Bandwidth Constraints Models for Differentiated Services (Diffserv)-aware MPLS Traffic Engineering: Performance Evaluation
RFC 4128

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Network Working Group                                             W. Lai
Request for Comments: 4128                                     AT&T Labs
Category: Informational                                        June 2005

                   Bandwidth Constraints Models for
  Differentiated Services (Diffserv)-aware MPLS Traffic Engineering:
                        Performance Evaluation

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 Notice

   Copyright (C) The Internet Society (2005).

IESG Note

   The content of this RFC has been considered by the IETF (specifically
   in the TE-WG working group, which has no problem with publication as
   an Informational RFC), and therefore it may resemble a current IETF
   work in progress or a published IETF work.  However, this document is
   an individual submission and not a candidate for any level of
   Internet Standard.  The IETF disclaims any knowledge of the fitness
   of this RFC for any purpose, and in particular notes that it has not
   had complete IETF review for such things as security, congestion
   control or inappropriate interaction with deployed protocols.  The
   RFC Editor has chosen to publish this document at its discretion.
   Readers of this RFC should exercise caution in evaluating its value
   for implementation and deployment.  See RFC 3932 for more
   information.

Abstract

   "Differentiated Services (Diffserv)-aware MPLS Traffic Engineering
   Requirements", RFC 3564, specifies the requirements and selection
   criteria for Bandwidth Constraints Models.  Two such models, the
   Maximum Allocation and the Russian Dolls, are described therein.
   This document complements RFC 3564 by presenting the results of a
   performance evaluation of these two models under various operational
   conditions: normal load, overload, preemption fully or partially
   enabled, pure blocking, or complete sharing.

Lai                         Standards Track                     [Page 1]
RFC 4128          BC Models for Diffserv-aware MPLS TE         June 2005

Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions used in this document ..........................4
   2. Bandwidth Constraints Models ....................................4
   3. Performance Model ...............................................5
      3.1. LSP Blocking and Preemption ................................6
      3.2. Example Link Traffic Model .................................8
      3.3. Performance under Normal Load ..............................9
   4. Performance under Overload .....................................10
      4.1. Bandwidth Sharing versus Isolation ........................10
      4.2. Improving Class 2 Performance at the Expense of Class 3 ...12
      4.3. Comparing Bandwidth Constraints of Different Models .......13
   5. Performance under Partial Preemption ...........................15
      5.1. Russian Dolls Model .......................................16
      5.2. Maximum Allocation Model ..................................16
   6. Performance under Pure Blocking ................................17
      6.1. Russian Dolls Model .......................................17
      6.2. Maximum Allocation Model ..................................18
   7. Performance under Complete Sharing .............................19
   8. Implications on Performance Criteria ...........................20
   9. Conclusions ....................................................21
   10. Security Considerations .......................................22
   11. Acknowledgements ..............................................22
   12. References ....................................................22
       12.1. Normative References ....................................22
       12.2. Informative References ..................................22

Lai                         Standards Track                     [Page 2]
RFC 4128          BC Models for Diffserv-aware MPLS TE         June 2005

1.  Introduction

   Differentiated Services (Diffserv)-aware MPLS Traffic Engineering
   (DS-TE) mechanisms operate on the basis of different Diffserv classes
   of traffic to improve network performance.  Requirements for DS-TE
   and the associated protocol extensions are specified in references
   [1] and [2] respectively.

   To achieve per-class traffic engineering, rather than on an aggregate
   basis across all classes, DS-TE enforces different Bandwidth
   Constraints (BCs) on different classes.  Reference [1] specifies the
   requirements and selection criteria for Bandwidth Constraints Models
   (BCMs) for the purpose of allocating bandwidth to individual classes.

   This document presents a performance analysis for the two BCMs
   described in [1]:

   (1) Maximum Allocation Model (MAM) - the maximum allowable bandwidth