draft-ietf-pim-drlb-07.txt		draft-ietf-pim-drlb-08.txt
	Network Working Group Yiqun. Cai		Network Working Group Yiqun. Cai
	Internet-Draft Heidi. Ou		Internet-Draft Heidi. Ou
	Intended status: Standards Track Alibaba Group		Intended status: Standards Track Alibaba Group
	Expires: July 20, 2018 Sri. Vallepalli		Expires: December 21, 2018 Sri. Vallepalli
	Mankamana. Mishra		Mankamana. Mishra
	Stig. Venaas		Stig. Venaas
	Cisco Systems		Cisco Systems
	Andy. Green		Andy. Green
	British Telecom		British Telecom
	January 16, 2018		June 19, 2018
	PIM Designated Router Load Balancing		PIM Designated Router Load Balancing
	draft-ietf-pim-drlb-07		draft-ietf-pim-drlb-08
	Abstract		Abstract
	On a multi-access network, one of the PIM routers is elected as a		On a multi-access network, one of the PIM routers is elected as a
	Designated Router (DR). On the last hop LAN, the PIM DR is		Designated Router (DR). On the last hop LAN, the PIM DR is
	responsible for tracking local multicast listeners and forwarding		responsible for tracking local multicast listeners and forwarding
	traffic to these listeners if the group is operating in PIM-SM. In		traffic to these listeners if the group is operating in PIM-SM. In
	this document, we propose a modification to the PIM-SM protocol that		this document, we propose a modification to the PIM-SM protocol that
	allows more than one of these last hop routers to be selected so that		allows more than one of these last hop routers to be selected so that
	the forwarding load can be distributed among these routers.		the forwarding load can be distributed among these routers.
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on July 20, 2018.		This Internet-Draft will expire on December 21, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 21 ¶		skipping to change at page 2, line 21 ¶
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
	3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 5		3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 5
	4. Functional Overview . . . . . . . . . . . . . . . . . . . . . 6		4. Functional Overview . . . . . . . . . . . . . . . . . . . . . 6
	4.1. GDR Candidates . . . . . . . . . . . . . . . . . . . . . 7		4.1. GDR Candidates . . . . . . . . . . . . . . . . . . . . . 6
	4.2. Hash Mask and Hash Algorithm . . . . . . . . . . . . . . 7		4.2. Hash Mask and Hash Algorithm . . . . . . . . . . . . . . 7
	4.3. Modulo Hash Algorithm . . . . . . . . . . . . . . . . . . 8		4.3. Modulo Hash Algorithm . . . . . . . . . . . . . . . . . . 8
	4.4. PIM Hello Options . . . . . . . . . . . . . . . . . . . . 9		4.4. PIM Hello Options . . . . . . . . . . . . . . . . . . . . 9
	5. Hello Option Formats . . . . . . . . . . . . . . . . . . . . 10		5. Hello Option Formats . . . . . . . . . . . . . . . . . . . . 9
	5.1. PIM DR Load Balancing Capability (DRLBC) Hello Option . . 10		5.1. PIM DR Load Balancing Capability (DRLBC) Hello Option . . 9
	5.2. PIM DR Load Balancing GDR (DRLBGDR) Hello Option . . . . 10		5.2. PIM DR Load Balancing GDR (DRLBGDR) Hello Option . . . . 10
	6. Protocol Specification . . . . . . . . . . . . . . . . . . . 11		6. Protocol Specification . . . . . . . . . . . . . . . . . . . 11
	6.1. PIM DR Operation . . . . . . . . . . . . . . . . . . . . 12		6.1. PIM DR Operation . . . . . . . . . . . . . . . . . . . . 11
	6.2. PIM GDR Candidate Operation . . . . . . . . . . . . . . . 12		6.2. PIM GDR Candidate Operation . . . . . . . . . . . . . . . 12
	6.2.1. Router receives new DRLBGDR . . . . . . . . . . . . . 13		6.2.1. Router Receives New DRLBGDR . . . . . . . . . . . . . 13
	6.2.2. Router receives updated DRLBGDR . . . . . . . . . . . 13		6.2.2. Router Receives Updated DRLBGDR . . . . . . . . . . . 13
	6.3. PIM Assert Modification . . . . . . . . . . . . . . . . . 14		6.3. PIM Assert Modification . . . . . . . . . . . . . . . . . 14
	7. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 15		7. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 15
	8. Manageability Considerations . . . . . . . . . . . . . . . . 15		8. Manageability Considerations . . . . . . . . . . . . . . . . 15
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
	10. Security Considerations . . . . . . . . . . . . . . . . . . . 16		10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
	11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 16		11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 16
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
	12.1. Normative References . . . . . . . . . . . . . . . . . . 16		12.1. Normative References . . . . . . . . . . . . . . . . . . 16
	12.2. Informative References . . . . . . . . . . . . . . . . . 17		12.2. Informative References . . . . . . . . . . . . . . . . . 17
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
	skipping to change at page 3, line 27 ¶		skipping to change at page 3, line 27 ¶
	Figure 1: Last Hop LAN		Figure 1: Last Hop LAN
	Assume R1 is elected as the Designated Router. According to		Assume R1 is elected as the Designated Router. According to
	[RFC4601], R1 will be responsible for forwarding traffic to that LAN		[RFC4601], R1 will be responsible for forwarding traffic to that LAN
	on behalf of any local members. In addition to keeping track of IGMP		on behalf of any local members. In addition to keeping track of IGMP
	and MLD membership reports, R1 is also responsible for initiating the		and MLD membership reports, R1 is also responsible for initiating the
	creation of source and/or shared trees towards the senders or the		creation of source and/or shared trees towards the senders or the
	RPs.		RPs.
	Forcing sole data plane forwarding responsibility on the PIM DR		Forcing sole data plane forwarding responsibility on the PIM DR
	proves a limitation in the protocol. In comparison, even though an		uncovers a limitation in the protocol. In comparison, even though an
	OSPF DR, or an IS-IS DIS, handles additional duties while running the		OSPF DR or an IS-IS DIS handles additional duties while running the
	OSPF or IS-IS protocols, they are not required to be solely		OSPF or IS-IS protocols, they are not required to be solely
	responsible for forwarding packets for the network. On the other		responsible for forwarding packets for the network. On the other
	hand, on a last hop LAN, only the PIM DR is asked to forward packets		hand, on a last hop LAN, only the PIM DR is asked to forward packets
	while the other routers handle only control traffic (and perhaps drop		while the other routers handle only control traffic (and perhaps drop
	packets due to RPF failures). The forwarding load of a last hop LAN		packets due to RPF failures). Hence the forwarding load of a last
	is concentrated on a single router.		hop LAN is concentrated on a single router.
	This leads to several issues. One of the issues is that the		This leads to several issues. One of the issues is that the
	aggregated bandwidth will be limited to what R1 can handle towards		aggregated bandwidth will be limited to what R1 can handle towards
	this particular interface. These days, it is very common that the		this particular interface. It is very common that the last hop LAN
	last hop LAN usually consists of switches that run IGMP/MLD or PIM		usually consists of switches that run IGMP/MLD or PIM snooping. This
	snooping. This allows the forwarding of multicast packets to be		allows the forwarding of multicast packets to be restricted only to
	restricted only to segments leading to receivers who have indicated		segments leading to receivers who have indicated their interest in
	their interest in multicast groups using either IGMP or MLD. The		multicast groups using either IGMP or MLD. The emergence of the
	emergence of the switched Ethernet allows the aggregated bandwidth to		switched Ethernet allows the aggregated bandwidth to exceed,
	exceed, some times by a large number, that of a single link. For		sometimes by a large number, that of a single link. For example, let
	example, let us modify Figure 1 and introduce an Ethernet switch in		us modify Figure 1 and introduce an Ethernet switch in Figure 2.
	Figure 2.
	( core networks )		( core networks )
	| | |		| | |
	| | |		| | |
	R1 R2 R3		R1 R2 R3
	| | |		| | |
	+=gi0===gi1===gi2=+		+=gi0===gi1===gi2=+
	+ +		+ +
	+ switch +		+ switch +
	+ +		+ +
	skipping to change at page 4, line 25 ¶		skipping to change at page 4, line 25 ¶
	| | |		| | |
	H1 H2 H3		H1 H2 H3
	Figure 2: Last Hop Network with Ethernet Switch		Figure 2: Last Hop Network with Ethernet Switch
	Let us assume that each individual link is a Gigabit Ethernet. Each		Let us assume that each individual link is a Gigabit Ethernet. Each
	router, R1, R2 and R3, and the switch have enough forwarding capacity		router, R1, R2 and R3, and the switch have enough forwarding capacity
	to handle hundreds of Gigabits of data.		to handle hundreds of Gigabits of data.
	Let us further assume that each of the hosts requests 500 Mbps of		Let us further assume that each of the hosts requests 500 Mbps of
	data and different traffic is requested by each host. This		unique multicast data. This totals to 1.5 Gbps of data, which is
	represents a total 1.5 Gbps of data, which is under what each switch		less than what each switch or the combined uplink bandwidth across
	or the combined uplink bandwidth across the routers can handle, even		the routers can handle, even under failure of a single router.
	under failure of a single router.
	On the other hand, the link between R1 and switch, via port gi0, can		On the other hand, the link between R1 and switch, via port gi0, can
	only handle a throughput of 1Gbps. And if R1 is the only router, the		only handle a throughput of 1Gbps. And if R1 is the only DR (the PIM
	PIM DR elected using the procedure defined by [RFC4601], at least 500		DR elected using the procedure defined by [RFC4601]) at least 500
	Mbps worth of data will be lost because the only link that can be		Mbps worth of data will be lost because the only link that can be
	used to draw the traffic from the routers to the switch is via gi0.		used to draw the traffic from the routers to the switch is via gi0.
	In other words, the entire network's throughput is limited by the		In other words, the entire network's throughput is limited by the
	single connection between the PIM DR and the switch (or the last hop		single connection between the PIM DR and the switch (or the last hop
	LAN as in Figure 1).		LAN as in Figure 1).
	The problem may also manifest itself in a different way. For		The problem may also manifest itself in a different way. For
	example, R1 happens to forward 500 Mbps worth of unicast data to H1,		example, R1 happens to forward 500 Mbps worth of unicast data to H1,
	and at the same time, H2 and H3 each requests 300 Mbps of different		and at the same time, H2 and H3 each request 300 Mbps of different
	multicast data. Once again packet drop happens on R1 while in the		multicast data. R1 experiences packet drop once again. while, in the
	mean time, there is sufficient forwarding capacity left on R2 and R3		meantime, there is sufficient forwarding capacity left on R2 and R3
	and link capacity between the switch and R2/R3.		and unused link capacity between the switch and R2/R3.
	Another important issue is related to failover. If R1 is the only		Another important issue is related to failover. If R1 is the only
	forwarder on the last hop router for shared LAN, in the event of a		forwarder on the last hop router for shared LAN, when R1 goes out of
	failure when R1 goes out of service, multicast forwarding for the		service, multicast forwarding for the entire LAN has to be rebuilt by
	entire LAN has to be rebuilt by the newly elected PIM DR. However,		the newly elected PIM DR. However, if there was a way that allowed
	if there was a way that allowed multiple routers to forward to the		multiple routers to forward to the LAN for different groups, failure
	LAN for different groups, failure of one of the routers would only		of one of the routers would only lead to disruption to a subset of
	lead to disruption to a subset of the flows, therefore improving the		the flows, therefore improving the overall resilience of the network.
	overall resilience of the network.
			There is limitation in the hash algorithm used in this document, but
			this draft provides the option to have different and more consistent
			hash algorithms in the future.
	In this document, we propose a modification to the PIM-SM protocol		In this document, we propose a modification to the PIM-SM protocol
	that allows more than one of these routers, called Group Designated		that allows more than one of these routers, called Group Designated
	Router (GDR) to be selected so that the forwarding load can be		Routers (GDR) to be selected so that the forwarding load can be
	distributed among a number of routers.		distributed among a number of routers.
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119] .		document are to be interpreted as described in [RFC2119].
	With respect to PIM, this document follows the terminology that has		With respect to PIM, this document follows the terminology that has
	been defined in [RFC4601] .		been defined in [RFC4601].
	This document also introduces the following new acronyms:		This document also introduces the following new acronyms:
	o GDR: GDR stands for "Group Designated Router". For each multicast		o GDR: GDR stands for "Group Designated Router". For each multicast
	flow, either a (*,G) for ASM, or an (S,G) for SSM, a hash		flow, either a (*,G) for ASM, or an (S,G) for SSM, a hash
	algorithm (described below) is used to select one of the routers		algorithm (described below) is used to select one of the routers
	as a GDR. The GDR is responsible for initiating the forwarding		as a GDR. The GDR is responsible for initiating the forwarding
	tree building for the corresponding multicast flow.		tree building process for the corresponding multicast flow.
	o GDR Candidate: a last hop router that has potential to become a		o GDR Candidate: a last hop router that has the potential to become
	GDR. A GDR Candidate must have the same DR priority and must run		a GDR. A GDR Candidate must have the same DR priority and must
	the same GDR election hash algorithm as the DR router. It must		run the same GDR election hash algorithm as the DR router. It
	send and process new PIM Hello Options as defined in this		must send and process new PIM Hello Options as defined in this
	document. There might be more than one GDR Candidate on a LAN.		document. There might be more than one GDR Candidate on a LAN,
	But only one can become GDR for a specific multicast flow.		but only one can become GDR for a specific multicast flow.
	3. Applicability		3. Applicability
	The proposed change described in this specification applies to PIM-SM		The proposed change described in this specification applies to PIM-SM
	last hop routers only.		last hop routers only.
	It does not alter the behavior of a PIM DR on the first hop network		It does not alter the behavior of a PIM DR on the first hop network.
	This is because the source tree is built using the IP address of the		This is because the source tree is built using the IP address of the
	sender, not the IP address of the PIM DR that sends the registers		sender, not the IP address of the PIM DR that sends the registers
	towards the RP. The load balancing between first hop routers can be		towards the RP. The load balancing between first hop routers can be
	achieved naturally if an IGP provides equal cost multiple paths		achieved naturally if an IGP provides equal cost multiple paths
	(which it usually does in practice). And distributing the load to do		(which it usually does in practice). Also distributing the load to
	registering does not justify the additional complexity required to		do registering does not justify the additional complexity required to
	support it.		support it.
	4. Functional Overview		4. Functional Overview
	In the existing PIM DR election, when multiple last hop routers are		In the existing PIM DR election, when multiple last hop routers are
	connected to a multi-access LAN (for example, an Ethernet), one of		connected to a multi-access LAN (for example, an Ethernet), one of
	them is selected to act as PIM DR. The PIM DR is responsible for		them is selected to act as PIM DR. The PIM DR is responsible for
	sending local Join/Prune messages towards the RP or source. To elect		sending local Join/Prune messages towards the RP or source. In order
	the PIM DR, each PIM router on the LAN examines the received PIM		to elect the PIM DR, each PIM router on the LAN examines the received
	Hello messages and compares its DR priority and IP address with those		PIM Hello messages and compares its DR priority and IP address with
	of its neighbors. The router with the highest DR priority is the PIM		those of its neighbors. The router with the highest DR priority is
	DR. If there are multiple such routers, their IP addresses are used		the PIM DR. If there are multiple such routers, their IP addresses
	as the tie-breaker, as described in [RFC4601].		are used as the tie-breaker, as described in [RFC4601].
	In order to share forwarding load among last hop routers, besides the		In order to share forwarding load among last hop routers, besides the
	normal PIM DR election, the GDR is also elected on the last hop		normal PIM DR election, the GDR is also elected on the last hop
	multi-access LAN. There is only one PIM DR on the multi-access LAN,		multi-access LAN. There is only one PIM DR on the multi-access LAN,
	but there might be multiple GDR Candidates.		but there might be multiple GDR Candidates.
	For each multicast flow, that is (*,G) for ASM and (S,G) for SSM, a		For each multicast flow, that is, (*,G) for ASM and (S,G) for SSM, a
	hash algorithm is used to select one of the routers to be the GDR. A		hash algorithm is used to select one of the routers to be the GDR. A
	new DR Load Balancing Capability (DRLBC) PIM Hello Option, which		new DR Load Balancing Capability (DRLBC) PIM Hello Option, which
	contains hash algorithm type, is announced by routers on interfaces		contains hash algorithm type, is announced by routers on interfaces
	where this specification is enabled. Last hop routers with the new		where this specification is enabled. Last hop routers with the new
	DRLBC Option advertised in its Hello, and using the same GDR election		DRLBC Option advertised in its Hello, and using the same GDR election
	hash algorithm and the same DR priority as the PIM DR, are considered		hash algorithm and the same DR priority as the PIM DR, are considered
	as GDR Candidates.		as GDR Candidates.
	Hash Masks are defined for Source, Group and RP separately, in order		Hash Masks are defined for Source, Group and RP separately, in order
	to handle PIM ASM/SSM. The masks, as well as a sorted list of GDR		to handle PIM ASM/SSM. The masks, as well as a sorted list of GDR
	Candidates' Addresses are announced by DR in a new DR Load Balancing		Candidates' Addresses, are announced by DR in a new DR Load Balancing
	GDR (DRLBGDR) PIM Hello Option.		GDR (DRLBGDR) PIM Hello Option.
	For each multicast flow, a hash algorithm is used to select one of		A hash algorithm based on the announced Source, Group, or RP masks
	the routers to be the GDR. The masks are announced in PIM Hello by
	DR as a DR Load Balancing GDR (DRLBGDR) Hello Option. Besides that,
	a DR Load Balancing Capability (DRLBC) Hello Option, which contains
	hash algorithm type, is also announced by the router on interfaces
	where this specification is enabled. Last hop routers with the new
	DRLBC Option advertised in its Hello, and using the same GDR election
	hash algorithm and the same DR priority as the PIM DR, are considered
	as GDR Candidates.
	A hash algorithm based on the announced Source, Group or RP masks
	allows one GDR to be assigned to a corresponding multicast state.		allows one GDR to be assigned to a corresponding multicast state.
	And that GDR is responsible for initiating the creation of the		And that GDR is responsible for initiating the creation of the
	multicast forwarding tree for multicast traffic.		multicast forwarding tree for multicast traffic.
	4.1. GDR Candidates		4.1. GDR Candidates
	GDR is the new concept introduced by this specification. GDR		GDR is the new concept introduced by this specification. GDR
	Candidates are routers eligible for GDR election on the LAN. To		Candidates are routers eligible for GDR election on the LAN. To
	become a GDR Candidate, a router MUST support this specification,		become a GDR Candidate, a router MUST support this specification,
	have the same DR priority and run the same GDR election hash		have the same DR priority and run the same GDR election hash
	algorithm as the DR on the LAN.		algorithm as the DR on the LAN.
	For example, assume there are 4 routers on the LAN: R1, R2, R3 and		For example, assume there are 4 routers on the LAN: R1, R2, R3 and
	R4, which all support this specification on the LAN. R1, R2 and R3		R4, which all support this specification. R1, R2 and R3 have the
	have the same DR priority while R4's DR priority is less preferred.		same DR priority while R4's DR priority is less preferred. In this
	In this example, R4 will not be eligible for GDR election, because R4		example, R4 will not be eligible for GDR election, because R4 will
	will not become a PIM DR unless all of R1, R2 and R3 go out of		not become a PIM DR unless all of R1, R2 and R3 go out of service.
	service.
	Further assume router R1 wins the PIM DR election, and R1, R2 run the		Furthermore, assume router R1 wins the PIM DR election, R1 and R2 run
	same hash algorithm for GDR election, while R3 runs a different one.		the same hash algorithm for GDR election, while R3 runs a different
	Then only R1 and R2 will be eligible for GDR election, R3 will not.		one. In this case, only R1 and R2 will be eligible for GDR election,
			while R3 will not.
	As a DR, R1 will include its own Load Balancing Hash Masks, and also		As a DR, R1 will include its own Load Balancing Hash Masks and the
	the identity of R1 and R2 (the GDR Candidates) in its DRLBGDR Hello		identity of R1 and R2 (the GDR Candidates) in its DRLBGDR Hello
	Option.		Option.
	4.2. Hash Mask and Hash Algorithm		4.2. Hash Mask and Hash Algorithm
	A Hash Mask is used to extract a number of bits from the		A Hash Mask is used to extract a number of bits from the
	corresponding IP address field (32 for v4, 128 for v6), and calculate		corresponding IP address field (32 for v4, 128 for v6) and calculate
	a hash value. A hash value is used to select a GDR from GDR		a hash value. A hash value is used to select a GDR from GDR
	Candidates advertised by PIM DR. For example, 0.0.255.0 defines a		Candidates advertised by PIM DR. For example, 0.0.255.0 defines a
	Hash Mask for an IPv4 address that masks the first, the second and		Hash Mask for an IPv4 address that masks the first, the second, and
	the fourth octets.		the fourth octets.
	There are three Hash Masks defined,		There are three Hash Masks defined,
	o RP Hash Mask		o RP Hash Mask
	o Source Hash Mask		o Source Hash Mask
	o Group Hash Mask		o Group Hash Mask
	The hask masks need to be configured on the PIM routers that can		The hash masks need to be configured on the PIM routers that can
	potentially become a PIM DR, unless the implementation provides		potentially become a PIM DR, unless the implementation provides
	default hash mask. An implementation SHOULD provide masks with		default Hash Mask. An implementation SHOULD provide masks with
	default values 255.255.255.255 (IPv4) and		default values 255.255.255.255 (IPv4) and
	FFFF:FFFF:FFFF:FFFF:FFFFF:FFFF:FFFF:FFFF (IPv6).		FFFF:FFFF:FFFF:FFFF:FFFFF:FFFF:FFFF:FFFF (IPv6).
	o If the group is ASM, and if the RP Hash Mask announced by the PIM		o If the group is ASM and the RP Hash Mask announced by the PIM DR
	DR is not 0, calculate the value of hashvalue_RP [Section 4.3] to		is not 0, calculate the value of hashvalue_RP [Section 4.3] to
	determine GDR.		determine GDR.
	o If the group is ASM and if the RP Hash Mask announced by the PIM		o If the group is ASM and the RP Hash Mask announced by the PIM DR
	DR is 0, obtain the value of hashvalue_Group [Section 4.3 ] to		is 0, obtain the value of hashvalue_Group [Section 4.3 ] to
	determine GDR.		determine GDR.
	o If the group is SSM, use hashvalue_SG [Section 4.3] to determine		o If the group is SSM, use hashvalue_SG [Section 4.3] to determine
	GDR.		GDR.
	A simple Modulo hash algorithm will be discussed in this document.		A simple Modulo hash algorithm will be discussed in this document.
	However, to allow other hash algorithm to be used, a 4-bytes "Hash		However, to allow another hash algorithms to be used, a 4-bytes "Hash
	Algorithm Type" field is included in DRLBC Hello Option to specify		Algorithm Type" field is included in DRLBC Hello Option to specify
	the hash algorithm used by a last hop router.		the hash algorithm used by a last hop router.
	If different hash algorithm types are advertised among last hop		If different hash algorithm types are advertised among last hop
	routers, only last hop routers running the same hash algorithm as the		routers, only last hop routers running the same hash algorithm as the
	DR (and having the same DR priority as the DR) are eligible for GDR		DR (and having the same DR priority as the DR) are eligible for GDR
	election.		election.
	4.3. Modulo Hash Algorithm		4.3. Modulo Hash Algorithm
	Modulo hash algorithm is discussed here as an example, with detailed		Modulo hash algorithm is discussed here with a detailed description
	description on hashvalue_RP.		on hashvalue_RP. The same algorithm is described in brief for
			hashvalue_Group using the group address instead of the RP address for
			an ASM group with RP_hashmask==0, and also with hashvalue_SG for a
			the source address of an (S,G), instead of the RP address,
	o For ASM groups, with a non-zero RP_hash mask, hash value is		o For ASM groups, with a non-zero RP_Hash Mask, hash value is
	calculated as:		calculated as:
	hashvalue_RP = (((RP_address & RP_hashmask) >> N) & 0xFFFF) % M		hashvalue_RP = (((RP_address & RP_hashmask) >> N) & 0xFFFF) % M
	RP_address is the address of the RP defined for the group. N		RP_address is the address of the RP defined for the group. N
	is the number of zeros, counted from the least significant bit		is the number of zeros, counted from the least significant bit
	of the RP_hashmask. M is the number of GDR Candidates.		of the RP_hashmask. M is the number of GDR Candidates.
	For example, Router X with IPv4 address 203.0.113.1, receives a		For example, Router X with IPv4 address 203.0.113.1 receives a
	DRLBGDR Hello Option from the DR, which announces RP Hash Mask		DRLBGDR Hello Option from the DR, which announces RP Hash Mask
	0.0.255.0, and a list of GDR Candidates, sorted by IP addresses		0.0.255.0 and a list of GDR Candidates, sorted by IP addresses
	from high to low, 203.0.113.3, 203.0.113.2 and 203.0.113.1.		from high to low: 203.0.113.3, 203.0.113.2 and 203.0.113.1.
	The ordinal number assigned to those addresses would be:		The ordinal number assigned to those addresses would be:
	0 for 203.0.113.3; 1 for 203.0.113.2; 2 for 203.0.113.1 (Router		0 for 203.0.113.3; 1 for 203.0.113.2; 2 for 203.0.113.1 (Router
	X)		X)
	Assume there are 2 RPs: RP1 192.0.2.1 for Group1 and RP2		Assume there are 2 RPs: RP1 192.0.2.1 for Group1 and RP2
	198.51.100.2 for Group2. Following the modulo hash algorithm:		198.51.100.2 for Group2. Following the modulo hash algorithm:
	N is 8 for 0.0.255.0, and M is 3 for the total number of GDR		N is 8 for 0.0.255.0, and M is 3 for the total number of GDR
	Candidates. The hashvalue_RP for RP1 192.0.2.1 is:		Candidates. The hashvalue_RP for RP1 192.0.2.1 is:
	(((192.0.2.1 & 0.0.255.0) >> 8) & 0xFFFF % 3) = 2 % 3 = 2		(((192.0.2.1 & 0.0.255.0) >> 8) & 0xFFFF % 3) = 2 % 3 = 2
	matches the ordinal number assigned to Router X. Router X will		matches the ordinal number assigned to Router X. Router X will
	be the GDR for Group1, which uses 192.0.2.1 as the RP.		be the GDR for Group1, which uses 192.0.2.1 as the RP.
	The hashvalue_RP for RP2 198.51.100.2 is:		The hashvalue_RP for RP2 198.51.100.2 is:
	(((198.51.100.2 & 0.0.255.0) >> 8) & 0xFFFF % 3) = 100 % 3 = 1		(((198.51.100.2 & 0.0.255.0) >> 8) & 0xFFFF % 3) = 100 % 3 = 1
	which is different from Router X's ordinal number 2, hence,		which is different from Router X's ordinal number(2) hence,
	Router X will not be GDR for Group2.		Router X will not be GDR for Group2.
	o If RP_hashmask is 0, a hash value for ASM group is calculated		o If RP_hashmask is 0, a hash value for ASM group is calculated
	using the group Hash Mask:		using the group Hash Mask:
	hashvalue_Group = (((Group_address & Group_hashmask) >> N) &		hashvalue_Group = (((Group_address & Group_hashmask) >> N) &
	0xFFFF) % M		0xFFFF) % M
	Compare hashvalue_Group with Ordinal number assigned to Router		Compare hashvalue_Group with Ordinal number assigned to Router
	X, to decide if Router X is the GDR.		X, to decide if Router X is the GDR.
	o For SSM groups, a hash value is calculated using both the source		o For SSM groups, a hash value is calculated using both the source
	and group Hash Mask		and group Hash Mask:
	hashvalue_SG = ((((Source_address & Source_hashmask) >> N_S) &		hashvalue_SG = ((((Source_address & Source_hashmask) >> N_S) &
	0xFFFF) ^ (((Group_address & Group_hashmask) >> N_G) & 0xFFFF))		0xFFFF) ^ (((Group_address & Group_hashmask) >> N_G) & 0xFFFF))
	% M		% M
	4.4. PIM Hello Options		4.4. PIM Hello Options
	When a last hop PIM router sends a PIM Hello from an interface with		When a last hop PIM router sends a PIM Hello from an interface with
	this specification enabled, it includes a new option, called "Load		this specification enabled, it includes a new option, called "Load
	Balancing Capability (DRLBC)".		Balancing Capability (DRLBC)".
	Besides this DRLBC Hello Option, the elected PIM DR also includes a		Besides this DRLBC Hello Option, the elected PIM DR also includes a
	new "DR Load Balancing GDR (DRLBGDR) Hello Option". The DRLBGDR		new "DR Load Balancing GDR (DRLBGDR) Hello Option". The DRLBGDR
	Hello Option consists of three Hash Masks as defined above and also		Hello Option consists of three Hash Masks as defined above and also
	the sorted list of all GDR Candidates' Address on the last hop LAN.		the sorted list of all GDR Candidates' Address on the last hop LAN.
	The elected PIM DR uses DRLBC Hello Option advertised by all routers		The elected PIM DR uses DRLBC Hello Option advertised by all routers
	on the last hop LAN to compose its DRLBGDR . The GDR Candidates use		on the last hop LAN to compose its DRLBGDR. The GDR Candidates use
	DRLBGDR Hello Option advertised by PIM DR to calculate hash value.		DRLBGDR Hello Option advertised by PIM DR to calculate hash value.
	5. Hello Option Formats		5. Hello Option Formats
	5.1. PIM DR Load Balancing Capability (DRLBC) Hello Option		5.1. PIM DR Load Balancing Capability (DRLBC) Hello Option
	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 = TBD | Length = 4 |		| Type = TBD | Length = 4 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Hash Algorithm Type |		| Hash Algorithm Type |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 3: Capability Hello Option		Figure 3: Capability Hello Option
	skipping to change at page 10, line 49 ¶		skipping to change at page 10, line 44 ¶
	| RP Mask |		| RP Mask |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| GDR Candidate Address(es) |		| GDR Candidate Address(es) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 4: GDR Hello Option		Figure 4: GDR Hello Option
	Type: TBD		Type: TBD
	Length: 3 x (4 byte or 16 byte) + n x (4 byte or 16 byte) where n		Length: 3 x (4 byte or 16 byte) + n x (4 byte or 16 byte) where n
	is number of GDR candidate		is the number of GDR candidates.
	Group Mask (32/128 bits): Mask		Group Mask (32/128 bits): Mask
	Source Mask (32/128 bits): Mask		Source Mask (32/128 bits): Mask
	RP Mask (32/128 bits): Mask		RP Mask (32/128 bits): Mask
	All masks MUST be in the same address family as the Hello IP		All masks MUST be in the same address family as the Hello IP
	header.		header.
	GDR Address (32/128 bits): Address(es) of GDR Candidate(s)		GDR Address (32/128 bits): Address(es) of GDR Candidate(s)
	All addresses must be in the same address family as the Hello		All addresses must be in the same address family as the Hello
	IP header. The addresses are sorted from high to low. The		IP header. The addresses are sorted in descending order. The
	order is converted to the ordinal number associated with each		order is converted to the ordinal number associated with each
	GDR candidate in hash value calculation. For example,		GDR candidate in hash value calculation. For example,
	addresses advertised are R3, R2, R1, the ordinal number		addresses advertised are R3, R2, R1, the ordinal number
	assigned to R3 is 0, to R2 is 1 and to R1 is 2.		assigned to R3 is 0, to R2 is 1 and to R1 is 2.
	If "Interface ID" option, as described in [RFC6395], presents		If "Interface ID" option, as described in [RFC6395], presents
	in a GDR Candicate's PIM Hello message, and the "Router ID"		in a GDR Candidate's PIM Hello message, and the "Router ID"
	portion is non-zero,		portion is non-zero,
	+ For IPv4, the "GDR Candidate Address" will be set directly		+ For IPv4, the "GDR Candidate Address" will be set directly
	to "Router ID".		to "Router ID".
	+ For IPv6, the "GDR Candidate Address" will be set to the		+ For IPv6, the "GDR Candidate Address" will be set to the
	IPv4-IPv6 translated address of "Router ID", as described in		IPv4-IPv6 translated address of "Router ID", as described in
	[RFC4291] , that is the "Router-ID" is appended to the		[RFC4291] , that is the "Router-ID" is appended to the
	prefix of 96-bits zeros.		prefix of 96-bits zeros.
	If the "Interface ID" option is not present in a GDR		If the "Interface ID" option is not present in a GDR
	Candidate's PIM Hello message, or if the "Interface ID" option		Candidate's PIM Hello message, or if the "Interface ID" option
	is present, but"Router ID" field is zero, the "GDR Candidate		is present but the "Router ID" field is zero, the "GDR
	Address" will be the IPv4 or IPv6 source address from PIM Hello		Candidate Address" will be the IPv4 or IPv6 source address from
	message.		PIM Hello message.
	This DRLBGDR Hello Option SHOULD only be advertised by the		This DRLBGDR Hello Option MUST only be advertised by the
	elected PIM DR.		elected PIM DR.
	6. Protocol Specification		6. Protocol Specification
	6.1. PIM DR Operation		6.1. PIM DR Operation
	The DR election process is still the same as defined in [RFC4601]. A		The DR election process is still the same as defined in [RFC4601]. A
	DR that has this specification enabled on the interface, advertises		DR that has this specification enabled on the interface advertises
	the new LBGRD Hello Option, which contains value of masks from user		the new DRLBGDR Hello Option, which contains value of masks from user
	configuration, followed by a sorted list of all GDR Candidates'		configuration, followed by a sorted list of all GDR Candidates'
	Addresses, from high to low. Moreover, same as non-DR routers, DR		Addresses, from the highest value to the lowest value. Moreover,
	also advertises DRLBC Hello Option to indicate its capability of		same as non-DR routers, DR also advertises DRLBC Hello Option to
	supporting this specification and the type of its GDR election hash		indicate its capability of supporting this specification and the type
	algorithm.		of its GDR election hash algorithm.
	If a PIM DR receives a PIM Hello with DRLBGRD Option, the PIM DR		If a PIM DR receives a PIM Hello with DRLBGDR Option, the PIM DR
	SHOULD ignore the TLV.		SHOULD ignore the TLV.
	If a PIM DR receives a neighbor DRLBC Hello Option, which contains		If a PIM DR receives a neighbor DRLBC Hello Option, which contains
	the same hash algorithm type as the DR, and the neighbor has the same		the same hash algorithm type as the DR, and the neighbor has the same
	DR priority as the DR, PIM DR SHOULD consider the neighbor as a GDR		DR priority as the DR, PIM DR SHOULD consider the neighbor as a GDR
	Candidate and insert the GDR Candidate's Address into the sorted list		Candidate and insert the GDR Candidate's Address into the sorted list
	of DRLBGRD Option.		of DRLBGDR Option.
	6.2. PIM GDR Candidate Operation		6.2. PIM GDR Candidate Operation
	When an IGMP/MLD join is received, without this proposal, only PIM DR		When an IGMP/MLD join is received, without this specification, only
	will handle the join and potentially run into the issues described		PIM DR will handle the join and potentially run into the issues
	earlier. Using this proposal, a hash algorithm is used on GDR		described earlier. Using this specification, a hash algorithm is
	Candidate to determine which router is going to be responsible for		used on GDR Candidate to determine which router is going to be
	building forwarding trees on behalf of the host.		responsible for building forwarding trees on behalf of the host.
	A router which supports this specification, a interface where this		If a router supports this specification then each of the interfaces
	protocol is enabled advertises DRLBC Hello Option in its PIM Hello,		where multicast protocol is enabled, it MUST advertise DRLBC Hello
	even if the router may not be considered as a GDR Candidate, for		Option in its PIM Hello. Though DRLBC option in PIM hello does not
	example, due to low DR priority. once DR election is done, DRLBGDR		guarantee that this router would be considered as a GDR candidate.
	Hello option would be received from the current PIM DR on link.		For example, this router may have lower priority configured on shared
			LAN compare to other PIM routers. Once DR election is done, DRLBGDR
			Hello option would be received from the current PIM DR on the link
			which would contain list of GDR.
	A GDR Candidate may receive a DRLBGDR Hello Option from PIM DR, with		A GDR Candidate may receive a DRLBGDR Hello Option from PIM DR with
	different Hash Masks from those configured on it, The GDR Candidate		different Hash Masks from those configured on it. The GDR Candidate
	must use the Hash Masks advertised by the PIM DR to calculate the		must use the Hash Masks advertised by the PIM DR to calculate the
	hash value.		hash value.
	A GDR Candidate may receive a DRLBGDR Hello Option from a PIM router		A GDR Candidate may receive a DRLBGDR Hello Option from a PIM router
	which is not DR. The GDR Candidate MUST ignore such DRLBGDR Hello		which is not DR. The GDR Candidate MUST ignore such DRLBGDR Hello
	Option.		Option.
	A GDR Candidate may receive a Hello from the elected PIM DR, and the		A GDR Candidate may receive a Hello from the elected PIM DR, and the
	PIM DR does not support this specification. The GDR election		PIM DR does not support this specification. The GDR election
	described by this specification will not take place, that is only the		described by this specification will not take place, that is only the
	PIM DR joins the multicast tree.		PIM DR joins the multicast tree.
	A router only act as GDR if it is included in the GDR list of DRLBGDR		A router only acts as GDR if it is included in the GDR list of
	Hello Option		DRLBGDR Hello Option
	6.2.1. Router receives new DRLBGDR		6.2.1. Router Receives New DRLBGDR
	When a router receives new DRLBGDR from the current PIM DR, it need		When a router receives a new DRLBGDR from the current PIM DR, it need
	to process and check if router is in list of of GDR		to process and check if router is in list of of GDR
	1. If router is not listed as a GDR candidate in DRLBGDR , no action		1. If a router is not listed as a GDR candidate in DRLBGDR, no
	needed.		action is needed.
	2. If router is listed as a GDR candidate in DRLBGDR, then it need		2. If a router is listed as a GDR candidate in DRLBGDR, then it need
	to process each of the groups in the IGMP/MLD reports. The masks		to process each of the groups in the IGMP/MLD reports. The masks
	are announced in the PIM Hello by DR as DRLBGDR Hello option.		are announced in the PIM Hello by DR as DRLBGDR Hello option.
	For each of groups in the reports it need to run hash algorithem		For each of groups in the reports it (PIM Router) needs to run
	(described in section 4.3) based on the announced Source, Group		hash algorithm (described in section 4.3) based on the announced
	or RP masks to determine if it is GDR for specified group. If		Source, Group or RP masks to determine if it is GDR for specified
	hash result is to be GDR for multicast flow, it does build		group. If the hash result is to be the GDR for the multicast
	multicast forwarding tree. if it is not GDR for flow, no action		flow, it does build the multicast forwarding tree. If it is not
	is needed.		the GDR for the multicast flow, no action is needed.
	6.2.2. Router receives updated DRLBGDR		6.2.2. Router Receives Updated DRLBGDR
	If router (GDR or non GDR) receives an unchanged DRLBGDR from the		If a router (GDR or non GDR) receives an unchanged DRLBGDR from the
	current PIM DR, no action needed.		current PIM DR, no action is needed.
	If router (GDR or non GDR) receives a new or modified DRLBGDR from		If a router (GDR or non GDR) receives a new or modified DRLBGDR from
	the current PIM DR. It requires processing as described below		the current PIM DR. It requires processing as described below:
	1. If it was GDR and still included in current GDR list: It need to		1. If it was GDR and still included in current GDR list: it needs to
	process each of the groups, run hash algorithem to check if it is		process each of the groups and run the hash algorithm to check if
	still GDR for given group.		it is still the GDR for the given group.
	If it was GDR for group earlier. and even new hash choose it		If it was the GDR for group G and the new hash result chose it
	as GDR, no processing required.		as the GDR, then no processing is required.
	If it was GDR for group earlier and now it is no more GDR,		If it was the GDR for a group earlier and now it is no longer
	then it sets its assert metric for this flow to be		the GDR, then it sets its assert metric for the multicast flow
	(PIM_ASSERT_INFINITY - 1), as explained in Sec 6.3		to be (PIM_ASSERT_INFINITY - 1), as explained in Sec 6.3
	If it was not GDR for group earlier, and even new hash does		If it was not the GDR for a group earlier, than even the new
	not make it GDR no processing required.		hash does not make it GDR. For the multicast group no
			processing is required.
	If it was not GDR earlier and now becomes GDR, it starts		If it was not the GDR for an earlier group and now becomes the
	building multicast forwarding tree for this flow.		GDR, it starts building multicast forwarding tree for this
			flow.
	2. If it was non GDR , and updated DRLBGDR from current PIM DR		2. If it was not the GDR , and updated DRLBGDR from current PIM DR
	contains this router as one of the GDR. In this case this router		contains this router as one of the GDR. In this case this router
	being new GDR candiate MUST run hash algorithem for each of the		being new GDR candidate MUST run hash algorithm for each of the
	groups (multicast flows) and for given group,		groups (multicast flows) and for given group,
	If it is not GDR, no processing is required.		If it is not the GDR, no processing is required.
	If it is hased as GDR , it need to build multicast forwarding
	tree.
	3. If a router receives IGMP/MLD report for flow for which the		If it is hashed as the GDR , it needs to build multicast
	router has been the GDR AND the DRLBGDR has changed since last		forwarding tree.
	report for this flow, then the router MUST determine if it is
	still the GDR. if it is, no action needed. if it is not, then the
	router sets its assert metric for this flow to be
	(PIM_ASSERT_INFINITY - 1) as explained in Sec 6.3.
	6.3. PIM Assert Modification		6.3. PIM Assert Modification
	It is possible that the identity of the GDR might change in the		It is possible that the identity of the GDR might change in the
	middle of an active flow. Examples this could happen include:		middle of an active flow. Examples this could happen include:
	When a new PIM router comes up		When a new PIM router comes up
	When a GDR restarts		When a GDR restarts
	When the GDR changes, existing traffic might be disrupted.		When the GDR changes, existing traffic might be disrupted.
	Duplicates or packet loss might be observed. To illustrate the case,		Duplicates or packet losses might be observed. To illustrate the
	consider the following scenario: there are two streams G1 and G2. R1		case, consider the following scenario where there are two streams G1
	is the GDR for G1, and R2 is the GDR for G2. When R3 comes up		and G2. R1 is the GDR for G1, and R2 is the GDR for G2. When R3
	online, it is possible that R3 becomes GDR for both G1 and G2, hence		comes up online, it is possible that R3 becomes GDR for both G1 and
	R3 starts to build the forwarding tree for G1 and G2. If R1 and R2		G2, hence R3 starts to build the forwarding tree for G1 and G2. If
	stop forwarding before R3 completes the process, packet loss might		R1 and R2 stop forwarding before R3 completes the process, packet
	occur. On the other hand, if R1 and R2 continue forwarding while R3		loss might occur. On the other hand, if R1 and R2 continue
	is building the forwarding trees, duplicates might occur.		forwarding while R3 is building the forwarding trees, duplicates
			might occur.
	This is not a typical deployment scenario but it still might happen.		This is not a typical deployment scenario but might still happen.
	Here we describe a mechanism to minimize the impact. The motivation		Here we describe a mechanism to minimize the impact. We essentially
	is that we want to minimize packet loss. And therefore, we would		want to minimize packet loss. Therefore, we would allow a small
	allow a small amount of duplicates and depend on PIM Assert to		amount of duplicates and depend on PIM Assert to minimize the
	minimize the duplication.		duplication.
	When the role of GDR changes as above, instead of immediately		When the role of GDR changes as above, instead of immediately
	stopping forwarding, R1 and R2 continue forwarding to G1 and G2		stopping forwarding, R1 and R2 continue forwarding to G1 and G2
	respectively, while at the same time, R3 build forwarding trees for		respectively, while, at the same time, R3 build forwarding trees for
	G1 and G2. This will lead to PIM Asserts.		G1 and G2. This will lead to PIM Asserts.
	With introduction of GDR, the following modification to the Assert		With the introduction of GDR, the following modification to the
	packet MUST be done: if a router enables this specification on its		Assert packet MUST be done: if a router enables this specification on
	downstream interface, but it is not a GDR (before network event it		its downstream interface, but it is not a GDR (before network event
	was GDR), it would adjust its Assert metric to (PIM_ASSERT_INFINITY -		it was GDR), it would adjust its Assert metric to
	1).		(PIM_ASSERT_INFINITY - 1).
	Using the above example, for G1, assume R1 and R3 agree on the new		Using the above example, for G1, assume R1 and R3 agree on the new
	GDR, which is R3. R1 will set its Assert metric as		GDR, which is R3. R1 will set its Assert metric as
	(PIM_ASSERT_INFINITY - 1). That will make R3, which has normal		(PIM_ASSERT_INFINITY - 1). That will make R3, which has normal
	metric in its Assert as the Assert winner.		metric in its Assert as the Assert winner.
	For G2, assume it takes a little bit longer time for R2 to find out		For G2, assume it takes a slightly longer time for R2 to find out
	that R3 is the new GDR and still thinks itself being the GDR while R3		that R3 is the new GDR and still considers itself being the GDR while
	already has assumed the role of GDR. Since both R2 and R3 think they		R3 already has assumed the role of GDR. Since both R2 and R3 think
	are GDRs, they further compare the metric and IP address. If R3 has		they are GDRs, they further compare the metric and IP address. If R3
	the better routing metric, or same metric but better tie-breaker, the		has the better routing metric, or the same metric but a better tie-
	result will be consistent with GDR selection. If unfortunately, R2		breaker, the result will be consistent during GDR selection. If
	has the better metric or same metric but better tie-breaker R2 will		unfortunately, R2 has the better metric or the same metric but a
	become the Assert winner and continues to forward traffic. This will		better tie-breaker, R2 will become the Assert winner and continues to
	continue until:		forward traffic. This will continue until:
	The next PIM Hello option from DR is seen that selects R3 as the GDR.		The next PIM Hello option from DR selects R3 as the GDR. R3 will
	R3 will then build the forwarding tree and send an Assert.		then build the forwarding tree and send an Assert.
	The process continues until R2 agrees to the selection of R3 as being		The process continues until R2 agrees to the selection of R3 as the
	the GDR, and set its own Assert metric to (PIM_ASSERT_INFINITY - 1),		GDR, and set its own Assert metric to (PIM_ASSERT_INFINITY - 1),
	which will make R3 the Assert winner. During the process, we will		which will make R3 the Assert winner. During the process, we will
	see intermittent duplication of traffic but packet loss will be		see intermittent duplication of traffic but packet loss will be
	minimized. In the unlikely case that R2 never relinquishes its role		minimized. In the unlikely case that R2 never relinquishes its role
	as GDR (while every other router thinks otherwise), the proposed		as GDR (while every other router thinks otherwise), the proposed
	mechanism also helps to keep the duplication to a minimum until		mechanism also helps to keep the duplication to a minimum until
	manual intervention takes place to remedy the situation.		manual intervention takes place to remedy the situation.
	7. Compatibility		7. Compatibility
	In case of hybrid Ethernet shared LAN ( where some PIM router enables		In case of the hybrid Ethernet shared LAN ( where some PIM router
	specification defined in this draft and some do not enable)		enables specification defined in this draft and some do not enable)
	o If router which does not support specification defined in this		o If a router which does not support specification defined in this
	draft becomes DR on link, it MUST be only DR on link as [RFC4601]		draft becomes DR on link, it MUST be only DR on link as [RFC4601]
	and there would be no router which would act as GDR.		and there would be no router which would act as GDR.
	o If router which does not support specification defined in this		o If a router which does not support specification defined in this
	draft becomes non DR on link, then it should act as non-DR defined		draft becomes non DR on link, then it should act as non-DR defined
	in [RFC4601].		in [RFC4601].
	8. Manageability Considerations		8. Manageability Considerations
	o All of the router in LAN who are supporting this specification		o All of the routers in LAN that support this specification MUST use
	MUST use identical Hash Algorithm Type (described in section 5.1).		identical Hash Algorithm Type (described in section 5.1). In the
	In case of hybrid Hash Algorithm Type router must go backward to		case of a hybrid Hash Algorithm Type, one MUST go backward to use
	use DR election method defined in PIM-SM [RFC4601]. Migration		DR election method defined in PIM-SM [RFC4601]. Migration between
	between different algorithem type is out of scope of this		different algorithm type is out of the scope of this document.
	document.
	9. IANA Considerations		9. IANA Considerations
	Two new PIM Hello Option Types have been assigned to the DR Load		IANA has temporarily assigned type 34 for the PIM DR Load Balancing
	Balancing messages. [HELLO-OPT], this document recommends 34(0x22)		Capability (DRLBC) Hello Option, and type 35 for the PIM DR Load
	as the new "PIM DR Load Balancing Capability Hello Option", and		Balancing GDR (DRLBGDR) Hello Option. IANA is requested to make
	35(0x23) as the new "PIM DR Load Balancing GDR Hello Option".		these assignments permanent when this document is published as an
			RFC. The string TBD should be replaced by the assigned values
			accordingly.
	10. Security Considerations		10. Security Considerations
	Security of the new DR Load Balancing PIM Hello Options is only		Security of the new DR Load Balancing PIM Hello Options is only
	guaranteed by the security of PIM Hello message, so the security		guaranteed by the security of PIM Hello message, so the security
	considerations for PIM Hello messages as described in PIM-SM		considerations for PIM Hello messages as described in PIM-SM
	[RFC4601] apply here.		[RFC4601] apply here.
	11. Acknowledgement		11. Acknowledgement
	The authors would like to thank Steve Simlo, Taki Millonis for		The authors would like to thank Steve Simlo, Taki Millonis for
	helping with the original idea, Bill Atwood, Bharat Joshi for review		helping with the original idea, Bill Atwood, Bharat Joshi for review
	comments, Toerless Eckert and Rishabh Parekh for helpful conversation		comments, Toerless Eckert and Rishabh Parekh for helpful conversation
	on the document.		on the document.
			Special thanks to Anish Kachinthaya, Anvitha Kachinthaya and Jake
			Holland for reviewing the document and providing comments.
	12. References		12. References
	12.1. Normative References		12.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing		[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
	skipping to change at page 17, line 29 ¶		skipping to change at page 17, line 29 ¶
	Alibaba Group		Alibaba Group
	Sri Vallepalli		Sri Vallepalli
	Cisco Systems		Cisco Systems
	3625 Cisco Way,		3625 Cisco Way,
	Sanjose, CALIFORNIA 95134		Sanjose, CALIFORNIA 95134
	UNITED STATES		UNITED STATES
	Email: svallepa@cisco.com		Email: svallepa@cisco.com
	Mankamana Prasad Mishra		Mankamana Mishra
	Cisco Systems		Cisco Systems
	821 Alder Drive,		821 Alder Drive,
	MILPITAS, CALIFORNIA 95035		MILPITAS, CALIFORNIA 95035
	UNITED STATES		UNITED STATES
	Email: mankamis@cisco.com		Email: mankamis@cisco.com
	Stig Venaas		Stig Venaas
	Cisco Systems		Cisco Systems
	821 Alder Drive,		821 Alder Drive,
End of changes. 90 change blocks.
	218 lines changed or deleted		215 lines changed or added
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