A Discrete-Event Network Simulator
API
tcp-reno.cc
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1 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
2 /*
3  * Copyright (c) 2010 Adrian Sai-wah Tam
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation;
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17  *
18  * Author: Adrian Sai-wah Tam <adrian.sw.tam@gmail.com>
19  */
20 
21 #define NS_LOG_APPEND_CONTEXT \
22  if (m_node) { std::clog << Simulator::Now ().GetSeconds () << " [node " << m_node->GetId () << "] "; }
23 
24 #include "tcp-reno.h"
25 #include "ns3/log.h"
26 #include "ns3/trace-source-accessor.h"
27 #include "ns3/simulator.h"
28 #include "ns3/abort.h"
29 #include "ns3/node.h"
30 
31 namespace ns3 {
32 
33 NS_LOG_COMPONENT_DEFINE ("TcpReno");
34 
36 
37 TypeId
39 {
40  static TypeId tid = TypeId ("ns3::TcpReno")
42  .AddConstructor<TcpReno> ()
43  .AddAttribute ("ReTxThreshold", "Threshold for fast retransmit",
44  UintegerValue (3),
46  MakeUintegerChecker<uint32_t> ())
47  .AddTraceSource ("CongestionWindow",
48  "The TCP connection's congestion window",
50  "ns3::TracedValue::Uint32Callback")
51  .AddTraceSource ("SlowStartThreshold",
52  "TCP slow start threshold (bytes)",
54  "ns3::TracedValue::Uint32Callback")
55  ;
56  return tid;
57 }
58 
59 TcpReno::TcpReno (void) : m_retxThresh (3), m_inFastRec (false)
60 {
61  NS_LOG_FUNCTION (this);
62 }
63 
65  : TcpSocketBase (sock),
66  m_cWnd (sock.m_cWnd),
67  m_ssThresh (sock.m_ssThresh),
68  m_initialCWnd (sock.m_initialCWnd),
69  m_initialSsThresh (sock.m_initialSsThresh),
70  m_retxThresh (sock.m_retxThresh),
71  m_inFastRec (false)
72 {
73  NS_LOG_FUNCTION (this);
74  NS_LOG_LOGIC ("Invoked the copy constructor");
75 }
76 
78 {
79 }
80 
81 /* We initialize m_cWnd from this function, after attributes initialized */
82 int
84 {
85  NS_LOG_FUNCTION (this);
86  InitializeCwnd ();
87  return TcpSocketBase::Listen ();
88 }
89 
90 /* We initialize m_cWnd from this function, after attributes initialized */
91 int
93 {
94  NS_LOG_FUNCTION (this << address);
95  InitializeCwnd ();
96  return TcpSocketBase::Connect (address);
97 }
98 
99 /* Limit the size of in-flight data by cwnd and receiver's rxwin */
100 uint32_t
102 {
103  NS_LOG_FUNCTION (this);
104  return std::min (m_rWnd.Get (), m_cWnd.Get ());
105 }
106 
109 {
110  return CopyObject<TcpReno> (this);
111 }
112 
113 /* New ACK (up to seqnum seq) received. Increase cwnd and call TcpSocketBase::NewAck() */
114 void
116 {
117  NS_LOG_FUNCTION (this << seq);
118  NS_LOG_LOGIC ("TcpReno receieved ACK for seq " << seq <<
119  " cwnd " << m_cWnd <<
120  " ssthresh " << m_ssThresh);
121 
122  // Check for exit condition of fast recovery
123  if (m_inFastRec)
124  { // RFC2001, sec.4; RFC2581, sec.3.2
125  // First new ACK after fast recovery: reset cwnd
126  m_cWnd = m_ssThresh;
127  m_inFastRec = false;
128  NS_LOG_INFO ("Reset cwnd to " << m_cWnd);
129  };
130 
131  // Increase of cwnd based on current phase (slow start or congestion avoidance)
132  if (m_cWnd < m_ssThresh)
133  { // Slow start mode, add one segSize to cWnd. Default m_ssThresh is 65535. (RFC2001, sec.1)
135  NS_LOG_INFO ("In SlowStart, updated to cwnd " << m_cWnd << " ssthresh " << m_ssThresh);
136  }
137  else
138  { // Congestion avoidance mode, increase by (segSize*segSize)/cwnd. (RFC2581, sec.3.1)
139  // To increase cwnd for one segSize per RTT, it should be (ackBytes*segSize)/cwnd
140  double adder = static_cast<double> (m_segmentSize * m_segmentSize) / m_cWnd.Get ();
141  adder = std::max (1.0, adder);
142  m_cWnd += static_cast<uint32_t> (adder);
143  NS_LOG_INFO ("In CongAvoid, updated to cwnd " << m_cWnd << " ssthresh " << m_ssThresh);
144  }
145 
146  // Complete newAck processing
147  TcpSocketBase::NewAck (seq);
148 }
149 
150 // Fast recovery and fast retransmit
151 void
152 TcpReno::DupAck (const TcpHeader& t, uint32_t count)
153 {
154  NS_LOG_FUNCTION (this << "t " << count);
155  if (count == m_retxThresh && !m_inFastRec)
156  { // triple duplicate ack triggers fast retransmit (RFC2581, sec.3.2)
157  m_ssThresh = std::max (2 * m_segmentSize, BytesInFlight () / 2);
159  m_inFastRec = true;
160  NS_LOG_INFO ("Triple dupack. Reset cwnd to " << m_cWnd << ", ssthresh to " << m_ssThresh);
161  DoRetransmit ();
162  }
163  else if (m_inFastRec)
164  { // In fast recovery, inc cwnd for every additional dupack (RFC2581, sec.3.2)
166  NS_LOG_INFO ("Increased cwnd to " << m_cWnd);
168  };
169 }
170 
171 // Retransmit timeout
173 {
174  NS_LOG_FUNCTION (this);
175  NS_LOG_LOGIC (this << " ReTxTimeout Expired at time " << Simulator::Now ().GetSeconds ());
176  m_inFastRec = false;
177 
178  // If erroneous timeout in closed/timed-wait state, just return
179  if (m_state == CLOSED || m_state == TIME_WAIT) return;
180  // If all data are received (non-closing socket and nothing to send), just return
181  if (m_state <= ESTABLISHED && m_txBuffer->HeadSequence () >= m_highTxMark) return;
182 
183  // According to RFC2581 sec.3.1, upon RTO, ssthresh is set to half of flight
184  // size and cwnd is set to 1*MSS, then the lost packet is retransmitted and
185  // TCP back to slow start
186  m_ssThresh = std::max (2 * m_segmentSize, BytesInFlight () / 2);
188  m_nextTxSequence = m_txBuffer->HeadSequence (); // Restart from highest Ack
189  NS_LOG_INFO ("RTO. Reset cwnd to " << m_cWnd <<
190  ", ssthresh to " << m_ssThresh << ", restart from seqnum " << m_nextTxSequence);
191  DoRetransmit (); // Retransmit the packet
192 }
193 
194 void
195 TcpReno::SetSegSize (uint32_t size)
196 {
197  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpReno::SetSegSize() cannot change segment size after connection started.");
198  m_segmentSize = size;
199 }
200 
201 void
202 TcpReno::SetInitialSSThresh (uint32_t threshold)
203 {
204  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpReno::SetSSThresh() cannot change initial ssThresh after connection started.");
205  m_initialSsThresh = threshold;
206 }
207 
208 uint32_t
210 {
211  return m_initialSsThresh;
212 }
213 
214 void
215 TcpReno::SetInitialCwnd (uint32_t cwnd)
216 {
217  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpReno::SetInitialCwnd() cannot change initial cwnd after connection started.");
218  m_initialCWnd = cwnd;
219 }
220 
221 uint32_t
223 {
224  return m_initialCWnd;
225 }
226 
227 void
229 {
230  /*
231  * Initialize congestion window, default to 1 MSS (RFC2001, sec.1) and must
232  * not be larger than 2 MSS (RFC2581, sec.3.1). Both m_initiaCWnd and
233  * m_segmentSize are set by the attribute system in ns3::TcpSocket.
234  */
237 }
238 
239 } // namespace ns3
virtual int Listen(void)
Listen for incoming connections.
Smart pointer class similar to boost::intrusive_ptr.
Definition: ptr.h:73
#define NS_LOG_FUNCTION(parameters)
If log level LOG_FUNCTION is enabled, this macro will output all input parameters separated by "...
TracedValue< uint32_t > m_cWnd
Congestion window.
Definition: tcp-reno.h:81
virtual void Retransmit(void)
Halving cwnd and call DoRetransmit()
Definition: tcp-reno.cc:172
#define NS_OBJECT_ENSURE_REGISTERED(type)
Register an Object subclass with the TypeId system.
Definition: object-base.h:44
TracedValue< uint32_t > m_ssThresh
Slow Start Threshold.
Definition: tcp-reno.h:82
virtual void SetSegSize(uint32_t size)
Set the segment size.
Definition: tcp-reno.cc:195
virtual Ptr< TcpSocketBase > Fork(void)
Call CopyObject<> to clone me.
Definition: tcp-reno.cc:108
#define NS_LOG_COMPONENT_DEFINE(name)
Define a Log component with a specific name.
Definition: log.h:201
uint32_t m_initialCWnd
Initial cWnd value.
Definition: tcp-reno.h:83
virtual int Listen(void)
Listen for incoming connections.
Definition: tcp-reno.cc:83
#define NS_LOG_INFO(msg)
Use NS_LOG to output a message of level LOG_INFO.
Definition: log.h:244
uint32_t m_segmentSize
Segment size.
virtual void NewAck(const SequenceNumber32 &seq)
Update buffers w.r.t.
Definition: tcp-reno.cc:115
TracedValue< SequenceNumber32 > m_nextTxSequence
Next seqnum to be sent (SND.NXT), ReTx pushes it back.
T Get(void) const
Get the underlying value.
Definition: traced-value.h:186
TracedValue< TcpStates_t > m_state
TCP state.
virtual void SetInitialCwnd(uint32_t cwnd)
Set the initial Congestion Window.
Definition: tcp-reno.cc:215
a polymophic address class
Definition: address.h:90
Ptr< const TraceSourceAccessor > MakeTraceSourceAccessor(T a)
Create a TraceSourceAccessor which will control access to the underlying trace source.
virtual uint32_t GetInitialSSThresh(void) const
Get the initial Slow Start Threshold.
Definition: tcp-reno.cc:209
An implementation of a stream socket using TCP.
Definition: tcp-reno.h:38
virtual int Connect(const Address &address)
Initiate a connection to a remote host.
Definition: tcp-reno.cc:92
bool m_inFastRec
currently in fast recovery
Definition: tcp-reno.h:86
Ptr< TcpTxBuffer > m_txBuffer
Tx buffer.
virtual void DupAck(const TcpHeader &t, uint32_t count)
Received dupack (duplicate ACK)
Definition: tcp-reno.cc:152
Hold an unsigned integer type.
Definition: uinteger.h:44
A base class for implementation of a stream socket using TCP.
#define NS_LOG_LOGIC(msg)
Use NS_LOG to output a message of level LOG_LOGIC.
Definition: log.h:252
virtual ~TcpReno(void)
Definition: tcp-reno.cc:77
virtual void SetInitialSSThresh(uint32_t threshold)
Set the initial Slow Start Threshold.
Definition: tcp-reno.cc:202
Every class exported by the ns3 library is enclosed in the ns3 namespace.
Header for the Transmission Control Protocol.
Definition: tcp-header.h:44
virtual uint32_t GetInitialCwnd(void) const
Get the initial Congestion Window.
Definition: tcp-reno.cc:222
uint32_t m_retxThresh
Fast Retransmit threshold.
Definition: tcp-reno.h:85
virtual uint32_t BytesInFlight(void)
Return total bytes in flight.
static TypeId GetTypeId(void)
Get the type ID.
Definition: tcp-reno.cc:38
virtual int Connect(const Address &address)
Initiate a connection to a remote host.
static Time Now(void)
Return the current simulation virtual time.
Definition: simulator.cc:223
TracedValue< SequenceNumber32 > m_highTxMark
Highest seqno ever sent, regardless of ReTx.
virtual void NewAck(SequenceNumber32 const &seq)
Update buffers w.r.t.
bool m_connected
Connection established.
#define NS_ABORT_MSG_UNLESS(cond, msg)
Abnormal program termination if a condition is false, with a message.
Definition: abort.h:144
tuple address
Definition: first.py:37
uint32_t m_initialSsThresh
Initial Slow Start Threshold value.
Definition: tcp-reno.h:84
TcpReno(void)
Create an unbound tcp socket.
Definition: tcp-reno.cc:59
Ptr< const AttributeAccessor > MakeUintegerAccessor(T1 a1)
Create an AttributeAccessor for a class data member, or a lone class get functor or set method...
Definition: uinteger.h:45
a unique identifier for an interface.
Definition: type-id.h:51
TypeId SetParent(TypeId tid)
Definition: type-id.cc:631
bool SendPendingData(bool withAck=false)
Send as much pending data as possible according to the Tx window.
TracedValue< uint32_t > m_rWnd
Flow control window at remote side.
virtual void DoRetransmit(void)
Retransmit the oldest packet.
virtual uint32_t Window(void)
Return the max possible number of unacked bytes.
Definition: tcp-reno.cc:101
void InitializeCwnd(void)
Set the congestion window when connection starts.
Definition: tcp-reno.cc:228