draft-ietf-quic-recovery-03.txt		draft-ietf-quic-recovery-04.txt
	QUIC J. Iyengar, Ed.		QUIC J. Iyengar, Ed.
	Internet-Draft I. Swett, Ed.		Internet-Draft I. Swett, Ed.
	Intended status: Standards Track Google		Intended status: Standards Track Google
	Expires: November 22, 2017 May 21, 2017		Expires: December 15, 2017 June 13, 2017
	QUIC Loss Detection and Congestion Control		QUIC Loss Detection and Congestion Control
	draft-ietf-quic-recovery-03		draft-ietf-quic-recovery-04
	Abstract		Abstract
	This document describes loss detection and congestion control		This document describes loss detection and congestion control
	mechanisms for QUIC.		mechanisms for QUIC.
	Note to Readers		Note to Readers
	Discussion of this draft takes place on the QUIC working group		Discussion of this draft takes place on the QUIC working group
	mailing list (quic@ietf.org), which is archived at		mailing list (quic@ietf.org), which is archived at
	https://mailarchive.ietf.org/arch/search/?email_list=quic .		https://mailarchive.ietf.org/arch/search/?email_list=quic.
	Working Group information can be found at https://github.com/quicwg ;		Working Group information can be found at https://github.com/quicwg;
	source code and issues list for this draft can be found at		source code and issues list for this draft can be found at
	https://github.com/quicwg/base-drafts/labels/recovery .		https://github.com/quicwg/base-drafts/labels/recovery.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 November 22, 2017.		This Internet-Draft will expire on December 15, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2017 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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 7, line 17 ¶		skipping to change at page 7, line 17 ¶
	tlp_count: The number of times a tail loss probe has been sent		tlp_count: The number of times a tail loss probe has been sent
	without receiving an ack.		without receiving an ack.
	rto_count: The number of times an rto has been sent without		rto_count: The number of times an rto has been sent without
	receiving an ack.		receiving an ack.
	largest_sent_before_rto: The last packet number sent prior to the		largest_sent_before_rto: The last packet number sent prior to the
	first retransmission timeout.		first retransmission timeout.
			time_of_last_sent_packet: The time the most recent packet was sent.
			latest_rtt: The most recent RTT measurement made when receiving an
			ack for a previously unacked packet.
	smoothed_rtt: The smoothed RTT of the connection, computed as		smoothed_rtt: The smoothed RTT of the connection, computed as
	described in [RFC6298]		described in [RFC6298]
	rttvar: The RTT variance, computed as described in [RFC6298]		rttvar: The RTT variance, computed as described in [RFC6298]
	reordering_threshold: The largest delta between the largest acked		reordering_threshold: The largest delta between the largest acked
	retransmittable packet and a packet containing retransmittable		retransmittable packet and a packet containing retransmittable
	frames before it's declared lost.		frames before it's declared lost.
	time_reordering_fraction: The reordering window as a fraction of		time_reordering_fraction: The reordering window as a fraction of
	skipping to change at page 8, line 19 ¶		skipping to change at page 8, line 19 ¶
	if (UsingTimeLossDetection())		if (UsingTimeLossDetection())
	reordering_threshold = infinite		reordering_threshold = infinite
	time_reordering_fraction = kTimeReorderingFraction		time_reordering_fraction = kTimeReorderingFraction
	else:		else:
	reordering_threshold = kReorderingThreshold		reordering_threshold = kReorderingThreshold
	time_reordering_fraction = infinite		time_reordering_fraction = infinite
	loss_time = 0		loss_time = 0
	smoothed_rtt = 0		smoothed_rtt = 0
	rttvar = 0		rttvar = 0
	largest_sent_before_rto = 0		largest_sent_before_rto = 0
			time_of_last_sent_packet = 0
	3.2.4. On Sending a Packet		3.2.4. On Sending a Packet
	After any packet is sent, be it a new transmission or a rebundled		After any packet is sent, be it a new transmission or a rebundled
	transmission, the following OnPacketSent function is called. The		transmission, the following OnPacketSent function is called. The
	parameters to OnPacketSent are as follows:		parameters to OnPacketSent are as follows:
	o packet_number: The packet number of the sent packet.		o packet_number: The packet number of the sent packet.
	o is_retransmittable: A boolean that indicates whether the packet		o is_retransmittable: A boolean that indicates whether the packet
	skipping to change at page 8, line 40 ¶		skipping to change at page 8, line 41 ¶
	retransmittability of various QUIC frames is described in		retransmittability of various QUIC frames is described in
	[QUIC-TRANSPORT]. If false, it is still acceptable for an ack to		[QUIC-TRANSPORT]. If false, it is still acceptable for an ack to
	be received for this packet. However, a caller MUST NOT set		be received for this packet. However, a caller MUST NOT set
	is_retransmittable to true if an ack is not expected.		is_retransmittable to true if an ack is not expected.
	o sent_bytes: The number of bytes sent in the packet.		o sent_bytes: The number of bytes sent in the packet.
	Pseudocode for OnPacketSent follows:		Pseudocode for OnPacketSent follows:
	OnPacketSent(packet_number, is_retransmittable, sent_bytes):		OnPacketSent(packet_number, is_retransmittable, sent_bytes):
			time_of_last_sent_packet = now;
	sent_packets[packet_number].packet_number = packet_number		sent_packets[packet_number].packet_number = packet_number
	sent_packets[packet_number].time = now		sent_packets[packet_number].time = now
	if is_retransmittable:		if is_retransmittable:
	sent_packets[packet_number].bytes = sent_bytes		sent_packets[packet_number].bytes = sent_bytes
	SetLossDetectionAlarm()		SetLossDetectionAlarm()
	3.2.5. On Ack Receipt		3.2.5. On Ack Receipt
	When an ack is received, it may acknowledge 0 or more packets.		When an ack is received, it may acknowledge 0 or more packets.
	The sender MUST abort the connection if it receives an ACK for a
	packet it never sent, see [QUIC-TRANSPORT].
	Pseudocode for OnAckReceived and UpdateRtt follow:		Pseudocode for OnAckReceived and UpdateRtt follow:
	OnAckReceived(ack):		OnAckReceived(ack):
	// If the largest acked is newly acked, update the RTT.		// If the largest acked is newly acked, update the RTT.
	if (sent_packets[ack.largest_acked]):		if (sent_packets[ack.largest_acked]):
	rtt_sample = now - sent_packets[ack.largest_acked].time		latest_rtt = now - sent_packets[ack.largest_acked].time
	if (rtt_sample > ack.ack_delay):		if (latest_rtt > ack.ack_delay):
	rtt_sample -= ack.delay		latest_rtt -= ack.delay
	UpdateRtt(rtt_sample)		UpdateRtt(latest_rtt)
	// The sender may skip packets for detecting optimistic ACKs
	if (packets acked that the sender skipped):
	abortConnection()
	// Find all newly acked packets.		// Find all newly acked packets.
	for acked_packet in DetermineNewlyAckedPackets():		for acked_packet in DetermineNewlyAckedPackets():
	OnPacketAcked(acked_packet.packet_number)		OnPacketAcked(acked_packet.packet_number)
	DetectLostPackets(ack.largest_acked_packet)		DetectLostPackets(ack.largest_acked_packet)
	SetLossDetectionAlarm()		SetLossDetectionAlarm()
	UpdateRtt(rtt_sample):		UpdateRtt(latest_rtt):
	// Based on {{RFC6298}}.		// Based on {{RFC6298}}.
	if (smoothed_rtt == 0):		if (smoothed_rtt == 0):
	smoothed_rtt = rtt_sample		smoothed_rtt = latest_rtt
	rttvar = rtt_sample / 2		rttvar = latest_rtt / 2
	else:		else:
	rttvar = 3/4 * rttvar + 1/4 * (smoothed_rtt - rtt_sample)		rttvar = 3/4 * rttvar + 1/4 * (smoothed_rtt - latest_rtt)
	smoothed_rtt = 7/8 * smoothed_rtt + 1/8 * rtt_sample		smoothed_rtt = 7/8 * smoothed_rtt + 1/8 * latest_rtt
	3.2.6. On Packet Acknowledgment		3.2.6. On Packet Acknowledgment
	When a packet is acked for the first time, the following		When a packet is acked for the first time, the following
	OnPacketAcked function is called. Note that a single ACK frame may		OnPacketAcked function is called. Note that a single ACK frame may
	newly acknowledge several packets. OnPacketAcked must be called once		newly acknowledge several packets. OnPacketAcked must be called once
	for each of these newly acked packets.		for each of these newly acked packets.
	OnPacketAcked takes one parameter, acked_packet, which is the packet		OnPacketAcked takes one parameter, acked_packet, which is the packet
	number of the newly acked packet, and returns a list of packet		number of the newly acked packet, and returns a list of packet
	skipping to change at page 16, line 41 ¶		skipping to change at page 16, line 41 ¶
	This document has no IANA actions. Yet.		This document has no IANA actions. Yet.
	6. References		6. References
	6.1. Normative References		6.1. Normative References
	[QUIC-TRANSPORT]		[QUIC-TRANSPORT]
	Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based		Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
	Multiplexed and Secure Transport", draft-ietf-quic-		Multiplexed and Secure Transport", draft-ietf-quic-
	transport (work in progress), May 2017.		transport (work in progress), June 2017.
	[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,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	6.2. Informative References		6.2. Informative References
	[LOSS-PROBE]		[LOSS-PROBE]
	Dukkipati, N., Cardwell, N., Cheng, Y., and M. Mathis,		Dukkipati, N., Cardwell, N., Cheng, Y., and M. Mathis,
End of changes. 15 change blocks.
	22 lines changed or deleted		23 lines changed or added
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