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linux-next/include/linux/tfrc.h
Gerrit Renker 1a21e49a8d [DCCP] ccid3: Finer-grained resolution of sending rates
This patch
 * resolves a bug where packets smaller than 32/64 bytes resulted in sending rates of 0
 * supports all sending rates from 1/64 bytes/second up to 4Gbyte/second
 * simplifies the present overflow problems in calculations

Current sending rate X and the cached value X_recv of the receiver-estimated
sending rate are both scaled by 64 (2^6) in order to
 * cope with low sending rates (minimally 1 byte/second)
 * allow upgrading to use a packets-per-second implementation of CCID 3
 * avoid calculation errors due to integer arithmetic cut-off

The patch implements a revised strategy from
http://www.mail-archive.com/dccp@vger.kernel.org/msg01040.html

The only difference with regard to that strategy is that t_ipi is already
used in the calculation of the nofeedback timeout, which saves one division.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
2006-12-11 14:34:42 -08:00

56 lines
1.9 KiB
C

#ifndef _LINUX_TFRC_H_
#define _LINUX_TFRC_H_
/*
* TFRC - Data Structures for the TCP-Friendly Rate Control congestion
* control mechanism as specified in RFC 3448.
*
* Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand.
* Copyright (c) 2005 Ian McDonald <iam4@cs.waikato.ac.nz>
* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
* Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <linux/types.h>
/** tfrc_rx_info - TFRC Receiver Data Structure
*
* @tfrcrx_x_recv: receiver estimate of sending rate (3.2.2)
* @tfrcrx_rtt: round-trip-time (communicated by sender)
* @tfrcrx_p: current estimate of loss event rate (3.2.2)
*/
struct tfrc_rx_info {
__u32 tfrcrx_x_recv;
__u32 tfrcrx_rtt;
__u32 tfrcrx_p;
};
/** tfrc_tx_info - TFRC Sender Data Structure
*
* @tfrctx_x: computed transmit rate (4.3 (4))
* @tfrctx_x_recv: receiver estimate of send rate (4.3)
* @tfrctx_x_calc: return value of throughput equation (3.1)
* @tfrctx_rtt: (moving average) estimate of RTT (4.3)
* @tfrctx_p: current loss event rate (5.4)
* @tfrctx_rto: estimate of RTO, equals 4*RTT (4.3)
* @tfrctx_ipi: inter-packet interval (4.6)
*
* Note: X and X_recv are both maintained in units of 64 * bytes/second. This
* enables a finer resolution of sending rates and avoids problems with
* integer arithmetic; u32 is not sufficient as scaling consumes 6 bits.
*/
struct tfrc_tx_info {
__u64 tfrctx_x;
__u64 tfrctx_x_recv;
__u32 tfrctx_x_calc;
__u32 tfrctx_rtt;
__u32 tfrctx_p;
__u32 tfrctx_rto;
__u32 tfrctx_ipi;
};
#endif /* _LINUX_TFRC_H_ */