rfc9002v4.txt		rfc9002.txt
	skipping to change at line 49 ¶		skipping to change at line 49 ¶
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	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		1. Introduction
	2. Conventions and Definitions		2. Conventions and Definitions
	3. Design of the QUIC Transmission Machinery		3. Design of the QUIC Transmission Machinery
	4. Relevant Differences Between QUIC and TCP		4. Relevant Differences between QUIC and TCP
	4.1. Separate Packet Number Spaces		4.1. Separate Packet Number Spaces
	4.2. Monotonically Increasing Packet Numbers		4.2. Monotonically Increasing Packet Numbers
	4.3. Clearer Loss Epoch		4.3. Clearer Loss Epoch
	4.4. No Reneging		4.4. No Reneging
	4.5. More ACK Ranges		4.5. More ACK Ranges
	4.6. Explicit Correction For Delayed Acknowledgments		4.6. Explicit Correction for Delayed Acknowledgments
	4.7. Probe Timeout Replaces RTO and TLP		4.7. Probe Timeout Replaces RTO and TLP
	4.8. The Minimum Congestion Window Is Two Packets		4.8. The Minimum Congestion Window Is Two Packets
	4.9. Handshake Packets Are Not Special		4.9. Handshake Packets Are Not Special
	5. Estimating the Round-Trip Time		5. Estimating the Round-Trip Time
	5.1. Generating RTT Samples		5.1. Generating RTT Samples
	5.2. Estimating min_rtt		5.2. Estimating min_rtt
	5.3. Estimating smoothed_rtt and rttvar		5.3. Estimating smoothed_rtt and rttvar
	6. Loss Detection		6. Loss Detection
	6.1. Acknowledgment-Based Detection		6.1. Acknowledgment-Based Detection
	6.1.1. Packet Threshold		6.1.1. Packet Threshold
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	performance of the QUIC handshake and use shorter timers for		performance of the QUIC handshake and use shorter timers for
	acknowledgment.		acknowledgment.
	* Packets containing frames besides ACK or CONNECTION_CLOSE frames		* Packets containing frames besides ACK or CONNECTION_CLOSE frames
	count toward congestion control limits and are considered to be in		count toward congestion control limits and are considered to be in
	flight.		flight.
	* PADDING frames cause packets to contribute toward bytes in flight		* PADDING frames cause packets to contribute toward bytes in flight
	without directly causing an acknowledgment to be sent.		without directly causing an acknowledgment to be sent.
	4. Relevant Differences Between QUIC and TCP		4. Relevant Differences between QUIC and TCP
	Readers familiar with TCP's loss detection and congestion control		Readers familiar with TCP's loss detection and congestion control
	will find algorithms here that parallel well-known TCP ones.		will find algorithms here that parallel well-known TCP ones.
	However, protocol differences between QUIC and TCP contribute to		However, protocol differences between QUIC and TCP contribute to
	algorithmic differences. These protocol differences are briefly		algorithmic differences. These protocol differences are briefly
	described below.		described below.
	4.1. Separate Packet Number Spaces		4.1. Separate Packet Number Spaces
	QUIC uses separate packet number spaces for each encryption level,		QUIC uses separate packet number spaces for each encryption level,
	skipping to change at line 256 ¶		skipping to change at line 256 ¶
	implementations on both sides and reducing memory pressure on the		implementations on both sides and reducing memory pressure on the
	sender.		sender.
	4.5. More ACK Ranges		4.5. More ACK Ranges
	QUIC supports many ACK ranges, as opposed to TCP's three SACK ranges.		QUIC supports many ACK ranges, as opposed to TCP's three SACK ranges.
	In high-loss environments, this speeds recovery, reduces spurious		In high-loss environments, this speeds recovery, reduces spurious
	retransmits, and ensures forward progress without relying on		retransmits, and ensures forward progress without relying on
	timeouts.		timeouts.
	4.6. Explicit Correction For Delayed Acknowledgments		4.6. Explicit Correction for Delayed Acknowledgments
	QUIC endpoints measure the delay incurred between when a packet is		QUIC endpoints measure the delay incurred between when a packet is
	received and when the corresponding acknowledgment is sent, allowing		received and when the corresponding acknowledgment is sent, allowing
	a peer to maintain a more accurate RTT estimate; see Section 13.2 of		a peer to maintain a more accurate RTT estimate; see Section 13.2 of
	[QUIC-TRANSPORT].		[QUIC-TRANSPORT].
	4.7. Probe Timeout Replaces RTO and TLP		4.7. Probe Timeout Replaces RTO and TLP
	QUIC uses a probe timeout (PTO; see Section 6.2), with a timer based		QUIC uses a probe timeout (PTO; see Section 6.2), with a timer based
	on TCP's retransmission timeout (RTO) computation; see [RFC6298].		on TCP's retransmission timeout (RTO) computation; see [RFC6298].
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