Apollo Advanced Lesson | Cyber RT RTPS

Posted 2022-12-06 Justin-Yip

Contents

• • • What`s RTPS
    • The Advanced Features of RTPS
    • RTPS Framework
    • • Structure module

–This article is excerpted from Baidu’s official about Apollo, please indicate the source for reprinting–

What`s RTPS

• RTPS is short for Real Time Publish Subscribe Protocol.
  Underlying Transport Protocol is UDP。
  rtps detais, see
  http://www.brixbot.com/ros2/fast_rtps-01-introduce_dds/
  RTPS 官方

The Advanced Features of RTPS

RTPS Framework

• Structure module

Structure module

• Structure Module

  • HistoryCache:
    • the interface between RTPS endpoints(Writer \\ Reader)
    • the corresponding DDS entities
    • store the exchanged information between endpoints.
  • CacheChange: ???

• Message Module

  • defines the content of the atomic information for exchanging between endpoints
  • three important message
    • DATA
    • HEARTBEAT : used to indicate the Writer is available.
      heartbeat two purposes
      • 1 . It informs Reader of the available sequence numbers in the Writer HistoryCache so that Reader may request(using an AckNack)any that it has missed.
      • 2 .it requests Reader to send and ack for the CacheChange changes that have been entered into the Readers ·HistoryCache such that Writer knows the state of the reader.
    • ACKNACK notifies the received is Success no not.

• Behavior Module

  • This Module describes the messages exchanges.
  • defines the changes in the state between endpoints

• Discovery Module
  this Module describes the protocol that how endpoints find each other.

  • metatraffic ???
  • two layers of the discovery module
    • PDP: Participant Discovery Protocol
    • EDP: Endpoint Discovery Protocol
  • how to ensure interoperability?