RFC 1151 (rfc1151) - Page 1 of 4
Version 2 of the Reliable Data Protocol (RDP)
Alternative Format: Original Text Document
Network Working Group C. Partridge Request for Comments: 1151 BBN Systems and Technologies Updates: RFC 908 R. Hinden BBN Communications Corp. April 1990 Version 2 of the Reliable Data Protocol (RDP) Status of this Memo This RFC suggests several updates to the specification of the Reliable Data Protocol (RDP) in RFC-908 based on experience with the protocol. This revised version of the protocol is experimental. Distribution of this memo is unlimited. Introduction Experiments in 1986 and 1987 turned up some ambiguities and problems with the RDP specification. At the time, it was hoped that the authors might find the time to revise the entire RDP specification to fix these problems, however given the limited demand for RDP implementations, the authors were never able to justify the time involved in revising the spec. This document lists the changes that we believe are appropriate to make to RDP version 1. Readers are expected to be familiar with RFC-908. Changes To The Protocol Header There are three changes to the protocol header: the checksum algorithm has been changed, the port size increased, and the version number incremented. The new header format is shown in Figure 1. The major discovery during the testing of the protocol is that cost of computing the the RDP checksum proved surprisingly variable; its performance was more heavily affected by the host's data representation than anticipated. Optimized checksum implementations on two comparable hardware bases gave performance that differed by a factor of five. Since the speed of the checksum is a key factor in the performance of the protocol itself, this variation caused a noticeable difference in throughput. The wide variation in performance on comparable machines was felt to be undesirable, so the checksum has been changed. RDP now uses the 16-bit TCP checksum, which is specified on page 16 of RFC-793. Partridge & Hinden
