RFC 3357 (rfc3357) - Page 3 of 15

One-way Loss Pattern Sample Metrics

RFC 3357          One-way Loss Pattern Sample Metrics        August 2002


1. Introduction

   In certain real-time applications (such as packet voice and video),
   the loss pattern or loss distribution is a key parameter that
   determines the performance observed by the users.  For the same loss
   rate, two different loss distributions could potentially produce
   widely different perceptions of performance.  The impact of loss
   pattern is also extremely important for non-real-time applications
   that use an adaptive protocol such as TCP.  Refer to [4], [5], [6],
   [11] for evidence as to the importance and existence of loss
   burstiness and its effect on packet voice and video applications.

   Previously, the focus of the IPPM had been on specifying base metrics
   such as delay, loss and connectivity under the framework described in
   RFC 2330.  However, specific Internet behaviors can also be captured
   under the umbrella of the IPPM framework, specifying new concepts
   while reusing existing guidelines as much as possible.  In this
   document, we propose two derived metrics, called "loss distance" and
   "loss period", with associated statistics, to capture packet loss
   patterns.  The loss period metric captures the frequency and length
   (burstiness) of loss once it starts, and the loss distance metric
   captures the spacing between the loss periods.  It is important to
   note that these metrics are derived based on the base metric Type-P-
   One-Way-packet-Loss.

2. Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and
   "silently ignore" in this document are to be interpreted as described
   in BCP 14, RFC 2119 [2].

3. The Approach

   This document closely follows the guidelines specified in [3].
   Specifically, the concepts of singleton, sample, statistic,
   measurement principles, Type-P packets, as well as standard-formed
   packets all apply.  However, since the document proposes to capture
   specific Internet behaviors, modifications to the sampling process
   MAY be needed.  Indeed, this is mentioned in [1], where it is noted
   that alternate sampling procedures may be useful depending on
   specific circumstances.  This document proposes that the specific
   behaviors be captured as "derived" metrics from the base metrics the
   behaviors are related to.  The reasons for adopting this position are
   the following:






Koodli & Ravikanth           Informational