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1.3 Overview

The Remote Desktop Protocol: UDP Transport Extension Protocol has been designed to improve the performance of the network connectivity compared to a corresponding RDP-TCP connection, especially on wide area networks (WANs) or wireless networks.

It has the following two primary goals:

  • Gain a higher network share while reducing the variation in packet transit delays.

  • Share network resources with other users.

To achieve these goals, the protocol has two modes of operation. The first mode is a reliable mode where data is transferred reliably through persistent retransmits. The second mode is an unreliable mode, where no guarantees are made about reliability and the timeliness of data is preserved by avoiding retransmits. In addition, the Remote Desktop Protocol: UDP Transport Extension Protocol includes a forward error correction (FEC) logic that can be used to recover from random packet losses.

The protocol’s two communicating parties, the endpoints of the UDP connection, are peers and use the same protocol. The connection between the two endpoints is bidirectional – data and acknowledgments (section 3.1.1.4) can be transmitted in both directions simultaneously. Logically, each single connection can be viewed as two unidirectional connections, as shown in the following figure. Both of these unidirectional connections are symmetrical and each endpoint has both a Sender and a Receiver entity. In this specification, the initiating endpoint A is referred to as the terminal client and endpoint B is referred to as the terminal server.

The UDP bidirectional endpoints connection

Figure 1: The UDP bidirectional endpoints connection