< draft-ietf-msdp-spec-00.txt		draft-ietf-msdp-spec-01.txt >
	Network Working Group Dino Farinacci		Network Working Group Dino Farinacci
	INTERNET DRAFT Procket Networks		INTERNET DRAFT Procket Networks
	Yakov Rekhter		Yakov Rekhter
	David Meyer		David Meyer
	Cisco Systems		Cisco Systems
	Peter Lothberg		Peter Lothberg
	Sprint		Sprint
	Hank Kilmer		Hank Kilmer
	Jeremy Hall		Jeremy Hall
	UUnet		UUnet
	Category Standards Track		Category Standards Track
	Decemeber, 1999		December, 1999
	Multicast Source Discovery Protocol (MSDP)		Multicast Source Discovery Protocol (MSDP)
	<draft-ietf-msdp-spec-00.txt>		<draft-ietf-msdp-spec-01.txt>
	1. Status of this Memo		1. 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 RFC Internet-Drafts.		all provisions of Section 10 of RFC 2026.
	2026 are working documents of the Internet Engineering Task Force		Internet Drafts are working documents of the Internet Engineering
	(IETF), its areas, and its working groups. Note that other groups		Task Force (IETF), its areas, and its working groups. Note that other
	may also distribute working documents as Internet- Drafts.		groups may also distribute working documents as Internet-Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet- Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	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		2. Abstract
	The Multicast Source Discovery Protocol, MSDP, describes a mechanism		The Multicast Source Discovery Protocol, MSDP, describes a mechanism
	to connect multiple PIM-SM domains together. Each PIM-SM domain uses		to connect multiple PIM-SM domains together. Each PIM-SM domain uses
	it's own independent RP(s) and do not have to depend on RPs in other		it's own independent RP(s) and does not have to depend on RPs in
	domains.		other domains.
	2. Copyright Notice		3. Copyright Notice
	Copyright (C) The Internet Society (1999). All Rights Reserved.		Copyright (C) The Internet Society (1999). All Rights Reserved.
	3. Introduction		4. Introduction
	The Multicast Source Discovery Protocol, MSDP, describes a mechanism		The Multicast Source Discovery Protocol, MSDP, describes a mechanism
	to connect multiple PIM-SM domains together. Each PIM-SM domain uses		to connect multiple PIM-SM domains together. Each PIM-SM domain uses
	its own independent RP(s) and does not have to depend on RPs in other		its own independent RP(s) and does not have to depend on RPs in other
	domains.		domains. Advantages of this approach include:
	Advantages of this approach include:		o No Third-party resource dependencies on RP
	3.1. No Third-party resource dependencies on RP		PIM-SM domains can rely on their own RPs only.
	PIM-SM domains can rely on their own RPs only.		o Receiver only Domains
	3.2. Receiver only Domains		Domains with only receivers get data without globally
			advertising group membership.
	Domains with only receivers get data without globally advertising		o Global Source State
	group membership.
	3.3. Global Source State		Global source state is not required, since a router need not
			cache Source Active (SA) messages (see below). MSDP is a
			periodic protocol.
	Global source state is not required, since a router need not cache		The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,
	Source Active (SA) messages (see below). MSDP is a periodic protocol.		SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined
			in RFC 2119 [RFC2119].
	4. Overview		5. Overview
	An RP (or other MSDP SA originator) in a PIM-SM domain will have a		An RP (or other MSDP SA originator) in a PIM-SM [RFC2362] domain will
	MSDP peering relationship with an RP in another domain. The peering		have a MSDP peering relationship with a MSDP speaker in another
	relationship will be made up of a TCP connection in which control		domain. The peering relationship will be made up of a TCP connection
	information is primarily exchanged. Each domain will have a		in which control information exchanged. Each domain will have one or
	connection to this virtual topology.		more connections to this virtual topology.
	The purpose of this topology is to have domains discover multicast		The purpose of this topology is to have domains discover multicast
	sources from other domains. If the multicast sources are of interest		sources from other domains. If the multicast sources are of interest
	to a domain which has receivers, the normal source-tree building		to a domain which has receivers, the normal source-tree building
	mechanism in PIM-SM will be used to deliver multicast data over an		mechanism in PIM-SM will be used to deliver multicast data over an
	inter-domain distribution tree.		inter-domain distribution tree.
	We envision this virtual topology will essentially be congruent to		We envision this virtual topology will essentially be congruent to
	the existing BGP topology used in the unicast-based Internet today.		the existing BGP topology used in the unicast-based Internet today.
	That is the TCP connections between RPs can be realized by the		That is, the TCP connections between MSDP speakers can be realized by
	underlying BGP routing system.		the underlying BGP routing system.
	5. Procedure		6. Procedure
	A source in a PIM-SM domain originates traffic to a multicast group.		A source in a PIM-SM domain originates traffic to a multicast group.
	The PIM DR which is directly connected to the source sends the data		The PIM DR which is directly connected to the source sends the data
	encapsulated in a PIM Register message to the RP in the domain.		encapsulated in a PIM Register message to the RP in the domain.
	The RP will construct a "Source-Active" (SA) message and send it to		The RP will construct a "Source-Active" (SA) message and send it to
	its MSDP peers. The SA message contains the following fields:		its MSDP peers. The SA message contains the following fields:
	o Source address of the data source.		o Source address of the data source.
	o Group address the data source sends to.		o Group address the data source sends to.
	o IP address of the RP.		o IP address of the RP.
	Each MSDP peer receives and forwards the message away from the RP		Each MSDP peer receives and forwards the message away from the RP
	address in a "peer-RPF flooding" fashion. The notion of peer-RPF		address in a "peer-RPF flooding" fashion. The notion of peer-RPF
	flooding is with respect to forwarding SA messages. The BGP routing		flooding is with respect to forwarding SA messages. The BGP routing
	table is examined to determine which peer is the next hop towards the		table is examined to determine which peer is the NEXT_HOP towards the
	originating RP of the SA message. Such a peer is called an "RPF		originating RP of the SA message. Such a peer is called an "RPF
	peer". See the section on "MSDP Peer-RPF Forwarding" for more		peer". See section 10 below for the details of peer-RPF fowarding.
	details.
	If the MSDP peer receives the SA from a non-RPF peer towards the		If the MSDP peer receives the SA from a non-RPF peer towards the
	originating RP, it will drop the message. Otherwise, it forwards the		originating RP, it will drop the message. Otherwise, it forwards the
	message to all it's MSDP peers.		message to all it's MSDP peers.
	The flooding can be further constrained to children of the peer by		The flooding can be further constrained to children of the peer by
	interrogating BGP reachability information. That is, if a BGP peer		interrogating BGP reachability information. That is, if a BGP peer
	advertises a route (back to you) and you are the next to last AS in		advertises a route (back to you) and you are the next to last AS in
	the AS-path, the peer is using you as the next-hop. In this case, an		the AS_PATH, the peer is using you as the NEXT_HOP. In this case, an
	implementation SHOULD forward an SA message (which was originated		implementation SHOULD forward an SA message (which was originated
	from the RP address covered by that route) to the peer. This is known		from the RP address covered by that route) to the peer. This is
	in other circles as Split-Horizon with Poison Reverse.		known in other circles as Split-Horizon with Poison Reverse.
	When an MSDP peer which is also an RP for its own domain receives an		When an MSDP peer which is also an RP for its own domain receives an
	SA message, it determines if it has any group members interested in		SA message, it determines if it has any group members interested in
	the group which the SA message describes. That is, the RP checks for		the group which the SA message describes. That is, the RP checks for
	an (*,G) entry with a non-empty outgoing interface list; this implies		a (*,G) entry with a non-empty outgoing interface list; this implies
	that the domain is interested in the group. In this case, the RP		that the domain is interested in the group. In this case, the RP
	triggers an (S,G) join event towards the data source as if a		triggers a (S,G) join event towards the data source as if a
	Join/Prune message was received addressed to the RP itself (See [1]		Join/Prune message was received addressed to the RP itself (See
	Section 3.2.2). This sets up a branch of the source-tree to this		[RFC2362] Section 3.2.2). This sets up a branch of the source-tree to
	domain. Subsequent data packets arrive at the RP which are forwarded		this domain. Subsequent data packets arrive at the RP which are
	down the shared-tree inside the domain. If leaf routers choose to		forwarded down the shared-tree inside the domain. If leaf routers
	join the source-tree they have the option to do so according to		choose to join the source-tree they have the option to do so
	existing PIM-SM conventions. Finally, if an RP in a domain receives		according to existing PIM-SM conventions. Finally, if an RP in a
	a PIM Join message for a new group G, and it is caching SA's, then		domain receives a PIM Join message for a new group G, and it is
	the RP should trigger an (S,G) join event for each SA for that group		caching SAs, then the RP should trigger a (S,G) join event for each
	in its cache.		SA for that group in its cache.
	This procedure has been affectionately named flood-and-join because		This procedure has been affectionately named flood-and-join because
	if any RP is not interested in the group, they can ignore the SA		if any RP is not interested in the group, they can ignore the SA
	message. Otherwise, they join a distribution tree.		message. Otherwise, they join a distribution tree.
	6. Controlling State		7. Controlling State
	While RPs which receive SA messages are not required to keep MSDP		While RPs which receive SA messages are not required to keep MSDP
	(S,G) state, an RP SHOULD cache SA messages by default. The advantage		(S,G) state, an RP SHOULD cache SA messages by default. The advantage
	of caching is that newly formed MSDP peers can get MSDP (S,G) state		of caching is that newly formed MSDP peers can get MSDP (S,G) state
	sooner and therefore reduce join latency for new joiners. In		sooner and therefore reduce join latency for new joiners. In
	addition, caching greatly aids in diagnosis and debugging of various		addition, caching greatly aids in diagnosis and debugging of various
	problems.		problems.
	6.1. Timers		7.1. Timers
	The main timers for MSDP are: SA Advertisement period, SA Hold-down		The main timers for MSDP are: SA Advertisement period, SA Hold-down
	period, the SA Cache timeout period, KeepAlive, HoldTimer, and		period, the SA Cache timeout period, KeepAlive, HoldTimer, and
	ConnectRetry. Each is described below.		ConnectRetry. Each is described below.
	6.1.1. SA Advertisement Period		7.1.1. SA Advertisement Period
	RPs which originate SA messages do it periodically as long as there		RPs which originate SA messages do it periodically as long as there
	is data being sent by the source. The SA Advertisement Period MUST be		is data being sent by the source. The SA Advertisement Period MUST be
	60 seconds. An RP will not send more than one SA message for a given		60 seconds. An RP will not send more than one SA message for a given
	(S,G) within an SA Advertisment period. Originating periodic SA		(S,G) within an SA Advertisement period. Originating periodic SA
	messages is important so that new receivers who join after a source		messages is important so that new receivers who join after a source
	has been active can get data quickly via the receiver's own RP when		has been active can get data quickly via the receiver's own RP when
	it is not caching SA state. Finally, if an RP in a domain receives a		it is not caching SA state. Finally, if an RP in a domain receives a
	PIM Join message for a new group G, and it is caching SAs, then the		PIM Join message for a new group G, and it is caching SAs, then the
	RP should trigger an (S,G) join for each SA for that group in its		RP should trigger a (S,G) join for each SA for that group in its
	cache.		cache.
	6.1.2. SA Hold-down Period		7.1.2. SA Hold-down Period
	A caching MSDP speaker SHOULD NOT forward a SA message it has		A caching MSDP speaker SHOULD NOT forward an SA message it has
	received in the last SA-Hold-down period. The SA-Hold-down period		received in the last SA-Hold-down period. The SA-Hold-down period
	SHOULD be set 30 seconds.		SHOULD be set to 30 seconds.
	6.1.3. SA Cache Timeout		7.1.3. SA Cache Timeout
	A caching MSDP speaker times out it's SA cache at SA-State-Timer.		A caching MSDP speaker times out it's SA cache at SA-State-Timer.
	The SA-State-Timer MUST NOT be less than 90 seconds minutes.		The SA-State-Timer MUST NOT be less than 90 seconds.
	6.1.4. KeepAlive, HoldTimer, and ConnectRetry		7.1.4. KeepAlive, HoldTimer, and ConnectRetry
	The KeepAlive, HoldTimer, and ConnectRetry timers are defined in		The KeepAlive, HoldTimer, and ConnectRetry timers are defined in RFC
	RFC1771 [3].		1771 [RFC1771].
	6.2. Intermediate MSDP Speakers		7.2. Intermediate MSDP Speakers
	Intermediate RPs do not originate periodic SA messages on behalf of		Intermediate RPs do not originate periodic SA messages on behalf of
	sources in other domains. In general, an RP MUST only originate an SA		sources in other domains. In general, an RP MUST only originate an SA
	for its own sources.		for its own sources.
	6.3. SA Filtering		7.3. SA Filtering and Policy
	As the number of (S,G) pairs increases in the Internet, an RP may		As the number of (S,G) pairs increases in the Internet, an RP may
	want to filter which sources it describes in SA messages. Also,		want to filter which sources it describes in SA messages. Also,
	filtering may be used as a matter of policy which at the same time		filtering may be used as a matter of policy which at the same time
	can reduce state. Only the RP colocated in the same domain as the		can reduce state. Only the RP co-located in the same domain as the
	source can restrict SA messages. Other MSDP peers in transit domains		source can restrict SA messages. Note, hoever, that MSDP peers in
	should not filter or the flood-and-join model does not guarantee that		transit domains should not filter SA messages or the flood-and-join
	sources will be known throughout the Internet. An exception occurs at		model can not guarantee that sources will be known throughout the
	an administrative scope [13] boundary. In particular, a SA message		Internet (i.e., SA filtering by transit domains can cause black
	for an (S,G) MUST NOT be sent to peers which are on the other side of		holes). In general, policy should be expressed using MBGP [RFC2283].
	an administrative scope boundary for G.		This will cause MSDP messages will flow in the desired direction and
			peer-RPF fail otherwise. An exception occurs at an administrative
			scope [RFC2365] boundary. In particular, a SA message for a (S,G)
			MUST NOT be sent to peers which are on the other side of an
			administrative scope boundary for G.
	6.4. Caching		7.4. SA Requests
	If an MSDP peer decides to cache SA state, it may accept SA-Requests		If an MSDP peer decides to cache SA state, it may accept SA-Requests
	from other MSDP peers. When a MSDP peer receives an SA-Request for a		from other MSDP peers. When an MSDP peer receives an SA-Request for a
	group range, it will respond to the peer with a set of SA entries, in		group range, it will respond to the peer with a set of SA entries, in
	a SA-Response message, for all active sources sending to the group		an SA-Response message, for all active sources sending to the group
	range requested in the SA-Request message. The peer that sends the		range requested in the SA-Request message. The peer that sends the
	request will not flood the responding SA-Response message to other		request will not flood the responding SA-Response message to other
	peers.		peers.
	If an implementation receives an SA-Request message and is not		If an implementation receives an SA-Request message and is not
	caching SA messages, it sends a notification with Error code 7		caching SA messages, it sends a notification with Error code 7
	subcode 1, as defined in section 11.2.7.		subcode 1, as defined in section 12.2.7.
	7. Encapsulated Data Packets		8. Encapsulated Data Packets
	For bursty sources, the RP may encapsulate multicast data from the		For bursty sources, the RP may encapsulate multicast data from the
	source. An interested RP may decapsulate the packet, which SHOULD be		source. An interested RP may decapsulate the packet, which SHOULD be
	forwarded as if a PIM register encapsulated packet was received. That		forwarded as if a PIM register encapsulated packet was received. That
	is, if packets are already arriving over the interface toward the		is, if packets are already arriving over the interface toward the
	source, then the packet is dropped. Otherwise, if the outgoing		source, then the packet is dropped. Otherwise, if the outgoing
	interface list is non-null, the packet is forwarded appropriately.		interface list is non-null, the packet is forwarded appropriately.
	Note that when doing data encapsulation, an implementation MUST bound		Note that when doing data encapsulation, an implementation MUST bound
	the number of packets from the source which are encapsulated.		the number of packets from the source which are encapsulated.
	This allows for small bursts to be received before the multicast tree		This allows for small bursts to be received before the multicast tree
	is built back toward the source's domain. For example, an		is built back toward the source's domain. For example, an
	implementation SHOULD encapsulate at least the first packet to		implementation SHOULD encapsulate at least the first packet to
	provide service to bursty sources.		provide service to bursty sources.
	Finally, if an implementation supports an encapsulation of SA data		Finally, if an implementation supports an encapsulation of SA data
	other than default TCP encapsulation, then it MUST support GRE		other than default TCP encapsulation, then it MUST support GRE
	encapsulation. In addition, an implementation MUST learn about not		encapsulation. In addition, an implementation MUST learn about not
	TCP encapsulations via capability advertisment (see section 11.2.5).		TCP encapsulations via capability advertisement (see section 11.2.5).
	8. Other Scenarios		9. Other Scenarios
	MSDP is not limited to deployment across different routing domains.		MSDP is not limited to deployment across different routing domains.
	It can be used within a routing domain when it is desired to deploy		It can be used within a routing domain when it is desired to deploy
	multiple RPs for different group ranges. As long as all RPs have a		multiple RPs for different group ranges. As long as all RPs have a
	interconnected MSDP topology, each can learn about active sources as		interconnected MSDP topology, each can learn about active sources as
	well as RPs in other domains. Another example is the Anycast RP		well as RPs in other domains. Another example is the Anycast RP
	mechanism [8].		mechanism [ANYCASTRP].
	9. MSDP Peer-RPF Forwarding		10. MSDP Peer-RPF Forwarding
	The MSDP Peer-RPF Forwarding rules are used for forwarding SA		The MSDP Peer-RPF Forwarding rules are used for forwarding SA
	messages throughout an MSDP enabled internet. An SA message		messages throughout an MSDP enabled internet. Unlike the RPF check
	originated by a MSDP originator R and received by a MSDP router from		used when forwarding data packets, the Peer-RPF check is against the
	MSDP peer N in AS A is accepted if any of the following are true:		RP address carried in the SA message.
	(i). If N is R.		10.1. Peer-RPF Forwarding Rules
	(ii). If A is the first AS in the AS-Path of the BGP		An SA message originated by an MSDP originator R and received by a
	route towards R.		MSDP router from MSDP peer N is accepted if N is the appropriate RPF
			neighbor for originator R. The RPF neighbor is chosen using the first
			of the following rules that matches:
	(iii). If N is the iBGP advertiser of the BGP route		(i). R is the RPF neighbor if we have an MSDP peering with R.
	towards R.
	(iv). If N is the MSDP default-peer.		(ii). The external MBGP neighbor towards which we are
			poison-reversing the MBGP route towards R is the RPF neighbor
			if we have an MSDP peering with it.
	If none of the conditions above is met, the SA message is discarded.		(iii). If we have an MSDP peering with a neighbor in the first
	This is the case where the SA message was received on a redundant		AS along the AS_PATH (the AS from which we learned this
	MSDP peering path.		route), but no exeternal MBGP peering with that neighbor,
			pick a neighbor via a deterministic rule if you have have
			several, and that is the RPF neighbor.
	Note that these rules are evaluated in the order shown here. This		(vi). The internal MBGP advertiser of the router towards R is
	selects a "peer-RPF neighbor" for the SA message, and allows for the		the RPF neighbor if we have an MSDP peering with it.
	construction of diagnostic tools such as MSDP-traceroute [7].
	9.1. MSDP default-peer semantics		(v). If none of the above match, and we have an MSDP
			default-peer configured, the MSDP default-peer is
			the RPF neighbor.
			Once an RPF neighbor is chosen (as defined above), an SA message is
			accepted if it was received from the RPF neighbor, and discarded
			otherwise.
			10.2. MSDP default-peer semantics
	A MSDP default-peer is much like a default route. It is intended to		A MSDP default-peer is much like a default route. It is intended to
	be used in those cases where a stub network isn't running BGP or		be used in those cases where a stub network isn't running BGP or
	MBGP. In this case, the MSDP speaker accepts all SA messages from the		MBGP. A MSDP speaker configured with a default-peer accepts all SA
	default-peer. Of course, if multiple default peers are configured,		messages from the default-peer. Note that a router running BGP or
	the possibility of looping exists, so care must be taken. Finally, a		MBGP SHOULD NOT allow configuration of default peers, since this
	router running BGP or multiprotol BGP [4] SHOULD NOT allow		allows the possibility for SA looping to occur.
	configuration of default peers.
	10. MSDP Connection Establishment		11. MSDP Connection Establishment
	MSDP speakers establish peering sessions according to the following		MSDP speakers establish peering sessions according to the following
	state machine:		state machine:
	Deconfigured or		De-configured or
	disabled		disabled
	+-------------------------------------------+		+-------------------------------------------+
	| |		| |
	+-----|--------->+----------+ |		+-----|--------->+----------+ |
	| | +->| INACTIVE |----------------+ |		| | +->| INACTIVE |----------------+ |
	| | | +----------+ | |		| | | +----------+ | |
	Deconf'ed | | | /|\ /|\ | Timer + Higher Address		Deconf'ed | | | /|\ /|\ | Timer + Higher Address
	or | | | | | | |		or | | | | | | |
	disabled | | | | | \|/ |		disabled | | | | | \|/ |
	| | | | | | +-------------+		| | | | | | +-------------+
	| | | | | +---------------| CONNNECTING |		| | | | | +---------------| CONNECTING |
	| | | | | Timeout or +-------------+		| | | | | Timeout or +-------------+
	| | | | | Router ID Change |		| | | | | Router ID Change |
	\|/ \|/ | | | |		\|/ \|/ | | | |
	+----------+ | | | |		+----------+ | | | |
	| DISABLED | | | +---------------------+ | TCP Established		| DISABLED | | | +---------------------+ | TCP Established
	+----------+ | | | |		+----------+ | | | |
	/|\ /|\ | | Connection Timeout or | |		/|\ /|\ | | Connection Timeout or | |
	| | | | Router ID change or | |		| | | | Router ID change or | |
	| | | | Authorization Failure | |		| | | | Authorization Failure | |
	| | | | | |		| | | | | |
	| | | | | \|/		| | | | | \|/
	| | | | +-------------+		| | | | +-------------+
	| | Router ID | | Timer + | ESTABLISHED |		| | Router ID | | Timer + | ESTABLISHED |
	| | Change | | Low Addresss +-------------+		| | Change | | Low Address +-------------+
	| | | \|/ /|\ |		| | | \|/ /|\ |
	| | | +--------+ | |		| | | +--------+ | |
	| | +--| LISTEN |--------------------+ |		| | +--| LISTEN |--------------------+ |
	| | +--------+ TCP Accept |		| | +--------+ TCP Accept |
	| | | |		| | | |
	| | | |		| | | |
	| +---------------+ |		| +---------------+ |
	| Deconfigured or |		| De-configured or |
	| disabled |		| disabled |
	| |		| |
	+------------------------------------------------------+		+------------------------------------------------------+
	Deconfigured or		De-configured or
	disabled		disabled
	11. Packet Formats		12. Packet Formats
	MSDP messages will be encapsulated in a TCP connection using well-		MSDP messages will be encapsulated in a TCP connection using well-
	known port 639. One side of the MSDP peering relationship will listen		known port 639. One side of the MSDP peering relationship will listen
	on the well-known port and the other side will do an active connect		on the well-known port and the other side will do an active connect
	on the well-known port. The side with the higher IP address will do		on the well-known port. The side with the higher peer IP address will
	the listen. This connection establishment algorithm avoids call		do the listen. This connection establishment algorithm avoids call
	collision. Therefore, there is no need for a call collision		collision. Therefore, there is no need for a call collision
	procedure. It should be noted, however, that the disadvantage of this		procedure. It should be noted, however, that the disadvantage of this
	approach is that it may result in longer startup times at the passive		approach is that it may result in longer startup times at the passive
	end.		end.
	Finally, if an implementation receives a TLV that has length that is		Finally, if an implementation receives a TLV that has length that is
	longer than expected, the TLV SHOULD be accepted. Any additional data		longer than expected, the TLV SHOULD be accepted. Any additional data
	SHOULD be ignored.		SHOULD be ignored.
	11.1. MSDP messages will be encoded in TLV format:		12.1. MSDP messages will be encoded in TLV format:
	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 .... |		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type (8 bits)		Type (8 bits)
	Describes the format of the Value field.		Describes the format of the Value field.
	Length (16 bits)		Length (16 bits)
	Length of Type, Length, and Value fields in octets. Minimum		Length of Type, Length, and Value fields in octets. The
	length required is 3 octets.		minimum length required is 3 octets.
	Value (variable length)		Value (variable length)
	Format is based on the Type value. See below. The length of		Format is based on the Type value. See below. The length of
	the value field is Length field minus 3.		the value field is Length field minus 3.
	11.2. The following TLV Types are defined:		12.2. The following TLV Types are defined:
	Code Type		Code Type
	================================================================		===========================================================
	1 IPv4 Source-Active		1 IPv4 Source-Active
	2 IPv4 Source-Active Request		2 IPv4 Source-Active Request
	3 IPv4 Source-Active Response		3 IPv4 Source-Active Response
	4 KeepAlive		4 KeepAlive
	5 Encapsulation Capability Advertisement		5 Encapsulation Capability Advertisement
	6 Encapsulation Capability Request		6 Encapsulation Capability Request
	7 Notification		7 Notification
	8 GRE Encapsulation		8 GRE Encapsulation
	Each TLV is described below.		Each TLV is described below.
	11.2.1. IPv4 Source-Active TLV		12.2.1. IPv4 Source-Active TLV
	The maximum size SA message that can be sent is 1400 bytes. If an		The maximum size SA message that can be sent is 1400 bytes. If an
	MSDP peer needs to originate a message with information greater than		MSDP peer needs to originate a message with information greater than
	1400 bytes, it sends successive 1400-byte messages. The 1400 byte		1400 bytes, it sends successive 1400-byte messages. The 1400 byte
	size does not include the TCP, IP, layer-2 headers.		size does not include the TCP, IP, layer-2 headers.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 1 | x + y | Entry Count |		| 1 | x + y | Entry Count |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RP Address |		| RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reserved | Gprefix Len | Sprefix Len | \		| Reserved | Gprefix Len | Sprefix Len | \
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \
	| Group Address Prefix | ) z		| Group Address Prefix | ) z
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
	| Source Address Prefix | /		| Source Address Prefix | /
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	IPv4 Source-Active TLV is type 1.		IPv4 Source-Active TLV is type 1.
	Length x		Length x
	Is the length of the control information in the message. x is		Is the length of the control information in the message. x is
	8 octets (for the first two 32-bit quantities) plus 12 times		8 octets (for the first two 32-bit quantities) plus 12 times
	Entry Count octets.		Entry Count octets.
	Length y		Length y
	If 0, then there is no data encapsulated. Otherwise an IPv4		If 0, then there is no data encapsulated. Otherwise an IPv4
	packet follows and y is the length of the total length field		packet follows and y is the length of the total length field
	of the IPv4 header encapsulated. If there are multiple SA TLVs		of the IPv4 header encapsulated. If there are multiple SA TLVs
	in a message, and data is also included, y must be 0 in all SA		in a message, and data is also included, y must be 0 in all SA
	TLVs except the last one. And the last SA TLV must reflect the		TLVs except the last one. And the last SA TLV must reflect the
	source and destination addresses in the IP header of the		source and destination addresses in the IP header of the
	encapsulated data.		encapsulated data.
	Entry Count		Entry Count
	Is the count of z entries (note above) which follow the RP		Is the count of z entries (note above) which follow the RP
	address field. This is so multiple (S,G)s from the same domain		address field. This is so multiple (S,G)s from the same domain
	can be encoded efficiently for the same RP address.		can be encoded efficiently for the same RP address.
	RP Address		RP Address
	The address of the RP in the domain the source has become		The address of the RP in the domain the source has become
	active in.		active in.
	Gprefix Len and Sprefix Len		Reserved
	The route prefix length associated with the group address		The Reserved field MUST be transmitted as zeros and ignored
	prefix and source address prefix, respectively.		by a receiver.
	Group Address Prefix		Gprefix Len and Sprefix Len
	The group address the active source has sent data to.		The route prefix length associated with the group address
			prefix and source address prefix, respectively.
	Source Address Prefix		Group Address Prefix
	The route prefix associated with the active source.		The group address the active source has sent data to.
			Source Address Prefix
			The route prefix associated with the active source.
	Multiple SA TLVs MAY appear in the same message and can be batched		Multiple SA TLVs MAY appear in the same message and can be batched
	for efficiency at the expense of data latency. This would typically		for efficiency at the expense of data latency. This would typically
	occur on intermediate forwarding of SA messages.		occur on intermediate forwarding of SA messages.
	11.2.2. IPv4 Source-Active Request TLV		12.2.2. IPv4 Source-Active Request TLV
	Used to request SA-state from a caching MSDP peer. If an RP in a		The Source-Active Request is used to request SA-state from a caching
	domain receives a PIM Join message for a group, creates (*,G) state		MSDP peer. If an RP in a domain receives a PIM Join message for a
	and wants to know all active sources for group G, and it has been		group, creates (*,G) state and wants to know all active sources for
	configured to peer with an SA-state caching peer, it may send an SA-		group G, and it has been configured to peer with an SA-state caching
	Request message for the group.		peer, it may send an SA-Request message for the group.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 2 | 8 | Gprefix Len |		| 2 | 8 | Gprefix Len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address Prefix |		| Group Address Prefix |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	IPv4 Source-Active Request TLV is type 2.		IPv4 Source-Active Request TLV is type 2.
	Gprefix Len		Gprefix Len
	The route prefix length associated with the group address prefix.		The route prefix length associated with the group address prefix.
	Group Address Prefix		Group Address Prefix
	The group address prefix the MSDP peer is requesting.		The group address prefix the MSDP peer is requesting.
	11.2.3. IPv4 Source-Active Response TLV		12.2.3. IPv4 Source-Active Response TLV
	Sent in response to a Source-Active Request message. The Source-		The Source-Active Response is sent in response to a Source-Active
	Active Response message has the same format as a Source-Active		Request message. The Source-Active Response message has the same
	message but does not allow encapsulation of multicast data.		format as a Source-Active message but does not allow encapsulation of
			multicast data.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 3 | x | .... |		| 3 | x | .... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	IPv4 Source-Active Response TLV is type 3.		IPv4 Source-Active Response TLV is type 3.
	Length x		Length x
	Is the length of the control information in the message. x is 8		Is the length of the control information in the message. x is 8
	octets (for the first two 32-bit quantities) plus 12 times Entry		octets (for the first two 32-bit quantities) plus 12 times Entry
	Count octets.		Count octets.
	11.2.4. KeepAlive TLV		12.2.4. KeepAlive TLV
	Sent to an MSDP peer if and only if there were no MSDP messages sent		A KeepAlive TLV is sent to an MSDP peer if and only if there were no
	to the peer after a period of time. This message is necessary for the		MSDP messages sent to the peer after a period of time. This message
	active connect side of the MSDP connection. The passive connect side		is necessary for the active connect side of the MSDP connection. The
	of the connection knows that the connection will be reestablished		passive connect side of the connection knows that the connection will
	when a TCP SYN packet is sent from the active connect side. However,		be reestablished when a TCP SYN packet is sent from the active
	the active connect side will not know when the passive connect side		connect side. However, the active connect side will not know when the
	goes down. Therefore, the KeepAlive timeout will be used to reset the		passive connect side goes down. Therefore, the KeepAlive timeout will
	TCP connection.		be used to reset the TCP connection.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 4 | 3 | |		| 4 | 3 | |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The length of the message is 3 bytes which encompasses the 1-byte		The length of the message is 3 bytes which encompasses the 1-byte
	Type field and the 2-byte Length field.		Type field and the 2-byte Length field.
	11.2.5. Encapsulation Capability Advertisement TLV		12.2.5. Encapsulation Capability Advertisement TLV
	This TLV implements encapsulation capability advertisement. This TLV		This TLV is sent by an MSDP speaker to advertise its ability to
	is sent by an MSDP speaker to advertise its ability to receive data		receive data packets encapsulated as described by the TLV (in
	packets encapsulated as described by the TLV (in addition to the		addition to the default TCP encapsulation).
	default TCP encapsulation).
	A MSDP speaker receiving this TLV can choose to either default TCP		A MSDP speaker receiving this TLV can choose to either default TCP
	encapsulation, or may send a IPv4 Encapsulation Request to change to		encapsulation, or may send a IPv4 Encapsulation Request to change to
	the advertised encapsulation type.		the advertised encapsulation type.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 8 | ENCAP_TYPE |		| 5 | 8 | ENCAP_TYPE |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Port | Reserved |		| Source Port | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	IPv4 Encapsulation Advertisement TLV is type 5.
	Length		Type
	Length is a two byte field with value 8.		IPv4 Encapsulation Advertisement TLV is type 5.
	ENCAP_TYPE		Length
	The following data encapsulation types are defined for MSDP:		Length is a two byte field with value 8.
	Value Meaning		ENCAP_TYPE
	-------------------------------------		The following data encapsulation types are defined for MSDP:
	0 TCP Encapsulation
	1 UDP Encapsulation [10]		Value Meaning
			---------------------------------------
			0 TCP Encapsulation
			1 UDP Encapsulation [RFC768]
			2 GRE Encapsulation [GRE]
	2 GRE Encapsulation [9]		Source Port
			Port for use by the requester.
	Soure Port		Reserved
	Port for use by the requester.		The Reserved field MUST be transmitted as zeros and ignored
			by a receiver.
	Note that since the TLV does not carry endpoint addresses for the GRE		Note that since the TLV does not carry endpoint addresses for the GRE
	or UDP tunnels, an implementation using these encapsulations MUST use		or UDP tunnels, an implementation using these encapsulations MUST use
	the endpoints that are used for the MSDP peering.		the endpoints that are used for the MSDP peering.
	11.2.6. Encapsulation Capability Request TLV		12.2.6. Encapsulation Capability Request TLV
	This TLV implements encapsulation capability request. This TLV should
	be sent in response to a capability advertisement.
	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		The Encapsulation Capability Request is sent to notify a peer that
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		has advertised an encapsulation capability that it will encapsulate
	| 6 | 4 | ENCAP_TYPE |		SA data according to the advertised ENCAP_TYPE.
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		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
	IPv4 Encapsulation Request TLV is type 6.		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| 6 | 4 | ENCAP_TYPE |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			Type
			IPv4 Encapsulation Request TLV is type 6.
	Length		Length
	Length is a two byte field with value 4.		Length is a two byte field with value 4.
	ENCAP_TYPE		ENCAP_TYPE
	ENCAP_TYPE is described above.		ENCAP_TYPE is described above.
	A requester MAY also provide a source port, in which case		A requester MAY also provide a source port, in which case
	the TLV has the following form:		the TLV has the following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 6 | 8 | ENCAP_TYPE |		| 6 | 8 | ENCAP_TYPE |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Port | Reserved |		| Source Port | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	11.2.7. NOTIFICATION TLV		12.2.7. NOTIFICATION TLV
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | x + 5 | Error Code |		| 7 | x + 5 | Error Code |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Error subcode | ... |		| Error subcode | ... |
	+-+-+-+-+-+-+-+-+ |		+-+-+-+-+-+-+-+-+ |
	| Data |		| Data |
	| ... |		| ... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	The Notification TLV is type 7.		The Notification TLV is type 7.
	Length		Length
	Length is a two byte field with value x + 5, where x is		Length is a two byte field with value x + 5, where x is
	the length of the notification data field.		the length of the notification data field.
	Error code		Error code
	See [3]. In addition, Error code 7 indicates an		See [RFC1771]. In addition, Error code 7 indicates an
	a SA-Request Error.		an SA-Request Error.
	Error subcode		Error subcode
	See [3]. In addition, Error code 7 subcode 1 indicates		See [RFC1771]. In addition, Error code 7 subcode 1 indicates
	the receipt of a SA-Request message by a non-caching		the receipt of an SA-Request message by a non-caching
	MSDP speaker.		MSDP speaker.
	Data		Data
	See [3]. In addition, for Error code 7 subcode 1 (receipt of		See [RFC1771]. In addition, for Error code 7 subcode 1 (receipt
	a SA-Request message by a non-caching MSDP speaker), the TLV		of an SA-Request message by a non-caching MSDP speaker), the
	has the follwing form:		TLV has the following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 20 | 7 |		| 7 | 20 | 7 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 1 | Reserved | Gprefix Len | Sprefix Len |		| 1 | Reserved | Gprefix Len | Sprefix Len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Advertising RP Address |		| Advertising RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address Prefix |		| Group Address Prefix |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Address Prefix |		| Source Address Prefix |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	See [3] for NOTIFICATION error handling.		See [RFC1771] for NOTIFICATION error handling.
	11.2.8. Encapsulation Capability State Machine		12.2.8. Encapsulation Capability State Machine
	The active connect side of an MSDP peering SHALL begin in ADVERTISING		The active connect side of an MSDP peering SHALL begin in ADVERTISING
	state, and the passive side of the TCP connection begins in DEFAULT		state, and the passive side of the TCP connection begins in DEFAULT
	state. This will cause the state machine to behave deterministically.		state. This will cause the state machine to behave deterministically.
	+-------+		+-------+
	| | Receive TLV which isn't		| | Receive TLV which isn't
	| | understood or		| | understood or
	| | Receive Request (TLV 6) or		| | Receive Request (TLV 6) or
	| | Receive Advertisement (TLV 5)		| | Receive Advertisement (TLV 5)
	skipping to change at page 18, line 5 ¶		skipping to change at page 18, line 5 ¶
	+------------>| AGREED |<------------------+		+------------>| AGREED |<------------------+
	+--------+		+--------+
	Note that if an advertiser transitions into the FAILED state, it		Note that if an advertiser transitions into the FAILED state, it
	SHOULD assume that it has an old-style peer which can only support		SHOULD assume that it has an old-style peer which can only support
	TCP encapsulation. If an implementation wishes to be backwardly		TCP encapsulation. If an implementation wishes to be backwardly
	compatible, it SHOULD support TCP encapsulation. In addition, a		compatible, it SHOULD support TCP encapsulation. In addition, a
	requester in any state other than AGREED MUST only encapsulate data		requester in any state other than AGREED MUST only encapsulate data
	in the TCP stream.		in the TCP stream.
	11.2.9. UDP Data Encapsulation		12.2.9. UDP Data Encapsulation
	When using UDP encapsulation, the UDP psuedo-header has the following		When using UDP encapsulation, the UDP psuedo-header has the following
	form:		form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Port | Dest Port |		| Source Port | Dest Port |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Length | Checksum |		| Length | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Origin RP Address |		| Origin RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	o Source Port
	When using UDP encapsulation, a capability requester
	uses the advertiser's Source Port as its destination
	port. The advertiser MUST provide a Source Port.
	o Destination Port		Source Port
			When using UDP encapsulation, a capability requester
			uses the advertiser's Source Port as its destination
			port. The advertiser MUST provide a Source Port.
	When using UDP encapsulation, a capability advertiser		Destination Port
	uses the well known port 639 as the destination port.		When using UDP encapsulation, a capability advertiser
	A capability requester MUST listen on this well-known		uses the well known port 639 as the destination port.
	port. The requester MAY provide a Source Port in it's		A capability requester MUST listen on this well-known
	reply to the advertiser.		port. The requester MAY provide a Source Port in it's
			reply to the advertiser.
	o Length is the length in octets of this user datagram		Length
	including this header and the data. The minimum value		Length is the length in octets of this user datagram
	of the length is twelve.		including this header and the data. The minimum value
			of the length is twelve.
	o Checksum is computed according to RFC768 [10].		Checksum
			The checksum is computed according to RFC 768 [RFC768].
	o Originating RP Address is the address of the RP sending		Originating RP Address
	the encapsulated data.		The Originating RP Address is the address of the RP sending
			the encapsulated data.
	11.2.10. GRE Encapsulation TLV		12.2.10. GRE Encapsulation TLV
	A TLV is defined to describe GRE encapsulated data packets. The TLV		A TLV is defined to describe GRE encapsulated data packets. The TLV
	has the following form:		has the following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 8 | 8 + x | Reserved |		| 8 | 8 + x | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Originating RP IPv4 Address |		| Originating RP IPv4 Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| (S,G) Data Packet ....		| (S,G) Data Packet ....
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	GRE encapsulated data packet TLV is type 8.		GRE encapsulated data packet TLV is type 8.
	Length		Length
	Length is a two byte field with value 8 + x, where		Length is a two byte field with value 8 + x, where
	x is the length of the (S,G) Data packet.		x is the length of the (S,G) Data packet.
			Reserved
			The Reserved field MUST be transmitted as zeros and ignored
			by a receiver.
	The entire GRE header, then, will have the following form:		The entire GRE header, then, will have the following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Delivery Headers ..... |		| Delivery Headers ..... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|C| Reserved | Ver | Protocol Type |\		|C| Reserved0 | Ver | Protocol Type |\
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header
	| Checksum (optional) | Reserved |/		| Checksum (optional) | Reserved1 |/
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+\
	| 8 | 8 + x | Reserved | \		| 8 | 8 + x | Reserved | \
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload
	| Originating RP IPv4 Address | /		| Originating RP IPv4 Address | /
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
	| (S,G) Data Packet .... .		| (S,G) Data Packet .... .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	11.3. MTU Exeeded		12.2.10.1. Problems with MTU Exceeded by Encapsulation
	If the outbound link MTU is execeeded by the newly encapsulated		Black holes can arise when PMTU [RFC1191] is used and the tunnel
	packet, the packet SHOULD be dropped.		entry point does not relay MTU exceeded errors back to the originator
			of the packet. A black hole can be realized by the following
			behavior: the originator sets the Don't Fragment bit in the Delivery
			Header, the packet gets dropped within the tunnel (MTU is exceeded),
			but since the originator doesn't receive feedback, it retransmits
			with the same PMTU, causing subsequently transmitted packets to be
			dropped. While GRE [GRE] does not require that such errors be relayed
			back to the originator, known implementations of GRE do not set the
			Don't Fragment bit in the Delivery Header.
	12. Security Considerations		13. Security Considerations
	A MSDP implementation MAY use IPsec [11] or keyed MD5 [12] to secure		An MSDP implementation MAY use IPsec [RFC1825] or keyed MD5 [RFC1828]
	control messages. Encapsulated data packets rely on the underlying		to secure control messages. When encapsulating SA data in GRE,
	security model.		security should be relatively similar to security in a normal IPv4
			network, as routing using GRE follows the same routing that IPv4 uses
			natively. Route filtering will remain unchanged. However packet
			filtering at a firewall requires either that a firewall look inside
			the GRE packet or that the filtering is done on the GRE tunnel
			endpoints. In those environments in which this is considered to be a
			security issue it may be desirable to terminate the tunnel at the
			firewall.
	13. Acknowledgments		14. Acknowledgments
	The authors would like to thank Dave Thaler, Bill Fenner, Bill		The authors would like to thank Dave Thaler, Bill Nickless, John
	Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, and		Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, and John Zwiebel
	John Zwiebel for their design feedback and comments.		for their design feedback and comments. Bill Fenner also made many
			contributions, including clarification of the Peer-RPF rules.
	14. Author's Address:		15. Author's Address:
	Dino Farinacci		Dino Farinacci
	Procket Networks		Procket Networks
			3850 No. First St., Ste. C
			San Jose, CA 95134
	Email: dino@procket.com		Email: dino@procket.com
	Yakov Rehkter		Yakov Rehkter
	Cisco Systems, Inc.		Cisco Systems, Inc.
	170 Tasman Drive		170 Tasman Drive
	San Jose, CA, 95134		San Jose, CA, 95134
	Email: yakov@cisco.com		Email: yakov@cisco.com
	David Meyer
	Cisco Systems, Inc.
	170 Tasman Drive
	San Jose, CA, 95134
	Email: dmm@cisco.com
	Peter Lothberg		Peter Lothberg
	Sprint		Sprint
	VARESA0104		VARESA0104
	12502 Sunrise Valley Drive		12502 Sunrise Valley Drive
	Reston VA, 20196		Reston VA, 20196
	Email: roll@sprint.net		Email: roll@sprint.net
	Hank Kilmer		Hank Kilmer
	Email: hank@rem.com		Email: hank@rem.com
	Jeremy Hall		Jeremy Hall
	UUnet Technologies		UUnet Technologies
	3060 Williams Drive		3060 Williams Drive
	Fairfax, VA 22031		Fairfax, VA 22031
	Email: jhall@uu.net		Email: jhall@uu.net
	15. REFERENCES		David Meyer
			Cisco Systems, Inc.
	[1] Estrin D., et al., "Protocol Independent Multicast - Sparse Mode		170 Tasman Drive
	(PIM-SM): Protocol Specification", RFC 2362, June 1998.		San Jose, CA, 95134
			Email: dmm@cisco.com
	[2] Thaler, D., Estrin, D., Meyer, D., "Border Gateway Multicast Protocol		16. REFERENCES
	(BGMP): Protocol Specification", draft-ietf-idmr-gum-01.txt,
	October 30, 1997.
	[3] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4)",		[ANYCASTRP] Meyer, et. al, "Anycast RP mechanism using PIM and
	RFC 1771, March 1995.		MSDP", draft-ietf-mboned-anycast-rp-04.txt, November,
			1999. Work in Progress.
	[4] Bates, T., Chandra, R., Katz, D., and Y. Rekhter., "Multiprotocol		[GRE] Farinacci, D., at el., "Generic Routing Encapsulation
	Extensions for BGP-4", RFC 2283, February 1998.		(GRE)", draft-meyer-gre-update-01.txt, December,
			1999. Work in Progress.
	[5] Deering, S., "Multicast Routing in a Datagram Internetwork", PhD		[RFC768] Postel, J. "User Datagram Protocol", RFC 768, August,
	thesis, Electric Engineering Dept., Stanford University, December		1980.
	1991.
	[6] Pusateri, T., "Distance Vector Multicast Routing Protocol",		[RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery",
	draft-ietf-idmr-dvmrp-v3-09.txt, October 1997.		RFC 1191, November 1990.
	[7] Meyer, et. al, "MSDP Traceroute",		[RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4
	draft-ietf-msdp-traceroute-00.txt, November, 1999.		(BGP-4)", RFC 1771, March 1995.
	[8] Meyer, et. al, "Anycast RP mechanism using PIM and MSDP",		[RFC1825] Atkinson, R., "Security Architecture for the Internet
	draft-ietf-mboned-anycast-rp-04.txt, November, 1999.		Protocol", RFC 1825, August, 1995.
	[9] Farinacci, D., at el., "Generic Routing Encapsulation (GRE)",		[RFC1828] P. Metzger and W. Simpson, "IP Authentication using
	draft-ietf-meyer-gre-update-01.txt, December, 1999.		Keyed MD5", RFC 1828, August, 1995.
	[10] Postel, J. "User Datagram Protocol", RFC768, August, 1980.		[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
			Requirement Levels", RFC 2119, March, 1997.
	[11] Atkinson, R., "Security architecture for the internet protocol",		[RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter.,
	RFC1825, August, 1995.		"Multiprotocol Extensions for BGP-4", RFC 2283,
			February 1998.
	[12] P. Metzger and W. Simpson, "IP Authentication using Keyed		[RFC2362] Estrin D., et al., "Protocol Independent Multicast -
	MD5", RFC 1828, August, 1995.		Sparse Mode (PIM-SM): Protocol Specification", RFC
			2362, June 1998.
	[13] Meyer, D. "Administratively Scoped IP Multicast", RFC2365,		[RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC
	July, 1998.		2365, July, 1998.
End of changes. 163 change blocks.
	403 lines changed or deleted		445 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/