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Version 2 of the Reliable Data Protocol (RDP) (RFC1151)

IP.com Disclosure Number: IPCOM000001962D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2019-Feb-11
Document File: 4 page(s) / 5K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

C. Partridge: AUTHOR [+1]

Related Documents

10.17487/RFC1151: DOI

Abstract

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.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 54% of the total text.

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 [Page 1]

RFC 1151 RDP - Version 2 April 1990

The 8-bit port size is probably too small to support a large range of applications. Accordingly, the port size is now 16-bits. Port numbers less than 1024 are reserved for well-defined applications. Allocable ports begin at port number 1024.

Finally, because the checksum and port size have been changed, the version number has been increased to 2.

0 0 0 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+---+---------------+ |S|A|E|R|N| |Ver| Header | 0 |Y|C|A|S|U|0|No.| Length | |N|K|K|T|L| | | | +-+-+-+-+-+-+---+---------------+ 1 | Source Port | +---------------+---------------+ 2 | Destination Port | +---------------+---------------+ 3 | Data Length | +---------------+---------------+ 4 | | +--- Sequence Number ---+ 5 | | +---------------+---------------+ 6 | | +--- Acknowledgement Number ---+ 7 | | +---------------+---------------+ 8 | Checksum | +---------------+---------------+ 9 | Variable Header Area | . . . . | | +---------------+---------------+

RDP Header Format Figure 1

Minor Errors and Ambiguities

Some ambiguities and...

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