rfc7600v4.txt		rfc7600.txt
	skipping to change at page 5, line 28		skipping to change at page 5, line 28
	by a PSID.		by a PSID.
	Mapping rule: A set of parameters that are used by BRs and CEs to		Mapping rule: A set of parameters that are used by BRs and CEs to
	derive 4rd IPv6 addresses from 4rd IPv4 addresses. Mapping		derive 4rd IPv6 addresses from 4rd IPv4 addresses. Mapping
	rules are also used by each CE to derive a 4rd IPv4 prefix from		rules are also used by each CE to derive a 4rd IPv4 prefix from
	an IPv6 prefix that has been delegated to it.		an IPv6 prefix that has been delegated to it.
	EA bits (Embedded Address bits): Bits that are the same in a 4rd		EA bits (Embedded Address bits): Bits that are the same in a 4rd
	IPv4 address and in the 4rd IPv6 address derived from it.		IPv4 address and in the 4rd IPv6 address derived from it.
	BR mapping rule: The mapping rule that is applicable to off-domain		BR Mapping rule: The Mapping rule that is applicable to off-domain
	IPv4 addresses (addresses reachable via BRs). It can also apply		IPv4 addresses (addresses reachable via BRs). It can also apply
	to some or all CE-assigned IPv4 addresses.		to some or all CE-assigned IPv4 addresses.
	CE mapping rule: A mapping rule that is applicable only to		CE Mapping rule: A Mapping rule that is applicable only to
	CE-assigned IPv4 addresses (shared or not).		CE-assigned IPv4 addresses (shared or not).
	NAT64+ mapping rule: The mapping rule that is applicable to IPv4		NAT64+ Mapping rule: The Mapping rule that is applicable to IPv4
	addresses reachable via a NAT64+.		addresses reachable via a NAT64+.
	CNP (Checksum Neutrality Preserver): A field of 4rd IPv6 addresses		CNP (Checksum Neutrality Preserver): A field of 4rd IPv6 addresses
	that ensures that TCP-like checksums do not change when IPv4		that ensures that TCP-like checksums do not change when IPv4
	addresses are replaced with 4rd IPv6 addresses.		addresses are replaced with 4rd IPv6 addresses.
	4rd Tag: A 16-bit tag whose value allows 4rd CEs, BRs, and NAT64+s		4rd Tag: A 16-bit tag whose value allows 4rd CEs, BRs, and NAT64+s
	to distinguish 4rd IPv6 addresses from other IPv6 addresses.		to distinguish 4rd IPv6 addresses from other IPv6 addresses.
	3. The 4rd Model		3. The 4rd Model
	skipping to change at page 9, line 29		skipping to change at page 9, line 29
	4. Well-Known Ports (WKPs) authorized (OPTIONAL)		4. Well-Known Ports (WKPs) authorized (OPTIONAL)
	B. Domain Path MTU (PMTU)		B. Domain Path MTU (PMTU)
	C. Hub-and-spoke topology (Yes or No)		C. Hub-and-spoke topology (Yes or No)
	D. Tunnel Traffic Class (OPTIONAL)		D. Tunnel Traffic Class (OPTIONAL)
	"Rule IPv4 prefix" is used to find, by a longest match, which Mapping		"Rule IPv4 prefix" is used to find, by a longest match, which Mapping
	rule applies to a 4rd IPv4 address (Section 4.5). A Mapping rule		rule applies to a 4rd IPv4 address (Section 4.5). A Mapping rule
	whose Rule IPv4 prefix is longer than /0 is a CE mapping rule. BR		whose Rule IPv4 prefix is longer than /0 is a CE Mapping rule. BR
	and NAT64+ mapping rules, which must apply to all off-domain IPv4		and NAT64+ Mapping rules, which must apply to all off-domain IPv4
	addresses, have /0 as their Rule IPv4 prefixes.		addresses, have /0 as their Rule IPv4 prefixes.
	"EA-bits length" is the number of bits that are common to 4rd IPv4		"EA-bits length" is the number of bits that are common to 4rd IPv4
	addresses and 4rd IPv6 addresses derived from them. In a CE mapping		addresses and 4rd IPv6 addresses derived from them. In a CE Mapping
	rule, it is also the number of bits that are common to a CE-delegated		rule, it is also the number of bits that are common to a CE-delegated
	IPv6 prefix and the 4rd IPv4 prefix derived from it. BR and NAT64+		IPv6 prefix and the 4rd IPv4 prefix derived from it. BR and NAT64+
	mapping rules have EA-bits lengths equal to 32.		Mapping rules have EA-bits lengths equal to 32.
	"Rule IPv6 prefix" is the prefix that is used as a substitute for the		"Rule IPv6 prefix" is the prefix that is used as a substitute for the
	Rule IPv4 prefix when a 4rd IPv6 address is derived from a 4rd IPv4		Rule IPv4 prefix when a 4rd IPv6 address is derived from a 4rd IPv4
	address (Section 4.5). In a BR mapping rule or a NAT64+ mapping		address (Section 4.5). In a BR Mapping rule or a NAT64+ Mapping
	rule, it MUST be a /80 prefix whose bits 64-79 are the 4rd Tag.		rule, it MUST be a /80 prefix whose bits 64-79 are the 4rd Tag.
	"WKPs authorized" may be set for mapping rules that assign shared		"WKPs authorized" may be set for Mapping rules that assign shared
	IPv4 addresses to CEs. (These rules are those whose length of the		IPv4 addresses to CEs. (These rules are those whose length of the
	Rule IPv4 prefix plus the EA-bits length exceeds 32.) If set,		Rule IPv4 prefix plus the EA-bits length exceeds 32.) If set,
	well-known ports may be assigned to some CEs having particular IPv6		well-known ports may be assigned to some CEs having particular IPv6
	prefixes. If not set, fairness is privileged: all IPv6 prefixes		prefixes. If not set, fairness is privileged: all IPv6 prefixes
	concerned with the Mapping rule have port sets having identical		concerned with the Mapping rule have port sets having identical
	values (no port set includes any of the well-known ports).		values (no port set includes any of the well-known ports).
	"Domain PMTU" is the IPv6 Path MTU that the ISP can guarantee for all		"Domain PMTU" is the IPv6 Path MTU that the ISP can guarantee for all
	of its IPv6 paths between CEs and between BRs and CEs. It MUST be at		of its IPv6 paths between CEs and between BRs and CEs. It MUST be at
	least 1280 octets [RFC2460].		least 1280 octets [RFC2460].
	skipping to change at page 11, line 7		skipping to change at page 11, line 7
	* The IPv4 packet is already fragmented, or may be fragmented		* The IPv4 packet is already fragmented, or may be fragmented
	later on, i.e., if MF = 1 OR offset > 0 OR (total length >		later on, i.e., if MF = 1 OR offset > 0 OR (total length >
	68 AND DF = 0).		68 AND DF = 0).
	In order to optimize cases where fragmentation headers are		In order to optimize cases where fragmentation headers are
	unnecessary, the NAT44 of a CE that has one SHOULD send packets		unnecessary, the NAT44 of a CE that has one SHOULD send packets
	with TTL = 254.		with TTL = 254.
	R-5: In Domains whose chosen topology is hub-and-spoke, BRs that		R-5: In Domains whose chosen topology is hub-and-spoke, BRs that
	receive 4rd IPv6 packets whose embedded destination IPv4		receive 4rd IPv6 packets whose embedded destination IPv4
	addresses match a CE mapping rule MUST do the equivalent of		addresses match a CE Mapping rule MUST do the equivalent of
	reversibly translating their headers to IPv4 and then		reversibly translating their headers to IPv4 and then
	reversibly translate them back to IPv6 as though packets would		reversibly translate them back to IPv6 as though packets would
	be entering the Domain.		be entering the Domain.
	(A) Without IPv6 fragment header		(A) Without IPv6 fragment header
	IPv4 packet Tunnel packet		IPv4 packet Tunnel packet
	+--------------------+ : : +--------------------+		+--------------------+ : : +--------------------+
	20| IPv4 Header | : <==> : | IPv6 Header | 40		20| IPv4 Header | : <==> : | IPv6 Header | 40
	+--------------------+ : : +--------------------+		+--------------------+ : : +--------------------+
	| IP Payload | <==> | IP Payload |		| IP Payload | <==> | IP Payload |
	skipping to change at page 16, line 46		skipping to change at page 16, line 46
	(by default) (If WKPs authorized)		(by default) (If WKPs authorized)
	: : : :		: : : :
	+---+----+---------+ +----+-------------+		+---+----+---------+ +----+-------------+
	Ports in |> 0|PSID|any value| OR |PSID| any value |		Ports in |> 0|PSID|any value| OR |PSID| any value |
	the CE port set +---+----+---------+ +----+-------------+		the CE port set +---+----+---------+ +----+-------------+
	: 4 : 12 : : 16 :		: 4 : 12 : : 16 :
	Figure 4: From CE IPv6 Prefix to 4rd IPv4 Address and Port Set		Figure 4: From CE IPv6 Prefix to 4rd IPv4 Address and Port Set
	R-7: A CE whose delegated IPv6 prefix matches the Rule IPv6 prefix		R-7: A CE whose delegated IPv6 prefix matches the Rule IPv6 prefix
	of one or several Mapping rules MUST select the CE mapping rule		of one or several Mapping rules MUST select the CE Mapping rule
	for which the match is the longest. It then derives its 4rd		for which the match is the longest. It then derives its 4rd
	IPv4 prefix as shown in Figure 4: (1) The CE replaces the Rule		IPv4 prefix as shown in Figure 4: (1) The CE replaces the Rule
	IPv6 prefix with the Rule IPv4 prefix. The result is the CE		IPv6 prefix with the Rule IPv4 prefix. The result is the CE
	4rd IPv4 prefix. (2) If this CE 4rd IPv4 prefix has less than		4rd IPv4 prefix. (2) If this CE 4rd IPv4 prefix has less than
	32 bits, the CE takes it as its assigned IPv4 prefix. If it		32 bits, the CE takes it as its assigned IPv4 prefix. If it
	has exactly 32 bits, the CE takes it as its IPv4 address. If		has exactly 32 bits, the CE takes it as its IPv4 address. If
	it has more than 32 bits, the CE MUST take the first 32 bits as		it has more than 32 bits, the CE MUST take the first 32 bits as
	its shared public IPv4 address and bits beyond the first 32 as		its shared public IPv4 address and bits beyond the first 32 as
	its Port-set identifier (PSID). Ports of its restricted port		its Port-Set identifier (PSID). Ports of its restricted port
	set are by default those that have any non-zero value in their		set are by default those that have any non-zero value in their
	first 4 bits (the PSID offset), followed by the PSID, and		first 4 bits (the PSID offset), followed by the PSID, and
	followed by any values in remaining bits. If the WKP		followed by any values in remaining bits. If the WKP
	authorized option applies to the Mapping rule, there is no		authorized option applies to the Mapping rule, there is no
	4-bit offset before the PSID so that all ports can be assigned.		4-bit offset before the PSID so that all ports can be assigned.
	NOTE: The choice of the default PSID position in Port fields		NOTE: The choice of the default PSID position in port fields
	has been guided by the following objectives: (1) for fairness,		has been guided by the following objectives: (1) for fairness,
	avoid having any of the well-known ports 0-1023 in the port set		avoid having any of the well-known ports 0-1023 in the port set
	specified by any PSID value; (2) for compatibility with RTP/		specified by any PSID value; (2) for compatibility with RTP/
	RTCP [RFC4961], include in each port set pairs of consecutive		RTCP [RFC4961], include in each port set pairs of consecutive
	ports; (3) in order to facilitate operation and training, have		ports; (3) in order to facilitate operation and training, have
	the PSID at a fixed position in port fields; (4) in order to		the PSID at a fixed position in port fields; (4) in order to
	facilitate documentation in hexadecimal notation, and to		facilitate documentation in hexadecimal notation, and to
	facilitate maintenance, have this position nibble-aligned.		facilitate maintenance, have this position nibble-aligned.
	Ports that are excluded from assignment to CEs are 0-4095,		Ports that are excluded from assignment to CEs are 0-4095,
	instead of just 0-1023, in a trade-off to favor nibble		instead of just 0-1023, in a trade-off to favor nibble
	alignment of PSIDs and overall simplicity.		alignment of PSIDs and overall simplicity.
	R-8: A CE whose delegated IPv6 prefix has its longest match with the		R-8: A CE whose delegated IPv6 prefix has its longest match with the
	Rule IPv6 prefix of the BR mapping rule MUST take as its IPv4		Rule IPv6 prefix of the BR Mapping rule MUST take as its IPv4
	address the 32 bits that, in the delegated IPv6 prefix, follow		address the 32 bits that, in the delegated IPv6 prefix, follow
	this Rule IPv6 prefix. If this is the case while the hub-and-		this Rule IPv6 prefix. If this is the case while the hub-and-
	spoke option applies to the Domain, or if the Rule IPv6 prefix		spoke option applies to the Domain, or if the Rule IPv6 prefix
	is not a /80, there is a configuration error in the Domain. An		is not a /80, there is a configuration error in the Domain. An
	implementation-dependent administrative action MAY be taken.		implementation-dependent administrative action MAY be taken.
	A CE whose delegated IPv6 prefix does not match the Rule IPv6		A CE whose delegated IPv6 prefix does not match the Rule IPv6
	prefix of either any CE Mapping rule or the BR mapping rule,		prefix of either any CE Mapping rule or the BR Mapping rule,
	and is in a Domain that has a NAT64+ mapping rule, MUST be		and is in a Domain that has a NAT64+ Mapping rule, MUST be
	noted as having the unspecified IPv4 address.		noted as having the unspecified IPv4 address.
	4.5. Address Mapping from 4rd IPv4 Addresses to 4rd IPv6 Addresses		4.5. Address Mapping from 4rd IPv4 Addresses to 4rd IPv6 Addresses
	: 32 : : 16 : \		: 32 : : 16 : \
	+----------------------------+ +---------------+ |		+----------------------------+ +---------------+ |
	| IPv4 address | |Port_or_ICMP_ID| | Shared-address		| IPv4 address | |Port_or_ICMP_ID| | Shared-address
	+----------------------------+ +---+------+----+ | case		+----------------------------+ +---+------+----+ | case
	: Longest match : : 4 : PSID : | (PSID length		: Longest match : : 4 : PSID : | (PSID length
	: with a Rule IPv4 prefix : :length: | of the rule > 0)		: with a Rule IPv4 prefix : :length: | of the rule > 0)
	skipping to change at page 18, line 30		skipping to change at page 18, line 30
	+--------------------------+--------+-----+ /		+--------------------------+--------+-----+ /
	| Rule IPv6 prefix | EA bits |		| Rule IPv6 prefix | EA bits |
	+--------------------------+--------------+		+--------------------------+--------------+
	: :		: :
	+-----------------------------------------+		+-----------------------------------------+
	| IPv6 prefix |		| IPv6 prefix |
	+-----------------------------------------+		+-----------------------------------------+
	:\_______________________________ / \		:\_______________________________ / \
	: ___________________\______/ \_______________		: ___________________\______/ \_______________
	: / \ \		: / \ \
	: / (CE mapping rule) \ (BR mapping rule) \		: / (CE Mapping rule) \ (BR Mapping rule) \
	: <= 64 : : 112 :		: <= 64 : : 112 :
	+----------+---+---+------+---+ +--------------+---+------+---+		+----------+---+---+------+---+ +--------------+---+------+---+
	|CE v6 prfx| 0 |tag|v4 add|CNP| |BR IPv6 prefix|tag|v4 add|CNP|		|CE v6 prfx| 0 |tag|v4 add|CNP| |BR IPv6 prefix|tag|v4 add|CNP|
	+----------+-|-+---+------+---+ +--------------+---+------+---+		+----------+-|-+---+------+---+ +--------------+---+------+---+
	: <= 64 : | :16 : 32 :16 : : 64 :16 : 32 :16 :		: <= 64 : | :16 : 32 :16 : : 64 :16 : 32 :16 :
	|		|
	Padding to /64		Padding to /64
	Figure 5: From 4rd IPv4 Address to 4rd IPv6 Address		Figure 5: From 4rd IPv4 Address to 4rd IPv6 Address
	skipping to change at page 19, line 24		skipping to change at page 19, line 24
	all 64 bits are set."		all 64 bits are set."
	and		and
	"the whole IID value MUST be viewed as an opaque bit string by		"the whole IID value MUST be viewed as an opaque bit string by
	third parties, except possibly in the local context."		third parties, except possibly in the local context."
	(1) If hub-and-spoke topology does not apply to the Domain, or		(1) If hub-and-spoke topology does not apply to the Domain, or
	if it applies but the IPv6 address to be derived is a		if it applies but the IPv6 address to be derived is a
	source address from a CE or a destination address from a		source address from a CE or a destination address from a
	BR, find the CE mapping rule whose Rule IPv4 prefix has		BR, find the CE Mapping rule whose Rule IPv4 prefix has
	the longest match with the IPv4 address.		the longest match with the IPv4 address.
	If no Mapping rule is thus obtained, take the BR mapping		If no Mapping rule is thus obtained, take the BR Mapping
	rule.		rule.
	If the obtained Mapping rule assigns IPv4 prefixes to CEs,		If the obtained Mapping rule assigns IPv4 prefixes to CEs,
	i.e., if the length of the Rule IPv4 prefix plus EA-bits		i.e., if the length of the Rule IPv4 prefix plus EA-bits
	length is 32 - k, with k >= 0, delete the last k bits of		length is 32 - k, with k >= 0, delete the last k bits of
	the IPv4 address.		the IPv4 address.
	Otherwise, if the length of the Rule IPv4 prefix plus the		Otherwise, if the length of the Rule IPv4 prefix plus the
	EA-bits length is 32 + k, with k > 0, take k as the PSID		EA-bits length is 32 + k, with k > 0, take k as the PSID
	length and append to the IPv4 address the PSID copied from		length and append to the IPv4 address the PSID copied from
	skipping to change at page 23, line 21		skipping to change at page 23, line 21
	For this, a BR MAY systematically reassemble fragmented IPv4 packets		For this, a BR MAY systematically reassemble fragmented IPv4 packets
	before tunneling them. But this consumes large memory space, creates		before tunneling them. But this consumes large memory space, creates
	opportunities for denial-of-service-attacks, and can significantly		opportunities for denial-of-service-attacks, and can significantly
	increase forwarding delays. This is the reason for the following		increase forwarding delays. This is the reason for the following
	requirement:		requirement:
	R-15: BRs SHOULD support an algorithm whereby received IPv4 packets		R-15: BRs SHOULD support an algorithm whereby received IPv4 packets
	can be forwarded on the fly. The following is an example of		can be forwarded on the fly. The following is an example of
	such an algorithm:		such an algorithm:
	(1) At BR initialization, if at least one CE mapping rule		(1) At BR initialization, if at least one CE Mapping rule
	deals with one or more shared public IPv4 addresses (i.e.,		deals with one or more shared public IPv4 addresses (i.e.,
	length of Rule IPv4 prefix + EA-bits length > 32), the BR		length of Rule IPv4 prefix + EA-bits length > 32), the BR
	initializes an empty "IPv4 packet table" whose entries		initializes an empty "IPv4 packet table" whose entries
	have the following items:		have the following items:
	- IPv4 source		- IPv4 source
	- IPv4 destination		- IPv4 destination
	- IPv4 identification		- IPv4 identification
	skipping to change at page 26, line 32		skipping to change at page 26, line 32
	Unreachable, Net unreachable), and ICMPv6 Type = 3 and Code = 0		Unreachable, Net unreachable), and ICMPv6 Type = 3 and Code = 0
	(Time Exceeded, Hop limit exceeded in transit) MUST be		(Time Exceeded, Hop limit exceeded in transit) MUST be
	translated into ICMPv4 Type = 11 and Code = 0 (Time Exceeded,		translated into ICMPv4 Type = 11 and Code = 0 (Time Exceeded,
	time to live exceeded in transit).		time to live exceeded in transit).
	4.9. Provisioning 4rd Parameters to CEs		4.9. Provisioning 4rd Parameters to CEs
	Domain parameters listed in Section 4.2 are subject to the following		Domain parameters listed in Section 4.2 are subject to the following
	constraints:		constraints:
	R-23: Each Domain MUST have a BR mapping rule and/or a NAT64+ mapping		R-23: Each Domain MUST have a BR Mapping rule and/or a NAT64+ Mapping
	rule. The BR mapping rule is only used by CEs that are		rule. The BR Mapping rule is only used by CEs that are
	assigned public IPv4 addresses, shared or not. The NAT64+		assigned public IPv4 addresses, shared or not. The NAT64+
	mapping rule is only used by CEs that are assigned the		Mapping rule is only used by CEs that are assigned the
	unspecified IPv4 address (Section 4.4) and therefore need an		unspecified IPv4 address (Section 4.4) and therefore need an
	ISP NAT64 to reach IPv4 destinations.		ISP NAT64 to reach IPv4 destinations.
	R-24: Each CE and each BR MUST support up to 32 Mapping rules.		R-24: Each CE and each BR MUST support up to 32 Mapping rules.
	Support for up to 32 Mapping rules ensures that independently		Support for up to 32 Mapping rules ensures that independently
	acquired CEs and BR nodes can always interwork.		acquired CEs and BR nodes can always interwork.
	ISPs that need Mapping rules for more IPv4 prefixes than this		ISPs that need Mapping rules for more IPv4 prefixes than this
	number SHOULD split their networks into multiple Domains.		number SHOULD split their networks into multiple Domains.
	Communication between these domains can be done in IPv4 or by		Communication between these domains can be done in IPv4 or by
	some other implementation-dependent, but equivalent, means.		some other implementation-dependent, but equivalent, means.
	R-25: For mesh topologies, where CE-CE paths don't go via BRs, all		R-25: For mesh topologies, where CE-CE paths don't go via BRs, all
	mapping rules of the Domain MUST be sent to all CEs. For		Mapping rules of the Domain MUST be sent to all CEs. For
	hub-and-spoke topologies, where all CE-CE paths go via BRs,		hub-and-spoke topologies, where all CE-CE paths go via BRs,
	each CE MAY be sent only the BR mapping rule of the Domain		each CE MAY be sent only the BR Mapping rule of the Domain
	plus, if different, the CE mapping rule that applies to its CE		plus, if different, the CE Mapping rule that applies to its CE
	IPv6 prefix.		IPv6 prefix.
	R-26: In a Domain where the chosen topology is hub-and-spoke, all CEs		R-26: In a Domain where the chosen topology is hub-and-spoke, all CEs
	MUST have IPv6 prefixes that match a CE mapping rule.		MUST have IPv6 prefixes that match a CE Mapping rule.
	(Otherwise, packets sent to CEs whose IPv6 prefixes would match		(Otherwise, packets sent to CEs whose IPv6 prefixes would match
	only the BR mapping rule would, with longest-match selected		only the BR Mapping rule would, with longest-match selected
	routes, be routed directly to these CEs. This would be		routes, be routed directly to these CEs. This would be
	contrary to the hub-and-spoke requirement.)		contrary to the hub-and-spoke requirement.)
	R-27: CEs MUST be able to acquire parameters of 4rd domains		R-27: CEs MUST be able to acquire parameters of 4rd domains
	(Section 4.2) in DHCPv6 [RFC3315]. Formats of DHCPv6 options		(Section 4.2) in DHCPv6 [RFC3315]. Formats of DHCPv6 options
	to be used are detailed in Figures 7, 8, and 9, with field		to be used are detailed in Figures 7, 8, and 9, with field
	values specified after each figure.		values specified after each figure.
	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
	skipping to change at page 36, line 16		skipping to change at page 36, line 16
	In the sections that follow, each Mapping rule will be represented as		In the sections that follow, each Mapping rule will be represented as
	follows, using 0bXXX to represent binary number XXX; square brackets		follows, using 0bXXX to represent binary number XXX; square brackets
	("[ ]") indicate optional items:		("[ ]") indicate optional items:
	{Rule IPv4 prefix, EA-bits length, Rule IPv6 prefix		{Rule IPv4 prefix, EA-bits length, Rule IPv6 prefix
	[, WKPs authorized]}		[, WKPs authorized]}
	EXAMPLES:		EXAMPLES:
	{0.0.0.0/0, 32, 2001:db8:0:1:300::/80}		{0.0.0.0/0, 32, 2001:db8:0:1:300::/80}
	a BR mapping rule		a BR Mapping rule
	{198.16.0.0/14, 22, 2001:db8:4000::/34}		{198.16.0.0/14, 22, 2001:db8:4000::/34}
	a CE mapping rule		a CE Mapping rule
	{0.0.0.0/0, 32, 2001:db8:0:1::/80}		{0.0.0.0/0, 32, 2001:db8:0:1::/80}
	a NAT64+ mapping rule		a NAT64+ Mapping rule
	{198.16.0.0/14, 22, 2001:db8:4000::/34, Yes}		{198.16.0.0/14, 22, 2001:db8:4000::/34, Yes}
	a CE mapping rule		a CE Mapping rule
	and hub-and-spoke topology		and hub-and-spoke topology
	Appendix B. Configuring Multiple Mapping Rules		Appendix B. Configuring Multiple Mapping Rules
	As far as mapping rules are concerned, the simplest deployment model		As far as Mapping rules are concerned, the simplest deployment model
	is that in which the Domain has only one rule (the BR mapping rule).		is that in which the Domain has only one rule (the BR Mapping rule).
	To assign an IPv4 address to a CE in this model, an IPv6 /112 is		To assign an IPv4 address to a CE in this model, an IPv6 /112 is
	assigned to it, comprising the BR /64 prefix, the 4rd Tag, and the		assigned to it, comprising the BR /64 prefix, the 4rd Tag, and the
	IPv4 address. However, this model has the following limitations: (1)		IPv4 address. However, this model has the following limitations: (1)
	shared IPv4 addresses are not supported; (2) IPv6 prefixes used for		shared IPv4 addresses are not supported; (2) IPv6 prefixes used for
	4rd are too long to also be used for native IPv6 addresses; (3) if		4rd are too long to also be used for native IPv6 addresses; (3) if
	the IPv4 address space of the ISP is split with many disjoint IPv4		the IPv4 address space of the ISP is split with many disjoint IPv4
	prefixes, the IPv6 routing plan must be as complex as an IPv4 routing		prefixes, the IPv6 routing plan must be as complex as an IPv4 routing
	plan based on these prefixes.		plan based on these prefixes.
	With more mapping rules, CE prefixes used for 4rd can be those used		With more Mapping rules, CE prefixes used for 4rd can be those used
	for native IPv6. How to choose CE mapping rules for a particular		for native IPv6. How to choose CE Mapping rules for a particular
	deployment does not need to be standardized.		deployment does not need to be standardized.
	The following is only a particular pragmatic approach that can be		The following is only a particular pragmatic approach that can be
	used for various deployment scenarios. It is applied in some of the		used for various deployment scenarios. It is applied in some of the
	use cases that follow.		use cases that follow.
	(1) Select a "Common_IPv6_prefix" that will appear at the beginning		(1) Select a "Common_IPv6_prefix" that will appear at the beginning
	of all 4rd CE IPv6 prefixes.		of all 4rd CE IPv6 prefixes.
	(2) Choose all IPv4 prefixes to be used, and assign one of them to		(2) Choose all IPv4 prefixes to be used, and assign one of them to
	each CE mapping rule i.		each CE Mapping rule i.
	(3) For each CE mapping rule i, do the following:		(3) For each CE Mapping rule i, do the following:
	A. Choose the length of its Rule IPv6 prefix (possibly the same		A. Choose the length of its Rule IPv6 prefix (possibly the same
	for all CE mapping rules).		for all CE Mapping rules).
	B. Determine its PSID_length(i). A CE mapping rule that		B. Determine its PSID_length(i). A CE Mapping rule that
	assigns shared addresses with a sharing ratio of 2^Ki has		assigns shared addresses with a sharing ratio of 2^Ki has
	PSID_length = Ki. A CE mapping rule that assigns IPv4		PSID_length = Ki. A CE Mapping rule that assigns IPv4
	prefixes of length L < 32 is considered to have a negative		prefixes of length L < 32 is considered to have a negative
	PSID_length (PSID_length = L - 32).		PSID_length (PSID_length = L - 32).
	C. Derive EA-bits length (i) = 32 - L(Rule IPv4 prefix(i)) +		C. Derive EA-bits length(i) = 32 - L(Rule IPv4 prefix(i)) +
	PSID_length(i).		PSID_length(i).
	D. Derive the length of Rule_code(i), the prefix to be appended		D. Derive the length of Rule_code(i), the prefix to be appended
	to the Common prefix to get the Rule IPv6 prefix of rule i:		to the common prefix to get the Rule IPv6 prefix of rule i:
	L(Rule_code(i)) = L(CE IPv6 prefix(i))		L(Rule_code(i)) = L(CE IPv6 prefix(i))
	- L(Common_IPv6_prefix)		- L(Common_IPv6_prefix)
	- (32 - L(Rule IPv4 prefix(i)))		- (32 - L(Rule IPv4 prefix(i)))
	- PSID_length(i)		- PSID_length(i)
	E. Derive Rule_code(i) with the following constraints: (1) its		E. Derive Rule_code(i) with the following constraints: (1) its
	length is L(Rule_code(i)); (2) it does not overlap with any		length is L(Rule_code(i)); (2) it does not overlap with any
	of the previously obtained Rule codes (for instance, 010 and		of the previously obtained Rule_codes (for instance, 010 and
	01011 do overlap, while 00, 011, and 010 do not); (3) it has		01011 do overlap, while 00, 011, and 010 do not); (3) it has
	the lowest possible value as a fractional binary number (for		the lowest possible value as a fractional binary number (for
	instance, 0100 < 10 < 11011 < 111). Thus, rules whose		instance, 0100 < 10 < 11011 < 111). Thus, rules whose
	Rule_code lengths are 4, 3, 5, and 2 give Rule_codes 0000,		Rule_code lengths are 4, 3, 5, and 2 give Rule_codes 0000,
	001, 00010, and 01.		001, 00010, and 01.
	F. Take Rule IPv6 prefix(i) = the Common_IPv6_prefix followed		F. Take Rule IPv6 prefix(i) = the Common_IPv6_prefix followed
	by Rule_code(i).		by Rule_code(i).
	:<--------------------- L(CE IPv6 prefix(i)) --------------------->:		:<--------------------- L(CE IPv6 prefix(i)) --------------------->:
	: :		: :
	: 32 - L(Rule IPv4 prefix(i)) PSID_length(i):		: 32 - L(Rule IPv4 prefix(i)) PSID_length(i):
	: \ | :		: \ | :
	: :<---------'--------><--'-->:		: :<---------'--------><--'-->:
	: : || :		: : || :
	: : \/ :		: : \/ :
	: :<------->:<--- EA-bits length(i) --->:		: :<------->:<--- EA-bits length(i) --->:
	: L(Rule code(i))		: L(Rule_code(i))
	: : :		: : :
	+----------------------------+---------+		+----------------------------+---------+
	| Common IPv6 prefix |Rule code|		| Common_IPv6_prefix |Rule_code|
	| | (i) |		| | (i) |
	+----------------------------+---------+		+----------------------------+---------+
	:<------ L(Rule IPv6 prefix(i)) ------>:		:<------ L(Rule IPv6 prefix(i)) ------>:
	Figure 10: Diagram of One Pragmatic Approach		Figure 10: Diagram of One Pragmatic Approach
	Appendix C. Adding Shared IPv4 Addresses to an IPv6 Network		Appendix C. Adding Shared IPv4 Addresses to an IPv6 Network
	C.1. With CEs within CPEs		C.1. With CEs within CPEs
	skipping to change at page 39, line 5		skipping to change at page 39, line 5
	192.2.0.0/16, and 192.1.0.0/16 (neither overlapping nor		192.2.0.0/16, and 192.1.0.0/16 (neither overlapping nor
	aggregatable). This gives 2^(32 - 15) + 3 * 2^(32 - 16) IPv4		aggregatable). This gives 2^(32 - 15) + 3 * 2^(32 - 16) IPv4
	addresses, i.e., 2^18 + 2^16. For the 2^20 customers to have the		addresses, i.e., 2^18 + 2^16. For the 2^20 customers to have the
	same sharing ratio, the number of IPv4 addresses to be shared has to		same sharing ratio, the number of IPv4 addresses to be shared has to
	be a power of 2. The ISP can therefore give up using one of its		be a power of 2. The ISP can therefore give up using one of its
	/16s, say the last one. (Whether or not it could be motivated to		/16s, say the last one. (Whether or not it could be motivated to
	return it to its Internet Registry is off-scope for this document.)		return it to its Internet Registry is off-scope for this document.)
	The sharing ratio to apply is then 2^20 / 2^18 = 2^2 = 4, giving a		The sharing ratio to apply is then 2^20 / 2^18 = 2^2 = 4, giving a
	PSID length of 2.		PSID length of 2.
	Applying the principles of Appendix B with L(Common IPv6 prefix) =		Applying the principles of Appendix B with L(Common_IPv6_prefix) =
	36, L(PSID) = 2 for all rules, and L(CE IPv6 prefix(i)) = 56 for all		36, L(PSID) = 2 for all rules, and L(CE IPv6 prefix(i)) = 56 for all
	rules, Rule codes and Rule IPv6 prefixes are as follows:		rules, Rule_codes and Rule IPv6 prefixes are as follows:
	+--------------+--------+-----------+-----------+-------------------+		+--------------+--------+-----------+-----------+-------------------+
	| CE Rule IPv4 | EA | Rule-Code | Code | CE Rule IPv6 |		| CE Rule IPv4 | EA | Rule-Code | Code | CE Rule IPv6 |
	| prefix | bits | length | (binary) | prefix |		| prefix | bits | length | (binary) | prefix |
	| | length | | | |		| | length | | | |
	+--------------+--------+-----------+-----------+-------------------+		+--------------+--------+-----------+-----------+-------------------+
	| 192.8.0.0/15 | 19 | 1 | 0 | 2001:db8:0::/37 |		| 192.8.0.0/15 | 19 | 1 | 0 | 2001:db8:0::/37 |
	| 192.4.0.0/16 | 18 | 2 | 10 | 2001:db8:800::/38 |		| 192.4.0.0/16 | 18 | 2 | 10 | 2001:db8:800::/38 |
	| 192.2.0.0/16 | 18 | 2 | 11 | 2001:db8:c00::/38 |		| 192.2.0.0/16 | 18 | 2 | 11 | 2001:db8:c00::/38 |
	+--------------+--------+-----------+-----------+-------------------+		+--------------+--------+-----------+-----------+-------------------+
	skipping to change at page 40, line 12		skipping to change at page 40, line 12
	Ports : 0bYYYY 11XX XXXX XXXX		Ports : 0bYYYY 11XX XXXX XXXX
	with YYYY > 0, and X...X any value		with YYYY > 0, and X...X any value
	An IPv4 packet sent to address 192.4.238.238 and port 7777 is		An IPv4 packet sent to address 192.4.238.238 and port 7777 is
	tunneled to the IPv6 address obtained as follows (Section 4.5):		tunneled to the IPv6 address obtained as follows (Section 4.5):
	IPv4 address : 192.4.238.238 (0xc004 eeee)		IPv4 address : 192.4.238.238 (0xc004 eeee)
	: 0b1100 0000 0000 0100 1110 1110 1110 1110		: 0b1100 0000 0000 0100 1110 1110 1110 1110
	Rule IPv4 prefix(i): 192.4.0.0/16 (longest match)		Rule IPv4 prefix(i): 192.4.0.0/16 (longest match)
	: 0b1100 0000 0000 0100		: 0b1100 0000 0000 0100
	IPv4 suffix (i) : 0b1110 1110 1110 1110		IPv4 suffix(i) : 0b1110 1110 1110 1110
	EA-bits length (i) : 18		EA-bits length(i) : 18
	PSID length (i) : 2 (= 16 + 18 - 32)		PSID length(i) : 2 (= 16 + 18 - 32)
	Port field : 0b 0001 1110 0110 0001 (7777)		Port field : 0b 0001 1110 0110 0001 (7777)
	PSID : 0b11		PSID : 0b11
	Rule IPv6 prefix(i): 2001:0db8:0800::/38		Rule IPv6 prefix(i): 2001:0db8:0800::/38
	CE IPv6 prefix : 2001:0db8:0bbb:bb00::/56		CE IPv6 prefix : 2001:0db8:0bbb:bb00::/56
	IPv6 address : 2001:0db8:0bbb:bb00:300:c004:eeee:YYYY		IPv6 address : 2001:0db8:0bbb:bb00:300:c004:eeee:YYYY
	with YYYY = the computed CNP		with YYYY = the computed CNP
	C.2. With Some CEs behind Third-Party Router CPEs		C.2. With Some CEs behind Third-Party Router CPEs
	We now consider an ISP that has the same need as the ISP described in		We now consider an ISP that has the same need as the ISP described in
	skipping to change at page 40, line 36		skipping to change at page 40, line 36
	IPv6 infrastructure, it uses that of a third-party provider and (2)		IPv6 infrastructure, it uses that of a third-party provider and (2)
	some of its customers use this provider's Customer Premises Equipment		some of its customers use this provider's Customer Premises Equipment
	(CPEs) so that they can use specific services offered by the		(CPEs) so that they can use specific services offered by the
	provider. In these CPEs, a non-zero index is used to route IPv6		provider. In these CPEs, a non-zero index is used to route IPv6
	packets to the physical port to which CEs are attached, say 0x2.		packets to the physical port to which CEs are attached, say 0x2.
	Each such CPE delegates to the CE nodes the customer-site IPv6 prefix		Each such CPE delegates to the CE nodes the customer-site IPv6 prefix
	followed by this index.		followed by this index.
	The ISP is supposed to have the same IPv4 prefixes as those in the		The ISP is supposed to have the same IPv4 prefixes as those in the
	previous use case -- 192.8.0.0/15, 192.4.0.0/16, and 192.2.0.0/16 --		previous use case -- 192.8.0.0/15, 192.4.0.0/16, and 192.2.0.0/16 --
	and to use the same Common IPv6 prefix, 2001:db8:0::/36.		and to use the same Common_IPv6_prefix, 2001:db8:0::/36.
	We also assume that only a minority of customers use third-party		We also assume that only a minority of customers use third-party
	CPEs, so that it is sufficient to use only one of the two /16s for		CPEs, so that it is sufficient to use only one of the two /16s for
	them.		them.
	Mapping rules are then (see Appendix C.1):		Mapping rules are then (see Appendix C.1):
	{192.8.0.0/15, 19, 2001:0db8:0000::/37}		{192.8.0.0/15, 19, 2001:0db8:0000::/37}
	{192.4.0.0/16, 18, 2001:0db8:0800::/38}		{192.4.0.0/16, 18, 2001:0db8:0800::/38}
	{192.2.0.0/16, 18, 2001:0db8:0c00::/38}		{192.2.0.0/16, 18, 2001:0db8:0c00::/38}
	skipping to change at page 41, line 14		skipping to change at page 41, line 14
	In a BR, and also in a CE if the topology is mesh, the IPv6 address		In a BR, and also in a CE if the topology is mesh, the IPv6 address
	that is derived from IPv4 address 192.4.238.238 and port 7777 is		that is derived from IPv4 address 192.4.238.238 and port 7777 is
	obtained as described in the previous section, except for the last		obtained as described in the previous section, except for the last
	two steps, which are modified as follows:		two steps, which are modified as follows:
	IPv4 address : 192.4.238.238 (0xc004 eeee)		IPv4 address : 192.4.238.238 (0xc004 eeee)
	: 0b1100 0000 0000 0100 1110 1110 1110 1110		: 0b1100 0000 0000 0100 1110 1110 1110 1110
	Rule IPv4 prefix(i): 192.4.0.0/16 (longest match)		Rule IPv4 prefix(i): 192.4.0.0/16 (longest match)
	: 0b1100 0000 0000 0100		: 0b1100 0000 0000 0100
	IPv4 suffix (i) : 0b1110 1110 1110 1110		IPv4 suffix(i) : 0b1110 1110 1110 1110
	EA-bits length (i) : 18		EA-bits length(i) : 18
	PSID length (i) : 2 (= 16 + 18 - 32)		PSID length(i) : 2 (= 16 + 18 - 32)
	Port field : 0b 0001 1110 0110 0001 (7777)		Port field : 0b 0001 1110 0110 0001 (7777)
	PSID : 0b11		PSID : 0b11
	Rule IPv6 prefix(i): 2001:0db8:0800::/38		Rule IPv6 prefix(i): 2001:0db8:0800::/38
	CE IPv6 prefix : 2001:0db8:0bbb:bb00::/60		CE IPv6 prefix : 2001:0db8:0bbb:bb00::/60
	IPv6 address : 2001:0db8:0bbb:bb00:300:192.4.238.238:YYYY		IPv6 address : 2001:0db8:0bbb:bb00:300:192.4.238.238:YYYY
	with YYYY = the computed CNP		with YYYY = the computed CNP
	Appendix D. Replacing Dual-Stack Routing with IPv6-Only Routing		Appendix D. Replacing Dual-Stack Routing with IPv6-Only Routing
	In this use case, we consider an ISP that offers IPv4 service with		In this use case, we consider an ISP that offers IPv4 service with
End of changes. 45 change blocks.
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