< draft-ietf-idmr-igmp-mrdisc-07.txt		draft-ietf-idmr-igmp-mrdisc-08.txt >
	IDMR Working Group S. Biswas		IDMR Working Group S. Biswas
	Internet Draft B. Haberman		Internet Draft Nortel Networks
	draft-ietf-idmr-igmp-mrdisc-07.txt Nortel Networks		draft-ietf-idmr-igmp-mrdisc-08.txt B. Cain
	June 2001 B. Cain		January 2002 B. Haberman
	Expires December 2001 Cereva Networks		Expires July 2002
	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 55 ¶		skipping to change at line 55 ¶
	Table of Contents		Table of Contents
	1. Introduction....................................................2		1. Introduction....................................................2
	2. Protocol Overview...............................................3		2. Protocol Overview...............................................3
	3. Multicast Router Advertisement..................................4		3. Multicast Router Advertisement..................................4
	3.1 Overview.......................................................4		3.1 Overview.......................................................4
	Biswas, Cain, Haberman 1		Biswas, Cain, Haberman 1
	3.2 IP Header Fields...............................................4		3.2 IP Header Fields...............................................4
	3.3 Multicast Router Advertisement Message Format..................5		3.3 Multicast Router Advertisement Message Format..................4
	3.4 Sending Multicast Router Advertisements........................6		3.4 Sending Multicast Router Advertisements........................6
	3.5 Receiving Multicast Router Advertisements......................6		3.5 Receiving Multicast Router Advertisements......................6
	3.6 Multicast Router Advertisement Configuration Variables.........7		3.6 Multicast Router Advertisement Configuration Variables.........6
	4. Multicast Router Solicitation...................................8		4. Multicast Router Solicitation...................................7
	4.1 Overview.......................................................8		4.1 Overview.......................................................8
	4.2 IP Header Fields...............................................8		4.2 IP Header Fields...............................................8
	4.3 Multicast Router Solicitation Message Format...................9		4.3 Multicast Router Solicitation Message Format...................8
	4.4 Sending Multicast Router Solicitations.........................9		4.4 Sending Multicast Router Solicitations.........................9
	4.5 Receiving Multicast Router Solicitations.......................9		4.5 Receiving Multicast Router Solicitations.......................9
	4.6 Multicast Router Solicitation Configuration Variables.........10		4.6 Multicast Router Solicitation Configuration Variables..........9
	5. Multicast Router Termination...................................10		5. Multicast Router Termination....................................9
	5.1 Overview......................................................10		5.1 Overview.......................................................9
	5.2 IP Header Fields..............................................10		5.2 IP Header Fields..............................................10
	5.3 Multicast Router Termination Message Format...................10		5.3 Multicast Router Termination Message Format...................10
	5.4 Sending Multicast Router Termination Messages.................11		5.4 Sending Multicast Router Termination Messages.................10
	5.5 Receiving Multicast Router Termination Messages...............11		5.5 Receiving Multicast Router Termination Messages...............11
	6. Multicast Router Discovery Protocol Constants..................11		6. Multicast Router Discovery Protocol Constants..................11
	7. Mandatory Advertisement Options................................11		7. Mandatory Advertisement Options................................11
	7.1 Overview of Options...........................................11		7.1 Overview of Options...........................................11
	7.2 Query Interval Advertisement Option...........................12		7.2 Query Interval Advertisement Option...........................11
	7.3 Robustness Variable Advertisement Option......................12		7.3 Robustness Variable Advertisement Option......................12
	8. IPv6 Support...................................................12		8. IPv6 Support...................................................12
	8.1 Router Advertisement Message..................................13		8.1 Router Advertisement Message..................................12
	8.2 Router Solicitations..........................................13		8.2 Router Solicitations..........................................13
	9. Security Considerations........................................14		9. Security Considerations........................................13
	10. IANA Considerations...........................................14		10. IANA Considerations...........................................14
	11. Acknowledgements..............................................14		11. Acknowledgements..............................................14
	12. References....................................................14		12. References....................................................14
	13. Authors' Addresses............................................14		13. Authors' Addresses............................................14
	14. Full Copyright Statement......................................15		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
	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
	discovery advertisements should not be listened to by hosts. Hosts
	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:
			Biswas, Cain, Haberman 2
	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
	multicast topologies may not be congruent. 2.) There is		multicast topologies may not be congruent. 2.) There is
	no way to tell from an ICMP router advertisement if a		no way to tell from an ICMP router advertisement if a
	router is running a multicast routing protocol.		router is running a multicast routing protocol.
	o By making multicast router discovery messages extensible,		o By making multicast router discovery messages extensible,
	future enhancements can be made.		future enhancements can be made.
	skipping to change at line 149 ¶		skipping to change at line 145 ¶
	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.
	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-Systems (224.0.0.1) 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-Systems multicast group (224.0.0.1).
			Biswas, Cain, Haberman 3
	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
	Advertisements.		Advertisements.
	3. Multicast Router Advertisement		3. Multicast Router Advertisement
	3.1 Overview		3.1 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.
	Router advertisements are sent upon expiration of a periodic timer,		Router advertisements are sent upon expiration of a periodic timer,
	when a router starts up, and when a router interface (that has IP		when a router starts up, and when a router interface (that has IP
	multicast forwarding enabled) initializes/restarts. Advertisements		multicast forwarding enabled) initializes/restarts. Advertisements
	are sent as IGMP messages to the All-Routers multicast address		are sent as IGMP messages to the All-Systems multicast address
	(224.0.0.2) and should be rate-limited.		(224.0.0.1) and should be rate-limited.
	Router advertisements may contain any number of options. Two options		Router advertisements may contain any number of options. Two options
	are defined in this document and MUST be supported by any		are defined in this document and MUST be supported by any
	implementation of IGMP multicast router discovery. These options are		implementation of IGMP multicast router discovery. These options are
	described in Section 5. Additional options may be defined as needed		described in Section 5. Additional options may be defined as needed
	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.
	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-Systems multicast address
	(224.0.0.2).		(224.0.0.1).
	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
			Biswas, Cain, Haberman 4
	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 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Unused | Number of Options (N) |		| Unused | Number of Options (N) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Option [1] (TLV encoded) |		| Option [1] (TLV encoded) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Option [...] (TLV encoded) |		| Option [...] (TLV encoded) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	skipping to change at line 250 ¶		skipping to change at line 247 ¶
	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.
	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
	Length: Length in bytes of Value field		Length: Length in bytes of Value field
			Biswas, Cain, Haberman 5
	Value: Option dependent value		Value: Option dependent value
	3.4 Sending Multicast Router Advertisements		3.4 Sending Multicast Router Advertisements
	Router Advertisements are sent when the following events occur:		Router Advertisements are sent when the following events occur:
	o When the periodic advertisement interval timer expires.		o 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.
	skipping to change at line 303 ¶		skipping to change at line 300 ¶
	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
	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-Systems 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.
	3.6 Multicast Router Advertisement Configuration Variables		3.6 Multicast Router Advertisement Configuration Variables
			Biswas, Cain, Haberman 6
	A router that implements multicast router discovery MUST allow for		A router that implements multicast router discovery MUST allow for
	the following variables to be configured by system management;		the following variables to be configured by system management;
	default values are specified so as to make it unnecessary to		default values are specified so as to make it unnecessary to
	configure any of these variables in many cases.		configure any of these variables in many cases.
	For each interface the following configurable variables are defined:		For each interface the following configurable variables are defined:
	3.6.1 MaxAdvertisementInterval		3.6.1 MaxAdvertisementInterval
	The maximum time allowed between sending router advertisements from		The maximum time allowed between sending router advertisements from
	skipping to change at line 355 ¶		skipping to change at line 352 ¶
	Default: 2 seconds		Default: 2 seconds
	3.6.4 MaxInitialAdvertisements		3.6.4 MaxInitialAdvertisements
	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
			Biswas, Cain, Haberman 7
	4.1 Overview		4.1 Overview
	Multicast Router Solicitations are used to solicit Multicast Router		Multicast Router Solicitations are used to solicit Multicast Router
	Advertisements. These messages are used when a device wishes to		Advertisements. These messages are used when a device wishes to
	discover multicast routers. Upon receiving a solicitation on an		discover multicast routers. Upon receiving a solicitation on an
	interface with IP multicast forwarding enabled and multicast router		interface with IP multicast forwarding enabled and multicast router
	discovery enabled, a router will respond with an advertisement.		discovery enabled, a router will respond with an advertisement.
	Router solicitations may be sent when a device starts up, when an		Router solicitations may be sent when a device starts up, when an
	interface (re)initializes, or when IGMP Multicast Router Discovery is		interface (re)initializes, or when IGMP Multicast Router Discovery is
	enabled. Solicitations are sent as IGMP messages to the All-Routers		enabled. Solicitations are sent as IGMP messages to the All-Systems
	multicast address (224.0.0.2) and must be rate-limited.		multicast address (224.0.0.1) and must be rate-limited.
	4.2 IP Header Fields		4.2 IP Header Fields
	4.2.1 Source Address		4.2.1 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.
	If the solicitation is being sent from a device that does not have an		If the solicitation is being sent from a device that does not have an
	IP address (i.e. non-managed layer-2 switch), then the source address		IP address (i.e. non-managed layer-2 switch), then the source address
	should be set to all zeros.		should be set to all zeros.
	4.2.2 Destination Address		4.2.2 Destination Address
	Solicitation messages are sent to the All-Routers multicast address		Solicitation messages are sent to the All-Systems multicast address
	(224.0.0.2).		(224.0.0.1).
	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
	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 YY (to be assigned by IANA).		The type field is set to YY (to be assigned by IANA).
	4.3.2 Reserved Field		4.3.2 Reserved Field
			Biswas, Cain, Haberman 8
	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.
	4.4 Sending Multicast Router Solicitations		4.4 Sending Multicast Router Solicitations
	skipping to change at line 449 ¶		skipping to change at line 446 ¶
	MUST be rate-limited; no more than MAX_SOLICITATIONS MUST be		MUST be rate-limited; no more than MAX_SOLICITATIONS MUST be
	sent in SOLICITATION_INTERVAL seconds.		sent in SOLICITATION_INTERVAL seconds.
	4.5 Receiving Multicast Router Solicitations		4.5 Receiving Multicast Router Solicitations
	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-Systems 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.
	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
	notification of a change in the status of a routers multicast		notification of a change in the status of a routers multicast
	forwarding functions.		forwarding functions.
			Biswas, Cain, Haberman 9
	5.2 IP Header Fields		5.2 IP Header Fields
	5.2.1 Source Address		5.2.1 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.
	5.2.2 Destination Address		5.2.2 Destination Address
	Multicast Router Termination messages are sent to the All-Routers		Multicast Router Termination messages are sent to the All-Systems
	multicast address (224.0.0.2).		multicast address (224.0.0.1).
	5.2.3 Time-to-Live		5.2.3 Time-to-Live
	The Time-to-Live field MUST be 1.		The Time-to-Live field MUST be 1.
	5.2.4 Protocol		5.2.4 Protocol
	The protocol field is set to IGMP (2).		The protocol field is set to IGMP (2).
	5.3 Multicast Router Termination Message Format		5.3 Multicast Router Termination Message Format
	skipping to change at line 510 ¶		skipping to change at line 507 ¶
	5.3.1 Type Field		5.3.1 Type Field
	The type field is set to ZZ (to be assigned by IANA).		The type field is set to ZZ (to be assigned by IANA).
	5.3.2 Reserved Field		5.3.2 Reserved Field
	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
	2. The interface is administratively disabled		2. The interface is administratively disabled
			Biswas, Cain, Haberman 10
	3. The router is gracefully shutdown		3. The router is gracefully shutdown
	5.5 Receiving Multicast Router Termination Messages		5.5 Receiving Multicast Router Termination Messages
	Upon receiving a termination message, routers will validate the		Upon receiving a termination message, routers will validate the
	message by the following criteria:		message by the following criteria:
	1. Verifying the IGMP checksum		1. Verifying the IGMP checksum
	2. IP Destination Address = All-Routers multicast address		2. IP Destination Address = All-Systems multicast address
	A termination message not meeting the validity requirements should be		A termination message 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.
	6. Multicast Router Discovery Protocol Constants		6. Multicast Router Discovery Protocol Constants
	o MAX_RESPONSE_DELAY 2 seconds		o MAX_RESPONSE_DELAY 2 seconds
	o MAX_SOLICITATION_DELAY 1 second		o MAX_SOLICITATION_DELAY 1 second
	skipping to change at line 559 ¶		skipping to change at line 556 ¶
	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 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,
	it MUST send all advertisements with the Query Interval Advertisement		it MUST send all advertisements with the Query Interval Advertisement
	Option. This option contains the IGMP "Query Interval" configured on		Option. This option contains the IGMP "Query Interval" configured on
	the interface on which advertisements are sent.		the interface on which advertisements are sent.
			Biswas, Cain, Haberman 11
	This option is sent regardless of whether the router is currently the		This option is sent regardless of whether the router is currently the
	IGMP querier for the subnet. This option is sent regardless of what		IGMP querier for the subnet. This option is sent regardless of what
	version of IGMP the router is running.		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.
	7.3 Robustness Variable Advertisement Option		7.3 Robustness Variable Advertisement Option
	skipping to change at line 610 ¶		skipping to change at line 607 ¶
	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 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:
			Biswas, Cain, Haberman 12
	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 | Code | Checksum |		| Type | Code | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Cur Hop Limit |M|O|H|D|E|Rsrvd| Router Lifetime |		| Cur Hop Limit |M|O|H|D|E|Rsrvd| Router Lifetime |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reachable Time |		| Reachable Time |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Retrans Timer |		| Retrans Timer |
	skipping to change at line 662 ¶		skipping to change at line 658 ¶
	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 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
			Biswas, Cain, Haberman 13
	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. IANA Considerations		10. IANA Considerations
	This document introduces three new IGMP messages. Each of these		This document introduces three new IGMP messages. Each of these
	messages requires a new IGMP 'Type' value.		messages requires a new IGMP 'Type' value.
	skipping to change at line 699 ¶		skipping to change at line 696 ¶
	[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., et al, "Internet Group Management Protocol,
	Management Protocol, Version 3", work in progress,		Version 3", work in progress, January 2002.
	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.
	13. 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		Email: bcain@mediaone.net
	Email: bcain@cereva.com
	Brian Haberman		Brian Haberman
	Nortel Networks		Email: haberman@innovationslab.net
	4309 Emperor Blvd		Phone: 1-919-949-4828
	Suite 200
	Durham, NC 27703
	Email: haberman@nortelnetworks.com
	Phone: 1-919-992-4439
			Biswas, Cain, Haberman 14
	14. Full Copyright Statement		14. Full Copyright Statement
	Copyright (C) The Internet Society (2001). All Rights Reserved.		Copyright (C) The Internet Society (2001). All Rights Reserved.
	This document and translations of it may be copied and furnished to		This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain it		others, and derivative works that comment on or otherwise explain it
	or assist in its implementation may be prepared, copied, published		or assist in its implementation may be prepared, copied, published
	and distributed, in whole or in part, without restriction of any		and distributed, in whole or in part, without restriction of any
	kind, provided that the above copyright notice and this paragraph		kind, provided that the above copyright notice and this paragraph
	are included on all such copies and derivative works. However, this		are included on all such copies and derivative works. However, this
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