A Discrete-Event Network Simulator
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1 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
2 /*
3  * Copyright (c) 2012 Andrew McGregor
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
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  * Codel, the COntrolled DELay Queueing discipline
19  * Based on ns2 simulation code presented by Kathie Nichols
20  *
21  * This port based on linux kernel code by
22  * Authors: Dave Täht <d@taht.net>
23  * Eric Dumazet <edumazet@google.com>
24  *
25  * Ported to ns-3 by: Andrew McGregor <andrewmcgr@gmail.com>
26  */
28 #ifndef CODEL_H
29 #define CODEL_H
31 #include "ns3/queue-disc.h"
32 #include "ns3/nstime.h"
33 #include "ns3/simulator.h"
34 #include "ns3/string.h"
35 #include "ns3/traced-value.h"
36 #include "ns3/trace-source-accessor.h"
38 class CoDelQueueDiscNewtonStepTest; // Forward declaration for unit test
39 class CoDelQueueDiscControlLawTest; // Forward declaration for unit test
41 namespace ns3 {
47 static const int CODEL_SHIFT = 10;
49 #define DEFAULT_CODEL_LIMIT 1000
50 #define REC_INV_SQRT_BITS (8 * sizeof(uint16_t))
53 class TraceContainer;
61 class CoDelQueueDisc : public QueueDisc
62 {
63 public:
69  static TypeId GetTypeId (void);
76  CoDelQueueDisc ();
78  virtual ~CoDelQueueDisc ();
85  Time GetTarget (void);
92  Time GetInterval (void);
99  uint32_t GetDropNext (void);
101  // Reasons for dropping packets
102  static constexpr const char* TARGET_EXCEEDED_DROP = "Target exceeded drop";
103  static constexpr const char* OVERLIMIT_DROP = "Overlimit drop";
105 private:
106  friend class::CoDelQueueDiscNewtonStepTest; // Test code
107  friend class::CoDelQueueDiscControlLawTest; // Test code
114  virtual bool DoEnqueue (Ptr<QueueDiscItem> item);
125  virtual Ptr<QueueDiscItem> DoDequeue (void);
127  virtual bool CheckConfig (void);
134  void NewtonStep (void);
145  uint32_t ControlLaw (uint32_t t);
155  bool OkToDrop (Ptr<QueueDiscItem> item, uint32_t now);
163  bool CoDelTimeAfter (uint32_t a, uint32_t b);
170  bool CoDelTimeAfterEq (uint32_t a, uint32_t b);
177  bool CoDelTimeBefore (uint32_t a, uint32_t b);
184  bool CoDelTimeBeforeEq (uint32_t a, uint32_t b);
192  uint32_t Time2CoDel (Time t);
194  virtual void InitializeParams (void);
196  uint32_t m_minBytes;
202  uint16_t m_recInvSqrt;
203  uint32_t m_firstAboveTime;
205  uint32_t m_state1;
206  uint32_t m_state2;
207  uint32_t m_state3;
208  uint32_t m_states;
209 };
211 } // namespace ns3
213 #endif /* CODEL_H */
virtual void InitializeParams(void)
Initialize parameters (if any) before the first packet is enqueued.
Simulation virtual time values and global simulation resolution.
Definition: nstime.h:102
virtual bool DoEnqueue(Ptr< QueueDiscItem > item)
Add a packet to the queue.
Smart pointer class similar to boost::intrusive_ptr.
Definition: ptr.h:73
static constexpr const char * TARGET_EXCEEDED_DROP
Sojourn time above target.
uint32_t GetDropNext(void)
Get the time for next packet drop while in the dropping state.
TracedValue< uint32_t > m_count
Number of packets dropped since entering drop state.
static constexpr const char * OVERLIMIT_DROP
Overlimit dropped packet.
virtual bool CheckConfig(void)
Check whether the current configuration is correct.
Time GetInterval(void)
Get the interval.
Test 3: NewtonStep unit test - test against explicit port of Linux implementation.
bool CoDelTimeAfterEq(uint32_t a, uint32_t b)
Check if CoDel time a is successive or equal to b.
QueueDisc is an abstract base class providing the interface and implementing the operations common to...
Definition: queue-disc.h:181
uint32_t ControlLaw(uint32_t t)
Determine the time for next drop CoDel control law is t + m_interval/sqrt(m_count).
bool CoDelTimeAfter(uint32_t a, uint32_t b)
Check if CoDel time a is successive to b.
TracedValue< bool > m_dropping
True if in dropping state.
bool OkToDrop(Ptr< QueueDiscItem > item, uint32_t now)
Determine whether a packet is OK to be dropped.
uint32_t m_states
Total number of times we are in state 1, state 2, or state 3.
uint32_t m_firstAboveTime
Time to declare sojourn time above target.
uint32_t m_state2
Number of times we perform next drop while in dropping state.
bool CoDelTimeBefore(uint32_t a, uint32_t b)
Check if CoDel time a is preceding b.
Time m_target
5 ms target queue delay
CoDelQueueDisc Constructor.
TracedValue< uint32_t > m_lastCount
Last number of packets dropped since entering drop state.
Time m_interval
100 ms sliding minimum time window width
virtual Ptr< QueueDiscItem > DoDequeue(void)
Remove a packet from queue based on the current state If we are in dropping state, check if we could leave the dropping state or if we should perform next drop If we are not currently in dropping state, check if we need to enter the state and drop the first packet.
Every class exported by the ns3 library is enclosed in the ns3 namespace.
uint16_t m_recInvSqrt
Reciprocal inverse square root.
Time GetTarget(void)
Get the target queue delay.
void NewtonStep(void)
Calculate the reciprocal square root of m_count by using Newton&#39;s method http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Iterative_methods_for_reciprocal_square_roots m_recInvSqrt (new) = (m_recInvSqrt (old) / 2) * (3 - m_count * m_recInvSqrt^2)
A CoDel packet queue disc.
static const int CODEL_SHIFT
Number of bits discarded from the time representation.
uint32_t m_state3
Number of times we enter drop state and drop the fist packet.
uint32_t Time2CoDel(Time t)
Return the unsigned 32-bit integer representation of the input Time object.
static TypeId GetTypeId(void)
Get the type ID.
bool CoDelTimeBeforeEq(uint32_t a, uint32_t b)
Check if CoDel time a is preceding or equal to b.
uint32_t m_minBytes
Minimum bytes in queue to allow a packet drop.
uint32_t m_state1
Number of times packet sojourn goes above target for interval.
Test 4: ControlLaw unit test - test against explicit port of Linux implementation.
a unique identifier for an interface.
Definition: type-id.h:58
TracedValue< uint32_t > m_dropNext
Time to drop next packet.