ns-3网络模拟器3.19操作手册：事件、PRNG与对象模型详解

需积分: 31 59 浏览量更新于2024-07-23 收藏 1.05MB PDF 举报

NS-3是一款强大的网络模拟器，主要用于研究、教学和开发目的。本手册针对NS-3的版本3.19，提供详细的用户指南，包括组织结构、随机变量处理、哈希函数、事件和模拟器、回调机制以及对象模型等核心概念。 **1. 组织结构与随机变量** - 随机变量是NS-3模拟中的关键组件，用于生成伪随机序列。手册首先概述了快速使用随机变量的方法，接着介绍了随机变量流的概念，如如何设置种子值以实现独立复制和重复性。BaseclasspublicAPI解释了基础类的接口，以及不同类型随机变量（如离散、连续等）的含义和用法。 **2. 哈希函数** - NS-3支持基本的哈希函数使用，用于数据校验和一致性检查。手册介绍了增量哈希、使用自定义哈希函数以及添加新实现的功能。此外，还提供了可用哈希函数的来源信息。 **3. 事件、模拟器与时间管理** - 事件是NS-3的核心，用户通过它们来控制模拟流程。章节详细阐述了Event对象的创建、调度以及与时间管理的关系。Simulator和Scheduler组件分别负责整个模拟过程的管理和调度。 **4. 回调机制** - 回调在NS-3中被广泛使用，用于事件触发时执行特定操作。这部分涵盖了回调的动机、背景、API使用方法，包括bound回调（与对象关联）、traced回调（记录日志）以及回调在代码中的位置和实现细节。 **5. 对象模型** - NS-3基于面向对象的设计，对象模型是理解其工作原理的关键。章节解释了对象行为，介绍了基础类（如Object、Node等），以及内存管理（如classPtr）。此外，还讨论了内存管理和对象实例化的过程。 NS-3 Manual是深入理解和使用这一网络模拟工具的重要资源，它为开发者提供了全面的指导，从基础概念到高级功能，帮助他们高效地构建和分析复杂的网络模拟场景。通过掌握这些知识点，用户能够更好地定制和扩展NS-3以满足其具体研究或项目需求。

ns-3 Manual, Release ns-3.19

• Decide whether you are running with a ﬁxed seed or random seed; a ﬁxed seed is the default,

• Decide how you are going to manage independent replications, if applicable,

• Convince yourself that you are not drawing more random values than the cycle length, if you are running a very

long simulation, and

• When you publish, follow the guidelines above about documenting your use of the random number generator.

10 Chapter 2. Random Variables

CHAPTER

FOUR

EVENTS AND SIMULATOR

ns-3 is a discrete-event network simulator. Conceptually, the simulator keeps track of a number of events that are

scheduled to execute at a speciﬁed simulation time. The job of the simulator is to execute the events in sequential time

order. Once the completion of an event occurs, the simulator will move to the next event (or will exit if there are no

more events in the event queue). If, for example, an event scheduled for simulation time “100 seconds” is executed,

and the next event is not scheduled until “200 seconds”, the simulator will immediately jump from 100 seconds to 200

seconds (of simulation time) to execute the next event. This is what is meant by “discrete-event” simulator.

To make this all happen, the simulator needs a few things:

1. a simulator object that can access an event queue where events are stored and that can manage the execution of

events

2. a scheduler responsible for inserting and removing events from the queue

3. a way to represent simulation time

4. the events themselves

This chapter of the manual describes these fundamental objects (simulator, scheduler, time, event) and how they are

used.

4.1 Event

To be completed

4.2 Simulator

The Simulator class is the public entry point to access event scheduling facilities. Once a couple of events have

been scheduled to start the simulation, the user can start to execute them by entering the simulator main loop (call

Simulator::Run). Once the main loop starts running, it will sequentially execute all scheduled events in order

from oldest to most recent until there are either no more events left in the event queue or Simulator::Stop has been

called.

To schedule events for execution by the simulator main loop, the Simulator class provides the Simulator::Schedule*

family of functions.

1. Handling event handlers with different signatures

These functions are declared and implemented as C++ templates to handle automatically the wide variety of C++ event

handler signatures used in the wild. For example, to schedule an event to execute 10 seconds in the future, and invoke

a C++ method or function with speciﬁc arguments, you might write this:

ns-3 Manual, Release ns-3.19

void handler (int arg0, int arg1)

{

std::cout << "handler called with argument arg0=" << arg0 << " and

arg1=" << arg1 << std::endl;

}

Simulator::Schedule(Seconds(10), &handler, 10, 5);

Which will output:

handler called with argument arg0=10 and arg1=5

Of course, these C++ templates can also handle transparently member methods on C++ objects:

To be completed: member method example

Notes:

• the ns-3 Schedule methods recognize automatically functions and methods only if they take less than 5 argu-

ments. If you need them to support more arguments, please, ﬁle a bug report.

• Readers familiar with the term ‘fully-bound functors’ will recognize the Simulator::Schedule methods as a way

to automatically construct such objects.

2. Common scheduling operations

The Simulator API was designed to make it really simple to schedule most events. It provides three variants to do so

(ordered from most commonly used to least commonly used):

• Schedule methods which allow you to schedule an event in the future by providing the delay between the current

simulation time and the expiration date of the target event.

• ScheduleNow methods which allow you to schedule an event for the current simulation time: they will execute

_after_ the current event is ﬁnished executing but _before_ the simulation time is changed for the next event.

• ScheduleDestroy methods which allow you to hook in the shutdown process of the Simulator to cleanup simu-

lation resources: every ‘destroy’ event is executed when the user calls the Simulator::Destroy method.

3. Maintaining the simulation context

There are two basic ways to schedule events, with and without context. What does this mean?

Simulator::Schedule (Time const &time, MEM mem_ptr, OBJ obj);

vs.

Simulator::ScheduleWithContext (uint32_t context, Time const &time, MEM mem_ptr, OBJ obj);

Readers who invest time and effort in developing or using a non-trivial simulation model will know the value of the

ns-3 logging framework to debug simple and complex simulations alike. One of the important features that is provided

by this logging framework is the automatic display of the network node id associated with the ‘currently’ running

event.

The node id of the currently executing network node is in fact tracked by the Simulator class. It can be accessed with

the Simulator::GetContext method which returns the ‘context’ (a 32-bit integer) associated and stored in the currently-

executing event. In some rare cases, when an event is not associated with a speciﬁc network node, its ‘context’ is set

to 0xffffffff.

To associate a context to each event, the Schedule, and ScheduleNow methods automatically reuse the context of the

currently-executing event as the context of the event scheduled for execution later.

In some cases, most notably when simulating the transmission of a packet from a node to another, this behavior is

undesirable since the expected context of the reception event is that of the receiving node, not the sending node. To

14 Chapter 4. Events and Simulator

剩余190页未读，继续阅读

gaoxiangeagle21

粉丝: 0
资源: 3

ns-3网络模拟器3.19操作手册：事件、PRNG与对象模型详解

ns-3 教程+手册（tutorial+manual）

ns3_manual

NS3.26手册manual.pdf

ns-3-manual

ns-3-manual_ns3_

ns-3-manual.pdf

ns2-manual.rar_ns2

ns-3-manual_r3.21

ns2-manual.pdf.gz_linux manual

ns-3-manual、model-library、tutorial

最新资源