RFC 3248 (rfc3248) - Page 2 of 11
A Delay Bound alternative revision of RFC 2598
Alternative Format: Original Text Document
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