RFC 3248 (rfc3248) - Page 2 of 11

A Delay Bound alternative revision of RFC 2598

RFC 3248      Delay Bound alternative revision of RFC 2598    March 2002


Specification of Requirements

   This document is for Informational purposes only.  If implementors
   choose to experiment with the DB PHB, key words "MUST", "MUST NOT",
   "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
   "RECOMMENDED", "MAY", and "OPTIONAL" are interpreted as described in
   RFC 2119 [3].

1 Introduction

   RFC 2598 was the Differentiated Services (DiffServ) working group's
   first standards track definition of the Expedited Forwarding (EF) Per
   Hop Behavior (PHB) [1].  As part of the DiffServ working group's
   ongoing refinement of the EF PHB, various issues were raised with the
   text in RFC 2598 [2].

   After the Pittsburgh IETF meeting in August 2000, a volunteer 'EF
   design team' was formed (the authors of this document) to propose a
   new expression of the EF PHB.  The remainder of this Informational
   document captures our feedback to the DiffServ working group at the
   San Diego IETF in December 2000.  Our solution focussed on a Delay
   Bound (DB) based re-expression of RFC 2598 which met the goals of RFC
   2598's original authors.  The DiffServ working group ultimately chose
   an alternative re-expression of the EF PHB text, developed by the
   authors of [2] and revised to additionally encompass our model
   described here.

   Our proposed Delay Bound solution is archived for historical
   interest.  Section 2 covers the minimum, necessary and sufficient
   description of what we believed qualifies as 'DB' behavior from a
   single node.  Section 3 then discusses a number of issues and
   assumptions made to support the definition in section 2.

2. Definition of Delay Bound forwarding

   For a traffic stream not exceeding a particular configured rate, the
   goal of the DB PHB is a strict bound on the delay variation of
   packets through a hop.

   This section will begin with the goals and necessary boundary
   conditions for DB behavior, then provide a descriptive definition of
   DB behavior itself, discuss what it means to conform to the DB
   definition, and assign the experimental DB PHB code point.








Armitage, et al.             Informational