1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
|
/* -*- Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
* Copyright (c) 1990, 1997 Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms are permitted
* provided that the above copyright notice and this paragraph are
* duplicated in all such forms and that any documentation,
* advertising materials, and other materials related to such
* distribution and use acknowledge that the software was developed
* by the University of California, Lawrence Berkeley Laboratory,
* Berkeley, CA. The name of the University may not be used to
* endorse or promote products derived from this software without
* specific prior written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static const char rcsid[] =
"@(#) $Header: /cvsroot/nsnam/ns-2/tcp/tcp-reno.cc,v 1.43 2006/06/14 18:05:30 sallyfloyd Exp $ (LBL)";
#endif
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include "ip.h"
#include "tcp.h"
#include "flags.h"
static class RenoTcpClass : public TclClass {
public:
RenoTcpClass() : TclClass("Agent/TCP/Reno") {}
TclObject* create(int, const char*const*) {
return (new RenoTcpAgent());
}
} class_reno;
int RenoTcpAgent::window()
{
//
// reno: inflate the window by dupwnd_
// dupwnd_ will be non-zero during fast recovery,
// at which time it contains the number of dup acks
//
int win = int(cwnd_) + dupwnd_;
if (frto_ == 2) {
// First ack after RTO has arrived.
// Open window to allow two new segments out with F-RTO.
win = force_wnd(2);
}
if (win > int(wnd_))
win = int(wnd_);
return (win);
}
double RenoTcpAgent::windowd()
{
//
// reno: inflate the window by dupwnd_
// dupwnd_ will be non-zero during fast recovery,
// at which time it contains the number of dup acks
//
double win = cwnd_ + dupwnd_;
if (win > wnd_)
win = wnd_;
return (win);
}
RenoTcpAgent::RenoTcpAgent() : TcpAgent(), dupwnd_(0)
{
}
void RenoTcpAgent::recv(Packet *pkt, Handler*)
{
hdr_tcp *tcph = hdr_tcp::access(pkt);
int valid_ack = 0;
if (qs_approved_ == 1 && tcph->seqno() > last_ack_)
endQuickStart();
if (qs_requested_ == 1)
processQuickStart(pkt);
#ifdef notdef
if (pkt->type_ != PT_ACK) {
fprintf(stderr,
"ns: confiuration error: tcp received non-ack\n");
exit(1);
}
#endif
/* W.N.: check if this is from a previous incarnation */
if (tcph->ts() < lastreset_) {
// Remove packet and do nothing
Packet::free(pkt);
return;
}
++nackpack_;
ts_peer_ = tcph->ts();
if (hdr_flags::access(pkt)->ecnecho() && ecn_)
ecn(tcph->seqno());
recv_helper(pkt);
recv_frto_helper(pkt);
if (tcph->seqno() > last_ack_) {
if (last_cwnd_action_ == CWND_ACTION_DUPACK)
last_cwnd_action_ = CWND_ACTION_EXITED;
dupwnd_ = 0;
recv_newack_helper(pkt);
if (last_ack_ == 0 && delay_growth_) {
cwnd_ = initial_window();
}
} else if (tcph->seqno() == last_ack_) {
if (hdr_flags::access(pkt)->eln_ && eln_) {
tcp_eln(pkt);
return;
}
if (++dupacks_ == numdupacks_) {
dupack_action();
if (!exitFastRetrans_)
dupwnd_ = numdupacks_;
} else if (dupacks_ > numdupacks_ && (!exitFastRetrans_
|| last_cwnd_action_ == CWND_ACTION_DUPACK )) {
++dupwnd_; // fast recovery
} else if (dupacks_ < numdupacks_ && singledup_ ) {
send_one();
}
}
if (tcph->seqno() >= last_ack_)
// Check if ACK is valid. Suggestion by Mark Allman.
valid_ack = 1;
Packet::free(pkt);
#ifdef notyet
if (trace_)
plot();
#endif
/*
* Try to send more data
*/
if (valid_ack || aggressive_maxburst_)
if (dupacks_ == 0 || dupacks_ > numdupacks_ - 1)
send_much(0, 0, maxburst_);
}
int
RenoTcpAgent::allow_fast_retransmit(int last_cwnd_action_)
{
return (last_cwnd_action_ == CWND_ACTION_DUPACK);
}
/*
* Dupack-action: what to do on a DUP ACK. After the initial check
* of 'recover' below, this function implements the following truth
* table:
*
* bugfix ecn last-cwnd == ecn action
*
* 0 0 0 reno_action
* 0 0 1 reno_action [impossible]
* 0 1 0 reno_action
* 0 1 1 retransmit, return
* 1 0 0 nothing
* 1 0 1 nothing [impossible]
* 1 1 0 nothing
* 1 1 1 retransmit, return
*/
void
RenoTcpAgent::dupack_action()
{
int recovered = (highest_ack_ > recover_);
int allowFastRetransmit = allow_fast_retransmit(last_cwnd_action_);
if (recovered || (!bug_fix_ && !ecn_) || allowFastRetransmit
|| (bugfix_ss_ && highest_ack_ == 0)) {
// (highest_ack_ == 0) added to allow Fast Retransmit
// when the first data packet is dropped.
// From bugreport from Mark Allman.
goto reno_action;
}
if (ecn_ && last_cwnd_action_ == CWND_ACTION_ECN) {
last_cwnd_action_ = CWND_ACTION_DUPACK;
/*
* What if there is a DUPACK action followed closely by ECN
* followed closely by a DUPACK action?
* The optimal thing to do would be to remember all
* congestion actions from the most recent window
* of data. Otherwise "bugfix" might not prevent
* all unnecessary Fast Retransmits.
*/
reset_rtx_timer(1,0);
output(last_ack_ + 1, TCP_REASON_DUPACK);
dupwnd_ = numdupacks_;
return;
}
if (bug_fix_) {
/*
* The line below, for "bug_fix_" true, avoids
* problems with multiple fast retransmits in one
* window of data.
*/
return;
}
reno_action:
// we are now going to fast-retransmit and will trace that event
trace_event("RENO_FAST_RETX");
recover_ = maxseq_;
last_cwnd_action_ = CWND_ACTION_DUPACK;
slowdown(CLOSE_SSTHRESH_HALF|CLOSE_CWND_HALF);
reset_rtx_timer(1,0);
output(last_ack_ + 1, TCP_REASON_DUPACK); // from top
dupwnd_ = numdupacks_;
return;
}
void RenoTcpAgent::timeout(int tno)
{
if (tno == TCP_TIMER_RTX) {
dupwnd_ = 0;
dupacks_ = 0;
if (bug_fix_) recover_ = maxseq_;
TcpAgent::timeout(tno);
} else {
timeout_nonrtx(tno);
}
}
|
