A Discrete-Event Network Simulator
API
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tcp-dctcp.cc
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1/*
2 * Copyright (c) 2017 NITK Surathkal
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation;
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program; if not, write to the Free Software
15 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
16 *
17 * Author: Shravya K.S. <shravya.ks0@gmail.com>
18 *
19 */
20
21#include "tcp-dctcp.h"
22
23#include "tcp-socket-state.h"
24
25#include "ns3/abort.h"
26#include "ns3/log.h"
27
28namespace ns3
29{
30
31NS_LOG_COMPONENT_DEFINE("TcpDctcp");
32
34
35TypeId
37{
38 static TypeId tid =
39 TypeId("ns3::TcpDctcp")
41 .AddConstructor<TcpDctcp>()
42 .SetGroupName("Internet")
43 .AddAttribute("DctcpShiftG",
44 "Parameter G for updating dctcp_alpha",
45 DoubleValue(0.0625),
47 MakeDoubleChecker<double>(0, 1))
48 .AddAttribute("DctcpAlphaOnInit",
49 "Initial alpha value",
50 DoubleValue(1.0),
52 MakeDoubleChecker<double>(0, 1))
53 .AddAttribute("UseEct0",
54 "Use ECT(0) for ECN codepoint, if false use ECT(1)",
55 BooleanValue(true),
58 .AddTraceSource("CongestionEstimate",
59 "Update sender-side congestion estimate state",
61 "ns3::TcpDctcp::CongestionEstimateTracedCallback");
62 return tid;
63}
64
65std::string
67{
68 return "TcpDctcp";
69}
70
72 : TcpLinuxReno(),
73 m_ackedBytesEcn(0),
74 m_ackedBytesTotal(0),
75 m_priorRcvNxt(SequenceNumber32(0)),
76 m_priorRcvNxtFlag(false),
77 m_nextSeq(SequenceNumber32(0)),
78 m_nextSeqFlag(false),
79 m_ceState(false),
80 m_delayedAckReserved(false),
81 m_initialized(false)
82{
83 NS_LOG_FUNCTION(this);
84}
85
87 : TcpLinuxReno(sock),
88 m_ackedBytesEcn(sock.m_ackedBytesEcn),
89 m_ackedBytesTotal(sock.m_ackedBytesTotal),
90 m_priorRcvNxt(sock.m_priorRcvNxt),
91 m_priorRcvNxtFlag(sock.m_priorRcvNxtFlag),
92 m_alpha(sock.m_alpha),
93 m_nextSeq(sock.m_nextSeq),
94 m_nextSeqFlag(sock.m_nextSeqFlag),
95 m_ceState(sock.m_ceState),
96 m_delayedAckReserved(sock.m_delayedAckReserved),
97 m_g(sock.m_g),
98 m_useEct0(sock.m_useEct0),
99 m_initialized(sock.m_initialized)
100{
101 NS_LOG_FUNCTION(this);
102}
103
105{
106 NS_LOG_FUNCTION(this);
107}
108
111{
112 NS_LOG_FUNCTION(this);
113 return CopyObject<TcpDctcp>(this);
114}
115
116void
118{
119 NS_LOG_FUNCTION(this << tcb);
120 NS_LOG_INFO(this << "Enabling DctcpEcn for DCTCP");
121 tcb->m_useEcn = TcpSocketState::On;
122 tcb->m_ecnMode = TcpSocketState::DctcpEcn;
123 tcb->m_ectCodePoint = m_useEct0 ? TcpSocketState::Ect0 : TcpSocketState::Ect1;
124 m_initialized = true;
125}
126
127// Step 9, Section 3.3 of RFC 8257. GetSsThresh() is called upon
128// entering the CWR state, and then later, when CWR is exited,
129// cwnd is set to ssthresh (this value). bytesInFlight is ignored.
132{
133 NS_LOG_FUNCTION(this << tcb << bytesInFlight);
134 return static_cast<uint32_t>((1 - m_alpha / 2.0) * tcb->m_cWnd);
135}
136
137void
139{
140 NS_LOG_FUNCTION(this << tcb << segmentsAcked << rtt);
141 m_ackedBytesTotal += segmentsAcked * tcb->m_segmentSize;
142 if (tcb->m_ecnState == TcpSocketState::ECN_ECE_RCVD)
143 {
144 m_ackedBytesEcn += segmentsAcked * tcb->m_segmentSize;
145 }
146 if (!m_nextSeqFlag)
147 {
148 m_nextSeq = tcb->m_nextTxSequence;
149 m_nextSeqFlag = true;
150 }
151 if (tcb->m_lastAckedSeq >= m_nextSeq)
152 {
153 double bytesEcn = 0.0; // Corresponds to variable M in RFC 8257
154 if (m_ackedBytesTotal > 0)
155 {
156 bytesEcn = static_cast<double>(m_ackedBytesEcn * 1.0 / m_ackedBytesTotal);
157 }
158 m_alpha = (1.0 - m_g) * m_alpha + m_g * bytesEcn;
160 NS_LOG_INFO(this << "bytesEcn " << bytesEcn << ", m_alpha " << m_alpha);
161 Reset(tcb);
162 }
163}
164
165void
167{
168 NS_LOG_FUNCTION(this << alpha);
169 NS_ABORT_MSG_IF(m_initialized, "DCTCP has already been initialized");
170 m_alpha = alpha;
171}
172
173void
175{
176 NS_LOG_FUNCTION(this << tcb);
177 m_nextSeq = tcb->m_nextTxSequence;
178 m_ackedBytesEcn = 0;
180}
181
182void
184{
185 NS_LOG_FUNCTION(this << tcb);
187 {
188 SequenceNumber32 tmpRcvNxt;
189 /* Save current NextRxSequence. */
190 tmpRcvNxt = tcb->m_rxBuffer->NextRxSequence();
191
192 /* Generate previous ACK without ECE */
193 tcb->m_rxBuffer->SetNextRxSequence(m_priorRcvNxt);
194 tcb->m_sendEmptyPacketCallback(TcpHeader::ACK);
195
196 /* Recover current RcvNxt. */
197 tcb->m_rxBuffer->SetNextRxSequence(tmpRcvNxt);
198 }
199
201 {
202 m_priorRcvNxtFlag = true;
203 }
204 m_priorRcvNxt = tcb->m_rxBuffer->NextRxSequence();
205 m_ceState = true;
206 tcb->m_ecnState = TcpSocketState::ECN_CE_RCVD;
207}
208
209void
211{
212 NS_LOG_FUNCTION(this << tcb);
214 {
215 SequenceNumber32 tmpRcvNxt;
216 /* Save current NextRxSequence. */
217 tmpRcvNxt = tcb->m_rxBuffer->NextRxSequence();
218
219 /* Generate previous ACK with ECE */
220 tcb->m_rxBuffer->SetNextRxSequence(m_priorRcvNxt);
221 tcb->m_sendEmptyPacketCallback(TcpHeader::ACK | TcpHeader::ECE);
222
223 /* Recover current RcvNxt. */
224 tcb->m_rxBuffer->SetNextRxSequence(tmpRcvNxt);
225 }
226
228 {
229 m_priorRcvNxtFlag = true;
230 }
231 m_priorRcvNxt = tcb->m_rxBuffer->NextRxSequence();
232 m_ceState = false;
233
234 if (tcb->m_ecnState.Get() == TcpSocketState::ECN_CE_RCVD ||
235 tcb->m_ecnState.Get() == TcpSocketState::ECN_SENDING_ECE)
236 {
237 tcb->m_ecnState = TcpSocketState::ECN_IDLE;
238 }
239}
240
241void
243{
244 NS_LOG_FUNCTION(this << tcb << event);
245 switch (event)
246 {
249 {
251 }
252 break;
255 {
256 m_delayedAckReserved = false;
257 }
258 break;
259 default:
260 /* Don't care for the rest. */
261 break;
262 }
263}
264
265void
267{
268 NS_LOG_FUNCTION(this << tcb << event);
269 switch (event)
270 {
272 CeState0to1(tcb);
273 break;
275 CeState1to0(tcb);
276 break;
279 UpdateAckReserved(tcb, event);
280 break;
281 default:
282 /* Don't care for the rest. */
283 break;
284 }
285}
286
287} // namespace ns3
AttributeValue implementation for Boolean.
Definition: boolean.h:37
This class can be used to hold variables of floating point type such as 'double' or 'float'.
Definition: double.h:42
Smart pointer class similar to boost::intrusive_ptr.
Definition: ptr.h:78
An implementation of DCTCP.
Definition: tcp-dctcp.h:39
Ptr< TcpCongestionOps > Fork() override
Copy the congestion control algorithm across sockets.
Definition: tcp-dctcp.cc:110
static TypeId GetTypeId()
Get the type ID.
Definition: tcp-dctcp.cc:36
SequenceNumber32 m_priorRcvNxt
Sequence number of the first missing byte in data.
Definition: tcp-dctcp.h:132
double m_alpha
Parameter used to estimate the amount of network congestion.
Definition: tcp-dctcp.h:134
double m_g
Estimation gain.
Definition: tcp-dctcp.h:140
bool m_initialized
Whether DCTCP has been initialized.
Definition: tcp-dctcp.h:142
bool m_ceState
DCTCP Congestion Experienced state.
Definition: tcp-dctcp.h:138
bool m_priorRcvNxtFlag
Variable used in setting the value of m_priorRcvNxt for first time.
Definition: tcp-dctcp.h:133
void InitializeDctcpAlpha(double alpha)
Initialize the value of m_alpha.
Definition: tcp-dctcp.cc:166
SequenceNumber32 m_nextSeq
TCP sequence number threshold for beginning a new observation window.
Definition: tcp-dctcp.h:136
uint32_t m_ackedBytesEcn
Number of acked bytes which are marked.
Definition: tcp-dctcp.h:130
void Init(Ptr< TcpSocketState > tcb) override
Set configuration required by congestion control algorithm, This method will force DctcpEcn mode and ...
Definition: tcp-dctcp.cc:117
TcpDctcp()
Create an unbound tcp socket.
Definition: tcp-dctcp.cc:71
void Reset(Ptr< TcpSocketState > tcb)
Resets the value of m_ackedBytesEcn, m_ackedBytesTotal and m_nextSeq.
Definition: tcp-dctcp.cc:174
uint32_t m_ackedBytesTotal
Total number of acked bytes.
Definition: tcp-dctcp.h:131
bool m_nextSeqFlag
Variable used in setting the value of m_nextSeq for first time.
Definition: tcp-dctcp.h:137
std::string GetName() const override
Get the name of the congestion control algorithm.
Definition: tcp-dctcp.cc:66
uint32_t GetSsThresh(Ptr< const TcpSocketState > tcb, uint32_t bytesInFlight) override
Get the slow start threshold after a loss event.
Definition: tcp-dctcp.cc:131
void PktsAcked(Ptr< TcpSocketState > tcb, uint32_t segmentsAcked, const Time &rtt) override
Timing information on received ACK.
Definition: tcp-dctcp.cc:138
void CwndEvent(Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCAEvent_t event) override
Trigger events/calculations on occurrence of congestion window event.
Definition: tcp-dctcp.cc:266
void CeState1to0(Ptr< TcpSocketState > tcb)
Changes state of m_ceState to false.
Definition: tcp-dctcp.cc:210
void UpdateAckReserved(Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCAEvent_t event)
Updates the value of m_delayedAckReserved.
Definition: tcp-dctcp.cc:242
bool m_delayedAckReserved
Delayed Ack state.
Definition: tcp-dctcp.h:139
TracedCallback< uint32_t, uint32_t, double > m_traceCongestionEstimate
Callback pointer for congestion state update.
Definition: tcp-dctcp.h:146
bool m_useEct0
Use ECT(0) for ECN codepoint.
Definition: tcp-dctcp.h:141
void CeState0to1(Ptr< TcpSocketState > tcb)
Changes state of m_ceState to true.
Definition: tcp-dctcp.cc:183
~TcpDctcp() override
Destructor.
Definition: tcp-dctcp.cc:104
Reno congestion control algorithm.
TcpCAEvent_t
Congestion avoidance events.
@ CA_EVENT_ECN_IS_CE
received CE marked IP packet.
@ CA_EVENT_ECN_NO_CE
ECT set, but not CE marked.
@ CA_EVENT_DELAYED_ACK
Delayed ack is sent.
@ CA_EVENT_NON_DELAYED_ACK
Non-delayed ack is sent.
@ DctcpEcn
ECN functionality as described in RFC 8257.
@ ECN_ECE_RCVD
Last ACK received had ECE bit set in TCP header.
@ ECN_IDLE
ECN is enabled but currently there is no action pertaining to ECE or CWR to be taken.
@ ECN_CE_RCVD
Last packet received had CE bit set in IP header.
@ ECN_SENDING_ECE
Receiver sends an ACK with ECE bit set in TCP header.
Simulation virtual time values and global simulation resolution.
Definition: nstime.h:105
a unique identifier for an interface.
Definition: type-id.h:59
TypeId SetParent(TypeId tid)
Set the parent TypeId.
Definition: type-id.cc:936
Ptr< const AttributeAccessor > MakeBooleanAccessor(T1 a1)
Definition: boolean.h:86
Ptr< const AttributeChecker > MakeBooleanChecker()
Definition: boolean.cc:124
Ptr< const AttributeAccessor > MakeDoubleAccessor(T1 a1)
Definition: double.h:43
#define NS_ABORT_MSG_IF(cond, msg)
Abnormal program termination if a condition is true, with a message.
Definition: abort.h:108
#define NS_LOG_COMPONENT_DEFINE(name)
Define a Log component with a specific name.
Definition: log.h:202
#define NS_LOG_FUNCTION(parameters)
If log level LOG_FUNCTION is enabled, this macro will output all input parameters separated by ",...
#define NS_LOG_INFO(msg)
Use NS_LOG to output a message of level LOG_INFO.
Definition: log.h:275
#define NS_OBJECT_ENSURE_REGISTERED(type)
Register an Object subclass with the TypeId system.
Definition: object-base.h:46
Ptr< const TraceSourceAccessor > MakeTraceSourceAccessor(T a)
Create a TraceSourceAccessor which will control access to the underlying trace source.
Every class exported by the ns3 library is enclosed in the ns3 namespace.