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Guidelines for Writers of RTP Payload Format Specifications (RFC2736)

IP.com Disclosure Number: IPCOM000003332D
Original Publication Date: 1999-Dec-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 8 page(s) / 23K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. Handley: AUTHOR [+2]

Abstract

This document provides general guidelines aimed at assisting the authors of RTP Payload Format specifications in deciding on good formats. These guidelines attempt to capture some of the experience gained with RTP as it evolved during its development.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 12% of the total text.

Network Working Group M. Handley

Request for Comments: 2736 ACIRI

BCP: 36 C. Perkins

Category: Best Current Practice UCL

December 1999

Guidelines for Writers of RTP Payload Format Specifications

Status of this Memo

This document specifies an Internet Best Current Practices for the

Internet Community, and requests discussion and suggestions for

improvements. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1999). All Rights Reserved.

Abstract

This document provides general guidelines aimed at assisting the

authors of RTP Payload Format specifications in deciding on good

formats. These guidelines attempt to capture some of the experience

gained with RTP as it evolved during its development.

1. Introduction

This document provides general guidelines aimed at assisting the

authors of RTP [9] Payload Format specifications in deciding on good

formats. These guidelines attempt to capture some of the experience

gained with RTP as it evolved during its development.

The principles outlined in this document are applicable to almost all

data types, but are framed in examples of audio and video codecs for

clarity.

2. Background

RTP was designed around the concept of Application Level Framing

(ALF), first described by Clark and Tennenhouse [2]. The key argument

underlying ALF is that there are many different ways an application

might be able to cope with misordered or lost packets. These range

from ignoring the loss, to re-sending the missing data (either from a

buffer or by regenerating it), and to sending new data which

supersedes the missing data. The application only has this choice if

the transport protocol is dealing with data in "Application Data

Units" (ADUs). An ADU contains data that can be processed out-of-

order with respect to other ADUs. Thus the ADU is the minimum unit

of error recovery.

The key property of a transport protocol for ADUs is that each ADU

contains sufficient information to be processed by the receiver

immediately. An example is a video stream, wherein the compressed

video data in an ADU must be capable of being decompressed regardless

of whether previous ADUs have been received. Additionally the ADU

must contain "header" information detailing its position in the video

image and the frame from which it came.

Although an ADU need not b...