Reliable Multicast Programming (PGM)

This section describes the Pragmatic General Multicast (PGM) multicast protocol implementation in Windows, often referred to as reliable multicast. Reliable multicast is implemented through Windows Sockets in Windows Server 2003 and later.

Windows XP:  PGM is only supported when Microsoft Message Queuing (MSMQ) 3.0 is installed.

PGM is a reliable and scalable multicast protocol that enables receivers to detect loss, request retransmission of lost data, or notify an application of unrecoverable loss. PGM is a receiver-reliable protocol, which means the receiver is responsible for ensuring all data is received, absolving the sender of reception responsibility.

PGM is appropriate for applications that require duplicate-free multicast data delivery from multiple sources to multiple receivers. PGM does not support acknowledged delivery, nor does it guarantee ordering of packets from multiple senders.

For more information about PGM, refer to RFC 3208 available at www.ietf.org.

This section describes how to use reliable multicast on Windows. The following topics explain the various aspects of creating a reliable multicast application using Windows Sockets:

• PGM Senders and Receivers
• PGM Sender Options
• Sending and Receiving PGM Data
• Multihoming and PGM
• PGM Socket Options

译文:

可靠多播编程(PGM)

本节讨论的是实际普通多播(PGM)协议在Windows下的实现，也就是通常说的可靠多播。可靠多播基于Windows 2003 和以后操作系统上的Windows Sockets实现。

Windows XP：仅当MSMQ3.0安装到操作系统时，PGM才能被支持。

PGM 是一个可靠并且伸缩的多播协议，它能够让接受者监测数据包丢失，要求重传丢失的数据包。PGM是一个对于接收者扶着可靠性的协议，这意味着接收者负责确认数据是否收到，免除了发送者这方面的负担。

PGM对于适用于多个数据源向多个接受者传输数据的程序。PGM既不支持基于收到确认的传输方式，也不保证从多个发送源收到的数据包的顺序。

需要了解关于PGM的更详细信息，可以从www.ietf.org查阅RFC3208。

本节讨论如何在Windows上使用可靠多播。以下章节将详细解释关于使用Windows Socket创建可靠多播程序的各个方面：

l  PGM 发送者和接收者

l  PGM 发送选择

l  发送和接收PGM数据

l  多寻址和PGM

l  PGM Socket 选项。