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/* -*- Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
* Copyright (c) 1997 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the Daedalus Research
* Group at the University of California at Berkeley.
* 4. Neither the name of the University nor of the Research Group may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* ack-recons.cc: contributed by the Daedalus Research Group,
* UC Berkeley (http://daedalus.cs.berkeley.edu).
*
* $Header: /cvsroot/nsnam/ns-2/tcp/ack-recons.cc,v 1.6 2000/09/01 03:04:05 haoboy Exp $
*/
/*
* TCP Ack reconstructor. This object sits on the other end of a constrained
* link and intersperses TCP acks to the source (without violating the e2e
* semantics of TCP acks). This allows us to get good performance for TCP
* over various asymmetric networks, in conjunction with techniques to reduce
* the frequency of acks (such as ack filtering) with making any changes to
* the TCP source (e.g., like those implemented in tcp-asym.cc).
*/
#include "template.h"
#include "ack-recons.h"
static class AckReconsControllerClass : public TclClass {
public:
AckReconsControllerClass() : TclClass("AckReconsControllerClass") { }
TclObject* create(int, const char*const*) {
return (new AckReconsController);
}
} class_ackrecons_controller;
static class AckReconsClass : public TclClass {
public:
AckReconsClass() : TclClass("Agent/AckReconsClass") { }
TclObject* create(int, const char*const* argv) {
return new AckRecons(atoi(argv[4]), atoi(argv[5]));
}
} class_ackrecons;
/*
* Demux a packet to the right ack reconstructor.
*/
void
AckReconsController::recv(Packet *p, Handler *)
{
Tcl& tcl = Tcl::instance();
hdr_ip *ip = hdr_ip::access(p);
tcl.evalf("%s demux %d %d", name(),
ip->saddr(), ip->daddr());
AckRecons *ackRecons =
(AckRecons *) TclObject::lookup(tcl.result());
if (ackRecons == NULL) {
printf("Error: malformed ack reconstructor\n");
abort();
}
ackRecons->spq_ = spq_;
ackRecons->recv(p);
}
void
AckRecons::recv(Packet *pkt)
{
double now = Scheduler::instance().clock();
hdr_tcp *tcph = hdr_tcp::access(pkt);
int &ack = tcph->seqno(), a, i;
Tcl& tcl = Tcl::instance();
#ifdef DEBUG
printf("%f\tRecd ack %d\n", now, ack);
#endif
if (ackTemplate_ == 0)
ackTemplate_ = pkt->copy();
if (adaptive_)
tcl.evalf("%s ackbw %d %f\n", name(), ack, now);
/* The ack spacing policy is implemented in Tcl for flexibility */
tcl.evalf("%s spacing %d\n", name(), ack);
/*
* If the difference in acks is less than a threshold, let
* it go through. Later, we will look for rapid ack arrivals
* to smooth them out and avoid the adverse effects of ack comp.
*/
if ((!ackPending_ && ack-lastAck_ <= deltaAckThresh_) || dupacks_) {
if (ack == lastRealAck_)
dupacks_++;
else if (ack > lastAck_) {
dupacks_ = 0;
lastAck_ = ack;
lastTime_ = now;
}
spq_->reconsAcks_ = 0;
spq_->enque(pkt);
spq_->reconsAcks_ = 1;
#ifdef DEBUG
printf("\t%f\tEnqueuing ack %d in order\n", now, ack);
#endif
} else {
if (ack == lastRealAck_)
dupacks_++;
/* Intersperse some acks and schedule their transmissions. */
double starttime = max(now, lastTime_);
for (a = lastAck_+delack_, i=0; a <= ack; a += delack_, i++)
sendack(a, starttime + i*ackSpacing_ - now);
if ((a-ack)%delack_)
sendack(ack, starttime + i*ackSpacing_ - now);
Packet::free(pkt);
}
if (ack >= lastRealAck_) {
lastRealAck_ = ack;
lastRealTime_ = now;
}
}
int
AckRecons::command(int argc, const char*const* argv)
{
return Agent::command(argc, argv);
}
/*
* Arrange to send ack a at time t from now.
*/
void
AckRecons::sendack(int ack, double t)
{
Packet *ackp = ackTemplate_->copy();
Scheduler &s = Scheduler::instance();
hdr_tcp *th = hdr_tcp::access(ackp);
th->seqno() = ack;
/* Set no_ts_ in flags because we don't want an rtt sample for this */
if (th->ts() == hdr_tcp::access(ackp)->ts()) {
hdr_flags *fh = hdr_flags::access(ackp);
fh->no_ts_ = 1;
th->ts_ = s.clock(); /* for debugging purposes only */
}
s.schedule((Handler *)this, (Event *)ackp, t);
ackPending_++;
#ifdef DEBUG
printf("\t%f\tScheduling ack %d to be sent at %f\n",
s.clock(), ack, s.clock() + t);
#endif
}
/*
* Handle scheduling of acks.
*/
void
AckRecons::handle(Event *e)
{
Packet *p = (Packet *) e;
hdr_tcp *th = hdr_tcp::access(p);
ackPending_--;
if (lastAck_ < th->seqno()) {
spq_->reconsAcks_ = 0;
/*
* need to do queue's recv here, so that a deque is
* forced if the queue isn't blocked. It's not
* sufficient to call spq_->recv() alone.
*/
target_->recv(p); /* maybe do acksfirst for this ack? */
spq_->reconsAcks_ = 1;
lastTime_ = Scheduler::instance().clock();
lastAck_ = th->seqno();
#ifdef DEBUG
printf("%f\tSending scheduled ack %d\n",lastTime_,th->seqno());
#endif
} else {
Packet::free(p);
#ifdef DEBUG
printf("%f\tack %d superceded by ack %d at %f\n",
Scheduler::instance().clock(), th->seqno(), lastAck_,
lastTime_);
#endif
}
}
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