< draft-ietf-msdp-spec-14.txt		draft-ietf-msdp-spec-15.txt >
	Network Working Group David Meyer		Network Working Group David Meyer
	(Editor)		(Editor)
	INTERNET DRAFT Bill Fenner		INTERNET DRAFT Bill Fenner
	(Editor)		(Editor)
	Category		Category
	Standards Track		Standards Track
	November, 2002		April, 2003
	Multicast Source Discovery Protocol (MSDP)		Multicast Source Discovery Protocol (MSDP)
	<draft-ietf-msdp-spec-14.txt>		<draft-ietf-msdp-spec-15.txt>
	1. 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 RFC 2026.		all provisions of Section 10 of RFC 2026.
	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 other		Task Force (IETF), its areas, and its working groups. Note that other
	groups 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.
	2. Abstract		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
	its own independent RP(s) and does not have to depend on RPs in other		its own independent Rendezvous Point (RP) and does not have to depend
	domains. This draft is intended to document existing MSDP		on RPs in other domains. This draft is intended to document existing
	implementations in the field.		MSDP implementations in the field.
	3. Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2002). All Rights Reserved.		Copyright (C) The Internet Society (2003). All Rights Reserved.
	4. Introduction		1. 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. Advantages of this approach include:		domains. Advantages of this approach include:
	o No Third-party resource dependencies on RP		o 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.
	skipping to change at line 69 ¶		skipping to change at line 68 ¶
	Domains with only receivers get data without globally		Domains with only receivers get data without globally
	advertising group membership.		advertising group membership.
	Note that MSDP may be used with protocols other than PIM-SM, but such		Note that MSDP may be used with protocols other than PIM-SM, but such
	usage is not specified in this memo.		usage is not specified in this memo.
	The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,		The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,
	SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined		SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined
	in RFC 2119 [RFC2119].		in RFC 2119 [RFC2119].
	5. Overview		2. Overview
	MSDP-speaking routers in a PIM-SM [RFC2362] domain have a MSDP		MSDP-speaking routers in a PIM-SM [RFC2362] domain have a MSDP
	peering relationship with MSDP peers in another domain. The peering		peering relationship with MSDP peers in another domain. The peering
	relationship is made up of a TCP connection in which control		relationship is made up of a TCP connection in which control
	information is exchanged. Each domain has one or more connections to		information is exchanged. Each domain has one or more connections to
	this virtual topology.		this virtual topology.
	The purpose of this topology is to allow domains to discover		The purpose of this topology is to allow domains to discover
	multicast sources from other domains. If the multicast sources are of		multicast sources from other domains. If the multicast sources are of
	interest to a domain which has receivers, the normal source-tree		interest to a domain which has receivers, the normal source-tree
	building mechanism in PIM-SM will be used to deliver multicast data		building mechanism in PIM-SM will be used to deliver multicast data
	over an inter-domain distribution tree.		over an inter-domain distribution tree.
	6. Procedure		3. Procedure
	When an RP in a PIM-SM domain first learns of a new sender, e.g. via		When an RP in a PIM-SM domain first learns of a new sender, e.g. via
	PIM register messages, it constructs a "Source-Active" (SA) message		PIM register messages, it constructs a "Source-Active" (SA) message
	and sends it to its MSDP peers. The SA message contains the following		and sends it to its MSDP peers. All RPs, which intend to originate
	fields:		or receive SA messages, must establish MSDP peering with other RPs,
			either directly or via an intermediate MSDP peer. 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.
	Note that an RP that isn't a DR on a shared network SHOULD NOT		Note that an RP that isn't a DR on a shared network SHOULD NOT
	originate SA's for directly connected sources on that shared network;		originate SA's for directly connected sources on that shared network;
	it should only originate in response to receiving Register messages		it should only originate in response to receiving Register messages
	from the DR.		from the DR.
	skipping to change at line 132 ¶		skipping to change at line 133 ¶
	the domain. If leaf routers choose to join the source-tree they have		the domain. If leaf routers choose to join the source-tree they have
	the option to do so according to existing PIM-SM conventions.		the option to do so according to existing PIM-SM conventions.
	Finally, if an RP in a domain receives a PIM Join message for a new		Finally, if an RP in a domain receives a PIM Join message for a new
	group G, the RP SHOULD trigger a (S,G) join event for each active		group G, the RP SHOULD trigger a (S,G) join event for each active
	(S,G) for that group in its SA cache.		(S,G) for that group in its SA 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.
	7. Caching		4. Caching
	A MSDP speaker MUST cache SA messages. Caching allows pacing of MSDP		A MSDP speaker MUST cache SA messages. Caching allows pacing of MSDP
	messages as well as reducing join latency for new receivers of a		messages as well as reducing join latency for new receivers of a
	group G at an originating RP which has existing MSDP (S,G) state. In		group G at an originating RP which has existing MSDP (S,G) state. In
	addition, caching greatly aids in diagnosis and debugging of various		addition, caching greatly aids in diagnosis and debugging of various
	problems.		problems.
	An MSDP speaker must provide a mechanism to reduce the forwarding of		An MSDP speaker must provide a mechanism to reduce the forwarding of
	new SA's. The SA-cache is used to reduce storms and performs this		new SA's. The SA-cache is used to reduce storms and performs this
	by not forwarding SA's unless they are in the cache or are new SA		by not forwarding SA's unless they are in the cache or are new SA
	packets that the MSDP speaker will cache for the first time. The		packets that the MSDP speaker will cache for the first time. The
	SA-cache also reduces storms by advertising from the cache at a		SA-cache also reduces storms by advertising from the cache at a
	period of no more than twice per SA-Advertisement-Timer interval and		period of no more than twice per SA-Advertisement-Timer interval and
	not less than 1 time per SA Advertisment period.		not less than 1 time per SA Advertisment period.
	8. Timers		5. Timers
	The main timers for MSDP are: SA-Advertisement-Timer, SA Cache Entry		The main timers for MSDP are: SA-Advertisement-Timer, SA Cache Entry
	timer, Peer Hold Timer, KeepAlive timer, and ConnectRetry timer.		timer, Peer Hold Timer, KeepAlive timer, and ConnectRetry timer.
	Each is considered below.		Each is considered below.
	8.1. SA-Advertisement-Timer		5.1. SA-Advertisement-Timer
	RPs which originate SA messages do so periodically as long as there		RPs which originate SA messages do so periodically as long as there
	is data being sent by the source. There is one SA-Advertisement-Timer		is data being sent by the source. There is one SA-Advertisement-Timer
	covering the sources that an RP may advertise. [SA-Advertisement-		covering the sources that an RP may advertise. [SA-Advertisement-
	Period] MUST be 60 seconds. An RP MUST not send more than one		Period] MUST be 60 seconds. An RP MUST not send more than one
	periodic SA message for a given (S,G) within an SA Advertisement		periodic SA message for a given (S,G) within an SA Advertisement
	interval. Originating periodic SA messages is required to keep		interval. Originating periodic SA messages is required to keep
	announcements alive in caches. Finally, an originating RP SHOULD		announcements alive in caches. Finally, an originating RP SHOULD
	trigger the transmission of an SA message as soon as it receives data		trigger the transmission of an SA message as soon as it receives data
	from an internal source for the first time. This initial SA message		from an internal source for the first time. This initial SA message
	may be in addition to the periodic sa-message forwarded in that first		may be in addition to the periodic sa-message forwarded in that first
	60 seconds for that S,G.		60 seconds for that S,G.
	8.2. SA-Advertisement-Timer Processing		5.2. SA-Advertisement-Timer Processing
	An RP MUST spread the generation of periodic SA messages (i.e.		An RP MUST spread the generation of periodic SA messages (i.e.
	messages advertising the active sources for which it is the RP) over		messages advertising the active sources for which it is the RP) over
	its reporting interval (i.e. SA-Advertisement-Period). An RP starts		its reporting interval (i.e. SA-Advertisement-Period). An RP starts
	the SA-Advertisement-Timer when the MSDP process is configured. When		the SA-Advertisement-Timer when the MSDP process is configured. When
	the timer expires, an RP resets the timer to [SA-Advertisement-		the timer expires, an RP resets the timer to [SA-Advertisement-
	Period] seconds, and begins the advertisement of its active sources.		Period] seconds, and begins the advertisement of its active sources.
	Active sources are advertised in the following manner: An RP packs		Active sources are advertised in the following manner: An RP packs
	its active sources into an SA message until the largest MSDP packet		its active sources into an SA message until the largest MSDP packet
	that can be sent is built or there are no more sources, and then		that can be sent is built or there are no more sources, and then
	sends the message. This process is repeated periodically within the		sends the message. This process is repeated periodically within the
	SA-Advertisement-Period in such a way that all of the RP's sources		SA-Advertisement-Period in such a way that all of the RP's sources
	are advertised. Note that since MSDP is a periodic protocol, an		are advertised. Note that since MSDP is a periodic protocol, an
	implemenation SHOULD send all cached SA messages when a connection is		implemenation SHOULD send all cached SA messages when a connection is
	established. Finally, the timer is deleted when the MSDP process is		established. Finally, the timer is deleted when the MSDP process is
	deconfigured.		deconfigured.
	8.3. SA Cache Timeout (SA-State Timer)		5.3. SA Cache Timeout (SA-State Timer)
	Each entry in an SA Cache has an associated SA-State Timer. A		Each entry in an SA Cache has an associated SA-State Timer. A
	(S,G)-SA-State-Timer is started when an (S,G)-SA message is initially		(S,G)-SA-State-Timer is started when an (S,G)-SA message is initially
	received by an MSDP peer. The timer is reset to [SG-State-Period] if		received by an MSDP peer. The timer is reset to [SG-State-Period] if
	another (S,G)-SA message is received before the (S,G)-SA-State Timer		another (S,G)-SA message is received before the (S,G)-SA-State Timer
	expires. [SG-State-Period] MUST NOT be less than		expires. [SG-State-Period] MUST NOT be less than
	[SA-Advertisement-Period] + [SA-Hold-Down-Period].		[SA-Advertisement-Period] + [SA-Hold-Down-Period].
	8.4. Peer Hold Timer		5.4. Peer Hold Timer
	The Hold Timer is initialized to [HoldTime-Period] when the peer's		The Hold Timer is initialized to [HoldTime-Period] when the peer's
	transport connection is established, and is reset to [HoldTime-		transport connection is established, and is reset to [HoldTime-
	Period] when any MSDP message is received. Finally, the timer is		Period] when any MSDP message is received. Finally, the timer is
	deleted when the peer's transport connection is closed.		deleted when the peer's transport connection is closed.
	[HoldTime-Period] MUST be at least three seconds. The recommended		[HoldTime-Period] MUST be at least three seconds. The recommended
	value for [HoldTime-Period] is 75 seconds.		value for [HoldTime-Period] is 75 seconds.
	8.5. KeepAlive Timer		5.5. KeepAlive Timer
	Once an MSDP transport connection is established, each side of the		Once an MSDP transport connection is established, each side of the
	connection sends a KeepAlive message and sets a KeepAlive timer. If		connection sends a KeepAlive message and sets a KeepAlive timer. If
	the KeepAlive timer expires, the local system sends a KeepAlive		the KeepAlive timer expires, the local system sends a KeepAlive
	message and restarts its KeepAlive timer.		message and restarts its KeepAlive timer.
	The KeepAlive timer is set to [KeepAlive-Period] when the peer comes		The KeepAlive timer is set to [KeepAlive-Period] when the peer comes
	up. The timer is reset to [KeepAlive-Period] each time an MSDP		up. The timer is reset to [KeepAlive-Period] each time an MSDP
	message is sent to the peer, and reset when the timer expires.		message is sent to the peer, and reset when the timer expires.
	Finally, the KeepAlive timer is deleted when the peer's transport		Finally, the KeepAlive timer is deleted when the peer's transport
	connection is closed.		connection is closed.
	[KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be		[KeepAlive-Period] MUST be less than [HoldTime-Period], and MUST be
	at least one second. The recommended value for [KeepAlive-Period] is		at least one second. The recommended value for [KeepAlive-Period] is
	60 seconds.		60 seconds.
	8.6. ConnectRetry Timer		5.6. ConnectRetry Timer
	The ConnectRetry timer is used by the MSDP peer with the lower IP		The ConnectRetry timer is used by the MSDP peer with the lower IP
	address to transition from INACTIVE to CONNECTING states. There is		address to transition from INACTIVE to CONNECTING states. There is
	one timer per peer, and the [ConnectRetry-Period] SHOULD be set to 30		one timer per peer, and the [ConnectRetry-Period] SHOULD be set to 30
	seconds. The timer is initialized to [ConnectRetry-Period] when an		seconds. The timer is initialized to [ConnectRetry-Period] when an
	MSDP speaker attempts to actively open a TCP connection to its peer		MSDP speaker attempts to actively open a TCP connection to its peer
	(see section 15, event E2, action A2 ). When the timer expires, the		(see section 15, event E2, action A2 ). When the timer expires, the
	peer retries the connection and the timer is reset to [ConnectRetry-		peer retries the connection and the timer is reset to [ConnectRetry-
	Period]. It is deleted if either the connection transitions into		Period]. It is deleted if either the connection transitions into
	ESTABLISHED state or the peer is deconfigured.		ESTABLISHED state or the peer is deconfigured.
	9. Intermediate MSDP Peers		6. Intermediate MSDP Peers
	Intermediate MSDP speakers do not originate periodic SA messages on		Intermediate MSDP speakers do not originate periodic SA messages on
	behalf of sources in other domains. In general, an RP MUST only		behalf of sources in other domains. In general, an RP MUST only
	originate an SA for a source which would register to it, and ONLY RPs		originate an SA for a source which would register to it, and ONLY RPs
	may originate SA messages.		may originate SA messages.
	10. SA Filtering and Policy		7. 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. MSDP peers in transit domains should not filter		can reduce state. MSDP peers in transit domains should not filter
	SA messages or the flood-and-join model can not guarantee that		SA messages or the flood-and-join model can not guarantee that
	sources will be known throughout the Internet (i.e., SA filtering		sources will be known throughout the Internet (i.e., SA filtering
	by transit domains may cause undesired lack of connectivity). In		by transit domains may cause undesired lack of connectivity). In
	general, policy should be expressed using MBGP [RFC2283]. This		general, policy should be expressed using MBGP [RFC2283]. This
	will cause MSDP messages to flow in the desired direction and		will cause MSDP messages to flow in the desired direction and
	peer-RPF fail otherwise. An exception occurs at an administrative		peer-RPF fail otherwise. An exception occurs at an administrative
	scope [RFC2365] boundary. In particular, a SA message for a (S,G)		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		MUST NOT be sent to peers which are on the other side of an
	administrative scope boundary for G.		administrative scope boundary for G.
	11. Encapsulated Data Packets		8. Encapsulated Data Packets
	The RP MAY encapsulate multicast data from the source. An interested		The RP MAY encapsulate multicast data from the source. An interested
	RP may decapsulate the packet, which SHOULD be forwarded as if a PIM		RP may decapsulate the packet, which SHOULD be forwarded as if a PIM
	register encapsulated packet was received. That is, if packets are		register encapsulated packet was received. That is, if packets are
	already arriving over the interface toward the source, then the		already arriving over the interface toward the source, then the
	packet is dropped. Otherwise, if the outgoing interface list is non-		packet is dropped. Otherwise, if the outgoing interface list is non-
	null, the packet is forwarded appropriately. Note that when doing		null, the packet is forwarded appropriately. Note that when doing
	data encapsulation, an implementation MUST bound the time during		data encapsulation, an implementation MUST bound the time during
	which packets are encapsulated.		which packets 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.
	12. 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 the same group ranges such as with Anycast RP's.		multiple RPs for the same group ranges such as with Anycast RP's.
	As long as all RPs have a interconnected MSDP topology, each can		As long as all RPs have a interconnected MSDP topology, each can
	learn about active sources as well as RPs in other domains.		learn about active sources as well as RPs in other domains.
	13. 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. Unlike the RPF check		messages throughout an MSDP enabled internet. Unlike the RPF check
	used when forwarding data packets, which generally compares the		used when forwarding data packets, which generally compares the
	packet's source address against the interface upon which the packet		packet's source address against the interface upon which the packet
	was received, the Peer-RPF check compares the RP address carried in		was received, the Peer-RPF check compares the RP address carried in
	the SA message against the MSDP peer from which the message was		the SA message against the MSDP peer from which the message was
	received.		received.
	13.1. Definitions		10.1. Definitions
	The following definitions are used in the description of the Peer-RPF		The following definitions are used in the description of the Peer-RPF
	Forwarding Rules:		Forwarding Rules:
	13.1.1. Multicast RPF Routing Information Base (MRIB)		10.1.1. Multicast RPF Routing Information Base (MRIB)
	The MRIB is the multicast topology table. It is typically derived		The MRIB is the multicast topology table. It is typically derived
	from the unicast routing table or from other routing protocols such		from the unicast routing table or from other routing protocols such
	as multi-protocol BGP [RFC2283].		as multi-protocol BGP [RFC2283].
	13.1.2. Peer-RPF Route		10.1.2. Peer-RPF Route
	The Peer-RPF route is the route that the MRIB chooses for a given		The Peer-RPF route is the route that the MRIB chooses for a given
	address. The Peer-RPF route for a SA's originating RP is used to		address. The Peer-RPF route for a SA's originating RP is used to
	select the peer from which the SA is accepted.		select the peer from which the SA is accepted.
	13.2. Peer-RPF Forwarding Rules		10.2. Peer-RPF Forwarding Rules
	An SA message originated by R and received by X from N is		An SA message originated by R and received by X from N is
	accepted if N is the peer-RPF neighbor for X, and is discarded		accepted if N is the peer-RPF neighbor for X, and is discarded
	otherwise.		otherwise.
	MPP(R,N) MP(N,X)		MPP(R,N) MP(N,X)
	R ---------....-------> N ------------------> X		R ---------....-------> N ------------------> X
	SA(S,G,R) SA(S,G,R)		SA(S,G,R) SA(S,G,R)
	MP(N,X) is an MSDP peering between N and X. MPP(R,N) is		MP(N,X) is an MSDP peering between N and X. MPP(R,N) is
	skipping to change at line 350 ¶		skipping to change at line 351 ¶
	(iv). N resides in the closest AS in the best path towards		(iv). N resides in the closest AS in the best path towards
	R. If multiple MSDP peers reside in the closest AS,		R. If multiple MSDP peers reside in the closest AS,
	the peer with the highest IP address is the rpf-peer.		the peer with the highest IP address is the rpf-peer.
	(v). N is configured as the static RPF-peer for R.		(v). N is configured as the static RPF-peer for R.
	MSDP peers, which are NOT in state ESTABLISHED (ie down peers), are		MSDP peers, which are NOT in state ESTABLISHED (ie down peers), are
	not eligible for peer RPF consideration.		not eligible for peer RPF consideration.
	13.3. MSDP mesh-group semantics		10.3. MSDP mesh-group semantics
	An MSDP mesh-group is a operational mechanism for reducing SA		An MSDP mesh-group is a operational mechanism for reducing SA
	flooding, typically in an intra-domain setting. In particular, when		flooding, typically in an intra-domain setting. In particular, when
	some subset of a domain's MSDP speakers are fully meshed, they can be		some subset of a domain's MSDP speakers are fully meshed, they can be
	configured into a mesh-group.		configured into a mesh-group.
	Note that mesh-groups assume that a member doesn't have to forward an		Note that mesh-groups assume that a member doesn't have to forward an
	SA to other members of the mesh-group because the originator will		SA to other members of the mesh-group because the originator will
	forward to all members. To be able for the originator to forward to		forward to all members. To be able for the originator to forward to
	all members (and to have each member also be a potential originator),		all members (and to have each member also be a potential originator),
	the mesh-group must be a full mesh of MSDP peering among all members.		the mesh-group must be a full mesh of MSDP peering among all members.
	The semantics of the mesh-group are as follows:		The semantics of the mesh-group are as follows:
	(i). If a member R of a mesh-group M receives a SA message from an		(i). If a member R of a mesh-group M receives a SA message from an
	MSDP peer that is also a member of mesh-group M, R accepts the		MSDP peer that is also a member of mesh-group M, R accepts the
	SA message and forwards it to all of its peers that are not		SA message and forwards it to all of its peers that are not
	part of any mesh-group. R MUST NOT forward the SA message to		part of mesh-group M. R MUST NOT forward the SA message to
	other members of mesh-group M.		other members of mesh-group M.
	(ii). If a member R of a mesh-group M receives a SA message from an		(ii). If a member R of a mesh-group M receives an SA message from an
	MSDP peer that is not a member of mesh-group M, and the SA		MSDP peer that is not a member of mesh-group M, and the SA
	message passes the peer-RPF check, then R forwards the SA		message passes the peer-RPF check, then R forwards the SA
	message to all members of mesh-group M.		message to all members of mesh-group M and to any other
			msdp peers.
	14. MSDP Connection State Machine		11. MSDP Connection State Machine
	MSDP uses TCP as its transport protocol. In a peering relationship,		MSDP uses TCP as its transport protocol. In a peering relationship,
	one MSDP peer listens for new TCP connections on the well-known port		one MSDP peer listens for new TCP connections on the well-known port
	639. The other side makes an active connect to this port. The peer		639. The other side makes an active connect to this port. The peer
	with the higher IP address will listen. This connection establishment		with the higher IP address will listen. This connection establishment
	algorithm avoids call collision. Therefore, there is no need for a		algorithm avoids call collision. Therefore, there is no need for a
	call collision procedure. It should be noted, however, that the		call collision procedure. It should be noted, however, that the
	disadvantage of this approach is that the startup time depends		disadvantage of this approach is that the startup time depends
	completely upon the active side and its connect retry timer; the		completely upon the active side and its connect retry timer; the
	passive side cannot cause the connection to be established.		passive side cannot cause the connection to be established.
	skipping to change at line 415 ¶		skipping to change at line 417 ¶
	| +------------+ |		| +------------+ |
	E7->A8 | |E4->A4 |		E7->A8 | |E4->A4 |
	E8->A8 | | |		E8->A8 | | |
	E9->A8 | V |		E9->A8 | V |
	\ +-------------+ /		\ +-------------+ /
	--------------| ESTABLISHED |<---------		--------------| ESTABLISHED |<---------
	+-------------+		+-------------+
	| ^		| ^
	| |		| |
	E10->A9\______/		E10->A9\______/
	14.1. Events		11.1. Events
	E1) Enable MSDP peering with P		E1) Enable MSDP peering with P
	E2) Own IP address < P's IP address		E2) Own IP address < P's IP address
	E3) Own IP address > P's IP address		E3) Own IP address > P's IP address
	E4) TCP established (active side)		E4) TCP established (active side)
	E5) TCP established (passive side)		E5) TCP established (passive side)
	E6) ConnectRetry timer expired		E6) ConnectRetry timer expired
	E7) Disable MSDP peering with P		E7) Disable MSDP peering with P
	(e.g. when one's own address is changed)		(e.g. when one's own address is changed)
	E8) Hold Timer expired		E8) Hold Timer expired
	E9) MSDP TLV format error detected		E9) MSDP TLV format error detected
	E10) Any other error detected		E10) Any other error detected
	14.2. Actions		11.2. Actions
	A1) Allocate resources for peering with P		A1) Allocate resources for peering with P
	Compare one's own and peer's IP addresses		Compare one's own and peer's IP addresses
	A2) TCP active OPEN		A2) TCP active OPEN
	Set ConnectRetry timer to [ConnectRetry-Period]		Set ConnectRetry timer to [ConnectRetry-Period]
	A3) TCP passive OPEN (listen)		A3) TCP passive OPEN (listen)
	A4) Delete ConnectRetry timer		A4) Delete ConnectRetry timer
	Send KeepAlive TLV		Send KeepAlive TLV
	Set KeepAlive timer to [KeepAlive-Period]		Set KeepAlive timer to [KeepAlive-Period]
	Set Hold Timer to [HoldTime-Period]		Set Hold Timer to [HoldTime-Period]
	skipping to change at line 451 ¶		skipping to change at line 453 ¶
	Set KeepAlive timer to [KeepAlive-Period]		Set KeepAlive timer to [KeepAlive-Period]
	Set Hold Timer to [HoldTime-Period]		Set Hold Timer to [HoldTime-Period]
	A6) Abort TCP active OPEN attempt		A6) Abort TCP active OPEN attempt
	Release resources allocated for peering with P		Release resources allocated for peering with P
	A7) Abort TCP passive OPEN attempt		A7) Abort TCP passive OPEN attempt
	Release resources allocated for peering with P		Release resources allocated for peering with P
	A8) Close the TCP connection		A8) Close the TCP connection
	Release resources allocated for peering with P		Release resources allocated for peering with P
	A9) Drop the packet		A9) Drop the packet
	14.3. Peer-specific Events		11.3. Peer-specific Events
	The following peer-specific events can occur in the ESTABLISHED		The following peer-specific events can occur in the ESTABLISHED
	state, they do not cause a state transition. Appropriate actions are		state, they do not cause a state transition. Appropriate actions are
	listed for each event.		listed for each event.
	*) KeepAlive timer expired:		*) KeepAlive timer expired:
	-> Send KeepAlive TLV		-> Send KeepAlive TLV
	-> Set KeepAlive timer to [KeepAlive-Period]		-> Set KeepAlive timer to [KeepAlive-Period]
	*) KeepAlive TLV received:		*) KeepAlive TLV received:
	-> Set Hold Timer to [HoldTime-Period]		-> Set Hold Timer to [HoldTime-Period]
	*) Source-Active TLV received:		*) Source-Active TLV received:
	-> Set Hold Timer to [HoldTime-Period]		-> Set Hold Timer to [HoldTime-Period]
	-> Run Peer-RPF Forwarding algorithm		-> Run Peer-RPF Forwarding algorithm
	-> Set KeepAlive timer to [KeepAlive-Period] for those peers		-> Set KeepAlive timer to [KeepAlive-Period] for those peers
	the Source-Active TLV is forwarded to		the Source-Active TLV is forwarded to
	-> Send information to PIM-SM		-> Send information to PIM-SM
	-> Store information in cache		-> Store information in cache
	14.4. Peer-independent Events		11.4. Peer-independent Events
	There are also a number of events that affect more than one peering		There are also a number of events that affect more than one peering
	session, but still require actions to be performed on a per-peer		session, but still require actions to be performed on a per-peer
	basis.		basis.
	*) SA-Advertisement-Timer expired:		*) SA-Advertisement-Timer expired:
	-> Start periodic transmission of Source-Active TLV(s)		-> Start periodic transmission of Source-Active TLV(s)
	-> Set KeepAlive timer to [KeepAlive-Period] each time a		-> Set KeepAlive timer to [KeepAlive-Period] each time a
	Source-Active TLV is sent		Source-Active TLV is sent
	*) MSDP learns of a new active internal source (e.g. PIM-SM		*) MSDP learns of a new active internal source (e.g. PIM-SM
	register received for a new source):		register received for a new source):
	-> Send Source-Active TLV		-> Send Source-Active TLV
	-> Set KeepAlive timer to [KeepAlive-Period]		-> Set KeepAlive timer to [KeepAlive-Period]
	*) SG-State-Timer expired (one timer per cache entry):		*) SG-State-Timer expired (one timer per cache entry):
	-> Implementation specific, typically mark the cache entry for		-> Implementation specific, typically mark the cache entry for
	deletion		deletion
	15. Packet Formats		12. Packet Formats
	MSDP messages will be encoded in TLV format. If an implementation		MSDP messages will be encoded in TLV format. If an implementation
	receives a TLV that has length that is longer than expected, the TLV		receives a TLV that has length that is longer than expected, the TLV
	SHOULD be accepted. Any additional data SHOULD be ignored and the		SHOULD be accepted. Any additional data SHOULD be ignored and the
	MSDP session should not be reset.		MSDP session should not be reset.
	15.1. MSDP TLV format:		12.1. MSDP TLV 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 | 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.
	skipping to change at line 517 ¶		skipping to change at line 519 ¶
	Length of Type, Length, and Value fields in octets.		Length of Type, Length, and Value fields in octets.
	Minimum length required is 4 octets, except for		Minimum length required is 4 octets, except for
	Keepalive messages. The maximum TLV length is 9192.		Keepalive messages. The maximum TLV length is 9192.
	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. All reserved fields		the value field is Length field minus 3. All reserved fields
	in the Value field MUST be transmitted as zeros and ignored on		in the Value field MUST be transmitted as zeros and ignored on
	receipt.		receipt.
	15.2. Defined TLVs		12.2. Defined TLVs
	The following TLV Types are defined:		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 Reserved (Previously: Notification)		5 Reserved (Previously: Notification)
	skipping to change at line 539 ¶		skipping to change at line 541 ¶
	Each TLV is described below.		Each TLV is described below.
	In addition, the following TLV Types are assigned but not described		In addition, the following TLV Types are assigned but not described
	in this memo:		in this memo:
	Code Type		Code Type
	===========================================================		===========================================================
	6 MSDP traceroute in progress		6 MSDP traceroute in progress
	7 MSDP traceroute reply		7 MSDP traceroute reply
	15.2.1. IPv4 Source-Active TLV		12.2.1. IPv4 Source-Active TLV
	The maximum size SA message that can be sent is 9192 octets. The 9192		The maximum size SA message that can be sent is 9192 octets. The 9192
	octet size does not include the TCP, IP, layer-2 headers.		octet size does not include the TCP, IP, layer-2 headers.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 1 | x + y | Entry Count |		| 1 | x + y | Entry Count |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RP Address |		| RP Address |
	skipping to change at line 568 ¶		skipping to change at line 570 ¶
	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 value of the total length field
	of the IPv4 header encapsulated. If there are multiple SA TLVs		in the header of the encapsulated IP packet. If there are
	in a message, and data is also included, y must be 0 in all SA		multiple (S,G) entries in an SA message, only the last entry
	TLVs except the last one and the last SA TLV must reflect the		may have encapsulated data and it must reflect the source and
	source and destination addresses in the IP header of the		destination addresses in the header of the encapsulated IP
	encapsulated data.		packet.
	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. An		can be encoded efficiently for the same RP address. An
	SA message containing encapsulated data typically has an		SA message containing encapsulated data typically has an
	entry count of 1 (i.e. only contains a single entry, for		entry count of 1 (i.e. only contains a single entry, for
	the (S,G) representing the encapsulated packet).		the (S,G) representing the encapsulated packet).
	RP Address		RP Address
	skipping to change at line 601 ¶		skipping to change at line 603 ¶
	Sprefix Len		Sprefix Len
	The route prefix length associated with source address.		The route prefix length associated with source address.
	This field MUST be transmitted as 32 (/32).		This field MUST be transmitted as 32 (/32).
	Group Address		Group Address
	The group address the active source has sent data to.		The group address the active source has sent data to.
	Source Address		Source Address
	The IP address of the active source.		The IP address of the active source.
	Multiple SA TLVs MAY appear in the same message and can be batched		Multiple (S,G) entries MAY appear in the same SA 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.
	15.2.2. KeepAlive TLV		12.2.2. KeepAlive TLV
	A KeepAlive TLV is sent to an MSDP peer if and only if there were no		A KeepAlive TLV is sent to an MSDP peer if and only if there were no
	MSDP messages sent to the peer within [KeepAlive-Period] seconds.		MSDP messages sent to the peer within [KeepAlive-Period] seconds.
	This message is necessary to keep the MSDP connection alive.		This message is necessary to keep the MSDP connection alive.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 4 | 3 |		| 4 | 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The length of the message is 3 octets which encompasses the one octet		The length of the message is 3 octets which encompasses the one octet
	Type field and the two octet Length field.		Type field and the two octet Length field.
	16. MSDP Error Handling		13. MSDP Error Handling
	If an MSDP SA is received with a TLV format error, the session SHOULD		If an MSDP message is received with a TLV format error, the session
	be reset with that peer. All other errors, received from MSDP peers,		SHOULD be reset with that peer. MSDP messages with other errors, such
	SHOULD silently discard the packets and the session SHOULD not be		as unrecognized type code, received from MSDP peers, SHOULD be silently
	reset.		discarded and the session SHOULD not be reset.
	17. SA Data Encapsulation		14. SA Data Encapsulation
	As discussed earlier, TCP encapsulation of data in SA messages MAY be		As discussed earlier, TCP encapsulation of data in SA messages MAY be
	supported for backwards compatibility with legacy MSDP peers.		supported for backwards compatibility with legacy MSDP peers.
	18. Security Considerations		15. Security Considerations
	An MSDP implementation MAY use IPsec [RFC2401] or MD5 to secure control		An MSDP implementation MAY use IPsec [RFC2401] or MD5 to secure control
	messages. In particular, the TCP connection between MSDP peers MAY		messages. In particular, the TCP connection between MSDP peers MAY
	be secured using IPsec or MD5. Implementations MUST be capable of		be secured using IPsec or MD5. Implementations MUST be capable of
	working with peers which do not provide IPsec or MD5 security.		working with peers which do not provide IPsec or MD5 security.
	19. Acknowledgments		16. Acknowledgments
	The editors would like to thank the original authors, Dino Farinacci,		The editors would like to thank the original authors, Dino Farinacci,
	Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their		Yakov Rehkter, Peter Lothberg, Hank Kilmer, and Jermey Hall for their
	orginal contribution to the MSDP specification. In addition, Bill		orginal contribution to the MSDP specification. In addition, Bill
	Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner,		Nickless, John Meylor, Liming Wei, Manoj Leelanivas, Mark Turner,
	John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina		John Zwiebel, Cristina Radulescu-Banu, Brian Edwards, Selina
	Priestley, IJsbrand Wijnands, Tom Pusateri, Kristofer Warell, Henning		Priestley, IJsbrand Wijnands, Tom Pusateri, Kristofer Warell, Henning
	Eriksson, Thomas Eriksson, Dave Thaler, and Ravi Shekhar provided		Eriksson, Thomas Eriksson, Dave Thaler, and Ravi Shekhar provided
	useful and productive design feedback and comments. Mike McBride,		useful and productive design feedback and comments. Mike McBride,
	Leonard Giuliano, Swapna Yelamanchi and Toerless Eckert worked on the		Leonard Giuliano, Swapna Yelamanchi, Toerless Eckert and Ishan Wu
	final version of the draft.		contributed to the final version of the draft.
	20. Editors' Address:		17. Editors' Address:
	David Meyer		David Meyer
	Sprint		Email: dmm@maoz.com
	12502 Sunrise Valley Drive
	Reston VA, 20191
	Email: dmm@sprint.net
	Bill Fenner		Bill Fenner
	AT&T Labs -- Research		AT&T Labs -- Research
	75 Willow Road		75 Willow Road
	Menlo Park, CA 94025		Menlo Park, CA 94025
	Email: fenner@research.att.com		Email: fenner@research.att.com
	21. REFERENCES		18. REFERENCES
	[IANA] http://www.iana.org		[IANA] http://www.iana.org
	[RFC768] Postel, J. "User Datagram Protocol", RFC 768, August,		[RFC768] Postel, J. "User Datagram Protocol", RFC 768, August,
	1980.		1980.
	[RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery",		[RFC1191] Mogul, J., and S. Deering, "Path MTU Discovery",
	RFC 1191, November 1990.		RFC 1191, November 1990.
	[RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4		[RFC1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4
	skipping to change at line 699 ¶		skipping to change at line 698 ¶
	[RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC		[RFC2365] Meyer, D. "Administratively Scoped IP Multicast", RFC
	2365, July, 1998.		2365, July, 1998.
	[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for		[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for
	the Internet Protocol", RFC 2401, November 1998.		the Internet Protocol", RFC 2401, November 1998.
	[RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation		[RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation
	(GRE)", RFC 2784, March 2000.		(GRE)", RFC 2784, March 2000.
	22. Full Copyright Statement		19. Full Copyright Statement
	Copyright (C) The Internet Society (2001). All Rights Reserved.		Copyright (C) The Internet Society (2003). 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 are		kind, provided that the above copyright notice and this paragraph are
	included on all such copies and derivative works. However, this		included on all such copies and derivative works. However, this
	document itself may not be modified in any way, such as by removing		document itself may not be modified in any way, such as by removing
	the copyright notice or references to the Internet Society or other		the copyright notice or references to the Internet Society or other
	Internet organizations, except as needed for the purpose of		Internet organizations, except as needed for the purpose of
End of changes. 56 change blocks.
	71 lines changed or deleted		70 lines changed or added
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