< draft-ietf-msdp-spec-13.txt		draft-ietf-msdp-spec-14.txt >
	Network Working Group David Meyer (Editor)
	INTERNET DRAFT Bill Fenner (Editor)		Network Working Group David Meyer
	Category Standards Track		(Editor)
	November, 2001		INTERNET DRAFT Bill Fenner
			(Editor)
			Category
			Standards Track
			November, 2002
	Multicast Source Discovery Protocol (MSDP)		Multicast Source Discovery Protocol (MSDP)
	<draft-ietf-msdp-spec-13.txt>		<draft-ietf-msdp-spec-14.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 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.
	skipping to change at page 1, line 35 ¶		skipping to change at line 39 ¶
	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		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
	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. This draft is intended to document existing MSDP
			implementations in the field.
	3. Copyright Notice		3. Copyright Notice
	Copyright (C) The Internet Society (2001). All Rights Reserved.		Copyright (C) The Internet Society (2002). All Rights Reserved.
	4. 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. 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
	skipping to change at page 2, line 46 ¶		skipping to change at line 83 ¶
	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.
	We envision this virtual topology will essentially be congruent to
	the existing BGP topology used in the unicast-based Internet today.
	That is, the TCP connections between MSDP peers are likely to be
	congruent to the connections in the BGP routing system.
	6. Procedure		6. 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. The SA message contains the following
	fields:		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.
	skipping to change at page 3, line 26 ¶		skipping to change at line 104 ¶
	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.
	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 Multicast RPF		flooding is with respect to forwarding SA messages. The Multicast RPF
	Routing Information Base (MRIB) is examined to determine which peer		Routing Information Base (MRIB) is examined to determine which peer
	towards the originating RP of the SA message is selected. Such a peer		towards the originating RP of the SA message is selected. Such a peer
	is called an "RPF peer". See section 14 for the details of peer-RPF		is called an "RPF peer". See section 13 for the details of peer-RPF
	forwarding.		forwarding.
	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 its MSDP peers (except the one from which it received		message to all its MSDP peers (except the one from which it received
	the SA message).		the SA message).
	When an MSDP peer which is also an RP for its own domain receives a		When an MSDP peer which is also an RP for its own domain receives a
	new SA message, it determines if there are any group members within		new SA message, it determines if there are any group members within
	the domain interested in any group described by an (S,G) entry within		the domain interested in any group described by an (S,G) entry within
	skipping to change at page 4, line 14 ¶		skipping to change at line 140 ¶
	message. Otherwise, they join a distribution tree.		message. Otherwise, they join a distribution tree.
	7. Caching		7. 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
			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
			packets that the MSDP speaker will cache for the first time. The
			SA-cache also reduces storms by advertising from the cache at a
			period of no more than twice per SA-Advertisement-Timer interval and
			not less than 1 time per SA Advertisment period.
	8. Timers		8. Timers
	The main timers for MSDP are: SA-Advertisement-Timer, SG-Rate-Limit-		The main timers for MSDP are: SA-Advertisement-Timer, SA Cache Entry
	Timer, SA Cache Entry timer, KeepAlive timer, ConnectRetry and Peer		timer, Peer Hold Timer, KeepAlive timer, and ConnectRetry timer.
	Hold Timer. Each is considered below.		Each is considered below.
	8.1. SA-Advertisement-Timer		8.1. 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.		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
			60 seconds for that S,G.
	8.2. SA-Advertisement-Timer Processing		8.2. 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
	skipping to change at page 5, line 12 ¶		skipping to change at line 190 ¶
	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)		8.3. 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 a 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. The timer is reset whether or not the (S,G) entry's SG-		expires. [SG-State-Period] MUST NOT be less than
	Rate-Limit timer is running. [SG-State-Period] MUST NOT be less than
	[SA-Advertisement-Period] + [SA-Hold-Down-Period].		[SA-Advertisement-Period] + [SA-Hold-Down-Period].
	8.4. SG-Rate-Limit Timer		8.4. Peer Hold Timer
	The SG-Rate-Limit Timer is a per-(S,G) timer which is used to limit
	possible SA storms. After an SA message passes the peer-RPF check,
	the SG-Rate-Limit timer for each (S,G) in the message is checked. If
	the SG-Rate-Limit timer is running for a given (S,G), it is removed
	from the message before forwarding. If this process causes the
	message to become empty, the empty message is discarded.
	When an SA message is forwarded, the SG-Rate-Limit timer for each
	(S,G) mentioned in the message is set to [SG-Rate-Limit-Period]
	seconds. Note that this sequence means that the SG-Rate-Limit timer
	will never be reset if it is running, since any (S,G) whose timer was
	running was removed from the forwarded message; it acts as a "one-
	shot" timer.
	[SG-Rate-Limit-Period] SHOULD be set to 30 seconds, and MUST NOT be
	greater than [SA-Advertisement-Period].
	8.5. Peer Hold Timer
	If a system has not received any MSDP message within the period
	specified by the Hold Timer, then a Notification message with Hold
	Timer Expired Error Code MUST be sent and the MSDP connection MUST be
	closed. [HoldTime-Period] MUST be at least three seconds. The
	recommended value for [HoldTime-Period] is 90 seconds.
	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
			value for [HoldTime-Period] is 75 seconds.
	8.6. KeepAlive Timer		8.5. 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
	75 seconds.		60 seconds.
	8.7. ConnectRetry Timer		8.6. 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.
	skipping to change at page 7, line 10 ¶		skipping to change at line 246 ¶
	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		10. 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 co-located in the same domain as the		can reduce state. MSDP peers in transit domains should not filter
	source can restrict SA messages. Note, however, that MSDP peers in		SA messages or the flood-and-join model can not guarantee that
	transit domains should not filter SA messages or the flood-and-join		sources will be known throughout the Internet (i.e., SA filtering
	model can not guarantee that sources will be known throughout the		by transit domains may cause undesired lack of connectivity). In
	Internet (i.e., SA filtering by transit domains can cause undesired		general, policy should be expressed using MBGP [RFC2283]. This
	lack of connectivity). In general, policy should be expressed using		will cause MSDP messages to flow in the desired direction and
	MBGP [RFC2283]. This will cause MSDP messages to flow in the desired		peer-RPF fail otherwise. An exception occurs at an administrative
	direction and peer-RPF fail otherwise. An exception occurs at an		scope [RFC2365] boundary. In particular, a SA message for a (S,G)
	administrative scope [RFC2365] boundary. In particular, a SA message		MUST NOT be sent to peers which are on the other side of an
	for a (S,G) MUST NOT be sent to peers which are on the other side of		administrative scope boundary for G.
	an administrative scope boundary for G.
	11. SA Requests
	A MSDP speaker MAY accept SA-Requests from other MSDP peers. When an
	MSDP speaker receives an SA-Request for a group range, it will
	respond to the peer with a set of SA entries, in an SA-Response
	message, for all active sources in its SA cache sending to the group
	requested in the SA-Request message. The peer that sends the request
	will not flood the responding SA-Response message to other peers. See
	section 17 for discussion of error handling relating to SA requests
	and responses.
	12. Encapsulated Data Packets		11. 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.
	13. Other Scenarios		12. 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. As long as all RPs have a		multiple RPs for the same group ranges such as with Anycast RP's.
	interconnected MSDP topology, each can learn about active sources as		As long as all RPs have a interconnected MSDP topology, each can
	well as RPs in other domains.		learn about active sources as well as RPs in other domains.
	14. MSDP Peer-RPF Forwarding		13. 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.
	14.1. Definitions		13.1. 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:
	14.1.1. Multicast RPF Routing Information Base (MRIB)		13.1.1. 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].
	14.1.2. Peer-RPF Route		13.1.2. 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.
	14.2. Peer-RPF Forwarding Rules		13.2. 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
	an MSDP peering path (zero or more MSDP peers) between R		an MSDP peering path (zero or more MSDP peers) between
	and N, e.g. MPP(R,N) = MP(R, A) + MP(A, B) + MP(B, N).		R and N, e.g. MPP(R,N) = MP(R, A) + MP(A, B) + MP(B,
	SA(S,G,R) is an SA message for source S on group G originated		N). SA(S,G,R) is an SA message for source S on group G
	by an RP R.		originated by an RP R.
	The peer-RPF neighbor P is chosen deterministically, using the		The peer-RPF neighbor N is chosen deterministically, using the
	first of the following rules that matches. In particular,		first of the following rules that matches. In particular,
	P is the RPF neighbor of X with respect to R if		N is the RPF neighbor of X with respect to R if
	(i). P == R (X has an MSDP peering with R).		(i). N == R (X has an MSDP peering with R).
	(ii). P is the BGP NEXT_HOP of the Peer-RPF route		(ii). N is the eBGP NEXT_HOP of the Peer-RPF route
	for R.		for R.
	(iii). The Peer-RPF route for R is learned through a		(iii). The Peer-RPF route for R is learned through a
	distance-vector or path-vector routing protocol		distance-vector or path-vector routing protocol
	(e.g. BGP, RIP, DVMRP) and P is the neighbor that		(e.g. BGP, RIP, DVMRP) and N is the neighbor that
	advertised the Peer-RPF route for R if the		advertised the Peer-RPF route for R (e.g. N is the
	route was learned via a distance-vector or		iBGP advertiser of the route for R), or N is the
	path-vector protocol, or P is the IGP next hop		IGP next hop for R if the route for R is learned
	for R if learned via a link-state protocol.		via a link-state protocol (e.g. OSPF or ISIS).
	(iv). P resides in an AS that is in the AS_PATH of the
	Peer-RPF route for R, and P has the highest IP address among
	the MSDP peers that reside in ASs in that AS_PATH.
	(v). P is configured as the static RPF-peer for R.
	When an SA message with RP R is received from neighbor N, it is
	discarded unless N == P as determined above.
	14.3. MSDP static RPF-peer semantics		(iv). N resides in the closest AS in the best path towards
			R. If multiple MSDP peers reside in the closest AS,
			the peer with the highest IP address is the rpf-peer.
	If none of the rules (i) - (iv) are able to determine an RPF peer for		(v). N is configured as the static RPF-peer for R.
	R, a longest-match lookup is performed in the static RPF peer table.
	This table MUST be able to contain a default entry, and SHOULD be
	able to contain prefix or per-host (RP) entries. This table
	statically maps RP addresses to peers, and allows configuration of
	topology that is e.g. unknown to the multicast topology gathering
	protocol.
	The result of the longest-match lookup of an RP address R in the		MSDP peers, which are NOT in state ESTABLISHED (ie down peers), are
	static RPF peer table is an MSDP peer, which is the RPF neighbor for		not eligible for peer RPF consideration.
	R.
	14.4. MSDP mesh-group semantics		13.3. MSDP mesh-group semantics
	A 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, then 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:
	skipping to change at page 10, line 48 ¶		skipping to change at line 376 ¶
	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 any mesh-group. 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 a 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.
	(iii). Cross mesh-group forwarding		14. MSDP Connection State Machine
	If a member R of a mesh-groups M and N receives an SA
	message from an MSDP peer in mesh-group M, R forwards the SA
	to its MSDP peers in mesh-group N if it receives that SA
	message from a peer that is in the same mesh-group as its
	peer-RPF neighbor for that SA.
	For example, consider the case in which three routers (R1, R2,
	and R3) and three mesh-groups (A, B, and C) are arranged in a
	triangle, e.g.,
	[R2] {A,B}
	/ \
	/ \
	/ \
	/ \
	{A,C} [R1]--------[R3] {B,C}
	Now, when R1 receives an SA message from R2 and R1's
	peer-RPF neighbor for this SA lies in mesh-group A, R1
	forwards the SA message its peers in other mesh-groups
	(in particular, R3 in mesh-group C). Similarly, if R3's
	peer-RPF neighbor lies in mesh-group B, R3 will forward an
	SA message from R2. In this case, both R1 and R3 will send
	SA messages to each other (because they share common mesh-group
	C), but neither of them will forward any further the SA messages
	received from each other (as their peer-RPF neighbors do
	not lie in mesh-group C).
	Note that since mesh-groups suspend peer-RPF checking of SAs received
	from a mesh-group member ((i). above), they allow for mis-
	configuration to cause SA looping.
	15. 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 page 12, line 33 ¶		skipping to change at line 404 ¶
	| / |E1->A1 |		| / |E1->A1 |
	| | | |		| | | |
	| | V |E7->A7		| | V |E7->A7
	| | +----------+ E3->A3 +--------+		| | +----------+ E3->A3 +--------+
	| | | INACTIVE |------->| LISTEN |		| | | INACTIVE |------->| LISTEN |
	| | +----------+ +--------+		| | +----------+ +--------+
	| | E2->A2| ^ |E5->A5		| | E2->A2| ^ |E5->A5
	| | | | |		| | | | |
	| |E7->A6 V |E6 |		| |E7->A6 V |E6 |
	| \ +------------+ |		| \ +------------+ |
	E7->A8 | ------| CONNECTING | |		| ------| CONNECTING | |
	E8->A9 | +------------+ |		| +------------+ |
	E9->A10| |E4->A4 |		E7->A8 | |E4->A4 |
	E10->A11| | |		E8->A8 | | |
	E11->A12| V |		E9->A8 | V |
	\ +-------------+ /		\ +-------------+ /
	--------------| ESTABLISHED |<---------		--------------| ESTABLISHED |<---------
	+-------------+		+-------------+
			| ^
	15.1. Events		| |
			E10->A9\______/
			14.1. 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
	An example of when to do this is when one's own address is		(e.g. when one's own address is changed)
	changed)
	E8) Hold Timer expired		E8) Hold Timer expired
	E9) Authorization failure		E9) MSDP TLV format error detected
	E10) Notification TLV received		E10) Any other error detected
	E11) Error detected
	15.2. Actions		14.2. 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]
	A5) Send KeepAlive TLV		A5) 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]
	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
			Release resources allocated for peering with P
			A9) Drop the packet
	In action sets 8)-12), the action "Close peering session" includes		14.3. Peer-specific Events
	the following steps:
	Close TCP connection
	Delete KeepAlive timer
	Delete Hold Timer
	Release resources allocated for peering with P
	A8) Send Notification TLV with Error Code "Cease"
	Close peering session
	A9) Send Notification TLV with Error Code "Hold Timer Expired"
	Close peering session
	A10) Notify management system unless this has already been done by
	the security mechanism
	Close peering session
	A11) Notify management system
	If the received Notification TLV's O-bit was cleared, close
	peering session. Otherwise, remain in ESTABLISHED state.
	A12) Send Notification TLV with appropriate Error Code
	Notify management system
	If the sent Notification TLV's O-bit was cleared, close peering
	session. Otherwise, remain in ESTABLISHED state.
	15.3. 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 (consider SG-Rate-Limit		-> Run Peer-RPF Forwarding algorithm
	Timer and SA-State Timer)
	-> 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
	*) Source-Active Request TLV received:
	-> Set Hold Timer to [HoldTime-Period]
	-> If SA-Requests are accepted, send Source-Active Response
	TLV and set KeepAlive timer to [KeepAlive-Period]
	*) Source-Active Response TLV received:
	-> Set Hold Timer to [HoldTime-Period]
	-> If a corresponding SA-Request were previously sent, send
	information to PIM-SM. If not, an error has occured
	(event 11 above)
	-> Store information in cache
	15.4. Peer-independent Events		14.4. 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]
	*) Source-Active Request triggered (event not specified here):
	-> Send Source-Active Request TLV
	-> 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
	16. Packet Formats		15. 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.		SHOULD be accepted. Any additional data SHOULD be ignored and the
			MSDP session should not be reset.
	16.1. MSDP TLV format:		15.1. 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 page 16, line 33 ¶		skipping to change at line 517 ¶
	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.
	16.2. Defined TLVs		15.2. 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 Notification		5 Reserved (Previously: Notification)
	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
	16.2.1. IPv4 Source-Active TLV		15.2.1. 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 page 18, line 16 ¶		skipping to change at line 593 ¶
	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.
	Reserved		Reserved
	The Reserved field MUST be transmitted as zeros and MUST be		The Reserved field MUST be transmitted as zeros and MUST be
	ignored by a receiver.		ignored by a receiver.
	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). An Invalid		This field MUST be transmitted as 32 (/32).
	Sprefix Len Notification SHOULD be sent upon receipt
	of any other value.
	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 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.
	16.2.2. IPv4 Source-Active Request TLV		15.2.2. KeepAlive TLV
	The Source-Active Request is used to request SA-state from a MSDP
	peer. If an RP in a domain receives a PIM Join message for a group,
	creates (*,G) state and wants to know all active sources for group G,
	it may send an SA-Request message for the group.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 2 | 8 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	IPv4 Source-Active Request TLV is type 2.
	Reserved
	Must be transmitted as zero and ignored on receipt.
	Group Address
	The group address the MSDP peer is requesting.
	16.2.3. IPv4 Source-Active Response TLV
	The Source-Active Response is sent in response to a Source-Active
	Request message. The Source-Active Response message has the same
	format as a Source-Active message but does not allow encapsulation of
	multicast data.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 3 | x | .... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	IPv4 Source-Active Response TLV is type 3.
	Length x
	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
	Count octets.
	16.2.4. 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.
	16.2.5. Notification TLV		16. MSDP Error Handling
	A Notification message is sent when an error condition is detected,
	and has the following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | x + 5 |O| Error Code |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Error subcode | ... |
	+-+-+-+-+-+-+-+-+ |
	| Data |
	| ... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	The Notification TLV is type 5.
	Length
	Length is a two octet field with value x + 5, where x is
	the length of the notification data field.
	O-bit
	Open-bit. If clear, the connection will be closed.
	Error code
	This 7-bit unsigned integer indicates the type of Notification.
	The following Error Codes have been defined:
	Error Code Symbolic Name Reference
	1 Message Header Error Section 17.1
	2 SA-Request Error Section 17.2
	3 SA-Message/SA-Response Error Section 17.3
	4 Hold Timer Expired Section 17.4
	5 Finite State Machine Error Section 17.5
	6 Notification Section 17.6
	7 Cease Section 17.7
	Error subcode:
	This one-octet unsigned integer provides more specific information
	about the reported error. Each Error Code may have one or more Error
	Subcodes associated with it. If no appropriate Error Subcode is
	defined, then a zero (Unspecific) value is used for the Error Subcode
	field, and the O-bit must be cleared (i.e. the connection will be
	closed). The used notation in the error description below is: MC =
	Must Close connection = O-bit clear; CC = Can Close connection =
	O-bit MAY be cleared.
	Message Header Error subcodes:
	0 - Unspecific (MC)
	2 - Bad Message Length (MC)
	3 - Bad Message Type (CC)
	SA-Request Error subcodes (the O-bit is always clear):
	0 - Unspecific (MC)
	1 - Invalid Group (MC)
	SA-Message/SA-Response Error subcodes
	0 - Unspecific (MC)
	1 - Invalid Entry Count (CC)
	2 - Invalid RP Address (MC)
	3 - Invalid Group Address (MC)
	4 - Invalid Source Address (MC)
	5 - Invalid Sprefix Length (MC)
	6 - Looping SA (Self is RP) (MC)
	7 - Unknown Encapsulation (MC)
	8 - Administrative Scope Boundary Violated (MC)
	Hold Timer Expired subcodes (the O-bit is always clear):
	0 - Unspecific (MC)
	Finite State Machine Error subcodes (the O-bit is always clear):
	0 - Unspecific (MC)
	1 - Unexpected Message Type FSM Error (MC)
	Notification subcodes (the O-bit is always clear):
	0 - Unspecific (MC)
	Cease subcodes (the O-bit is always clear):
	0 - Unspecific (MC)
	17. MSDP Error Handling
	This section describes actions to be taken when errors are detected
	while processing MSDP messages. MSDP Error Handling is similar to
	that of BGP [RFC1771].
	When any of the conditions described here are detected, a
	Notification message with the indicated Error Code, Error Subcode,
	and Data fields is sent. In addition, the MSDP connection MAY be
	closed. If no Error Subcode is specified, then a zero (Unspecific)
	must be used.
	The phrase "the MSDP connection is closed" means that the transport
	protocol connection has been closed and that all resources for that
	MSDP connection have been deallocated.
	17.1. Message Header Error Handling
	All errors detected while processing the Message Header are indicated
	by sending the Notification message with Error Code Message Header
	Error. The Error Subcode describes the specific nature of the error.
	The Data field contains the erroneous Message (including the message
	header).
	If the Length field of the message header is less than 4 or greater
	than 9192, or the length of a KeepAlive message is not equal to 3,
	then the Error Subcode is set to Bad Message Length.
	If the Type field of the message header is not recognized, then the
	Error Subcode is set to Bad Message Type.
	17.2. SA-Request Error Handling
	The SA-Request Error code is used to signal the receipt of a SA
	request at a MSDP peer when an invalid group address requested.
	When a MSDP peer receives a request for an invalid group, it returns
	the following notification:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 12 |O| 2 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 1 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.3. SA-Message/SA-Response Error Handling
	The SA-Message/SA-Response Error code is used to signal the receipt
	of a erroneous SA Message at an MSDP peer, or the receipt of an SA-
	Response Message by a peer that did not issue a SA-Request. It has
	the following form:
	17.3.1. Invalid Entry Count (IEC)
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 6 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 1 | Entry Count |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.3.2. Invalid RP Address
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 2 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.3.3. Invalid Group Address
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 3 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.3.4. Invalid Source Address
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 4 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.3.5. Invalid Sprefix Length (ISL)
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 6 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | Sprefix Len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.3.6. Looping SAs (Self is RP in received SA)
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | x + 5 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 6 | SA Message ....
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Length x
	x is the length of the looping SA message contained in the data
	field of the Notification message.
	17.3.7. Unknown Encapsulation
	This notification is sent on receipt of SA data that is encapsulated
	in an unknown encapsulation type. See section 18 for known
	encapsulations.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | x + 5 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | SA Message ....
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Length x
	x is the length of the SA message (which contained data which
	was encapsulated in some unknown way) that is contained in the
	data field of the Notification message.
	17.3.8. Administrative Scope Boundary Violated
	This notification is used when an SA message is received for a group
	G from a peer which is across an administrative scope boundary for G.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 8 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	17.4. Hold Time Expired
	If a system has not received any MSDP message within the period
	specified in the Hold Timer, the notification message with Hold Timer
	Expired Error Code and no additional data MUST be sent and the MSDP
	connection closed.
	17.5. Finite State Machine Error Handling
	Any error detected by the MSDP Finite State Machine (e.g., receipt of
	an unexpected event) is indicated by sending the Notification message
	with Error Code Finite State Machine Error.
	17.6. Notification Message Error Handling
	If a node sends a Notification message, and there is an error in that
	message, and the O-bit of that message is not clear, a Notification
	with O-bit clear, Error Code of Notification Error, and subcode
	Unspecific must be sent. In addition, the Data field must include
	the Notification message that triggered the error. However, if the
	erroneous Notification message had the O-bit clear, then any error,
	such as an unrecognized Error Code or Error Subcode, should be
	noticed, logged locally, and brought to the attention of the
	administrator of the remote node.
	17.7. Cease
	In absence of any fatal errors (that are indicated in this section),
	an MSDP node may choose at any given time to close its MSDP
	connection by sending the Notification message with Error Code Cease.
	However, the Cease Notification message MUST NOT be used when a fatal
	error indicated by this section does exist.
	18. SA Data Encapsulation
	This section describes UDP, GRE, and TCP encapsulation of data
	packets to be included with SA messages. Encapsulation type is a
	configuration option.
	18.1. UDP Data Encapsulation
	Data packets MAY be encapsulated in UDP. In this case, the UDP
	pseudo-header has the following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Port | Destination Port |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Length | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Origin RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The Source port, Destination Port, Length, and Checksum are used
	according to RFC 768. Source and Destination ports are known via
	an implementation-specific method (e.g. per-peer configuration).
	Checksum
	The checksum is computed according to RFC 768 [RFC768].
	Originating RP Address
	The Originating RP Address is the address of the RP sending
	the encapsulated data.
	18.2. GRE Encapsulation
	MSDP SA-data MAY be encapsulated in GRE using protocol type [MSDP-
	GRE-ProtocolType]. The GRE header and payload packet have the
	following form:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|C| Reserved0 | Ver | [MSDP-GRE-ProtocolType] |\
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header
	| Checksum (optional) | Reserved1 |/
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Originating RP IPv4 Address |\
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload
	| (S,G) Data Packet .... /
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	18.2.1. Encapsulation and Path MTU Discovery [RFC1191]
	Existing implementations of GRE, when using IPv4 as the Delivery		If an MSDP SA is received with a TLV format error, the session SHOULD
	Header, do not implement Path MTU discovery and do not set the Don't		be reset with that peer. All other errors, received from MSDP peers,
	Fragment bit in the Delivery Header. This can cause large packets to		SHOULD silently discard the packets and the session SHOULD not be
	become fragmented within the tunnel and reassembled at the tunnel		reset.
	exit (independent of whether the payload packet is using PMTU). If a
	tunnel entry point were to use Path MTU discovery, however, that
	tunnel entry point would also need to relay ICMP unreachable error
	messages (in particular the "fragmentation needed and DF set" code)
	back to the originator of the packet, which is not required by the
	GRE specification [RFC2784]. Failure to properly relay Path MTU
	information to an originator can result in the following behavior:
	the originator sets the don't fragment bit, the packet gets dropped
	within the tunnel, but since the originator doesn't receive proper
	feedback, it retransmits with the same PMTU, causing subsequently
	transmitted packets to be dropped.
	18.3. TCP Data Encapsulation		17. SA Data Encapsulation
	As discussed earlier, 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.
	19. IANA Considerations		18. Security Considerations
	The IANA should assign 0x0009 from the IANA SNAP Protocol IDs [IANA]
	to MSDP-GRE-ProtocolType.
	20. Security Considerations
	An MSDP implementation MUST use IPsec [RFC2401] to secure control		An MSDP implementation MAY use IPsec [RFC2401] or MD5 to secure control
	messages. In particular, the TCP connection between MSDP peers MUST		messages. In particular, the TCP connection between MSDP peers MAY
	be secured using IPsec. When encapsulating data packets in GRE,		be secured using IPsec or MD5. Implementations MUST be capable of
	security should be relatively similar to security in a normal IPv4		working with peers which do not provide IPsec or MD5 security.
	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.
	21. Acknowledgments		19. 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 and IJsbrand Wijnands provided useful and productive design		Priestley, IJsbrand Wijnands, Tom Pusateri, Kristofer Warell, Henning
	feedback and comments. In addition to many other contributions, Tom		Eriksson, Thomas Eriksson, Dave Thaler, and Ravi Shekhar provided
	Pusateri, Kristofer Warell, Henning Eriksson, and Thomas Eriksson		useful and productive design feedback and comments. Mike McBride,
	helped to clarify the connection state machine, Dave Thaler helped to		Leonard Giuliano, Swapna Yelamanchi and Toerless Eckert worked on the
	clarify the Notification message types. Ravi Shekhar helped clarify		final version of the draft.
	the semantics of mesh-groups, and countless others helped to clarify
	the Peer-RPF rules.
	22. Editors' Address:		20. Editors' Address:
	David Meyer		David Meyer
	Sprint		Sprint
	12502 Sunrise Valley Drive		12502 Sunrise Valley Drive
	Reston VA, 20191		Reston VA, 20191
	Email: dmm@sprint.net		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
	23. REFERENCES		21. 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 page 32, line 38 ¶		skipping to change at line 699 ¶
	[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.
	24. Full Copyright Statement		22. Full Copyright Statement
	Copyright (C) The Internet Society (2001). All Rights Reserved.		Copyright (C) The Internet Society (2001). All Rights Reserved.
	This document and translations of it may be copied and furnished to		This document and translations of it may be copied and furnished to
	others, and derivative works that comment on or otherwise explain it		others, and derivative works that comment on or otherwise explain it
	or assist in its implementation may be prepared, copied, published		or assist in its implementation may be prepared, copied, published
	and distributed, in whole or in part, without restriction of any		and distributed, in whole or in part, without restriction of any
	kind, provided that the above copyright notice and this paragraph 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
End of changes. 69 change blocks.
	640 lines changed or deleted		130 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/