide billing information, or otherwise authenticate a user prior
	to allowing them to access the Internet.
	Captive portals intercept and redirect user requests in a number of
	ways, including:
	o DNS Redirection
	o IP Redirection
	o HTTP Redirection
	o Restricted scope addresses
	o Traffic blocking (until the user is authenticated)
	In order to ensure that the user is unable to access the Internet
	until they have satisfied the requirements, captive portals usually
	implement IP based filters, or place the user into a restricted VLAN
	(or restricted IP range) until after they have been authorized /
	satisfied.
	These techniques are very similar to attacks that protocols (such as
	VPNs, DNSSEC, TLS) are designed to protect against. The interaction
	of these protections and the interception leads to poor user
	experiences, such as long timeouts, inability to reach the captive
	portal web page, etc. The interception may also leak user
	information (for example, if the captive portal intercepts and logs
	an HTTP Cookie, or URL of the form http://fred:password@example.com).
	The user is often unaware of what is causing the issue (their browser
	appears to hang, saying something like "Downloading Proxy Script", or
	simply "The Internet doesn't work"), and they become frustrated.
	This may result in them not purchasing the Internet access provided
	by the captive portal. The connectivity attempts may also facilitate
	OS fingerprinting even before a client attempts to connect to the
	portal itself.
	2.1. DNS Redirection
	The CP either intercepts all DNS traffic or advertises itself (for
	example using DHCP) as the recursive server for the network. Until
	the user has authenticated to the captive portal, the CP responds to
	all DNS requests listing the address of its web portal. Once the
	user has authenticated, the CP returns the "correct" addresses.
	This technique has many shortcomings. It fails if the client is
	performing DNSSEC validation, is running their own resolver, is using
	a VPN, or already has the DNS information cached.
	2.2. HTTP Redirection
	In this implementation, the CP acts like a transparent HTTP proxy;
	but when it sees an HTTP request from an unauthenticated client using
	HTTP/1.0, it intercepts the request and responds with an HTTP status
	code 302 to redirect the client to the Captive Portal Login. If the
	client is using HTTP/1.1, we respond with a status code 303 See
	Other.
	This technique has a number of issues, including:
	o It fails if the user is only using HTTPS.
	o It exposes various private user information, such as HTTP Cookies,
	etc.
	o It doesn't work if the client has a VPN and / or proxies their web
	traffic to an external web proxy.
	2.3. IP Hijacking
	In this scenario, the captive portal intercepts connections to any IP
	address. It spoofs the destination IP address and "pretends" to be
	whatever the user tried to access.
	This technique has issues similar to the HTTP solution, but may also
	break other protocols, and may expose more of the user's private
	information.
	3. The Captive-Portal Option
	The Captive Portal DHCP / RA Option informs the client that it is		The Captive Portal DHCP / RA Option informs the client that it is
	behind a captive portal and provides the URI to access an		behind a captive portal and provides the URI to access an
	authentication page. This is primarily intended to improve the user		authentication page. This is primarily intended to improve the user
	experience; for the foreseeable future (until such time that most		experience by getting them to the captive portal faster; for the
	systems implement this technique) captive portals will still need to		foreseeable future, captive portals will still need to implement the
	implement the interception techniques to serve legacy clients.		interception techniques to serve legacy clients, and clients will
			need to perform probing to detect captive portals.
	In order to support multiple "classes" of clients (e.g: IPv4 only,		In order to support multiple "classes" of clients (e.g: IPv4 only,
	IPv6 only with DHCPv6([RFC3315]), IPv6 only with RA) the captive		IPv6 only with DHCPv6([RFC3315]), IPv6 only with RA) the captive
	portal can provide the URI via multiple methods (IPv4 DHCP, IPv6		portal can provide the URI via multiple methods (IPv4 DHCP, IPv6
	DHCP, IPv6 RA). The captive portal operator should ensure that the		DHCP, IPv6 RA). The captive portal operator should ensure that the
	URIs handed out are equivalent to reduce the chance of operational		URIs handed out are equivalent to reduce the chance of operational
	problems.		problems.
	In order to avoid having to perform DNS interception, the URI SHOULD		In order to avoid having to perform DNS interception, the URI SHOULD
	contain an address literal, but MAY contain a DNS name if the captive		contain an address literal, but MAY contain a DNS name if the captive
	portal allows the client to perform DNS requests to resolve the name.		portal allows the client to perform DNS requests to resolve the name.
	[ED NOTE: Using an address literal is less than ideal, but better		2.1. IPv4 DHCP Option
	than the alternatives. Recommending a DNS name means that the CP
	would need to allow DNS from unauthenticated clients (as we don't
	want to force users to use the CP's provided DNS) and some users
	would use this to DNS Tunnel out, which may make the CP admin block
	external recursives). DNS is needed to allow operators to serve SSL/
	TLS for e.g billing (certificates with IP addresses are frowned upon
	:-))]
	3.1. IPv4 DHCP Option
	The format of the IPv4 Captive-Portal DHCP option is shown below.		The format of the IPv4 Captive-Portal DHCP option is shown below.
	Code Len Data		Code Len Data
	+------+------+------+------+------+-- --+-----+		+------+------+------+------+------+-- --+-----+
	| code | len | URI ... |		| code | len | URI ... |
	+------+------+------+------+------+-- --+-----+		+------+------+------+------+------+-- --+-----+
	o Code: The Captive-Portal DHCPv4 Option (TBA1) (one octet)		o Code: The Captive-Portal DHCPv4 Option (TBA1) (one octet)
	o Len: The length, in octets of the URI.		o Len: The length, in octets of the URI.
	o URI: The URI of the authentication page that the user should		o URI: The URI of the authentication page that the user should
	connect to.		connect to.
	3.2. IPv6 DHCP Option		2.2. IPv6 DHCP Option
	The format of the IPv6 Captive-Portal DHCP option is shown below.		The format of the IPv6 Captive-Portal DHCP option is shown below.
	0 1 2 3		0 1 2 3
	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		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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| option-code | option-len |		| option-code | option-len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	. URI (variable length) .		. URI (variable length) .
	| ... |		| ... |
	skipping to change at page 6, line 28 ¶		skipping to change at page 4, line 28 ¶
	o option-code: The Captive-Portal DHCPv6Option (TBA2) (two octets)		o option-code: The Captive-Portal DHCPv6Option (TBA2) (two octets)
	o option-len: The length, in octets of the URI.		o option-len: The length, in octets of the URI.
	o URI: The URI of the authentication page that the user should		o URI: The URI of the authentication page that the user should
	connect to.		connect to.
	See [RFC7227], Section 5.7 for more examples of DHCP Options with		See [RFC7227], Section 5.7 for more examples of DHCP Options with
	URIs.		URIs.
	4. The Captive-Portal IPv6 RA Option		3. The Captive-Portal IPv6 RA Option
	This section describes the Captive-Portal Router Advertisement		This section describes the Captive-Portal Router Advertisement
	option.		option.
	0 1 2 3		0 1 2 3
	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		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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length | URI .		| Type | Length | URI .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
	. .		. .
	skipping to change at page 7, line 7 ¶		skipping to change at page 5, line 7 ¶
	Length 8-bit unsigned integer. The length of the option (including		Length 8-bit unsigned integer. The length of the option (including
	the Type and Length fields) in units of 8 bytes.		the Type and Length fields) in units of 8 bytes.
	URI The URI of the authentication page that the user should connect		URI The URI of the authentication page that the user should connect
	to. For the reasons described above, the implementer might want		to. For the reasons described above, the implementer might want
	to use an IP address literal instead of a DNS name. This should		to use an IP address literal instead of a DNS name. This should
	be padded with NULL (0x0) to make the total option length		be padded with NULL (0x0) to make the total option length
	(including the Type and Length fields) a multiple of 8 bytes.		(including the Type and Length fields) a multiple of 8 bytes.
	5. Use of the Captive-Portal Option		4. IANA Considerations
	[ED NOTE: This option provides notice to the OS / User applications
	that there is a CP. Because of differences in UI design between
	Operating Systems, the exact behaviour by OS and Applications is left
	to the OS vendor/Application Developer.]
	The purpose of the Captive-Portal Option is to inform the operating
	system and applications that they are behind a captive portal type
	device and will need to authenticate before getting network access
	(and how to reach the authentication page). What is done with this
	information is left up to the operating system and application
	vendors. This document provides a very high level example of what
	could be done with this information.
	Many operating systems / applications already include a "connectivity
	test" to determine if they are behind a captive portal (for example,
	attempting to fetch a specific URL and looking for a specific string
	(such as "Success"). These tests sometimes fail or take a long time
	to determine when they are behind a CP, but are usually effective for
	determining that the captive portal has been satisfied. These tests
	will continue to be needed, because there is currently no definitive
	signal from the captive portal that it has been satisfied. [ Editor
	note: It may be useful to write another document that specifies how a
	client can determine that it has passed the CP. This document could
	also contain advice to implementors on only intercepting actually
	needed ports, how to advertise that the CP needs to be satisfied
	*again*, etc. This should not be done in this document though. ] The
	connectivity test may also need to be used if the captive portal
	times out the user session and needs the user to re-authenticate.
	The operating system may still find the information about the captive
	portal URI useful in this case.
	When the device is informed that it is behind a captive portal on a
	particular network interface, it should:
	1. Not initiate new IP connections through that interface until
	until the CP has been satisfied (other than those to the captive
	portal browser session and connectivity checks). Existing
	connections should be quiesced (this will happen more often than
	some expect -- for example, the user purchases 1 hour of Internet
	at a cafe and stays there for 3 hours -- this will "interrupt"
	the user a few times).
	2. Present a dialog box to the user informing them that they are
	behind a captive portal and ask if they wish to proceed.
	3. If the user elects to proceed, the device should initiate a
	connection to the captive portal login page using a web browser
	configured with a separate cookie store, and without a proxy
	server. If there is a VPN in place, this connection should be
	made outside of the VPN and the user should be informed that
	connection is outside the VPN. Some captive portals send the
	user a cookie when they authenticate (so that the user can re-
	authenticate more easily in the future) - the browser should keep
	these CP cookies separate from other cookies.
	4. Once the user has authenticated, normal IP connectivity should
	resume. The CP success page should contain a string, e.g
	"CP_SATISFIED." The OS can then use this string to provide
	further information to the user.
	5. The device should (using an OS dependent method) expose to the
	user / user applications that they have connected though a
	captive portal (for example by creating a file in /proc/net/
	containing the interface and captive portal URI). This should
	continue until the network changes, or a new DHCP message without
	the CP is received.
	6. IANA Considerations
	This document defines two DHCP Captive-Portal options, one for IPv6		This document defines two DHCP Captive-Portal options, one for IPv6
	and one for IPv6. It requires assignment of an option code (TBA1) to		and one for IPv6. It requires assignment of an option code (TBA1) to
	be assigned from "Bootp and DHCP options" registry (http://www.iana		be assigned from "Bootp and DHCP options" registry
	.org/assignments/ bootp-dhcp-parameters/bootp-dhcp-parameters.xml),		(http://www.iana.org/assignments/ bootp-dhcp-parameters/bootp-dhcp-
	as specified in [RFC2939]. It also requires assignment of an option		parameters.xml), as specified in [RFC2939]. It also requires
	code (TBA2) from the "DHCPv6 and DHCPv6 options" registry		assignment of an option code (TBA2) from the "DHCPv6 and DHCPv6
	(http://www.iana.org/assignments/dhcpv6-parameters/		options" registry (http://www.iana.org/assignments/dhcpv6-parameters/
	dhcpv6-parameters.xml).		dhcpv6-parameters.xml).
	IANA is also requested to assign an IPv6 RA Option Type code (TBA3)		IANA is also requested to assign an IPv6 RA Option Type code (TBA3)
	from the "IPv6 Neighbor Discovery Option Formats" registry. Thanks		from the "IPv6 Neighbor Discovery Option Formats" registry. Thanks
	IANA!		IANA!
	7. Security Considerations		5. Security Considerations
	An attacker with the ability to inject DHCP messages could include		An attacker with the ability to inject DHCP messages could include
	this option and so force users to contact an address of his choosing.		this option and so force users to contact an address of his choosing.
	As an attacker with this capability could simply list himself as the		As an attacker with this capability could simply list himself as the
	default gateway (and so intercept all the victim's traffic), this		default gateway (and so intercept all the victim's traffic); this
	does not provide them with significantly more capabilities. Fake		does not provide them with significantly more capabilities. Fake
	DHCP servers / fake RAs are currently a security concern - this		DHCP servers / fake RAs are currently a security concern - this
	doesn't make them any better or worse.		doesn't make them any better or worse.
	Devices and systems that automatically connect to an open network		Devices and systems that automatically connect to an open network
	could potentially be tracked using the techniques described in this		could potentially be tracked using the techniques described in this
	document (forcing the user to continually authenticate, or exposing		document (forcing the user to continually authenticate, or exposing
	their browser fingerprint.) However, similar tracking can already be		their browser fingerprint). However, similar tracking can already be
	performed with the standard captive portal mechanisms, so this		performed with the standard captive portal mechanisms, so this
	technique does not give the attackers more capabilities.		technique does not give the attackers more capabilities.
	By simplifying the interaction with the captive portal systems, and		By simplifying the interaction with the captive portal systems, and
	doing away with the need for interception, we think that users will		doing away with the need for interception, we think that users will
	be less likely to disable useful security safeguards like DNSSEC		be less likely to disable useful security safeguards like DNSSEC
	validation, VPNs, etc. In addition, because the system knows that it		validation, VPNs, etc. In addition, because the system knows that it
	is behind a captive portal, it can know not to send cookies,		is behind a captive portal, it can know not to send cookies,
	credentials, etc. Redirection to a portal where TLS can be used		credentials, etc. Redirection to a portal where TLS can be used
	without hijacking can ameliorate some of the implications of		without hijacking can ameliorate some of the implications of
	connecting to a potentially malicious captive portal.		connecting to a potentially malicious captive portal.
	8. Acknowledgements		6. Acknowledgements
	Thanks to Vint Cerf for the initial idea / asking me to write this.		Thanks to Vint Cerf for the initial idea / asking me to write this.
	Thanks to Wes George for supplying the IPv6 text. Thanks to Lorenzo		Thanks to Wes George for supplying the IPv6 text. Thanks to Lorenzo
	and Erik for the V6 RA kick in the pants.		and Erik for the V6 RA kick in the pants.
	Thanks to Fred Baker, Ted Lemon, Ole Troan and Asbjorn Tonnesen for		Thanks to Fred Baker, Paul Hoffman, Ted Lemon, Martin Nilsson, Ole
	detailed review and comments. Also great thanks to Joel Jaeggli for		Troan and Asbjorn Tonnesen for detailed review and comments. Also
	providing feedback and text.		great thanks to Joel Jaeggli for providing feedback and text.
	9. Normative References		7. 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, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC		[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
	2131, March 1997.		2131, March 1997.
	[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,		[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
	and M. Carney, "Dynamic Host Configuration Protocol for		and M. Carney, "Dynamic Host Configuration Protocol for
	IPv6 (DHCPv6)", RFC 3315, July 2003.		IPv6 (DHCPv6)", RFC 3315, July 2003.
	skipping to change at page 10, line 9 ¶		skipping to change at page 6, line 39 ¶
	September 2007.		September 2007.
	[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and		[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
	S. Krishnan, "Guidelines for Creating New DHCPv6 Options",		S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
	BCP 187, RFC 7227, May 2014.		BCP 187, RFC 7227, May 2014.
	Appendix A. Changes / Author Notes.		Appendix A. Changes / Author Notes.
	[RFC Editor: Please remove this section before publication ]		[RFC Editor: Please remove this section before publication ]
			From 13.2 to 13(posted):
			o Shortened the document by removing most of the [Editors notes],
			Section 2, Section 5 and Appendix A. They were mainly background
			and have served their purpose. This change suggested by Paul
			Hoffman.
			From 13.1 to 13.2:
			o Moved all of the "what an OS could do with this info" to an
			Appendix, to make it even clearer that this is simply an example.
			From -12 to -13.1:
			There was a Captive Portal Bar BoF held at the Dallas IETF meeting.
			See https://github.com/httpwg/wiki/wiki/Captive-Portals for some
			details. This document was discussed, and I got a fair bit of
			feedback. Incorporating some of this in -13.
			o "In the text discussing why a captive portal notification might be
			useful (section 2.2 maybe?), perhaps you should say something
			about HSTS and HTTP2.0, since they will further erode the ability
			to use common captive portal redirection techniques." - Wes
			George.
			o Integrated a bunch of useful comments from Martin Nilsson
	From -11 to -12:		From -11 to -12:
	o Integrated a whole bunch of comments from Ted Lemon, including		o Integrated a whole bunch of comments from Ted Lemon, including
	missing references, track, missing size of DHCP option,		missing references, track, missing size of DHCP option,
	From 10 to 11:		From 10 to 11:
	o Updared Olafur's affiliation.		o Updated Olafur's affiliation.
	From 09 to 10:		From 09 to 10:
	o Ted Lemon and Joel Jaeggli: there's no benefit to insisting on an		o Ted Lemon and Joel Jaeggli: there's no benefit to insisting on an
	ordering. I think you should just say that the ordering is		ordering. I think you should just say that the ordering is
	indeterminate, and if different mechanisms give non-equivalent		indeterminate, and if different mechanisms give non-equivalent
	answers, this is likely to cause operational problems in practice.		answers, this is likely to cause operational problems in practice.
	From 08 to 09:		From 08 to 09:
	skipping to change at page 10, line 44 ¶		skipping to change at page 8, line 5 ¶
	o Some cleanup.		o Some cleanup.
	From 06 to 07:		From 06 to 07:
	o Incoroprated a bunch of comments from Asbjorn Tonnesen		o Incoroprated a bunch of comments from Asbjorn Tonnesen
	o Clarified that this document is only for the DHCP bits, not		o Clarified that this document is only for the DHCP bits, not
	everything.		everything.
	o CP's *can* do HTTP redirects to DNS banes, as long as they allow		o CP's *can* do HTTP redirects to DNS names, as long as they allow
	access to all needed services.		access to all needed services.
	From 05 to 06:		From 05 to 06:
	o Integrated comments from Joel, as below		o Integrated comments from Joel, as below
	o Better introduction text, around the "kludgy hacks" section.		o Better introduction text, around the "kludgy hacks" section.
	o Better "neither condones nor condems" text		o Better "neither condones nor condemns" text
	o Fingerprint text.		o Fingerprint text.
	o Some discussions on the v4 literal stuff.		o Some discussions on the v4 literal stuff.
	o More Security Consideration text.		o More Security Consideration text.
	From 04 to 05:		From 04 to 05:
	o Integrated comments, primarily from Fred Baker.		o Integrated comments, primarily from Fred Baker.
End of changes. 26 change blocks.
	222 lines changed or deleted		92 lines changed or added
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