< draft-ietf-idmr-igmp-mrdisc-01.txt		draft-ietf-idmr-igmp-mrdisc-02.txt >
	INTERNET DRAFT S. Biswas		INTERNET DRAFT S. Biswas
	IDMR Working Group B. Cain		IDMR Working Group B. Cain
	Nortel Networks		Nortel Networks
	draft-ietf-idmr-igmp-mrdisc-01.txt February 1999		B. Haberman
	Expires August 1999		IBM
			August 1999
			Expires February 1999
	IGMP Multicast Router Discovery		IGMP Multicast Router Discovery
	<draft-ietf-idmr-igmp-mrdisc-01.txt>		<draft-ietf-idmr-igmp-mrdisc-02.txt>
	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
	other groups may also distribute working documents as Internet-		other groups may also distribute working documents as Internet-
	Drafts.		Drafts.
	skipping to change at page 1, line 36 ¶		skipping to change at page 1, line 37 ¶
	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" type schemes for		Companies have been proposing "IGMP snooping" type schemes for
	layer-2 bridging devices. A method for discovery multicast capable		layer-2 bridging devices. A method for discovering multicast capable
	routers is necessary for these schemes. An IGMP query message is		routers is necessary for these schemes. An IGMP query message is
	inadequate for discoverying multicast routers as one querier is		inadequate for discoverying multicast routers as one querier is
	elected. In order to "discover" multicast routers, we introduce		elected. In order to "discover" multicast routers, we introduce
	two new types of IGMP messages: Multicast Router Advertisement and		two new types of IGMP messages: Multicast Router Advertisement and
	Multicast Router Solicitation. These two messages can be used by		Multicast Router Solicitation. These two messages can be used by
	any device which listens to IGMP to discovery multicast routers.		any device which listens to IGMP to discovery multicast routers.
	Multicast ROuter Solicitation messages may be used by any network		Multicast Router Solicitation messages may be used by any network
	device (e.g. layer-2 switch) to solicit discovery messages from		device (e.g. layer-2 switch) to solicit discovery messages from
	multicast routers.		multicast routers.
	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		to multicast router discovery messages, layer-2 devices can
	determine where to send multicast source data and IGMP Host		determine where to send multicast source data and IGMP Host
	skipping to change at page 2, line 40 ¶		skipping to change at page 2, line 40 ¶
	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
	multicast topologies may not be congruent. 2.) It is		multicast topologies may not be congruent. 2.) It is
	desirable to have advertisements sent to a special link-		desirable to have advertisements sent to a special link-
	local group address. 3.) There is no way to tell from a		local group address. 3.) There is no way to tell from a
	ICMP router advertisement if a router is running a multicast		ICMP router advertisement if a router is running a multicast
	routing protocol.		routing protocol.
	2. By making multicast router discovery messages extensible		2. By making multicast router discovery messages extensible
	and sending messages to a special address, future		and sending messages to a special address, future
	enhancements can be made.		enhancements can be made.
	3. By inventing a generic IP layer message, multiple type of		3. By inventing a generic IP layer message, multiple types of
	messages per link layer are not needed (i.e. including this		messages per link layer are not needed (i.e. including this
	functionality as part of IP is better than inventing N		functionality as part of IP is better than inventing N
	discovery protocols for N layer-2 technologies).		discovery protocols for N layer-2 technologies).
	Although multicast router discovery messages could be sent as		Although multicast router discovery messages could be sent as
	ICMP messages, IGMP was chosen because IGMP snooping switches		ICMP messages, IGMP was chosen because IGMP snooping switches
	already snoop IGMP messages and because the first use of these		already snoop IGMP messages and because the intended first use
	messages is multicast specific.		of these protocol messages is multicast specific.
	1.1 Protocol Overview		1.1 Protocol Overview
	IGMP Multicast Router Discovery consists of two messages for		IGMP Multicast Router Discovery consists of three messages for
	discovering multicast routers. The Multicast Router Advertisement		discovering multicast routers. The Multicast Router Advertisement
	is sent by routers to advertise IP multicast forwarding enabled		is sent by routers to advertise IP multicast forwarding enabled
	on an interface. The Multicast Router Solicitation is used by		on an interface. The Multicast Router Solicitation is used by
	routers to solicit Multicast Router Advertisements.		routers to solicit Multicast Router Advertisements. The Multicast
			Router Termination message is sent when a router terminates its
			multicast 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. These messages are sent to the		multicast forwarding is enabled.
	IGMP-MRDISC multicast group.
	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.		Advertisements from all multicast routers on a subnet.
	Solicitations are sent to the IGMP-MRDISC multicast group.		Solicitations are sent to the IGMP-MRDISC multicast group.
	Multicast Router Solicitations are sent whenever a router wishes		Multicast Router Solicitations are sent whenever a router wishes
	to discover multicast routers on a directly attached subnet.		to discover multicast routers on a directly attached subnet.
			Multicast Router Termination messages are sent when a router
			terminates its multicast routing functions.
	All IGMP Multicast Router Discovery messages are sent with an		All IGMP Multicast Router Discovery messages are sent with an
	IP TLL of 1 and contain the IP Router Alert Option [RFC2113] in		IP TLL of 1 and contain the IP Router Alert Option [RFC2113] in
	their IP header.		their IP header. All IGMP Multicast Router Discovery messages
			are sent with to the IGMP-MRDISC multicast group (224.0.0.x).
	Other non-router networking devices (e.g. layer-2 switches) may		Other non-IP forwarding devices (e.g. layer-2 switches) may
	send Multicast Router Solicitations to solicit Multicast Router		send Multicast Router Solicitations to solicit Multicast Router
	Advertisements.		Advertisements.
	2. Multicast Router Advertisement		2. Multicast Router Advertisement
	2.1 Overview		2.1 Overview
	Multicast Router Advertisements are sent periodically on all router		Multicast Router Advertisements are sent periodically on all router
	interfaces on which multicast forwarding is enabled. They are also		interfaces on which multicast forwarding is enabled. They are also
	sent in response to Multicast Router Solicitations.		sent in response to Multicast Router Solicitations.
	skipping to change at page 3, line 48 ¶		skipping to change at page 4, line 4 ¶
	Advertisements are sent as IGMP messages to the IGMP-MRDISC		Advertisements are sent as IGMP messages to the IGMP-MRDISC
	multicast address (224.0.0.x) and should be rate-limited.		multicast address (224.0.0.x) and should be rate-limited.
	Router advertisements may contain any number of options. Two		Router advertisements may contain any number of options. Two
	options are defined in this document and MUST be supported by any		options are defined in this document and MUST be supported by any
	implementation of IGMP multicast router discovery. These options		implementation of IGMP multicast router discovery. These options
	are described in Section 5. Additional options may be defined as		are described in Section 5. Additional options may be defined as
	needed by future work.		needed by future work.
	2.2 IP Header Fields		2.2 IP Header Fields
	2.2.1 Source Address		2.2.1 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.
	2.2.1 Destination Address		2.2.2 Destination Address
	Router Advertisements are sent to the IGMP-MRDISC multicast		Router Advertisements are sent to the IGMP-MRDISC multicast
	address (224.0.0.x).		address (224.0.0.x).
	2.2.2 Time-to-Live		2.2.3 Time-to-Live
	The Time-to-Live field MUST be 1.		The Time-to-Live field MUST be 1.
	2.2.3 Protocol		2.2.4 Protocol
	The protocol field is set to IGMP (2).		The protocol field is set to IGMP (2).
	2.3 Multicast Router Advertisement Message Format		2.3 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 page 4, line 59 ¶		skipping to change at page 5, line 14 ¶
	2.3.4 Number of Options (N)		2.3.4 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.
	2.3.5 Option[1..N]		2.3.5 Option[1..N]
	Options are encoded as TLV in the following manner:		Options are encoded as TLV in the following manner:
	@
	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, all options MUST be		If the Number of Options field is not zero, all options MUST be
	examined by a receiver. No strict ordering of options is enforced.		examined by a receiver. No strict ordering of options is enforced.
	Type: Set to option type being advertised		Type: Set to option type being advertised
	Length: Length in bytes of Value field		Length: Length in bytes of Value field
	Value: Option dependent value		Value: Option dependent value
	2.4 Sending Multicast Router Advertisements		2.4 Sending Multicast Router Advertisements
	Router Advertisements are sent when the following events occur:		Router Advertisements are sent when the following events occur:
	1. When the a periodic advertisement interval timer expires.		1. When the periodic advertisement interval timer expires.
	Note that it is not strictly periodic because the		Note that it is not strictly periodic because the
	advertisement interval is a random number between		advertisement interval is a random number between
	MaxAdvertisementInterval and MinAdvertisementInterval.		MaxAdvertisementInterval and MinAdvertisementInterval.
	(Default Value: 7-10 seconds).		(Default Value: 7-10 seconds).
	2. After waiting for a random delay less than		2. After waiting for a random delay less than
	MaxInitialAdvertisementInterval when an interface first		MaxInitialAdvertisementInterval when an interface first
	comes up, is (re)initialized, or IGMP Multicast Router		comes up, is (re)initialized, or IGMP Multicast Router
	Discovery is enabled. A router may send up to a maximum of		Discovery is enabled. A router may send up to a maximum of
	MaxInitialAdvertisements advertisements, waiting for a		MaxInitialAdvertisements advertisements, waiting for a
	skipping to change at page 8, line 13 ¶		skipping to change at page 9, line 25 ¶
	silently discarded.		silently discarded.
	Solicitation message IP source addresses MUST NOT be used as part		Solicitation message IP source addresses MUST NOT be used as part
	of the validity check.		of the validity check.
	3.6 Multicast Router Solicitation Configuration Variables		3.6 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.
	4. Multicast Router Discovery Protocol Constants		4. Multicast Router Termination
	MAX_RESPONSE_DELAY 2 seconds		4.1 Overview
	MAX_SOLICITATION_DELAY 1 second		The Multicast Router Termination message is used to expedite the
			notification of a change in the status of a routers multicast
			forwarding functions.
	SOLICITATION_INTERVAL 3 seconds		4.2 IP Header Fields
	MAX_SOLICITATIONS 3 transmissions		4.2.1 Source Address
	5. Mandatory Advertisement Options		An IP address belonging to the interface from which this message is
			sent. If multiple source addresses are configured on an interface,
			then the one chosen is implementation dependent.
	5.1 Overview of Options		4.2.2 Destination Address
			Multicast Router Termination messages are sent to the IGMP-MRDISC
			multicast address (224.0.0.x).
			4.2.3 Time-to-Live
			The Time-to-Live field MUST be 1.
			4.2.4 Protocol
			The protocol field is set to IGMP (2).
			4.3 Multicast Router Termination Message Format
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Type | Reserved | Checksum |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			4.3.1 Type Field
			The type field is set to 0x26.
			4.3.2 Checksum
			The 16-bit one's complement of the one's complement sum of the IGMP
			message, starting with the IGMP type. For computing the checksum,
			the Checksum field is set to 0.
			4.4 Sending Multicast Router Termination Messages
			Multicast Router Termination messages are sent for three reasons :
			1. Multicast forwarding is disabled on the interface
			2. The interface is administratively disabled
			3. The router is gracefully shutdown
			4.5 Receiving Multicast Router Termination Messages
			Upon receiving a termination message, routers will validate the
			message by the following criteria:
			1. Verifying that the IGMP type is 0x26
			2. Verifying the IGMP checksum
			3. IP Destination Address = IGMP-MRDISC multicast address
			A termination message not meeting the validity requirements will
			be silently discarded.
			5. Multicast Router Discovery Protocol Constants
			MAX_RESPONSE_DELAY 2 seconds
			MAX_SOLICITATION_DELAY 1 second
			SOLICITATION_INTERVAL 3 seconds
			MAX_SOLICITATIONS 3 transmissions
			6. Mandatory Advertisement Options
			6.1 Overview of Options
	The following options MUST be supported by an implementation of		The following options MUST be supported by an implementation of
	IGMP Multicast Router Disovery: Query Interval Advertisement		IGMP Multicast Router Disovery: Query Interval Advertisement
	Option and Robustness Variable Advertisement Option. These options		Option and Robustness Variable Advertisement Option. These options
	advertise specific IGMP variables and are sent in an advertisement		advertise specific IGMP variables and are sent in an advertisement
	depending on the version of IGMP enabled on an interface. Although		depending on the version of IGMP enabled on an interface. Although
	no requirements exist for multicast routers at this time, it is		no requirements exist for multicast routers at this time, it is
	assumed that all multicast routers support the IGMP protocol.		assumed that all multicast routers support the IGMP protocol.
	5.1 Query Interval Advertisement Option		6.2 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		If a multicast router has any version of IGMP [RFC1112] enabled on
	an interface on which IGMP Multicast Router Discovery is also		an interface on which IGMP Multicast Router Discovery is also
	enabled, it MUST send all advertisements with the Query Interval		enabled, it MUST send all advertisements with the Query Interval
	skipping to change at page 9, line 9 ¶		skipping to change at page 11, line 37 ¶
	sent.		sent.
	This option is sent regardless of whether the router is currently		This option is sent regardless of whether the router is currently
	the IGMP querier for the subnet. This option is sent regardless of		the IGMP querier for the subnet. This option is sent regardless of
	what version of IGMP the router is running.		what version of IGMP the router is running.
	IGMP Query Interval field is equal (in seconds) to the configured		IGMP Query Interval field is equal (in seconds) to the configured
	IGMP "query interval" on the interface from which the advertisement		IGMP "query interval" on the interface from which the advertisement
	was sent.		was sent.
	5.2 Robustness Variable Advertisement Option		6.3 Robustness Variable 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=2 | Length=2 | Robustness Variable |		| Type=2 | Length=2 | Robustness Variable |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	If a multicast router has IGMPv2 [IGMPv2] or IGMPv3 [IGMPv3]		If a multicast router has IGMPv2 [IGMPv2] or IGMPv3 [IGMPv3]
	enabled on an interface on which IGMP Multicast Router Discovery		enabled on an interface on which IGMP Multicast Router Discovery
	is also enabled, it MUST send all advertisements with the		is also enabled, it MUST send all advertisements with the
	skipping to change at page 9, line 31 ¶		skipping to change at page 12, line 8 ¶
	the IGMP "Robustness Variable" configured on the interface on		the IGMP "Robustness Variable" configured on the interface on
	which advertisements are sent.		which advertisements are sent.
	This option is sent regardless of whether the router is currently		This option is sent regardless of whether the router is currently
	the IGMP querier for the subnet. This option may be omitted if		the IGMP querier for the subnet. This option may be omitted if
	IGMPv1 is enabled on the interface.		IGMPv1 is enabled on the interface.
	Robustness Variable is an integer which MUST not be zero [IGMPv2]		Robustness Variable is an integer which MUST not be zero [IGMPv2]
	and is equal to the IGMPv2 robustness variable.		and is equal to the IGMPv2 robustness variable.
	6. Acknowledgements		7. IPv6 Support
			The Multicast Router Discovery function for IPv6 is accomplished
			using the Neighbor Discovery Protocol for IPv6 [RFC2461] (hereafter
			called NDP). Specifically, the Router Advertisement message
			contains new fields to support the discovery of multicast routers.
			For this reason, the timing mechanisms defined for NDP will be used
			instead of those defined in this document for IPv4 support.
			7.1 Router Advertisement Message
			The Router Advertisement message contains two new fields to support
			the multicast router discovery mechanism. The modified message
			format is :
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Type | Code | Checksum |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Cur Hop Limit |M|O|D|E| Rsrvd | Router Lifetime |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Reachable Time |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Retrans Timer |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Options ...
			+-+-+-+-+-+-+-+-+-+-+-+-
			The two new fields are the 'D' and 'E' bits. All other fields
			retain their defintions and functions as described in Section 4.2
			of the NDP specification [RFC2461].
			7.1.1 Discovery (D) bit
			The 'D' bit is used by a router to indicate support for the
			Multicast Router Discovery protocol. A value of '1' indicates that
			the router supports the discovery protocol. A value of '0'
			indicates no support. This allows for backwards compatibility of
			the Router Advertisement message.
			7.1.2 Enabled (E) bit
			The 'E' bit indicates whether multicast routing is enabled on the
			router's interface. A value of '1' indicates that multicast
			forwarding is enabled on the router's interface. A value of '0'
			indicates that multicast forwarding is disabled.
			7.2 Router Solicitations
			An NDP Router Solicitation message can be sent to solicit a Router
			Advertisement message in order to determine the multicast
			forwarding state of a router. The periodic transmission of
			solicitation messages is outlined in RFC 2461.
			8. Acknowledgements
	ICMP Router Discovery [RFC1256] was used as a general model for		ICMP Router Discovery [RFC1256] was used as a general model for
	IGMP Multicast Router Discovery.		IGMP Multicast Router Discovery.
	7. References		9. 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", RFC 1112,		[RFC1112] Deering, S., "Host Extensions for IP Multicasting", RFC 1112,
	August 1989.		August 1989.
	[IGMPv2] Fenner, W., "Internet Group Management Protocol, Version 2",		[IGMPv2] Fenner, W., "Internet Group Management Protocol, Version 2",
	Internet-Draft, November 1997.		Internet-Draft, November 1997.
	[IGMPv3] Cain, B., Deering, S., Thyagarajan, A., "Internet Group		[IGMPv3] Cain, B., Deering, S., Thyagarajan, A., "Internet Group
	Management Protocol, Version 3", Internet-Draft, November		Management Protocol, Version 3", Internet-Draft, November
	1997.		1997.
	[RFC2113] Katz, D., "IP Router Alert Option," RFC 2113, April 1996.		[RFC2113] Katz, D., "IP Router Alert Option," RFC 2113, April 1996.
	8. Authors' Addresses		[RFC2461] Narten, T., Nordmark, E., and Simpson, W., "Neighbor
			Discovery IP Version 6 (IPv6)", RFC 2461, December 1998.
			10. Authors' Addresses
	Shantam Biswas		Shantam Biswas
	Nortel Networks		Nortel Networks
	600 Technology Park Drive		600 Technology Park Drive
	Billerica, MA 01821		Billerica, MA 01821
	EMail: sbiswas@baynetworks.com		EMail: sbiswas@baynetworks.com
	Phone: 1-978-916-8048		Phone: 1-978-916-8048
	Brad Cain		Brad Cain
	Nortel Networks		Nortel Networks
	3 Federal Street		3 Federal Street
	Billerica, MA 01821		Billerica, MA 01821
	EMail: bcain@baynetworks.com		EMail: bcain@baynetworks.com
	Phone: 1-978-916-1316		Phone: 1-978-916-1316
			Brian Haberman
			IBM Corporation
			800 Park Office Drive
			Research Triangle Park, NC 27709
			EMail: haberman@raleigh.ibm.com
			Phone: 1-919-254-2673
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