A Proposed Media Delivery Index (MDI)
Network Working Group J. Welch
Request for Comments: 4445 IneoQuest Technologies
Category: Informational J. Clark
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 (C) The Internet Society (2006).
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
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
Welch & Clark Informational [Page 1]
RFC 4445 A Proposed Media Delivery Index (MDI) April 2006
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
Network packet delivery time variation and various statistics to
characterize the same are described in a generic approach in [i10].
The approach is capable of being parameterized for various purposes
with the intent of defining a flexible, customizable definition that
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