Performance Analysis of Inter-Domain Path Computation Methodologies
RFC 5468

Network Working Group                                        S. Dasgupta
Request for Comments: 5468                                J. de Oliveira
Category: Informational                                Drexel University
                                                             JP. Vasseur
                                                           Cisco Systems
                                                              April 2009

  Performance Analysis of Inter-Domain Path Computation Methodologies

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.

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Abstract

   This document presents a performance comparison between the per-
   domain path computation method and the Path Computation Element (PCE)
   Architecture-based Backward Recursive Path Computation (BRPC)
   procedure.  Metrics to capture the significant performance aspects
   are identified, and detailed simulations are carried out on realistic
   scenarios.  A performance analysis for each of the path computation
   methods is then undertaken.

Dasgupta, et al.             Informational                      [Page 1]
RFC 5468       Analysis of Inter-Domain Path Computation      April 2009

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Evaluation Metrics ..............................................4
   4. Simulation Setup ................................................5
   5. Results and Analysis ............................................6
      5.1. Path Cost ..................................................7
      5.2. Crankback/Setup Delay ......................................7
      5.3. Signaling Failures .........................................8
      5.4. Failed TE-LSPs/Bandwidth on Link Failures ..................8
      5.5. TE LSP/Bandwidth Setup Capacity ............................8
   6. Security Considerations .........................................9
   7. Acknowledgment ..................................................9
   8. Informative References ..........................................9

1.  Introduction

   The IETF has specified two approaches for the computation of inter-
   domain (Generalized) Multi-Protocol Label Switching ((G)MPLS) Traffic
   Engineering (TE) Label Switched Paths (LSP): the per-domain path
   computation approach defined in [RFC5152] and the PCE-based approach
   specified in [RFC4655].  More specifically, we study the PCE-based
   path computation model that makes use of the BRPC method outlined in
   [RFC5441].  In the rest of this document, we will call PD and PCE the
   per-domain path computation approach and the PCE path computation
   approach, respectively.

   In the per-domain path computation approach, each path segment within
   a domain is computed during the signaling process by each entry node
   of the domain up to the next-hop exit node of that same domain.

   In contrast, the PCE-based approach and, in particular, the BRPC
   method defined in [RFC5441] rely on the collaboration between a set
   of PCEs to find to shortest inter-domain path after the computation
   of which the corresponding TE LSP is signaled: path computation is
   undertaken using multiple PCEs in a backward recursive fashion from
   the destination domain to the source domain.  The notion of a Virtual
   Shortest Path Tree (VSPT) is introduced.  Each link of a VSPT
   represents the shortest path satisfying the set of required
   constraints between the border nodes of a domain and the destination
   LSR.  The VSPT of each domain is returned by the corresponding PCE to
   create a new VSPT by PCEs present in other domains.  [RFC5441]
   discusses the BRPC procedure in complete detail.

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RFC 5468       Analysis of Inter-Domain Path Computation      April 2009

   This document presents some simulation results and analysis to
   compare the performance of the above two inter-domain path
   computation approaches.  Two realistic topologies with accompanying
   traffic matrices are used to undertake the simulations.