< draft-ietf-idmr-igmp-mrdisc-06.txt		draft-ietf-idmr-igmp-mrdisc-07.txt >
	IDMR Working Group S. Biswas		IDMR Working Group S. Biswas
	Internet Draft B. Haberman		Internet Draft B. Haberman
	draft-ietf-idmr-igmp-mrdisc-06.txt Nortel Networks		draft-ietf-idmr-igmp-mrdisc-07.txt Nortel Networks
	May 2001 B. Cain		June 2001 B. Cain
	Expires November 2001 Cereva Networks		Expires December 2001 Cereva Networks
	IGMP Multicast Router Discovery		IGMP Multicast Router Discovery
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.		all provisions of Section 10 of RFC2026.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at line 32 ¶		skipping to change at line 32 ¶
	progress."		progress."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	Abstract		Abstract
	Companies have been proposing IGMP snooping schemes for layer-2		The concept of IGMP snooping requires the ability to identify the
	bridging devices. A method for discovering multicast capable routers		location of multicast routers. Since IGMP snooping is not
	is necessary for these schemes. An IGMP query message is inadequate		standardized, there are many mechanisms in use to identify the
	for discovering multicast routers as one querier is elected. In		multicast routers. However, this scenario can lead to
	order to "discover" multicast routers, we introduce three new types		interoperability issues between multicast routers and layer-2
	of IGMP messages: Multicast Router Advertisement, Multicast Router		switches from different vendors.
	Solicitation, and Multicast Router Termination. These messages can
	be used by any device which listens to IGMP to discovery multicast		This document introduces a general mechanism that allows for the
	routers. Multicast Router Solicitation messages may be used by any		discovery of multicast routers. By introducing these new messages,
	network device (e.g. layer-2 switch) to solicit discovery messages		IGMP snooping devices have a uniform means of identifying multicast
	from multicast routers.		routers without dependency on particular routing protocols. In
			addition, other devices that may need to discover multicast routers
			can use these messages.
			Table of Contents
			1. Introduction....................................................2
			2. Protocol Overview...............................................3
			3. Multicast Router Advertisement..................................4
			3.1 Overview.......................................................4
			Biswas, Cain, Haberman 1
			3.2 IP Header Fields...............................................4
			3.3 Multicast Router Advertisement Message Format..................5
			3.4 Sending Multicast Router Advertisements........................6
			3.5 Receiving Multicast Router Advertisements......................6
			3.6 Multicast Router Advertisement Configuration Variables.........7
			4. Multicast Router Solicitation...................................8
			4.1 Overview.......................................................8
			4.2 IP Header Fields...............................................8
			4.3 Multicast Router Solicitation Message Format...................9
			4.4 Sending Multicast Router Solicitations.........................9
			4.5 Receiving Multicast Router Solicitations.......................9
			4.6 Multicast Router Solicitation Configuration Variables.........10
			5. Multicast Router Termination...................................10
			5.1 Overview......................................................10
			5.2 IP Header Fields..............................................10
			5.3 Multicast Router Termination Message Format...................10
			5.4 Sending Multicast Router Termination Messages.................11
			5.5 Receiving Multicast Router Termination Messages...............11
			6. Multicast Router Discovery Protocol Constants..................11
			7. Mandatory Advertisement Options................................11
			7.1 Overview of Options...........................................11
			7.2 Query Interval Advertisement Option...........................12
			7.3 Robustness Variable Advertisement Option......................12
			8. IPv6 Support...................................................12
			8.1 Router Advertisement Message..................................13
			8.2 Router Solicitations..........................................13
			9. Security Considerations........................................14
			10. IANA Considerations...........................................14
			11. Acknowledgements..............................................14
			12. References....................................................14
			13. Authors' Addresses............................................14
			14. Full Copyright Statement......................................15
	1. Introduction		1. Introduction
	Multicast router discovery messages are useful for discovering		Multicast router discovery messages are useful for discovering
	multicast capable routers. This capability is useful in a layer-2		multicast capable routers. This capability is useful in a layer-2
	bridging domain with "IGMP snooping" type of schemes. By listening		bridging domain with "IGMP snooping" type of schemes. By listening
	to multicast router discovery messages, layer-2 devices can determine		to multicast router discovery messages, layer-2 devices can determine
	Biswas, Cain, Haberman 1
	where to send multicast source data and IGMP Host Membership Reports		where to send multicast source data and IGMP Host Membership Reports
	[RFC1112] [RFC2236]. Multicast source data and IGMP Host Membership		[RFC1112] [RFC2236]. Multicast source data and IGMP Host Membership
	Reports must be received by all multicast routers on a segment.		Reports must be received by all multicast routers on a segment.
	Using IGMP Host Membership Queries to discover multicast routers is		Using IGMP Host Membership Queries to discover multicast routers is
	not useful because of query suppression in IGMP.		not useful because of query suppression in IGMP.
	Unlike ICMP router discovery messages [RFC1256], multicast router		Unlike ICMP router discovery messages [RFC1256], multicast router
	discovery advertisements should not be listened to by hosts. Hosts		discovery advertisements should not be listened to by hosts. Hosts
	need not know the identity of multicast routers.		need not know the identity of multicast routers.
			Biswas, Cain, Haberman 2
	The use of the multicast router advertisement is not precluded from		The use of the multicast router advertisement is not precluded from
	being used for other purposes. Extensible options have been included		being used for other purposes. Extensible options have been included
	in the advertisement message for future enhancements.		in the advertisement message for future enhancements.
	The following are justifications for inventing another router		The following are justifications for inventing another router
	discovery protocol:		discovery protocol:
	o Using ICMP router discovery is not an appropriate solution		o Using ICMP router discovery is not an appropriate solution
	for multicast router discovery because: 1.) It may confuse		for multicast router discovery because: 1.) It may confuse
	hosts listening to ICMP router advertisements; unicast and		hosts listening to ICMP router advertisements; unicast and
	skipping to change at line 103 ¶		skipping to change at line 145 ¶
	sent by routers to advertise IP multicast forwarding enabled on an		sent by routers to advertise IP multicast forwarding enabled on an
	interface. The Multicast Router Solicitation is used by routers to		interface. The Multicast Router Solicitation is used by routers to
	solicit Multicast Router Advertisements. The Multicast Router		solicit Multicast Router Advertisements. The Multicast Router
	Termination message is sent when a router terminates its multicast		Termination message is sent when a router terminates its multicast
	routing functions.		routing functions.
	Multicast routers send Multicast Router Advertisements (hereafter		Multicast routers send Multicast Router Advertisements (hereafter
	called advertisements) periodically on all interfaces on which		called advertisements) periodically on all interfaces on which
	multicast forwarding is enabled.		multicast forwarding is enabled.
	Biswas, Cain, Haberman 2
	Multicast Router Advertisements are also sent in response to		Multicast Router Advertisements are also sent in response to
	Multicast Router Solicitations (hereafter called solicitations).		Multicast Router Solicitations (hereafter called solicitations).
	These are sent to solicit a response of Multicast Router		These are sent to solicit a response of Multicast Router
	Advertisements from all multicast routers on a subnet. Solicitations		Advertisements from all multicast routers on a subnet. Solicitations
	are sent to the ALL-Routers (224.0.0.2) multicast group.		are sent to the ALL-Routers (224.0.0.2) multicast group.
	Multicast Router Solicitations are sent whenever a device wishes to		Multicast Router Solicitations are sent whenever a device wishes to
	discover multicast routers on a directly attached subnet.		discover multicast routers on a directly attached subnet.
			Biswas, Cain, Haberman 3
	Multicast Router Termination messages are sent when a router		Multicast Router Termination messages are sent when a router
	terminates its multicast routing functions.		terminates its multicast routing functions.
	All IGMP Multicast Router Discovery messages are sent with an IP TTL		All IGMP Multicast Router Discovery messages are sent with an IP TTL
	of 1 and contain the IP Router Alert Option [RFC2113] in their IP		of 1 and contain the IP Router Alert Option [RFC2113] in their IP
	header. All IGMP Multicast Router Discovery messages are sent with		header. All IGMP Multicast Router Discovery messages are sent with
	to the All-Routers multicast group (224.0.0.2).		to the All-Routers multicast group (224.0.0.2).
	Other non-IP forwarding devices (e.g. layer-2 switches) may send		Other non-IP forwarding devices (e.g. layer-2 switches) may send
	Multicast Router Solicitations to solicit Multicast Router		Multicast Router Solicitations to solicit Multicast Router
	skipping to change at line 153 ¶		skipping to change at line 195 ¶
	by future work.		by future work.
	3.2 IP Header Fields		3.2 IP Header Fields
	3.2.1 Source Address		3.2.1 Source Address
	An IP address belonging to the interface from which this message is		An IP address belonging to the interface from which this message is
	sent. If multiple source addresses are configured on an interface,		sent. If multiple source addresses are configured on an interface,
	then the one chosen is implementation dependent.		then the one chosen is implementation dependent.
	Biswas, Cain, Haberman 3
	3.2.2 Destination Address		3.2.2 Destination Address
	Router Advertisements are sent to the All-Routers multicast address		Router Advertisements are sent to the All-Routers multicast address
	(224.0.0.2).		(224.0.0.2).
	3.2.3 Time-to-Live		3.2.3 Time-to-Live
	The Time-to-Live field MUST be 1.		The Time-to-Live field MUST be 1.
			Biswas, Cain, Haberman 4
	3.2.4 Protocol		3.2.4 Protocol
	The protocol field is set to IGMP (2).		The protocol field is set to IGMP (2).
	3.3 Multicast Router Advertisement Message Format		3.3 Multicast Router Advertisement Message Format
	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 | Ad. Interval | Checksum |		| Type | Ad. Interval | Checksum |
	skipping to change at line 185 ¶		skipping to change at line 227 ¶
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Option [1] (TLV encoded) |		| Option [1] (TLV encoded) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Option [...] (TLV encoded) |		| Option [...] (TLV encoded) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Option [N] (TLV encoded) |		| Option [N] (TLV encoded) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.3.1 Type Field		3.3.1 Type Field
	The type field is set to 0x24.		The type field is set to XX (to be assigned by IANA).
	3.3.2 Advertisement Interval		3.3.2 Advertisement Interval
	This specifies the periodic time interval at which Multicast Router		This specifies the periodic time interval at which Multicast Router
	Advertisements are sent in units of seconds. This value is set to		Advertisements are sent in units of seconds. This value is set to
	the configured MaxAdvertisementInterval variable.		the configured MaxAdvertisementInterval variable.
	3.3.3 Checksum		3.3.3 Checksum
	The checksum is the 16-bit one's complement of the one's complement		The checksum is the 16-bit one's complement of the one's complement
	sum of the IGMP message, starting with the IGMP type. For computing		sum of the IGMP message, starting with the IGMP type. For computing
	the checksum, the Checksum field is set to 0.		the checksum, the Checksum field is set to 0.
	3.3.4 Number of Options (N)		3.3.4 Number of Options (N)
	The number of options contained in the router advertisement. If no		The number of options contained in the router advertisement. If no
	options are sent this field MUST be set to 0.		options are sent this field MUST be set to 0.
	Biswas, Cain, Haberman 4
	3.3.5 Option[1..N]		3.3.5 Option[1..N]
	Options are encoded as TLV in the following manner:		Options are encoded as TLV in the following manner:
			Biswas, Cain, Haberman 5
	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 | Value |		| Type | Length | Value |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	If the Number of Options field is not zero, a receiver MUST examine		If the Number of Options field is not zero, a receiver MUST examine
	all options. No strict ordering of options is enforced.		all options. No strict ordering of options is enforced.
	Type: Set to option type being advertised		Type: Set to option type being advertised
	skipping to change at line 256 ¶		skipping to change at line 298 ¶
	is sent in response with a random delay less than MAX_RESPONSE_DELAY.		is sent in response with a random delay less than MAX_RESPONSE_DELAY.
	If a solicitation is received while an advertisement is pending		If a solicitation is received while an advertisement is pending
	(because of a recent solicitation), that solicitation will be		(because of a recent solicitation), that solicitation will be
	ignored.		ignored.
	Whenever an advertisement is sent, the periodic advertisement		Whenever an advertisement is sent, the periodic advertisement
	interval timer must be reset.		interval timer must be reset.
	3.5 Receiving Multicast Router Advertisements		3.5 Receiving Multicast Router Advertisements
	Biswas, Cain, Haberman 5
	Upon receiving a router advertisement, devices will validate the		Upon receiving a router advertisement, devices will validate the
	message by the following criteria:		message by the following criteria:
	1. Verifying the IGMP checksum		1. Verifying the IGMP checksum
			Biswas, Cain, Haberman 6
	2. IP Destination Address = All-Routers multicast address		2. IP Destination Address = All-Routers multicast address
	A router advertisement not meeting the validity requirements should		A router advertisement not meeting the validity requirements should
	be silently discarded or logged in a rate-limited manner. Devices		be silently discarded or logged in a rate-limited manner. Devices
	MUST process all options, discarding options that are not recognized.		MUST process all options, discarding options that are not recognized.
	If a router advertisement is not received for a particular neighbor		If a router advertisement is not received for a particular neighbor
	within NeighborDeadInterval time interval, then the neighbor is		within NeighborDeadInterval time interval, then the neighbor is
	considered to be unreachable.		considered to be unreachable.
	skipping to change at line 308 ¶		skipping to change at line 350 ¶
	The first router advertisement out of an interface is sent after		The first router advertisement out of an interface is sent after
	waiting for a random interval less than this variable. This will		waiting for a random interval less than this variable. This will
	prevent a flood of router advertisements when many routers start up		prevent a flood of router advertisements when many routers start up
	at the same time.		at the same time.
	Default: 2 seconds		Default: 2 seconds
	3.6.4 MaxInitialAdvertisements		3.6.4 MaxInitialAdvertisements
	Biswas, Cain, Haberman 6
	The maximum number of router advertisements that will be sent on a		The maximum number of router advertisements that will be sent on a
	subnet after a router boots.		subnet after a router boots.
	Default: 3		Default: 3
			Biswas, Cain, Haberman 7
	3.6.5 NeighborDeadInterval		3.6.5 NeighborDeadInterval
	The maximum time allowed before a neighbor can be declared "dead".		The maximum time allowed before a neighbor can be declared "dead".
	This variable is defined in seconds. In order for all devices to have		This variable is defined in seconds. In order for all devices to have
	a consistent state, it is necessary for the MaxAdvertisementInterval		a consistent state, it is necessary for the MaxAdvertisementInterval
	to be configured the same on all routers per subnet.		to be configured the same on all routers per subnet.
	Default: 3 * MaxAdvertisementInterval		Default: 3 * MaxAdvertisementInterval
	4. Multicast Router Solicitation		4. Multicast Router Solicitation
	skipping to change at line 361 ¶		skipping to change at line 403 ¶
	Solicitation messages are sent to the All-Routers multicast address		Solicitation messages are sent to the All-Routers multicast address
	(224.0.0.2).		(224.0.0.2).
	4.2.3 Time-to-Live		4.2.3 Time-to-Live
	The time-to-live field MUST be 1.		The time-to-live field MUST be 1.
	4.2.4 Protocol		4.2.4 Protocol
	Biswas, Cain, Haberman 7
	The protocol field is set to IGMP (2).		The protocol field is set to IGMP (2).
			Biswas, Cain, Haberman 8
	4.3 Multicast Router Solicitation Message Format		4.3 Multicast Router Solicitation Message Format
	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 | Reserved | Checksum |		| Type | Reserved | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	4.3.1 Type Field		4.3.1 Type Field
	The type field is set to 0x25.		The type field is set to YY (to be assigned by IANA).
	4.3.2 Reserved Field		4.3.2 Reserved Field
	Sent as 0; ignored on reception.		Sent as 0; ignored on reception.
	4.3.3 Checksum		4.3.3 Checksum
	The checksum is the 16-bit one's complement of the one's complement		The checksum is the 16-bit one's complement of the one's complement
	sum of the IGMP message, starting with the IGMP type. For computing		sum of the IGMP message, starting with the IGMP type. For computing
	the checksum, the Checksum field is set to 0.		the checksum, the Checksum field is set to 0.
	skipping to change at line 412 ¶		skipping to change at line 454 ¶
	Upon receiving a router solicitation, routers will validate the		Upon receiving a router solicitation, routers will validate the
	message by:		message by:
	1. Verifying the IGMP checksum		1. Verifying the IGMP checksum
	2. IP Destination Address = All-Routers multicast address		2. IP Destination Address = All-Routers multicast address
	A router solicitation not meeting the validity requirements should be		A router solicitation not meeting the validity requirements should be
	silently discarded or logged in a rate-limited manner.		silently discarded or logged in a rate-limited manner.
	Biswas, Cain, Haberman 8
	Solicitation message IP source addresses MUST NOT be used as part of		Solicitation message IP source addresses MUST NOT be used as part of
	the validity check.		the validity check.
			Biswas, Cain, Haberman 9
	4.6 Multicast Router Solicitation Configuration Variables		4.6 Multicast Router Solicitation Configuration Variables
	There are no configurable variables with respect to router		There are no configurable variables with respect to router
	solicitations.		solicitations.
	5. Multicast Router Termination		5. Multicast Router Termination
	5.1 Overview		5.1 Overview
	The Multicast Router Termination message is used to expedite the		The Multicast Router Termination message is used to expedite the
	skipping to change at line 460 ¶		skipping to change at line 502 ¶
	5.3 Multicast Router Termination Message Format		5.3 Multicast Router Termination Message Format
	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 | Reserved | Checksum |		| Type | Reserved | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	5.3.1 Type Field		5.3.1 Type Field
	The type field is set to 0x26.		The type field is set to ZZ (to be assigned by IANA).
	5.3.2 Reserved Field		5.3.2 Reserved Field
	Biswas, Cain, Haberman 9
	Sent as 0; ignored on reception.		Sent as 0; ignored on reception.
	5.3.3 Checksum		5.3.3 Checksum
			Biswas, Cain, Haberman 10
	The checksum is the 16-bit one's complement of the one's complement		The checksum is the 16-bit one's complement of the one's complement
	sum of the IGMP message, starting with the IGMP type. For computing		sum of the IGMP message, starting with the IGMP type. For computing
	the checksum, the Checksum field is set to 0.		the checksum, the Checksum field is set to 0.
	5.4 Sending Multicast Router Termination Messages		5.4 Sending Multicast Router Termination Messages
	Multicast Router Termination messages are sent for three reasons:		Multicast Router Termination messages are sent for three reasons:
	1. Multicast forwarding is disabled on the interface		1. Multicast forwarding is disabled on the interface
	skipping to change at line 517 ¶		skipping to change at line 559 ¶
	7.1 Overview of Options		7.1 Overview of Options
	The following options MUST be supported by an implementation of IGMP		The following options MUST be supported by an implementation of IGMP
	Multicast Router Discovery: Query Interval Advertisement Option and		Multicast Router Discovery: Query Interval Advertisement Option and
	Robustness Variable Advertisement Option. These options advertise		Robustness Variable Advertisement Option. These options advertise
	specific IGMP variables and are sent in an advertisement depending on		specific IGMP variables and are sent in an advertisement depending on
	the version of IGMP enabled on an interface. Although no		the version of IGMP enabled on an interface. Although no
	requirements exist for multicast routers at this time, it is assumed		requirements exist for multicast routers at this time, it is assumed
	that all multicast routers support the IGMP protocol.		that all multicast routers support the IGMP protocol.
	Biswas, Cain, Haberman 10		Biswas, Cain, Haberman 11
	7.2 Query Interval Advertisement Option		7.2 Query Interval Advertisement 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=1 | Length=2 | IGMP Query Interval |		| Type=1 | Length=2 | IGMP Query Interval |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	If a multicast router has any version of IGMP [RFC1112] enabled on an		If a multicast router has any version of IGMP [RFC1112] enabled on an
	interface on which IGMP Multicast Router Discovery is also enabled,		interface on which IGMP Multicast Router Discovery is also enabled,
	skipping to change at line 569 ¶		skipping to change at line 611 ¶
	Robustness Variable is an integer that MUST not be zero [IGMPv2] and		Robustness Variable is an integer that MUST not be zero [IGMPv2] and
	is equal to the IGMPv2 robustness variable.		is equal to the IGMPv2 robustness variable.
	8. IPv6 Support		8. IPv6 Support
	The Multicast Router Discovery function for IPv6 is accomplished		The Multicast Router Discovery function for IPv6 is accomplished
	using the Neighbor Discovery Protocol for IPv6 [RFC2461] (hereafter		using the Neighbor Discovery Protocol for IPv6 [RFC2461] (hereafter
	called NDP). Specifically, the Router Advertisement message contains		called NDP). Specifically, the Router Advertisement message contains
	new fields to support the discovery of multicast routers. For this		new fields to support the discovery of multicast routers. For this
	Biswas, Cain, Haberman 11		Biswas, Cain, Haberman 12
	reason, the timing mechanisms defined for NDP will be used instead of		reason, the timing mechanisms defined for NDP will be used instead of
	those defined in this document for IPv4 support.		those defined in this document for IPv4 support.
	8.1 Router Advertisement Message		8.1 Router Advertisement Message
	The Router Advertisement message contains two new fields to support		The Router Advertisement message contains two new fields to support
	the multicast router discovery mechanism. The modified message		the multicast router discovery mechanism. The modified message
	format is:		format is:
	0 1 2 3		0 1 2 3
	skipping to change at line 620 ¶		skipping to change at line 662 ¶
	indicates that multicast forwarding is disabled.		indicates that multicast forwarding is disabled.
	When the state of multicast forwarding changes on an interface, a		When the state of multicast forwarding changes on an interface, a
	router must stop its Router Advertisement timer, transmit a Router		router must stop its Router Advertisement timer, transmit a Router
	Advertisement with the 'E' bit set to the value associated with the		Advertisement with the 'E' bit set to the value associated with the
	new multicast forwarding state, and restart its Router Advertisement		new multicast forwarding state, and restart its Router Advertisement
	timer.		timer.
	8.2 Router Solicitations		8.2 Router Solicitations
	Biswas, Cain, Haberman 12		Biswas, Cain, Haberman 13
	An NDP Router Solicitation message can be sent to solicit a Router		An NDP Router Solicitation message can be sent to solicit a Router
	Advertisement message in order to determine the multicast forwarding		Advertisement message in order to determine the multicast forwarding
	state of a router. The periodic transmission of solicitation		state of a router. The periodic transmission of solicitation
	messages is outlined in RFC 2461.		messages is outlined in RFC 2461.
	9. Security Considerations		9. Security Considerations
	The Multicast Router Advertisement message may allow rogue machines		The Multicast Router Advertisement message may allow rogue machines
	to masquerade as multicast routers. This could allow those machines		to masquerade as multicast routers. This could allow those machines
	to eavesdrop on multicast data transmission or create a denial of		to eavesdrop on multicast data transmission or create a denial of
	service attack on multicast flows. However, these new messages are		service attack on multicast flows. However, these new messages are
	extensible and that allows for the introduction of security		extensible and that allows for the introduction of security
	associations into the protocol. These security extensions could be		associations into the protocol. These security extensions could be
	used to authenticate or encrypt the messages.		used to authenticate or encrypt the messages.
	10. Acknowledgements		10. IANA Considerations
			This document introduces three new IGMP messages. Each of these
			messages requires a new IGMP 'Type' value.
			11. Acknowledgements
	ICMP Router Discovery [RFC1256] was used as a general model for IGMP		ICMP Router Discovery [RFC1256] was used as a general model for IGMP
	Multicast Router Discovery.		Multicast Router Discovery.
	11. References		12. References
	[RFC1256] Deering, S., "ICMP Router Discovery Messages", RFC 1256,		[RFC1256] Deering, S., "ICMP Router Discovery Messages", RFC 1256,
	September 1991.		September 1991.
	[RFC1112] Deering, S., "Host Extensions for IP Multicasting",		[RFC1112] Deering, S., "Host Extensions for IP Multicasting",
	RFC 1112, August 1989.		RFC 1112, August 1989.
	[RFC2236] Fenner, W., "Internet Group Management Protocol,		[RFC2236] Fenner, W., "Internet Group Management Protocol,
	Version 2", RFC 2236, November 1997.		Version 2", RFC 2236, November 1997.
	[IGMPv3] Cain, B., Deering, S., Thyagarajan, A., "Internet Group		[IGMPv3] Cain, B., Deering, S., Thyagarajan, A., "Internet Group
	Management Protocol, Version 3", work in progress,		Management Protocol, Version 3", work in progress,
	March 2001.		March 2001.
	[RFC2113] Katz, D., "IP Router Alert Option," RFC 2113, April 1996.		[RFC2113] Katz, D., "IP Router Alert Option," RFC 2113, April 1996.
	[RFC2461] Narten, T., Nordmark, E., and Simpson, W., "Neighbor		[RFC2461] Narten, T., Nordmark, E., and Simpson, W., "Neighbor
	Discovery IP Version 6 (IPv6)", RFC 2461, December 1998.		Discovery IP Version 6 (IPv6)", RFC 2461, December 1998.
	10. Authors' Addresses		13. Authors' Addresses
	Shantam Biswas		Shantam Biswas
	Nortel Networks		Nortel Networks
	600 Technology Park Drive		600 Technology Park Drive
	Billerica, MA 01821		Billerica, MA 01821
			Biswas, Cain, Haberman 14
	Email: sbiswas@baynetworks.com		Email: sbiswas@baynetworks.com
	Phone: 1-978-916-8048		Phone: 1-978-916-8048
	Brad Cain		Brad Cain
	Cereva Networks		Cereva Networks
	Biswas, Cain, Haberman 13
	Email: bcain@cereva.com		Email: bcain@cereva.com
	Brian Haberman		Brian Haberman
	Nortel Networks		Nortel Networks
	4309 Emperor Blvd		4309 Emperor Blvd
	Suite 200		Suite 200
	Durham, NC 27703		Durham, NC 27703
	Email: haberman@nortelnetworks.com		Email: haberman@nortelnetworks.com
	Phone: 1-919-992-4439		Phone: 1-919-992-4439
	Biswas, Cain, Haberman 14		14. Full Copyright Statement
			Copyright (C) The Internet Society (2001). All Rights Reserved.
			This document and translations of it may be copied and furnished to
			others, and derivative works that comment on or otherwise explain it
			or assist in its implementation may be prepared, copied, published
			and distributed, in whole or in part, without restriction of any
			kind, provided that the above copyright notice and this paragraph
			are included on all such copies and derivative works. However, this
			document itself may not be modified in any way, such as by removing
			the copyright notice ore references to the Internet Society or other
			Internet organizations, except as needed for the purpose of
			developing Internet standards in which case the procedures for
			copyrights defined in the Internet Standards process must be
			followed, or as required to translate it into languages other than
			English.
			The limited permissions granted above are perpetual and will not be
			revoked by the Internet Society or its successors or assigns.
			This document and the information contained herein is provided on an
			"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
			TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
			BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
			HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
			MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
			Biswas, Cain, Haberman 15
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