A Proposed Media Delivery Index (MDI)
RFC 4445

 
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Type RFC - Informational (April 2006; No errata)
Last updated 2013-03-02
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IESG state RFC 4445 (Informational)
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Network Working Group                                           J. Welch
Request for Comments: 4445                        IneoQuest Technologies
Category: Informational                                         J. Clark
                                                           Cisco Systems
                                                              April 2006

                 A Proposed Media Delivery Index (MDI)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

IESG Note

   This RFC is not a candidate for any level of Internet Standard.
   There are IETF standards which are highly applicable to the space
   defined by this document as its applicability, in particular, RFCs
   3393 and 3611, and there is ongoing IETF work in these areas as well.
   The IETF also notes that the decision to publish this RFC is not
   based on IETF review for such things as security, congestion control,
   MIB fitness, or inappropriate interaction with deployed protocols.
   The RFC Editor has chosen to publish this document at its discretion.
   Readers of this document should exercise caution in evaluating its
   value for implementation and deployment.  See RFC 3932 for more
   information.

Abstract

   This memo defines a Media Delivery Index (MDI) measurement that can
   be used as a diagnostic tool or a quality indicator for monitoring a
   network intended to deliver applications such as streaming media,
   MPEG video, Voice over IP, or other information sensitive to arrival
   time and packet loss.  It provides an indication of traffic jitter, a
   measure of deviation from nominal flow rates, and a data loss
   at-a-glance measure for a particular flow.  For instance, the MDI may
   be used as a reference in characterizing and comparing networks
   carrying UDP streaming media.

   The MDI measurement defined in this memo is intended for Information
   only.

Welch & Clark                Informational                      [Page 1]
RFC 4445         A Proposed Media Delivery Index (MDI)        April 2006

1.  Introduction

   There has been considerable progress over the last several years in
   the development of methods to provide for Quality of Service (QoS)
   over packet-switched networks to improve the delivery of streaming
   media and other time-sensitive and packet-loss-sensitive applications
   such as [i1], [i5], [i6], [i7].  QoS is required for many practical
   networks involving applications such as video transport to assure the
   availability of network bandwidth by providing upper limits on the
   number of flows admitted to a network, as well as to bound the packet
   jitter introduced by the network.  These bounds are required to
   dimension a receiver`s buffer to display the video properly in real
   time without buffer overflow or underflow.

   Now that large-scale implementations of such networks based on RSVP
   and Diffserv are undergoing trials [i3] and being specified by major
   service providers for the transport of streaming media such as MPEG
   video [i4], there is a need to diagnose issues easily and to monitor
   the real-time effectiveness of networks employing these QoS methods
   or to assess whether they are required.  Furthermore, due to the
   significant installed base of legacy networks without QoS methods, a
   delivery system`s transitional solution may be composed of networks
   with and without these methods, thus increasing the difficulty in
   characterizing the dynamic behavior of these networks.

   The purpose of this memo is to describe a set of measurements that
   can be used to derive a Media Delivery Index (MDI) that indicates the
   instantaneous and longer-term behavior of networks carrying streaming
   media such as MPEG video.

   While this memo addresses monitoring MPEG Transport Stream (TS)
   packets [i8] over UDP, the general approach is expected to be
   applicable to other streaming media and protocols.  The approach is
   applicable to both constant and variable bit rate streams though the
   variable bit rate case may be somewhat more difficult to calculate.
   This document focuses on the constant bit rate case as the example to
   describe the measurement, but as long as the dynamic bit rate of the
   encoded stream can be determined (the "drain rate" as described below
   in Section 3), then the MDI provides the measurement of network-
   induced cumulative jitter.  Suggestions and direction for calculation
   of MDI for a variable bit rate encoded stream may be the subject of a
   future document.

   Network packet delivery time variation and various statistics to
   characterize the same are described in a generic approach in [i10].
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