rfc9768v5.txt		rfc9768.txt
	skipping to change at line 176 ¶		skipping to change at line 176 ¶
	supporting the pre-existing TCP congestion controllers that use just		supporting the pre-existing TCP congestion controllers that use just
	one feedback signal per round. Congestion control is the term the		one feedback signal per round. Congestion control is the term the
	IETF uses to describe data rate management. It is the algorithm that		IETF uses to describe data rate management. It is the algorithm that
	a sender uses to optimize its sending rate so that it transmits data		a sender uses to optimize its sending rate so that it transmits data
	as fast as the network can carry it, but no faster. A fuller		as fast as the network can carry it, but no faster. A fuller
	description of the motivation for this specification is given in the		description of the motivation for this specification is given in the
	associated requirements document [RFC7560].		associated requirements document [RFC7560].
	This document specifies a Standards Track scheme for ECN feedback in		This document specifies a Standards Track scheme for ECN feedback in
	the TCP header to provide more than one feedback signal per RTT. It		the TCP header to provide more than one feedback signal per RTT. It
	is called the more "Accurate ECN" feedback scheme, or AccECN for		is called the more "Accurate ECN feedback" scheme, or AccECN for
	short. This document updates RFC 3168 with respect to negotiation		short. This document updates RFC 3168 with respect to negotiation
	and use of the feedback scheme for TCP. All aspects of RFC 3168		and use of the feedback scheme for TCP. All aspects of RFC 3168
	other than the TCP feedback scheme and its negotiation remain		other than the TCP feedback scheme and its negotiation remain
	unchanged by this specification. In particular, the definition of		unchanged by this specification. In particular, the definition of
	ECN at the IP layer is unaffected. Section 4 details the aspects of		ECN at the IP layer is unaffected. Section 4 details the aspects of
	RFC 3168 that are updated by this document.		RFC 3168 that are updated by this document.
	This document uses the term "Classic ECN feedback" when it needs to		This document uses the term "Classic ECN feedback" when it needs to
	distinguish the TCP/ECN feedback scheme defined in [RFC3168] from the		distinguish the TCP/ECN feedback scheme defined in [RFC3168] from the
	AccECN TCP feedback scheme. AccECN is intended to offer a complete		AccECN TCP feedback scheme. AccECN is intended to offer a complete
	skipping to change at line 269 ¶		skipping to change at line 269 ¶
	The requirements document recognizes that a protocol as ubiquitous as		The requirements document recognizes that a protocol as ubiquitous as
	TCP needs to be able to serve as-yet-unspecified requirements.		TCP needs to be able to serve as-yet-unspecified requirements.
	Therefore, an AccECN receiver acts as a generic (mechanistic)		Therefore, an AccECN receiver acts as a generic (mechanistic)
	reflector of congestion information with the aim that new sender		reflector of congestion information with the aim that new sender
	behaviours can be deployed unilaterally (see Section 2.5) in the		behaviours can be deployed unilaterally (see Section 2.5) in the
	future.		future.
	1.3. Terminology		1.3. Terminology
	AccECN: The more Accurate ECN feedback scheme is called AccECN for		Accurate ECN feedback: The more Accurate ECN feedback scheme is
	short.		called AccECN for short.
	Classic ECN: The ECN protocol specified in [RFC3168].		Classic ECN: The ECN protocol specified in [RFC3168].
	Classic ECN feedback: The feedback aspect of the ECN protocol		Classic ECN feedback: The feedback aspect of the ECN protocol
	specified in [RFC3168], including generation, encoding,		specified in [RFC3168], including generation, encoding,
	transmission and decoding of feedback, but not the Data Sender's		transmission and decoding of feedback, but not the Data Sender's
	subsequent response to that feedback.		subsequent response to that feedback.
	ACK: A TCP acknowledgement, with or without a data payload (ACK=1).		ACK: A TCP acknowledgement, with or without a data payload (ACK=1).
	skipping to change at line 1950 ¶		skipping to change at line 1950 ¶
	If a host is in the mode that assumes incoming AccECN Options are not		If a host is in the mode that assumes incoming AccECN Options are not
	available, but it receives an AccECN Option at any later point during		available, but it receives an AccECN Option at any later point during
	the connection, this clearly indicates that AccECN Options are no		the connection, this clearly indicates that AccECN Options are no
	longer blocked on the respective path, and the AccECN endpoint MAY		longer blocked on the respective path, and the AccECN endpoint MAY
	switch out of the mode that assumes AccECN Options are not available		switch out of the mode that assumes AccECN Options are not available
	for this half-connection.		for this half-connection.
	3.2.3.2.4. Test for Zeroing of the AccECN Option		3.2.3.2.4. Test for Zeroing of the AccECN Option
	For a related test for invalid initialization of the ACE field, see		For a related test for invalid initialization of the ACE field, see
	Section 3.2.2.4		Section 3.2.2.4.
	Section 3.2.1 required the Data Receiver to initialize the r.e0b and		Section 3.2.1 required the Data Receiver to initialize the r.e0b and
	r.e1b counters to a non-zero value. Therefore, in either direction		r.e1b counters to a non-zero value. Therefore, in either direction
	the initial value of the EE0B field or EE1B field in an AccECN Option		the initial value of the EE0B field or EE1B field in an AccECN Option
	(if one exists) ought to be non-zero. If AccECN has been negotiated:		(if one exists) ought to be non-zero. If AccECN has been negotiated:
	* the TCP Server MAY check that the initial value of the EE0B field		* the TCP Server MAY check that the initial value of the EE0B field
	or the EE1B field is non-zero in the first segment that		or the EE1B field is non-zero in the first segment that
	acknowledges sequence space that at least covers the ISN plus 1.		acknowledges sequence space that at least covers the ISN plus 1.
	If it runs a test and either initial value is zero, the Server		If it runs a test and either initial value is zero, the Server
End of changes. 3 change blocks.
	4 lines changed or deleted		4 lines changed or added
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