< draft-ietf-msdp-spec-02.txt		draft-ietf-msdp-spec-03.txt >
	Network Working Group Dino Farinacci		Network Working Group Dino Farinacci
	INTERNET DRAFT Procket Networks		INTERNET DRAFT Procket Networks
	Yakov Rekhter		Yakov Rekhter
	David Meyer		David Meyer
	Cisco Systems		Cisco Systems
	Peter Lothberg		Peter Lothberg
	Sprint		Sprint
	Hank Kilmer		Hank Kilmer
	Jeremy Hall		Jeremy Hall
	UUnet		UUnet
	Category Standards Track		Category Standards Track
	January, 2000		January, 2000
	Multicast Source Discovery Protocol (MSDP)		Multicast Source Discovery Protocol (MSDP)
	<draft-ietf-msdp-spec-02.txt>		<draft-ietf-msdp-spec-03.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 2, line 14 ¶		skipping to change at page 2, line 14 ¶
	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.
	3. Copyright Notice		3. Copyright Notice
	Copyright (C) The Internet Society (20000). All Rights Reserved.		Copyright (C) The Internet Society (2000). 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 3, line 8 ¶		skipping to change at page 3, line 8 ¶
	cache Source Active (SA) messages (see below). MSDP is a		cache Source Active (SA) messages (see below). MSDP is a
	periodic protocol.		periodic protocol.
	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		5. Overview
	An RP (or other MSDP SA originator) in a PIM-SM [RFC2362] domain will		An RP (or other MSDP SA originator) in a PIM-SM [RFC2362] domain will
	have a MSDP peering relationship with a MSDP speaker in another		have a MSDP peering relationship with a MSDP peers in another domain.
	domain. The peering relationship will be made up of a TCP connection		The peering relationship will be made up of a TCP connection in which
	in which control information exchanged. Each domain will have one or		control information exchanged. Each domain will have one or more
	more connections to this virtual topology.		connections to this virtual topology.
	The purpose of this topology is to have domains discover multicast		The purpose of this topology is to have domains discover multicast
	sources from other domains. If the multicast sources are of interest		sources from other domains. If the multicast sources are of interest
	to a domain which has receivers, the normal source-tree building		to a domain which has receivers, the normal source-tree building
	mechanism in PIM-SM will be used to deliver multicast data over an		mechanism in PIM-SM will be used to deliver multicast data over an
	inter-domain distribution tree.		inter-domain distribution tree.
	We envision this virtual topology will essentially be congruent to		We envision this virtual topology will essentially be congruent to
	the existing BGP topology used in the unicast-based Internet today.		the existing BGP topology used in the unicast-based Internet today.
	That is, the TCP connections between MSDP speakers can be realized by		That is, the TCP connections between MSDP peers can be realized by
	the underlying BGP routing system.		the underlying BGP routing system.
	6. Procedure		6. Procedure
	A source in a PIM-SM domain originates traffic to a multicast group.		A source in a PIM-SM domain originates traffic to a multicast group.
	The PIM DR which is directly connected to the source sends the data		The PIM DR which is directly connected to the source sends the data
	encapsulated in a PIM Register message to the RP in the domain.		encapsulated in a PIM Register message to the RP in the domain.
	The RP will construct a "Source-Active" (SA) message and send it to		The RP will construct a "Source-Active" (SA) message and send it to
	its MSDP peers. The SA message contains the following fields:		its MSDP peers. The SA message contains the following fields:
	o Source address of the data source.		o Source address of the data source.
	o Group address the data source sends to.		o Group address the data source sends to.
	o IP address of the RP.		o IP address of the RP.
	Each MSDP peer receives and forwards the message away from the RP		Each MSDP peer receives and forwards the message away from the RP
	address in a "peer-RPF flooding" fashion. The notion of peer-RPF		address in a "peer-RPF flooding" fashion. The notion of peer-RPF
	flooding is with respect to forwarding SA messages. The BGP routing		flooding is with respect to forwarding SA messages. The BGP routing
	table is examined to determine which peer is the NEXT_HOP towards the		table is examined to determine which peer is the NEXT_HOP towards the
	originating RP of the SA message. Such a peer is called an "RPF		originating RP of the SA message. Such a peer is called an "RPF
	peer". See section 10 below for the details of peer-RPF forwarding.		peer". See section 14 below for the details of peer-RPF 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.		message to all its MSDP peers.
	The flooding can be further constrained to children of the peer by		The flooding can be further constrained to children of the peer by
	interrogating BGP reachability information. That is, if a BGP peer		interrogating BGP reachability information. That is, if a BGP peer
	advertises a route (back to you) and you are the next to last AS in		advertises a route (back to you) and you are the next to last AS in
	the AS_PATH, the peer is using you as the NEXT_HOP. This is known in		the AS_PATH, the peer is using you as the NEXT_HOP. This is known in
	other circles as Split-Horizon with Poison Reverse. An implementation		other circles as Split-Horizon with Poison Reverse. An implementation
	skipping to change at page 4, line 38 ¶		skipping to change at page 4, line 38 ¶
	7. Controlling State		7. Controlling State
	While RPs which receive SA messages are not required to keep MSDP		While RPs which receive SA messages are not required to keep MSDP
	(S,G) state, an RP SHOULD cache SA messages by default. The advantage		(S,G) state, an RP SHOULD cache SA messages by default. The advantage
	of caching is that newly formed MSDP peers can get MSDP (S,G) state		of caching is that newly formed MSDP peers can get MSDP (S,G) state
	sooner and therefore reduce join latency for new joiners. In		sooner and therefore reduce join latency for new joiners. In
	addition, caching greatly aids in diagnosis and debugging of various		addition, caching greatly aids in diagnosis and debugging of various
	problems.		problems.
	7.1. Timers		8. Timers
	The main timers for MSDP are: SA-Advertisement-Timer, SA-Hold-Down-		The main timers for MSDP are: SA-Advertisement-Timer, SA-Hold-Down-
	Timer, SA Cache entry timers, and KeepAlive timer.		Timer, SA Cache Entry timer, KeepAlive timer, and ConnectRetry and
			Peer Hold Timer. Each is considered below.
	7.1.1. SA-Advertisement-Timer		8.1. SA-Advertisement-Timer
	RPs which originate SA messages do it periodically as long as there		RPs which originate SA messages do it periodically as long as there
	is data being sent by the source. 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-
	Timer] MUST be 60 seconds. An RP will not send more than one SA		Period] MUST be 60 seconds. An RP will not send more than one
	message for a given (S,G) within an SA Advertisement interval.		periodic SA message for a given (S,G) within an SA Advertisement
	Originating periodic SA messages is important so that new receivers		interval. Originating periodic SA messages is important so that new
	who join after a source has been active can get data quickly via the		receivers who join after a source has been active can get data
	receiver's own RP when it is not caching SA state.		quickly via the receiver's own RP when it is not caching SA state.
	7.1.1.1. SA-Advertisement-Timer Processing
	When an RP is processing a PIM register message, it encapsulates the
	data (if any) in an SA message and sends the SA message it to each of
	its peers. The RP starts the SA Advertisement-Timer for the (S,G) at
	this time. When the timer expires, and there is (S,G) state for a
	source within the RP's domain, an (S,G)-SA message is sent to each
	peer and the timer is reset to [SA-Advertisement-Timer] seconds. If
	no (S,G) state exists, the timer is deleted.
	The following table summarizes (S,G)-SA-Advertisement-Timer
	processing:
	Set to | When | Applies to
	[SA-Advertisement-Timer] | created off Register packet | (S,G)
	Reset to | When | Applies to
	[SA-Advertisement-Timer] | Timer expires and (S,G) | (S,G)
	| state exists and was |
	| created by a register |
	Deleted | When | Applies to		8.2. SA-Advertisement-Timer Processing
	[SA-Advertisement-Timer] | Timer expires and (S,G) | (S,G)
	| state has expired |
	Note that a caching implementation may also wish to check the SA-		An RP starts the SA-Advertisement-Timer when the MSDP process is
	Cache on this timer event.		configured. When the timer expires, an RP advertises any candidate
			internal sources to its peers and resets the timer to [SA-
			Advertisement-Period] seconds. The timer is deleted when the MSDP
			process is deconfigured. Note that a caching implementation may also
			wish to check the SA-Cache on this timer event.
	7.1.2. 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 is started when an (S,G)-SA message is		(S,G)-SA-State-Timer is started when an (S,G)-SA message is initially
	initially received by a caching MSDP speaker. The timer is reset to		received by a caching MSDP peer. The timer is reset to [SA-State-
	[SA-State-Timer] if another (S,G)-SA message is received before the		Period] if another (S,G)-SA message is received before the (S,G)-SA-
	(S,G)-SA-State-Timer expires. [SA-State-Timer] MUST NOT be less than		State-Timer expires. [SA-State-Period] MUST NOT be less than 90
	90 seconds. The following table summarizes SA-State-Timer		seconds.
	processing:
	Set to | When | Applies to
	[SA-State-Timer] | creating (S,G)-SA cache | (S,G)-SA Cache Entry
	| entry (on receipt of a |
	| (S,G)-SA message) |
	Reset to | When | Applies to
	[SA-State-Timer] | On receipt of (S,G)-SA | (S,G)-SA Cache Entry
	| message |
	Deleted | When | Applies to
	(S,G) SA Cache | Timer expires | (S,G)-SA Cache Entry
	entry | |
	7.1.3. SA-Hold-Down-Timer		8.4. SA-Hold-Down-Timer
	A caching MSDP speaker SHOULD NOT forward an SA message it has		A caching MSDP peer SHOULD NOT forward an SA message it has received
	received in the last SA-Hold-Down interval. [SA-Hold-Down-Timer]		in during the previous [SA-Hold-Down-Period] seconds. [SA-Hold-Down-
	SHOULD be set to 30 seconds. The following table summarizes SA-Hold-		Period] SHOULD be set to 30 seconds. The timer is set to [SA-Hold-
	Down-Timer processing:		Down-Period] upon receipt of an (S,G)-SA message, and reset to [SA-
			Hold-Down-Period] when forwarding an (S,G)-SA message. Finally, the
			timer is deleted when the (S,G)-SA cache entry is deleted.
	Set to | When | Applies to		8.5. KeepAlive Timer
	[SA-Hold-Down-Timer] | Upon receipt of | (S,G)-SA Cache Entry
	| (S,G)-SA message |
	Reset to | When | Applies to		The KeepAlive timer is used by the active connect side of the MSDP
	[SA-Hold-Down-Timer] | When forwarding (S,G)-SA | (S,G)-SA Cache Entry		connection to track the state of the passive-connect side of the
	| message |		connection. In particular, the KeepAlive timer is be used to reset
			the TCP connection when the passive-connect side of the connection
			goes down. The KeepAlive timer is set to [KeepAlive-Period] when
			passive-connect peer comes up. [KeepAlive-Period] SHOULD NOT be less
			that 75 seconds. The timer is reset to [KeepAlive-Period] upon
			receipt of data from peer, and deleted when the timer expires or the
			passive-connect peer closes the connection.
	Deleted | When | Applies to		8.6. ConnectRetry Timer
	(S,G)-SA-Hold-Down-Timer] | (S,G)-SA entry is | (S,G)-SA Cache Entry
	deleted
	7.1.4. KeepAlive Timer		The ConnectRetry timer is used by an MSDP peer to transition from
			INACTIVE to CONNECTING states. There is one timer per peer, and the
			[ConnectRetry-Period] SHOULD be set to 30 seconds. The timer is
			initialized to [ConnectRetry-Period] when an MSDP peer's active
			connect attempt fails. When the timer expires, the peer retries the
			connection and the timer is is reset to [ConnectRetry-Period]. It is
			deleted deleted if either the connection transitions into ESTABLISHED
			state or the peer is deconfigured.
	Set to | When | Applies to		8.7. Peer Hold Timer
	[KeepAliver-Timer] | passive-connect peer comes | each peer
	| up |
	Reset to | When | Applies to		If a system does not receive successive KeepAlive messages (or any SA
	[KeepAliver-Timer] | Receipt of data from peer | each peer		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 MUST be connection closed. [Hold-Time-Period] MUST be at
			least three seconds. A suggested value for [Hold-Time-Period] is 90
			seconds.
	Deleted | When | Applies to		The Hold Timer is initialized to [Hold-Time-Period] when the peer's
	KeepAliver-Timer | Timer expires | each peer		transport connection is established, and is reset to [Hold-Time-
	| or passive-connect peer |		Period] when either a KeepAlive or any SA message is received.
	| closes connection |
	7.2. Intermediate MSDP Speakers		9. Intermediate MSDP Peers
	Intermediate RPs do not originate periodic SA messages on behalf of		Intermediate RPs do not originate periodic SA messages on behalf of
	sources in other domains. In general, an RP MUST only originate an SA		sources in other domains. In general, an RP MUST only originate an SA
	for its own sources.		for its own sources.
	7.3. 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. Only the RP co-located in the same domain as the
	source can restrict SA messages. Note, however, that MSDP peers in		source can restrict SA messages. Note, however, that MSDP peers in
	transit domains should not filter SA messages or the flood-and-join		transit domains should not filter SA messages or the flood-and-join
	model can not guarantee that sources will be known throughout the		model can not guarantee that sources will be known throughout the
	Internet (i.e., SA filtering by transit domains can cause undesired		Internet (i.e., SA filtering by transit domains can cause undesired
	lack of connectivity). In general, policy should be expressed using		lack of connectivity). In general, policy should be expressed using
	MBGP [RFC2283]. This will cause MSDP messages will flow in the		MBGP [RFC2283]. This will cause MSDP messages will flow in the
	desired direction and peer-RPF fail otherwise. An exception occurs at		desired direction and peer-RPF fail otherwise. An exception occurs at
	an administrative scope [RFC2365] boundary. In particular, a SA		an administrative scope [RFC2365] boundary. In particular, a SA
	message for a (S,G) MUST NOT be sent to peers which are on the other		message for a (S,G) MUST NOT be sent to peers which are on the other
	side of an administrative scope boundary for G.		side of an administrative scope boundary for G.
	7.4. SA Requests		11. SA Requests
	If an MSDP peer decides to cache SA state, it MAY accept SA-Requests		If an MSDP peer decides to cache SA state, it MAY accept SA-Requests
	from other MSDP peers. When an MSDP peer receives an SA-Request for a		from other MSDP peers. When an MSDP peer receives an SA-Request for a
	group range, it will respond to the peer with a set of SA entries, in		group range, it will respond to the peer with a set of SA entries, in
	an SA-Response message, for all active sources sending to the group		an SA-Response message, for all active sources sending to the group
	range requested in the SA-Request message. The peer that sends the		range requested in the SA-Request message. The peer that sends the
	request will not flood the responding SA-Response message to other		request will not flood the responding SA-Response message to other
	peers. See section 12 for discussion of error handling relating to SA		peers. See section 17 for discussion of error handling relating to SA
	requests and responses.		requests and responses.
	8. Encapsulated Data Packets		12. Encapsulated Data Packets
	For bursty sources, the RP may encapsulate multicast data from the		For bursty sources, the RP may encapsulate multicast data from the
	source. An interested RP may decapsulate the packet, which SHOULD be		source. An interested RP may decapsulate the packet, which SHOULD be
	forwarded as if a PIM register encapsulated packet was received. That		forwarded as if a PIM register encapsulated packet was received. That
	is, if packets are already arriving over the interface toward the		is, if packets are already arriving over the interface toward the
	source, then the packet is dropped. Otherwise, if the outgoing		source, then the packet is dropped. Otherwise, if the outgoing
	interface list is non-null, the packet is forwarded appropriately.		interface list is non-null, the packet is forwarded appropriately.
	Note that when doing data encapsulation, an implementation MUST bound		Note that when doing data encapsulation, an implementation MUST bound
	the time during which the source which are encapsulated.		the time during which the source which are encapsulated.
	This allows for small bursts to be received before the multicast tree		This allows for small bursts to be received before the multicast tree
	is built back toward the source's domain. For example, an		is built back toward the source's domain. For example, an
	implementation SHOULD encapsulate at least the first packet to		implementation SHOULD encapsulate at least the first packet to
	provide service to bursty sources.		provide service to bursty sources.
	9. Other Scenarios		13. Other Scenarios
	MSDP is not limited to deployment across different routing domains.		MSDP is not limited to deployment across different routing domains.
	It can be used within a routing domain when it is desired to deploy		It can be used within a routing domain when it is desired to deploy
	multiple RPs for different group ranges. As long as all RPs have a		multiple RPs for different group ranges. As long as all RPs have a
	interconnected MSDP topology, each can learn about active sources as		interconnected MSDP topology, each can learn about active sources as
	well as RPs in other domains. Another example is the Anycast RP		well as RPs in other domains.
	mechanism [ANYCASTRP].
	10. MSDP Peer-RPF Forwarding		14. 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, the Peer-RPF check is against the		used when forwarding data packets, the Peer-RPF check is against the
	RP address carried in the SA message.		RP address carried in the SA message.
	10.1. Peer-RPF Forwarding Rules		14.1. Peer-RPF Forwarding Rules
	An SA message originated by an MSDP originator R and received by a		An SA message originated by an MSDP originator R and received by a
	MSDP router from MSDP peer N is accepted if N is the appropriate RPF		MSDP router from MSDP peer N is accepted if N is the appropriate RPF
	neighbor for originator R, and discarded otherwise.		neighbor for originator R, and discarded otherwise.
	The RPF neighbor is chosen using the first of the following rules		The RPF neighbor is chosen using the first of the following rules
	that matches:		that matches:
	(i). R is the RPF neighbor if we have an MSDP peering with R.		(i). R is the RPF neighbor if we have an MSDP peering with R.
	skipping to change at page 9, line 23 ¶		skipping to change at page 9, line 5 ¶
	route), but no external MBGP peerings with them,		route), but no external MBGP peerings with them,
	pick one via a deterministic rule.		pick one via a deterministic rule.
	(vi). The internal MBGP advertiser of the router towards R is		(vi). The internal MBGP advertiser of the router towards R is
	the RPF neighbor if we have an MSDP peering with it.		the RPF neighbor if we have an MSDP peering with it.
	(v). If none of the above match, and we have an MSDP		(v). If none of the above match, and we have an MSDP
	default-peer configured, the MSDP default-peer is		default-peer configured, the MSDP default-peer is
	the RPF neighbor.		the RPF neighbor.
	10.2. MSDP default-peer semantics		14.2. MSDP default-peer semantics
	A MSDP default-peer is much like a default route. It is intended to		A MSDP default-peer is much like a default route. It is intended to
	be used in those cases where a stub network isn't running BGP or		be used in those cases where a stub network isn't running BGP or
	MBGP. A MSDP speaker configured with a default-peer accepts all SA		MBGP. An MSDP peer configured with a default-peer accepts all SA
	messages from the default-peer. Note that a router running BGP or		messages from the default-peer. Note that a router running BGP or
	MBGP SHOULD NOT allow configuration of default peers, since this		MBGP SHOULD NOT allow configuration of default peers, since this
	allows the possibility for SA looping to occur.		allows the possibility for SA looping to occur.
	11. MSDP Connection Establishment		15. MSDP Connection Establishment
	MSDP messages will be encapsulated in a TCP connection using well-		MSDP messages will be encapsulated in a TCP connection. An MSDP peer
	known port 639. One side of the MSDP peering relationship will listen		listens for new TCP connections on port 639. One side of the MSDP
	on the well-known port and the other side will do an active connect		peering relationship will listen on the well-known port and the other
	on the well-known port. The side with the higher peer IP address will		side will do an active connect on the well-known port. The side with
	do the listen. This connection establishment algorithm avoids call		the higher peer IP address will do the listen. This connection
	collision. Therefore, there is no need for a call collision		establishment algorithm avoids call collision. Therefore, there is no
	procedure. It should be noted, however, that the disadvantage of this		need for a call collision procedure. It should be noted, however,
	approach is that it may result in longer startup times at the passive		that the disadvantage of this approach is that it may result in
	end.		longer startup times at the passive end.
	An MSDP speaker starts in the INACTIVE state. MSDP speakers establish		An MSDP peer starts in the INACTIVE state. MSDP peers establish
	peering sessions according to the following state machine:		peering sessions according to the following state machine:
	De-configured or		De-configured or
	disabled		disabled
	+-------------------------------------------+		+-------------------------------------------+
	| |		| |
	| |		| |
	Enable |		Enable |
	+-----|--------->+----------+ |		+-----|--------->+----------+ |
	| | +->| INACTIVE |----------------+ |		| | +->| INACTIVE |----------------+ |
	| | | +----------+ | |		| | | +----------+ | |
	Deconf'ed | | | /|\ /|\ | Higher Address		Deconf'ed | | | /|\ /|\ | | Lower Address
	or | | | | | | |		or | | | | | | |
	disabled | | | | | \|/ |		disabled | | | | | \|/ |
	| | | | | | +-------------+		| | | | | | +-------------+
	| | | | | +---------------| CONNECTING |		| | | | | +---------------| CONNECTING |
	| | | | | Timeout or +-------------+		| | | | | Timeout or +-------------+
	| | | | | Local Address Change |		| | | | | Local Address Change |
	\|/ \|/ | | | |		\|/ \|/ | | | |
	+----------+ | | | |		+----------+ | | | |
	| DISABLED | | | +---------------------+ | TCP Established		| DISABLED | | | +---------------------+ | TCP Established
	+----------+ | | | |		+----------+ | | | |
	/|\ /|\ | | Connection Timeout, | |		/|\ /|\ | | Connection Timeout, | |
	| | | | Local Address change, | |		| | | | Local Address change, | |
	| | | | Authorization Failure | |		| | | | Authorization Failure | |
	| | | | | |		| | | | | |
	| | | | | \|/		| | | | | \|/
	| | | | +-------------+		| | | | +-------------+
	| | Local | | | ESTABLISHED |		| | Local | | | ESTABLISHED |
	| | Address | | Lower Address +-------------+		| | Address | | Higher Address +-------------+
	| | Change | \|/ /|\ |		| | Change | \|/ /|\ |
	| | | +--------+ | |		| | | +--------+ | |
	| | +--| LISTEN |--------------------+ |		| | +--| LISTEN |--------------------+ |
	| | +--------+ TCP Accept |		| | +--------+ TCP Accept |
	| | | |		| | | |
	| | | |		| | | |
	| +---------------+ |		| +---------------+ |
	| De-configured or |		| De-configured or |
	| disabled |		| disabled |
	| |		| |
	+------------------------------------------------------+		+------------------------------------------------------+
	De-configured or		De-configured or
	disabled		disabled
	12. Packet Formats		16. 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.
	12.1. MSDP TLV format:		16.1. MSDP TLV format:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length | Value .... |		| Type | Length | Value .... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type (8 bits)		Type (8 bits)
	Describes the format of the Value field.		Describes the format of the Value field.
	Length (16 bits)		Length (16 bits)
	Length of Type, Length, and Value fields in octets. The		Length of Type, Length, and Value fields in octets. The
	minimum length required is 3 octets.		minimum length required is 4 octets. The total length
			of the TLV should be a multiple of 2 octets.
	Value (variable length)		Value (variable length)
	Format is based on the Type value. See below. The length of		Format is based on the Type value. See below. The length of
	the value field is Length field minus 3.		the value field is Length field minus 3. All reserved fields
			in the Value field MUST be transmitted as zeros and ignored on
			receipt.
	12.2. Defined TLVs		16.2. 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 Notification
	Each TLV is described below.		Each TLV is described below.
	12.2.1. IPv4 Source-Active TLV		16.2.1. IPv4 Source-Active TLV
	The maximum size SA message that can be sent is 1400 octets. If an		The maximum size SA message that can be sent is 1400 octets. If an
	MSDP peer needs to originate a message with information greater than		MSDP peer needs to originate a message with information greater than
	1400 octets, it sends successive 1400-octet messages. The 1400 octet		1400 octets, it sends successive 1400-octet messages. The 1400 octet
	size does not include the TCP, IP, layer-2 headers.		size does not include the TCP, IP, layer-2 headers.
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 1 | x + y | Entry Count |		| 1 | x + y | Entry Count |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RP Address |		| RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reserved | Sprefix Len | \		| Reserved | Sprefix Len | \
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \
	| Group Address | ) z		| Group Address | ) z
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
	| Source Address | /		| Source Address | /
	skipping to change at page 12, line 50 ¶		skipping to change at page 13, line 8 ¶
	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 ignored		The Reserved field MUST be transmitted as zeros and ignored
	by a receiver.		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
			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.
	12.2.2. IPv4 Source-Active Request TLV		16.2.2. IPv4 Source-Active Request TLV
	The Source-Active Request is used to request SA-state from a caching		The Source-Active Request is used to request SA-state from a caching
	MSDP peer. If an RP in a domain receives a PIM Join message for 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, creates (*,G) state and wants to know all active sources for
	group G, and it has been configured to peer with an SA-state caching		group G, and it has been configured to peer with an SA-state caching
	peer, it may send an SA-Request message for the group.		peer, it may send an SA-Request message for the group.
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 2 | 8 | Reserved |		| 2 | 8 | Gprefix Len |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address |		| Group Address Prefix |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	IPv4 Source-Active Request TLV is type 2.		IPv4 Source-Active Request TLV is type 2.
	Reserved		Gprefix Len
	The Reserved field MUST be transmitted as zeros and ignored		The route prefix length associated with the group address prefix.
	by a receiver.
	Group Address		Group Address
	The group address the MSDP peer is requesting.		The group address the MSDP peer is requesting.
	12.2.3. IPv4 Source-Active Response TLV		16.2.3. IPv4 Source-Active Response TLV
	The Source-Active Response is sent in response to a Source-Active		The Source-Active Response is sent in response to a Source-Active
	Request message. The Source-Active Response message has the same		Request message. The Source-Active Response message has the same
	format as a Source-Active message but does not allow encapsulation of		format as a Source-Active message but does not allow encapsulation of
	multicast data.		multicast data.
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 3 | x | .... |		| 3 | x | .... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	IPv4 Source-Active Response TLV is type 3.		IPv4 Source-Active Response TLV is type 3.
	Length x		Length x
	Is the length of the control information in the message. x is 8		Is the length of the control information in the message. x is 8
	octets (for the first two 32-bit quantities) plus 12 times Entry		octets (for the first two 32-bit quantities) plus 12 times Entry
	Count octets.		Count octets.
	12.2.4. KeepAlive TLV		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 after a period of time. This message		MSDP messages sent to the peer after a period of time. This message
	is necessary for the active connect side of the MSDP connection. The		is necessary for the active connect side of the MSDP connection. The
	passive connect side of the connection knows that the connection will		passive connect side of the connection knows that the connection will
	be reestablished when a TCP SYN packet is sent from the active		be reestablished when a TCP SYN packet is sent from the active
	connect side. However, the active connect side will not know when the		connect side. However, the active connect side will not know when the
	passive connect side goes down. Therefore, the KeepAlive timeout will		passive connect side goes down. Therefore, the KeepAlive timeout will
	be used to reset the TCP connection.		be used to reset the TCP connection.
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 4 | 4 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| 4 | 3 |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The length of the message is 4 octets which encompasses the 1-octet		The length of the message is 3 octets which encompasses the one octet
	Type field and the 2-octet Length field, plus the Reserved field. The		Type field and the two octet Length field.
	Reserved field MUST be transmitted as zeros and ignored by a
	receiver.
	12.2.5. Notification TLV		16.2.5. Notification TLV
	A Notification message is sent when an error condition is detected,		A Notification message is sent when an error condition is detected,
	and has the following form:		and has the following form:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 5 | x + 5 |O| Error Code |		| 5 | x + 5 |O| Error Code |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Error subcode | ... |		| Error subcode | ... |
	+-+-+-+-+-+-+-+-+ |		+-+-+-+-+-+-+-+-+ |
	| Data |		| Data |
	| ... |		| ... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Type
	The Notification TLV is type 7.		The Notification TLV is type 5.
	Length		Length
	Length is a two octet field with value x + 5, where x is		Length is a two octet field with value x + 5, where x is
	the length of the notification data field.		the length of the notification data field.
	O-bit		O-bit
	Open-bit. If reset, the connection will be closed [MASC].		Open-bit. If clear, the connection will be closed.
	Error code		Error code
	This 7-bit unsigned integer indicates the type of Notification.		This 7-bit unsigned integer indicates the type of Notification.
	The following Error Codes have been defined:		The following Error Codes have been defined:
	Error Code Symbolic Name Reference		Error Code Symbolic Name Reference
	1 Message Header Error Section 12.3		1 Message Header Error Section 17.1
			2 SA-Request Error Section 17.2
	2 Finite State Machine Error Section 12.4		3 SA-Message/SA-Response Error Section 17.3
			4 Hold Timer Expired Section 17.4
	3 Notification Message Error Section 12.5		5 Finite State Machine Error Section 17.5
			6 Notification Section 17.6
	4 SA-Request Error Section 12.6		7 Cease Section 17.7
	5 SA-Response Error Section 12.7
	6 SA-Message Error Section 12.8
	Error subcode:		Error subcode:
	This one-octet unsigned integer provides more specific information		This one-octet unsigned integer provides more specific information
	about the reported error. Each Error Code may have one or more Error		about the reported error. Each Error Code may have one or more Error
	Subcodes associated with it. If no appropriate Error Subcode is		Subcodes associated with it. If no appropriate Error Subcode is
	defined, then a zero (Unspecific) value is used for the Error Subcode		defined, then a zero (Unspecific) value is used for the Error Subcode
	field, and the O-bit must be reset (i.e. the connection will be		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 =		closed). The used notation in the error description below is: MC =
	Must Close connection = O-bit reset; CC = Can Close connection =		Must Close connection = O-bit clear; CC = Can Close connection =
	O-bit might be reset [MASC].		O-bit might be cleared.
	Message Header Error subcodes:		Message Header Error subcodes:
	0 - Unspecific (MC)		0 - Unspecific (MC)
	1 - Bad Message Length (MC)		2 - Bad Message Length (MC)
	2 - Bad Message Type (MC)		3 - Bad Message Type (CC)
			SA-Request Error subcodes:
			0 - Unspecific (MC)
			1 - Does not cache SA (MC)
			2 - 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:		Finite State Machine Error subcodes:
	0 - Unspecific (MC)		0 - Unspecific (MC)
	1 - Unexpected Message Type FSM Error (MC)		1 - Unexpected Message Type FSM Error (MC)
	Notification subcodes (the O-bit is always reset):		Notification subcodes (the O-bit is always clear):
	0 - Unspecific (CC)		0 - Unspecific (MC)
	SA-Request Error subcodes:		Cease subcodes (the O-bit is always clear):
	0 - Not caching (MC)		0 - Unspecific (MC)
	0 - Invalid Group Address prefix (CC)
	SA-Reponse Error subcodes:		17. MSDP Error Handling
	0 - Didn't send Request (MC)		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].
	SA-Message Error subcodes		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 might be
			closed. If no Error Subcode is specified, then a zero (Unspecific)
			must be used.
	0 - Invalid Entry Count (CC)		The phrase "the MSDP connection is closed" means that the transport
	1 - Invalid RP Address (CC)		protocol connection has been closed and that all resources for that
	2 - Invalid Group Address (CC)		MSDP connection have been deallocated.
	3 - Invalid Source Address (CC)
	4 - Invalid Sprefix Length (CC)
	5 - Looping SA (Self is RP) (CC)
	6 - Unknown Encapsulation (MC)
	12.3. Message Header Error Handling		17.1. Message Header Error Handling
	All errors detected while processing the Message Header are indicated		All errors detected while processing the Message Header are indicated
	by sending the Notification message with Error Code Message Header		by sending the Notification message with Error Code Message Header
	Error. The Error Subcode describes the specific nature of the error.		Error. The Error Subcode describes the specific nature of the error.
	The Data field contains the erroneous Message (including the message		The Data field contains the erroneous Message (including the message
	header).		header).
	If the Length field of the message header is less than 4 or greater		If the Length field of the message header is less than 4 or greater
	than 1400, or the length of a Keepalive message is not equal to 4,		than 1400, or the length of a KeepAlive message is not equal to 3,
	then the Error Subcode is set to Bad Message Length.		then the Error Subcode is set to Bad Message Length.
	If the Type field of the message header is not recognized, then the		If the Type field of the message header is not recognized, then the
	Error Subcode is set to Bad Message Type.		Error Subcode is set to Bad Message Type.
	12.4. Finite State Machine Error Handling		17.2. SA-Request 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.
	12.5. 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 reset, a Notification
	with O-bit reset, 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 reset, 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.
	12.6. SA-Request Error Handling
	The SA-Request Error code is used to signal the receipt of a SA		The SA-Request Error code is used to signal the receipt of a SA
	request at a non-caching MSDP speaker, or at a caching MSDP speaker		request at a non-caching MSDP peer, or at a caching MSDP peer when an
	when an invalid group address requested.		invalid group address requested.
	When a non-caching MSDP speaker receives an SA-Request, it returns		When a non-caching MSDP peer receives an SA-Request, it returns the
	the following notification and closes the connection:		following notification:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 16 |O| 4 |		| 5 | 12 |O| 2 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x0 | Reserved |		| 1 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Group Address |		| Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	If a caching MSDP speaker receives a request for an invalid group, it		If a caching MSDP peer receives a request for an invalid group, it
	returns the following notification and closes the connection:		returns the following notification:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 12 |O| 4 |		| 5 | 12 |O| 2 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x1 | Reserved |		| 2 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Invalid Group Address |		| Invalid Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.7. SA-Response Error Handling		17.3. SA-Message/SA-Response Error Handling
	The SA-Response Error code is used to signal the receipt of a SA
	Response at MSDP speaker which did not issue a SA-Request to the
	peer. It has the following form:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 8 |O| 5 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x0 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.8. SA-Message Error Handling
	The SA-Message Error code is used to signal the receipt of an SA		The SA-Message/SA-Response Error code is used to signal the receipt
	message that contains invalid data.		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:
	12.8.1. Invalid Entry Count		17.3.1. Invalid Entry Count (IEC)
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 12 |O| 6 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x0 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Invalid Entry Count |		| 5 | 6 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| 1 | IEC |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.8.2. Invalid RP Address		17.3.2. Invalid RP Address
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 12 |O| 6 |		| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x1 | Reserved |		| 2 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Invalid RP Address |		| Invalid RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.8.3. Invalid Group Address		17.3.3. Invalid Group Address
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 12 |O| 6 |		| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x2 | Reserved |		| 3 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Invalid Group Address |		| Invalid Group Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.8.4. Invalid Source Address		17.3.4. Invalid Source Address
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 12 |O| 6 |		| 5 | 12 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x3 | Reserved |		| 4 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Invalid Source Address |		| Invalid Source Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.9. Invalid Sprefix Length		17.3.5. Invalid Sprefix Length (ISL)
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 12 |O| 6 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x4 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Invalid Sprefix Length |		| 5 | 6 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| 5 | ISL |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.10. Looping SAs (Self is RP in received SA)		17.3.6. Looping SAs (Self is RP in received SA)
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 8 |O| 6 |		| 5 | x + 5 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x5 | Reserved |		| 6 | Looping SA Message ....
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.11. Unknown Encapsulation		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		This notification is sent on receipt of SA data that is encapsulated
	in an unknown encapsulation type. See section 12.12 for known		in an unknown encapsulation type. See section 18 for known
	encapsulations.		encapsulations.
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 7 | 8 |O| 6 |		| 5 | x + 5 |O| 3 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| 0x6 | Reserved |		| 7 | SA Message ....
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.12. SA Data Encapsulation		Length x
			x is the length of the SA message (which contained data which
			was encapsulated in some unknown way) that is with contained in the
			data field of the Notification message.
	This section describes UDP and GRE encapsulation of SA data.		17.3.8. Adminstrative 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 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 | 16 |O| 3 |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| 8 | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Peer IP Address |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Group Address |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			17.4. Hold Time Expired
			If a system does not receive successive KEEPALIVE or any SA Message
			and/or Notification messages within the period specified in the Hold
			Timer, then the notification message with Hold Timer Expired Error
			Code 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 TCPC encapsulation of SA data.
	Encapsulation type is a configuration option.		Encapsulation type is a configuration option.
	12.12.1. UDP Data Encapsulation		18.1. UDP Data Encapsulation
	MSDP SA-data MAY be encapsulated in UDP. In this case, the UDP		Data packets MAY be encapsulated in UDP. In this case, the UDP
	psuedo-header has the following form:		pseudo-header has the following form:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Source Port | Destination Port |		| Source Port | Destination Port |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Length | Checksum |		| Length | Checksum |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Origin RP Address |		| Origin RP Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			The Source port, Destination Port, Length, and Checksum are used
	Source Port		according to RFC 768. Source and Destination ports are known via an
	Port to be used by the remote end, and is known via		implementation-specific method (e.g. per-peer configuration).
	configuration.
	Destination Port
	The Destination Port is set to the remote endpoint's Source port,
	and is known via configuration.
	Length
	Length is the length in octets of this user datagram
	including this header and the data. The minimum value
	of the length is twelve.
	Checksum		Checksum
	The checksum is computed according to RFC 768 [RFC768].		The checksum is computed according to RFC 768 [RFC768].
	Originating RP Address		Originating RP Address
	The Originating RP Address is the address of the RP sending		The Originating RP Address is the address of the RP sending
	the encapsulated data.		the encapsulated data.
	12.12.2. GRE Encapsulation		18.2. GRE Encapsulation
	MSDP SA-data MAY be encapsulated in GRE using protocol type [MSDP-		MSDP SA-data MAY be encapsulated in GRE using protocol type [MSDP-
	GRE-ProtocolType].		GRE-ProtocolType]. The GRE header and payload packet have the
			following form:
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Delivery Headers ..... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|C| Reserved0 | Ver | [MSDP-GRE-ProtocolType] |\		|C| Reserved0 | Ver | [MSDP-GRE-ProtocolType] |\
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GRE Header
	| Checksum (optional) | Reserved1 |/		| Checksum (optional) | Reserved1 |/
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Originating RP IPv4 Address |\		| Originating RP IPv4 Address |\
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Payload
	| (S,G) Data Packet .... /		| (S,G) Data Packet .... /
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	12.12.2.1. GRE Encapsulation and PMTU Discovery [RFC1191]		18.2.1. GRE Encapsulation and Path MTU Discovery [RFC1191]
	Existing implementations of GRE, when using IPv4 as the Delivery		Existing implementations of GRE, when using IPv4 as the Delivery
	Header, do not implement Path MTU discovery and do not set the Don't		Header, do not implement Path MTU discovery and do not set the Don't
	Fragment bit in the Delivery Header. This can cause large packets to		Fragment bit in the Delivery Header. This can cause large packets to
	become fragmented within the tunnel and reassembled at the tunnel		become fragmented within the tunnel and reassembled at the tunnel
	exit (independent of whether the payload packet is using PMTU). If a		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 were to use Path MTU discovery, however, that
	tunnel entry point would also need to relay ICMP unreachable error		tunnel entry point would also need to relay ICMP unreachable error
	messages (in particular the "fragmentation needed and DF set" code)		messages (in particular the "fragmentation needed and DF set" code)
	back to the originator of the packet, which is not required by the		back to the originator of the packet, which is not required by the
	GRE specification [GRE]. Failure to properly relay Path MTU		GRE specification [GRE]. Failure to properly relay Path MTU
	information to an originator can result in the following behavior:		information to an originator can result in the following behavior:
	the originator sets the don't fragment bit, the packet gets dropped		the originator sets the don't fragment bit, the packet gets dropped
	within the tunnel, but since the originator doesn't receive proper		within the tunnel, but since the originator doesn't receive proper
	feedback, it retransmits with the same PMTU, causing subsequently		feedback, it retransmits with the same PMTU, causing subsequently
	transmitted packets to be dropped.		transmitted packets to be dropped.
	13. Security Considerations		18.3. TCP Data Encapsulation
			As discussed earlier, encapsulation of data in SA messages MAY be
			supported for backwards compatibility with legacy MSDP peers.
			19. Security Considerations
	An MSDP implementation MAY use IPsec [RFC1825] or keyed MD5 [RFC1828]		An MSDP implementation MAY use IPsec [RFC1825] or keyed MD5 [RFC1828]
	to secure control messages. When encapsulating SA data in GRE,		to secure control messages. When encapsulating SA data in GRE,
	security should be relatively similar to security in a normal IPv4		security should be relatively similar to security in a normal IPv4
	network, as routing using GRE follows the same routing that IPv4 uses		network, as routing using GRE follows the same routing that IPv4 uses
	natively. Route filtering will remain unchanged. However packet		natively. Route filtering will remain unchanged. However packet
	filtering at a firewall requires either that a firewall look inside		filtering at a firewall requires either that a firewall look inside
	the GRE packet or that the filtering is done on the GRE tunnel		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		endpoints. In those environments in which this is considered to be a
	security issue it may be desirable to terminate the tunnel at the		security issue it may be desirable to terminate the tunnel at the
	firewall.		firewall.
	14. Acknowledgments		20. Acknowledgments
	The authors would like to thank Dave Thaler, Bill Nickless, John		The authors would like to thank Bill Nickless, John Meylor, Liming
	Meylor, Liming Wei, Manoj Leelanivas, Mark Turner, John Zwiebel, and		Wei, Manoj Leelanivas, Mark Turner, John Zwiebel, and Cristina
	Cristina Radulescu-Banu for their design feedback and comments. Bill		Radulescu-Banu for their design feedback and comments. In addition to
	Fenner also made many contributions, including clarification of the		many other contributions, Tom Pusateri helped to clarify the
			connection state machine, Dave Thaler helped to clarify the
			Notification message types, and Bill Fenner helped to clarify the
	Peer-RPF rules.		Peer-RPF rules.
	15. Author's Address:		21. Author's Address:
	Dino Farinacci		Dino Farinacci
	Procket Networks		Procket Networks
	3850 No. First St., Ste. C		3850 No. First St., Ste. C
	San Jose, CA 95134		San Jose, CA 95134
	Email: dino@procket.com		Email: dino@procket.com
	Yakov Rehkter		Yakov Rehkter
	Cisco Systems, Inc.		Cisco Systems, Inc.
	170 Tasman Drive		170 Tasman Drive
	skipping to change at page 25, line 5 ¶		skipping to change at page 25, line 5 ¶
	3060 Williams Drive		3060 Williams Drive
	Fairfax, VA 22031		Fairfax, VA 22031
	Email: jhall@uu.net		Email: jhall@uu.net
	David Meyer		David Meyer
	Cisco Systems, Inc.		Cisco Systems, Inc.
	170 Tasman Drive		170 Tasman Drive
	San Jose, CA, 95134		San Jose, CA, 95134
	Email: dmm@cisco.com		Email: dmm@cisco.com
	16. REFERENCES		22. REFERENCES
	[ANYCASTRP] Meyer, et. al, "Anycast RP mechanism using PIM and
	MSDP", draft-ietf-mboned-anycast-rp-04.txt, November,
	1999. Work in Progress.
	[GRE] Farinacci, D., et al., "Generic Routing Encapsulation		[GRE] Farinacci, D., et al., "Generic Routing Encapsulation
	(GRE)", draft-meyer-gre-update-02.txt, January,		(GRE)", draft-meyer-gre-update-02.txt, January,
	2000. Work in Progress.		2000. Work in Progress.
	[MASC] Estrin, D., et al., "The Multicast Address-Set Claim
	(MASC) Protocol", draft-ietf-malloc-masc-04.txt,
	October, 1999. Work in Progress.
	[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
			(BGP-4)", RFC 1771, March 1995.
	[RFC1825] Atkinson, R., "Security Architecture for the Internet		[RFC1825] Atkinson, R., "Security Architecture for the Internet
	Protocol", RFC 1825, August, 1995.		Protocol", RFC 1825, August, 1995.
	[RFC1828] P. Metzger and W. Simpson, "IP Authentication using		[RFC1828] P. Metzger and W. Simpson, "IP Authentication using
	Keyed MD5", RFC 1828, August, 1995.		Keyed MD5", RFC 1828, August, 1995.
	[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate		[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
	Requirement Levels", RFC 2119, March, 1997.		Requirement Levels", RFC 2119, March, 1997.
	[RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter.,		[RFC2283] Bates, T., Chandra, R., Katz, D., and Y. Rekhter.,
End of changes. 137 change blocks.
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