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67bf1d6c9e
Tests performed between a 1 Gbps connected server and a 100 mbps client,
distant by 95ms showed that:
- we need 1.1 MB in flight to fill the link
- rare but inevitable losses are sufficient to make cubic's window
collapse fast and long to recover
- a 100 MB object takes 69s to download
- tolerance for 1 loss between two ACKs suffices to shrink the download
time to 20-22s
- 2 losses go to 17-20s
- 4 losses reach 14-17s
At 100 concurrent connections that fill the server's link:
- 0 loss tolerance shows 2-3% losses
- 1 loss tolerance shows 3-5% losses
- 2 loss tolerance shows 10-13% losses
- 4 loss tolerance shows 23-29% losses
As such while there can be a significant gain sometimes in setting this
tolerance above zero, it can also significantly waste bandwidth by sending
far more than can be received. While it's probably not a solution to real
world problems, it repeatedly proved to be a very effective troubleshooting
tool helping to figure different root causes of low transfer speeds. In
spirit it is comparable to the no-cc congestion algorithm, i.e. it must
not be used except for experimentation.
130 lines
3.3 KiB
C
130 lines
3.3 KiB
C
/*
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* include/haproxy/quic_cc-t.h
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* This file contains definitions for QUIC congestion control.
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*
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* Copyright 2020 HAProxy Technologies, Frederic Lecaille <flecaille@haproxy.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _HAPROXY_QUIC_CC_H
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#define _HAPROXY_QUIC_CC_H
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#ifdef USE_QUIC
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#ifndef USE_OPENSSL
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#error "Must define USE_OPENSSL"
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#endif
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#include <inttypes.h>
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#include <stddef.h> /* size_t */
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#include <haproxy/buf-t.h>
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#include <haproxy/quic_loss-t.h>
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#define QUIC_CC_INFINITE_SSTHESH ((uint32_t)-1)
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extern struct quic_cc_algo quic_cc_algo_nr;
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extern struct quic_cc_algo quic_cc_algo_cubic;
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extern struct quic_cc_algo *default_quic_cc_algo;
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/* Fake algorithm with its fixed window */
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extern struct quic_cc_algo quic_cc_algo_nocc;
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extern unsigned long long last_ts;
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enum quic_cc_algo_state_type {
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/* Slow start. */
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QUIC_CC_ST_SS,
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/* Conservative slow start (HyStart++ only) */
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QUIC_CC_ST_CS,
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/* Congestion avoidance. */
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QUIC_CC_ST_CA,
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/* Recovery period. */
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QUIC_CC_ST_RP,
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};
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enum quic_cc_event_type {
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/* ACK receipt. */
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QUIC_CC_EVT_ACK,
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/* Packet loss. */
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QUIC_CC_EVT_LOSS,
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/* ECN-CE. */
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QUIC_CC_EVT_ECN_CE,
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};
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struct quic_cc_event {
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enum quic_cc_event_type type;
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union {
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struct ack {
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uint64_t acked;
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uint64_t pn;
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unsigned int time_sent;
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} ack;
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struct loss {
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unsigned int time_sent;
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unsigned int count; // #pkt lost for this event
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} loss;
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};
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};
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enum quic_cc_algo_type {
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QUIC_CC_ALGO_TP_NEWRENO,
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QUIC_CC_ALGO_TP_CUBIC,
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QUIC_CC_ALGO_TP_NOCC,
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};
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struct quic_cc {
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/* <conn> is there only for debugging purpose. */
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struct quic_conn *qc;
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struct quic_cc_algo *algo;
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uint32_t priv[20];
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};
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struct quic_cc_path {
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/* Control congestion. */
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struct quic_cc cc;
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/* Packet loss detection information. */
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struct quic_loss loss;
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/* MTU. Must be constant for GSO support. */
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const size_t mtu;
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/* Congestion window. */
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uint64_t cwnd;
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/* The current maximum congestion window value reached. */
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uint64_t mcwnd;
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/* The maximum congestion window value which can be reached. */
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uint64_t max_cwnd;
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/* Minimum congestion window. */
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uint64_t min_cwnd;
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/* Prepared data to be sent (in bytes). */
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uint64_t prep_in_flight;
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/* Outstanding data (in bytes). */
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uint64_t in_flight;
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/* Number of in flight ack-eliciting packets. */
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uint64_t ifae_pkts;
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};
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struct quic_cc_algo {
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enum quic_cc_algo_type type;
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int (*init)(struct quic_cc *cc);
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void (*event)(struct quic_cc *cc, struct quic_cc_event *ev);
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void (*slow_start)(struct quic_cc *cc);
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void (*state_trace)(struct buffer *buf, const struct quic_cc *cc);
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void (*state_cli)(struct buffer *buf, const struct quic_cc_path *path);
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void (*hystart_start_round)(struct quic_cc *cc, uint64_t pn);
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};
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#endif /* USE_QUIC */
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#endif /* _HAPROXY_QUIC_CC_H */
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