RFC 2680 (rfc2680) - Page 2 of 15

A One-way Packet Loss Metric for IPPM

RFC 2680          One Way Packet Loss Metric for IPPM     September 1999


   +  Using this singleton metric, a 'sample', called Type-P-One-way-
      Loss-Poisson-Stream, is introduced to measure a sequence of
      singleton transmissions and/or losses measured at times taken from
      a Poisson process.

   +  Using this sample, several 'statistics' of the sample are defined
      and discussed.

   This progression from singleton to sample to statistics, with clear
   separation among them, is important.

   Whenever a technical term from the IPPM Framework document is first
   used in this memo, it will be tagged with a trailing asterisk.  For
   example, "term*" indicates that "term" is defined in the Framework.

1.1. Motivation:

   Understanding one-way packet loss of Type-P* packets from a source
   host* to a destination host is useful for several reasons:

   +  Some applications do not perform well (or at all) if end-to-end
      loss between hosts is large relative to some threshold value.

   +  Excessive packet loss may make it difficult to support certain
      real-time applications (where the precise threshold of "excessive"
      depends on the application).

   +  The larger the value of packet loss, the more difficult it is for
      transport-layer protocols to sustain high bandwidths.

   +  The sensitivity of real-time applications and of transport-layer
      protocols to loss become especially important when very large
      delay-bandwidth products must be supported.

   The measurement of one-way loss instead of round-trip loss is
   motivated by the following factors:

   +  In today's Internet, the path from a source to a destination may
      be different than the path from the destination back to the source
      ("asymmetric paths"), such that different sequences of routers are
      used for the forward and reverse paths.  Therefore round-trip
      measurements actually measure the performance of two distinct
      paths together.  Measuring each path independently highlights the
      performance difference between the two paths which may traverse
      different Internet service providers, and even radically different
      types of networks (for example, research versus commodity
      networks, or ATM versus packet-over-SONET).




Almes, et al.               Standards Track