rfc9856v2.txt		rfc9856.txt
	skipping to change at line 373 ¶		skipping to change at line 373 ¶
	* For example, if PE1 uses "IR", it will forward (S1,G1) only to		* For example, if PE1 uses "IR", it will forward (S1,G1) only to
	downstream PEs that have issued a "SMET" route for (S1,G1),		downstream PEs that have issued a "SMET" route for (S1,G1),
	such as PE2 and PE3.		such as PE2 and PE3.
	* If PE1 uses a P-tunnel type other than IR (e.g., AR or BIER),		* If PE1 uses a P-tunnel type other than IR (e.g., AR or BIER),
	PE1 will advertise an "S-PMSI Auto-Discovery (A-D)" route for		PE1 will advertise an "S-PMSI Auto-Discovery (A-D)" route for
	(S1,G1). Downstream PEs, such as PE2 and PE3, will then join		(S1,G1). Downstream PEs, such as PE2 and PE3, will then join
	the corresponding multicast tree to receive the flow.		the corresponding multicast tree to receive the flow.
	Procedures for Model (b) are specified in [RFC9251].		Procedures for Model (b) are specified in [RFC9251] and [RFC9572].
	1.2.2. Inter-Subnet IP Multicast Forwarding		1.2.2. Inter-Subnet IP Multicast Forwarding
	When the sources and receivers are connected to different BDs within		When the sources and receivers are connected to different BDs within
	the same tenant domain, the EVPN network can deliver IP multicast		the same tenant domain, the EVPN network can deliver IP multicast
	traffic using either Inclusive or Selective Multicast Trees, as		traffic using either Inclusive or Selective Multicast Trees, as
	illustrated in Figure 2 with models (a) and (b), respectively.		illustrated in Figure 2 with models (a) and (b), respectively.
	S1 + S1 +		S1 + S1 +
	(a) + | (b) + |		(a) + | (b) + |
	skipping to change at line 577 ¶		skipping to change at line 577 ¶
	redundant multicast sources while maintaining high reliability and		redundant multicast sources while maintaining high reliability and
	operational efficiency.		operational efficiency.
	2. Solution Overview		2. Solution Overview
	An SFG can be represented as (*,G) if any source transmitting		An SFG can be represented as (*,G) if any source transmitting
	multicast traffic to group G is considered a redundant G-source.		multicast traffic to group G is considered a redundant G-source.
	Alternatively, this document allows an SFG to be represented as		Alternatively, this document allows an SFG to be represented as
	(S,G), where the source IP address S is a prefix of variable length.		(S,G), where the source IP address S is a prefix of variable length.
	In this case, a source is deemed a redundant G-source for the SFG if		In this case, a source is deemed a redundant G-source for the SFG if
	its address falls within the specified prefix. The use of variable-		its address falls within the specified prefix. In the remainder of
	length prefixes in source advertisements via S-PMSI A-D routes is		this document, some examples use (*,G) state for brevity. Wherever
	permitted in this document only for the specific application of		an SFG is represented as (*,G), it should be understood as being
	redundant G-sources.		interchangeable with (S,G). The use of variable-length prefixes in
			source advertisements via S-PMSI A-D routes is permitted in this
			document only for the specific application of redundant G-sources.
	This document describes two solutions for handling redundant		This document describes two solutions for handling redundant
	G-sources:		G-sources:
	* Warm Standby Solution		* Warm Standby Solution
	* Hot Standby Solution		* Hot Standby Solution
	2.1. Warm Standby Solution		2.1. Warm Standby Solution
	The Warm Standby solution is an upstream PE-based solution, where		The Warm Standby solution is an upstream PE-based solution, where
	downstream PEs do not participate in the procedures. In this		downstream PEs do not participate in the procedures. In this
	solution, all upstream PEs connected to redundant G-sources for an		solution, all upstream PEs connected to redundant G-sources for an
	SFG (*,G) or (S,G) elect a "Single Forwarder (SF)" among themselves.		SFG (*,G) or (S,G) elect a "Single Forwarder (SF)" among themselves.
	After the Single Forwarder is elected, the upstream PEs apply Reverse		After the Single Forwarder is elected, the upstream PEs apply Reverse
	Path Forwarding checks to the multicast state for the SFG:		Path Forwarding checks to the multicast state for the SFG:
	* Non-Single Forwarder Behavior: A non-Single Forwarder upstream PE		* Non-Single Forwarder (Non-SF) Behavior: A Non-SF upstream PE
	discards all (*,G) or (S,G) packets received over its local AC.		discards all (*,G) or (S,G) packets received over its local AC.
	* Single Forwarder Behavior: The Single Forwarder accepts and		* Single Forwarder Behavior: The Single Forwarder accepts and
	forwards (*,G) or (S,G) packets received on a single local AC for		forwards (*,G) or (S,G) packets received on a single local AC for
	the SFG. If packets are received on multiple local ACs, the		the SFG. If packets are received on multiple local ACs, the
	Single Forwarder discards packets on all but one. The selection		Single Forwarder discards packets on all but one. The selection
	of the AC for forwarding is a local implementation detail.		of the AC for forwarding is a local implementation detail.
	In the event of a failure of the Single Forwarder, a new Single		In the event of a failure of the Single Forwarder, a new Single
	Forwarder is elected among the upstream PEs. This election process		Forwarder is elected among the upstream PEs. This election process
	skipping to change at line 754 ¶		skipping to change at line 756 ¶
	* MUST advertise an S-PMSI A-D route for the SFG:		* MUST advertise an S-PMSI A-D route for the SFG:
	- An (*,G) route if the SFG is configured for any source.		- An (*,G) route if the SFG is configured for any source.
	- An (S,G) route (where S can have any prefix length) if the		- An (S,G) route (where S can have any prefix length) if the
	SFG is configured for a source prefix.		SFG is configured for a source prefix.
	* MUST include the following attributes in the S-PMSI A-D route:		* MUST include the following attributes in the S-PMSI A-D route:
	- Route Targets (RTs): The Supplementary Broadcast Domain		- Route Targets (RTs): The Broadcast Domain Route Target (BD-
	Route Target (SBD-RT), if applicable, and the Broadcast		RT) of the BD receiving the traffic and, if applicable, the
	Domain Route Target (BD-RT) of the Broadcast Domain		Supplementary Broadcast Domain Route Target (SBD-RT), which
	receiving the traffic. The SBD-RT is needed so that the		is needed so that the route is imported by all PEs attached
	route is imported by all PEs attached to the tenant domain		to the tenant domain in an OISM solution.
	in an OISM solution.
	- Multicast Flags Extended Community: MUST include the SFG		- Multicast Flags Extended Community: MUST include the SFG
	flag to indicate that the route conveys an SFG.		flag to indicate that the route conveys an SFG.
	- Designated Forwarder Election Extended Community: Specifies		- Designated Forwarder Election Extended Community: Specifies
	the algorithm and preferences for the Single Forwarder		the algorithm and preferences for the Single Forwarder
	election, using the DF election defined in [RFC8584].		election, using the DF election defined in [RFC8584].
	* Advertises the route:		* Advertises the route:
	skipping to change at line 816 ¶		skipping to change at line 817 ¶
	capabilities, the tie-breaker is the lowest PE IP address		capabilities, the tie-breaker is the lowest PE IP address
	(as advertised in the Originator Address field of the		(as advertised in the Originator Address field of the
	S-PMSI A-D route).		S-PMSI A-D route).
	4. Reverse Path Forwarding Checks on the Upstream PEs		4. Reverse Path Forwarding Checks on the Upstream PEs
	All PEs with a local G-source for an SFG apply a Reverse Path		All PEs with a local G-source for an SFG apply a Reverse Path
	Forwarding check to the (*,G) or (S,G) state based on the Single		Forwarding check to the (*,G) or (S,G) state based on the Single
	Forwarder election result:		Forwarder election result:
	1. Non-Single Forwarder PEs: MUST discard all (*,G) or (S,G)		1. Non-SF PEs: MUST discard all (*,G) or (S,G) packets received
	packets received on local ACs.		on local ACs.
	2. Single Forwarder PEs: MUST forward (*,G) or (S,G) packets		2. Single Forwarder PEs: MUST forward (*,G) or (S,G) packets
	received on one (and only one) local AC.		received on one (and only one) local AC.
	Key Features of the Warm Standby Solution:		Key Features of the Warm Standby Solution:
	* The solution ensures redundancy for SFGs without requiring		* The solution ensures redundancy for SFGs without requiring
	upgrades to downstream PEs (where no redundant G-sources are		upgrades to downstream PEs (where no redundant G-sources are
	connected).		connected).
	* Existing procedures for non-SFG G-sources remain unchanged.		* Existing procedures for Non-SFG G-sources remain unchanged.
	* Redundant G-sources can be either single-homed or multi-homed.		* Redundant G-sources can be either single-homed or multi-homed.
	Multi-homing does not alter the above procedures.		Multi-homing does not alter the above procedures.
	Examples of the Warm Standby solution are provided in Sections 4.2		Examples of the Warm Standby solution are provided in Sections 4.2
	and 4.3.		and 4.3.
	4.2. Warm Standby Example in an OISM Network		4.2. Warm Standby Example in an OISM Network
	Figure 4 illustrates an example where S1 and S2 are redundant		Figure 4 illustrates an example where S1 and S2 are redundant
	skipping to change at line 912 ¶		skipping to change at line 913 ¶
	* Based on the Designated Forwarder Election Extended Community,		* Based on the Designated Forwarder Election Extended Community,
	PE1 and PE2 perform Single Forwarder election.		PE1 and PE2 perform Single Forwarder election.
	* Assuming they use Preference-based Election [RFC9785], PE1		* Assuming they use Preference-based Election [RFC9785], PE1
	(with a higher preference) is elected as the Single Forwarder		(with a higher preference) is elected as the Single Forwarder
	for (*,G1).		for (*,G1).
	4. Reverse Path Forwarding check on the PEs attached to a redundant		4. Reverse Path Forwarding check on the PEs attached to a redundant
	G-source		G-source
	a. Non-Single Forwarder Behavior: PE2 discards all (*,G1)		a. Non-SF Behavior: PE2 discards all (*,G1) packets received on
	packets received on its local AC.		its local AC.
	b. Single Forwarder Behavior: PE1 forwards (*,G1) packets		b. Single Forwarder Behavior: PE1 forwards (*,G1) packets
	received on one (and only one) local AC.		received on one (and only one) local AC.
	The outcome:		The outcome:
	* Upon receiving IGMP/MLD reports for (*,G1) or (S,G1), downstream		* Upon receiving IGMP/MLD reports for (*,G1) or (S,G1), downstream
	PEs (PE3 and PE5) issue SMET routes to pull the multicast Single		PEs (PE3 and PE5) issue SMET routes to pull the multicast Single
	Flow Group traffic from PE1 only.		Flow Group traffic from PE1 only.
End of changes. 7 change blocks.
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