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tcp-tahoe.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-tahoe.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 NS_LOG_COMPONENT_DEFINE ("TcpTahoe");
32 
33 namespace ns3 {
34 
36 
37 TypeId
39 {
40  static TypeId tid = TypeId ("ns3::TcpTahoe")
42  .AddConstructor<TcpTahoe> ()
43  .AddAttribute ("ReTxThreshold", "Threshold for fast retransmit",
44  UintegerValue (3),
45  MakeUintegerAccessor (&TcpTahoe::m_retxThresh),
46  MakeUintegerChecker<uint32_t> ())
47  .AddTraceSource ("CongestionWindow",
48  "The TCP connection's congestion window",
50  ;
51  return tid;
52 }
53 
54 TcpTahoe::TcpTahoe (void) : m_initialCWnd (1), m_retxThresh (3)
55 {
56  NS_LOG_FUNCTION (this);
57 }
58 
60  : TcpSocketBase (sock),
61  m_cWnd (sock.m_cWnd),
62  m_ssThresh (sock.m_ssThresh),
63  m_initialCWnd (sock.m_initialCWnd),
64  m_retxThresh (sock.m_retxThresh)
65 {
66  NS_LOG_FUNCTION (this);
67  NS_LOG_LOGIC ("Invoked the copy constructor");
68 }
69 
71 {
72 }
73 
74 /* We initialize m_cWnd from this function, after attributes initialized */
75 int
77 {
78  NS_LOG_FUNCTION (this);
79  InitializeCwnd ();
80  return TcpSocketBase::Listen ();
81 }
82 
83 /* We initialize m_cWnd from this function, after attributes initialized */
84 int
86 {
87  NS_LOG_FUNCTION (this << address);
88  InitializeCwnd ();
89  return TcpSocketBase::Connect (address);
90 }
91 
92 /* Limit the size of in-flight data by cwnd and receiver's rxwin */
93 uint32_t
95 {
96  NS_LOG_FUNCTION (this);
97  return std::min (m_rWnd.Get (), m_cWnd.Get ());
98 }
99 
102 {
103  return CopyObject<TcpTahoe> (this);
104 }
105 
106 /* New ACK (up to seqnum seq) received. Increase cwnd and call TcpSocketBase::NewAck() */
107 void
109 {
110  NS_LOG_FUNCTION (this << seq);
111  NS_LOG_LOGIC ("TcpTahoe receieved ACK for seq " << seq <<
112  " cwnd " << m_cWnd <<
113  " ssthresh " << m_ssThresh);
114  if (m_cWnd < m_ssThresh)
115  { // Slow start mode, add one segSize to cWnd. Default m_ssThresh is 65535. (RFC2001, sec.1)
117  NS_LOG_INFO ("In SlowStart, updated to cwnd " << m_cWnd << " ssthresh " << m_ssThresh);
118  }
119  else
120  { // Congestion avoidance mode, increase by (segSize*segSize)/cwnd. (RFC2581, sec.3.1)
121  // To increase cwnd for one segSize per RTT, it should be (ackBytes*segSize)/cwnd
122  double adder = static_cast<double> (m_segmentSize * m_segmentSize) / m_cWnd.Get ();
123  adder = std::max (1.0, adder);
124  m_cWnd += static_cast<uint32_t> (adder);
125  NS_LOG_INFO ("In CongAvoid, updated to cwnd " << m_cWnd << " ssthresh " << m_ssThresh);
126  }
127  TcpSocketBase::NewAck (seq); // Complete newAck processing
128 }
129 
130 /* Cut down ssthresh upon triple dupack */
131 void
132 TcpTahoe::DupAck (const TcpHeader& t, uint32_t count)
133 {
134  NS_LOG_FUNCTION (this << "t " << count);
135  if (count == m_retxThresh)
136  { // triple duplicate ack triggers fast retransmit (RFC2001, sec.3)
137  NS_LOG_INFO ("Triple Dup Ack: old ssthresh " << m_ssThresh << " cwnd " << m_cWnd);
138  // fast retransmit in Tahoe means triggering RTO earlier. Tx is restarted
139  // from the highest ack and run slow start again.
140  // (Fall & Floyd 1996, sec.1)
141  m_ssThresh = std::max (static_cast<unsigned> (m_cWnd / 2), m_segmentSize * 2); // Half ssthresh
142  m_cWnd = m_segmentSize; // Run slow start again
143  m_nextTxSequence = m_txBuffer.HeadSequence (); // Restart from highest Ack
144  NS_LOG_INFO ("Triple Dup Ack: new ssthresh " << m_ssThresh << " cwnd " << m_cWnd);
145  NS_LOG_LOGIC ("Triple Dup Ack: retransmit missing segment at " << Simulator::Now ().GetSeconds ());
146  DoRetransmit ();
147  }
148 }
149 
150 /* Retransmit timeout */
152 {
153  NS_LOG_FUNCTION (this);
154  NS_LOG_LOGIC (this << " ReTxTimeout Expired at time " << Simulator::Now ().GetSeconds ());
155  // If erroneous timeout in closed/timed-wait state, just return
156  if (m_state == CLOSED || m_state == TIME_WAIT) return;
157  // If all data are received (non-closing socket and nothing to send), just return
158  if (m_state <= ESTABLISHED && m_txBuffer.HeadSequence () >= m_highTxMark) return;
159 
160  m_ssThresh = std::max (static_cast<unsigned> (m_cWnd / 2), m_segmentSize * 2); // Half ssthresh
161  m_cWnd = m_segmentSize; // Set cwnd to 1 segSize (RFC2001, sec.2)
162  m_nextTxSequence = m_txBuffer.HeadSequence (); // Restart from highest Ack
163  m_rtt->IncreaseMultiplier (); // Double the next RTO
164  DoRetransmit (); // Retransmit the packet
165 }
166 
167 void
168 TcpTahoe::SetSegSize (uint32_t size)
169 {
170  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpTahoe::SetSegSize() cannot change segment size after connection started.");
171  m_segmentSize = size;
172 }
173 
174 void
175 TcpTahoe::SetSSThresh (uint32_t threshold)
176 {
177  m_ssThresh = threshold;
178 }
179 
180 uint32_t
182 {
183  return m_ssThresh;
184 }
185 
186 void
188 {
189  NS_ABORT_MSG_UNLESS (m_state == CLOSED, "TcpTahoe::SetInitialCwnd() cannot change initial cwnd after connection started.");
190  m_initialCWnd = cwnd;
191 }
192 
193 uint32_t
195 {
196  return m_initialCWnd;
197 }
198 
199 void
201 {
202  /*
203  * Initialize congestion window, default to 1 MSS (RFC2001, sec.1) and must
204  * not be larger than 2 MSS (RFC2581, sec.3.1). Both m_initiaCWnd and
205  * m_segmentSize are set by the attribute system in ns3::TcpSocket.
206  */
208 }
209 
210 } // namespace ns3
virtual Ptr< TcpSocketBase > Fork(void)
Call CopyObject<> to clone me.
Definition: tcp-tahoe.cc:101
TracedValue< uint32_t > m_cWnd
Congestion window.
Definition: tcp-tahoe.h:85
virtual int Listen(void)
Listen for incoming connections.
smart pointer class similar to boost::intrusive_ptr
Definition: ptr.h:60
#define NS_LOG_FUNCTION(parameters)
If log level LOG_FUNCTION is enabled, this macro will output all input parameters separated by "...
virtual void SetSegSize(uint32_t size)
Set the segment size.
Definition: tcp-tahoe.cc:168
uint32_t m_retxThresh
Fast Retransmit threshold.
Definition: tcp-tahoe.h:88
virtual uint32_t Window(void)
Return the max possible number of unacked bytes.
Definition: tcp-tahoe.cc:94
#define NS_OBJECT_ENSURE_REGISTERED(type)
Register the class in the ns-3 factory.
Definition: object-base.h:38
SequenceNumber32 HeadSequence(void) const
Returns the first byte's sequence number.
virtual uint32_t GetInitialCwnd(void) const
Get the initial Congestion Window.
Definition: tcp-tahoe.cc:194
#define NS_LOG_COMPONENT_DEFINE(name)
Define a Log component with a specific name.
Definition: log.h:170
#define NS_LOG_INFO(msg)
Use NS_LOG to output a message of level LOG_INFO.
Definition: log.h:223
uint32_t m_segmentSize
Segment size.
TracedValue< SequenceNumber32 > m_nextTxSequence
Next seqnum to be sent (SND.NXT), ReTx pushes it back.
uint32_t m_ssThresh
Slow Start Threshold.
Definition: tcp-tahoe.h:86
T Get(void) const
Definition: traced-value.h:99
TracedValue< TcpStates_t > m_state
TCP state.
An implementation of a stream socket using TCP.
Definition: tcp-tahoe.h:42
a polymophic address class
Definition: address.h:86
virtual void SetInitialCwnd(uint32_t cwnd)
Set the initial Congestion Window.
Definition: tcp-tahoe.cc:187
TcpTxBuffer m_txBuffer
Tx buffer.
virtual int Listen(void)
Listen for incoming connections.
Definition: tcp-tahoe.cc:76
Hold an unsigned integer type.
Definition: uinteger.h:46
static TypeId GetTypeId(void)
Get the type ID.
Definition: tcp-tahoe.cc:38
A base class for implementation of a stream socket using TCP.
Ptr< RttEstimator > m_rtt
Round trip time estimator.
virtual ~TcpTahoe(void)
Definition: tcp-tahoe.cc:70
#define NS_LOG_LOGIC(msg)
Use NS_LOG to output a message of level LOG_LOGIC.
Definition: log.h:233
uint32_t m_initialCWnd
Initial cWnd value.
Definition: tcp-tahoe.h:87
virtual void Retransmit(void)
Halving cwnd and call DoRetransmit()
Definition: tcp-tahoe.cc:151
Ptr< const TraceSourceAccessor > MakeTraceSourceAccessor(T a)
Header for the Transmission Control Protocol.
Definition: tcp-header.h:43
virtual int Connect(const Address &address)
Initiate a connection to a remote host.
virtual void DupAck(const TcpHeader &t, uint32_t count)
Received dupack (duplicate ACK)
Definition: tcp-tahoe.cc:132
static Time Now(void)
Return the "current simulation time".
Definition: simulator.cc:180
TracedValue< SequenceNumber32 > m_highTxMark
Highest seqno ever sent, regardless of ReTx.
virtual void NewAck(SequenceNumber32 const &seq)
Update buffers w.r.t.
#define NS_ABORT_MSG_UNLESS(cond, msg)
Abnormal program termination if cond is false.
Definition: abort.h:136
virtual uint32_t GetSSThresh(void) const
Get the Slow Start Threshold.
Definition: tcp-tahoe.cc:181
virtual void NewAck(SequenceNumber32 const &seq)
Update buffers w.r.t.
Definition: tcp-tahoe.cc:108
TcpTahoe(void)
Create an unbound tcp socket.
Definition: tcp-tahoe.cc:54
void InitializeCwnd(void)
Set the congestion window when connection starts.
Definition: tcp-tahoe.cc:200
virtual int Connect(const Address &address)
Initiate a connection to a remote host.
Definition: tcp-tahoe.cc:85
tuple address
Definition: first.py:37
virtual void SetSSThresh(uint32_t threshold)
Set the Slow Start Threshold.
Definition: tcp-tahoe.cc:175
a unique identifier for an interface.
Definition: type-id.h:49
TypeId SetParent(TypeId tid)
Definition: type-id.cc:610
TracedValue< uint32_t > m_rWnd
Flow control window at remote side.
virtual void DoRetransmit(void)
Retransmit the oldest packet.