DDS中自适应网络传输模块的设计与实现

论文总字数：26615字

摘 要

DDS中间件是一种以数据为中心、基于发布/订阅模型的通信中间件，具有传输效率高且实时性强的特点，因此被广泛应用。然而现有的DDS产品具有不足：与底层网络协议的耦合度较高，一旦网络环境发送变化需要使用其它网络协议时，需要修改大量源码，可拓展性较低。与此同时，随着应用规模的扩大，系统中设备对数据的实时性要求也各不相同，因此DDS中间件中需要存在调度机制，使得对实时性要求高的设备能够更快地接收到数据。

本文设计了一种位于RTPS层实体与底层网络协议之间的自适应网络传输模块，能够降低DDS与底层网络协议之间的耦合度。在该模块中，抽象出了各类协议的相关操作，总结出有关数据传输的接口，使得DDS更易于拓展。同时本文在网络传输模块中添加了调度部分，可以在节点匹配的过程中读取调度信息，改变存放订阅者信息容器中元素的排列顺序，从而实现对多个订阅者接收数据的顺序进行调度。

对该模块的测试表明改进后的DDS中间件拓展性较强，能够通过修改配置文件适配到各种网络环境，同时该模块的存在不会影响到DDS中间件的性能。自适应网络传输模块中调度机制的存在，使得DDS可以根据预先设定好的调度策略，控制订阅者们接收数据的顺序。

关键词：DDS中间件，网络传输模块，拓展性，调度策略

ABSTRACT

DDS middleware is a data-centric and publish/subscribe model-based communication middleware that is widely used because of its high transmission efficiency and real-time performance. However, the existing DDS products have the disadvantages: the degree of coupling with the underlying network protocol is relatively high. Once the network environment sends changes requiring the use of other network protocols, a large amount of source code needs to be modified, and the scalability is low. At the same time, with the expansion of the application scale, the real-time requirements of the devices in the system are also different. Therefore, there is a need for a scheduling mechanism in the DDS middleware, so that devices with high real-time requirements can receive data more quickly.

This paper designs an adaptive network transmission module between the RTPS layer entity and the underlying network protocol, which can reduce the coupling between the DDS and the underlying network protocol. In this module, the related operations of various protocols are abstracted, and the interface about data transmission is summarized, which makes DDS easier to expand. At the same time, the scheduling part is added in the network transmission module, which can read the scheduling information in the process of node matching, and change the order of the elements in the subscriber information container, so as to realize the scheduling of the data received by multiple subscribers.

Tests on this module show that the improved DDS middleware is more scalable and can be adapted to various network environments by modifying the configuration file, and the presence of the module does not affect the performance of the DDS middleware. The existence of a scheduling mechanism in the adaptive network transmission module enables the DDS to control the order in which subscribers receive data according to a preset scheduling policy.

Keywords: DDS middleware, network transmission module, scalability, scheduling strategy

目 录

摘要Ⅰ

AbstractⅡ

插图及附表清单Ⅴ

第一章 绪论1

1.1论文背景与研究意义1

1.2国内外现状2

1.3作者的主要研究工作2

1.4论文的主要内容以及组织结构2

第二章DDS中间件相关原理与结构 4

2.1 DDS中间件的通信模型4

2.2 DDS中间件的底层协议及数据类型6

2.3 DDS中间件的逻辑结构7

2.3.1逻辑业务层(DDS层)8

2.3.2通信服务层(RTPS层)10

2.4本章总结11

第三章自适应网络传输模块的设计与实现 12

3.1需求分析12

3.2 协议适配部分的设计与实现13

3.3 DDS在FC协议环境下的拓展14

3.3.1 FC协议特点14

3.3.2 FC协议对消息传输基类的继承15

3.4 调度部分的设计与实现16

3.4.1两种调度策略的设计与实现16

3.4.2 调度机制自由配置的设计与实现17

3.5本章总结17

第四章 测试与分析 18

4.1 对协议适配部分的测试18

4.1.1测试方案18

4.1.2测试结果20

4.1.3总结22

4.2 对调度部分的测试23

4.2.1 测试方案23

4.2.2 测试结果24

4.2.3 总结24

4.3 本章小结25

第五章 总结与展望 26

5.1总结26

5.2展望26

参考文献 27

致谢 28

插图及附表清单

图2.1:P2P通信模型………………………………………………………………………………4

图2.2:C/S通信模型………………………………………………………………………………4

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