Network Working Group
   Expires in: December 2003
                                                   Scott Poretsky
                                                   Avici Systems

                                                   June 2003

                   Benchmarking Applicability for
                  IGP Data Plane Route Convergence


   Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force  (IETF), its areas, and its working groups.  Note that
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   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   This draft describes the applicability of IGP Route Convergence
   benchmarking methodology [1] and IGP Route Convergence bechmarking
   terminology [2].  The methodology and terminology is to be used
   for benchmarking route convergence and can be applied to any
   link-state IGP such as ISIS [3] and OSPF [4].  The data plane is
   measured to obtain the convergence benchmarking metrics described
   in [1].

   Table of Contents
     1. Introduction ...............................................2
     2. Existing definitions .......................................2
     3. Factors for IGP Route Convergence Time......................2
     4. Network Events that Cause Route Convergence.................3
     5. Use of Data Traffic for IGP Route Convergence Benchmarking..3
     6. Security Considerations.....................................4
     7. Acknowledgements............................................4
     8. References..................................................4

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     9. Author's Address............................................5
     10. Full Copyright Statement...................................5

   1. Introduction
   IGP Convergence is a critical performance parameter.  Customers
   of Service Providers use packet loss due to IGP Convergence as a
   key metric of their network service quality.  Service Providers
   use IGP Convergence time as a key metric of router design and
   architecture.  Fast network convergence can be optimally achieved
   through deployment of fast converging routers.  The fundamental
   basis by which customers of service providers benchmark convergence
   is packet loss, which is an externally observable event having
   direct impact on their application performance.  IGP Route
   Convergence is a Direct Measure of Quality (DMOQ) when benchmarking
   the data plane.  For this reason it is important to develop a standard
   router benchmarking methodology and terminology for measuring IGP
   convergence that uses the data plane as described in [1] and [2].
   This document describes all of the factors that influence a
   convergence measurement and how a purely black box test can be
   designed to account for all of these factors.  This enables accurate
   benchmarking and evaluation for route convergence time.

   2.  Existing definitions

   For the sake of clarity and continuity this RFC adopts the template
   for definitions set out in Section 2 of RFC 1242.  Definitions are
   indexed and grouped together in sections for ease of reference.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in RFC 2119.

   3. Factors for IGP Route Convergence Time

   There are four major categories of factors for the measured Router
   IGP Convergence Time, as described in [5], [6], [7], [8] and [9].
   These are Event Detection, SPF Processing, IGP Advertisement, and
   FIB Update.  Each of these factors has numerous components to
   influence the convergence time.  These are listed as follow:

        -Event Detection-
        SONET failure indication time
        PPP failure indication time
        IGP Hello Dead Interval

        -SPF Processing-
        SPF Delay Time
        SPF Hold time
        SPF Execution time

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        -IGP Advertisement-
        LSA/LSP Flood Packet Pacing
        LSA/LSP Retransmission Packet Pacing
        LSA/LSP Generation time

        -FIB Update-
        Tree Build time
        Hardware Update time

   Each of the factors listed above will have a varying amount of
   influence on the convergence result with each router vendors'
   architecture and IGP implementation.  It is necessary to design a
   convergence test that considers not just one or a few of these
   components, but instead all of these components.  The additional
   benefit of designing a test for all components is that it enables
   black-box testing in which knowledge of the routers' internal
   implementations is not required.  It is then possible to make
   valid use of the benchmarking metrics when comparing routers from
   different vendors.

   4. Network Events that Cause Convergence

   There are different types of network events that can cause IGP
   convergence.  These network events are administrative link
   removal, unplanned link removal, and route change such as
   withdrawal, flap, next-hop change, and cost change.  When
   benchmarking a router it is important to measure the convergence
   time for local and remote occurrence of these network events.
   The convergence time measured will vary whether the network event
   occurred locally or remotely due to varying combinations of
   factors listed in the previous sections.  This behavior makes it
   possible to design purely black-box tests that isolate
   measurements for each of the components of convergence time.

   5. Use of Data Plane for IGP Route Convergence Benchmarking

   Customers of service providers use packet loss as the metric for
   convergence time.  Packet loss is an externally observable event
   having direct impact on customers' application performance.
   For this reason it is important to develop a standard router
   benchmarking methodology and terminology that is a Direct Measure
   of Quality (DMOQ)for measuring IGP convergence.  Such a
   methodology uses the data plane as described in [1] and [2].

   An additional benefit of using packet loss for calculation of
   IGP Route Convergence time is that it enables black-box tests to
   be designed.  Data traffic can be offered at line-rate to the
   device under test (DUT), an emulated network event can be forced
   to occur, and packet loss can be externally
   observed to measure the convergence time.  Knowledge of the DUT
   architecture and IGP implementation is not required. There is no
   need to rely on the DUT to produce the test results.  There is no
   need to build intrusive test harnasses for the DUT.

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   Use of data traffic and measurement of packet loss on the data
   plane also enables Route Convergence methodology test cases that
   consider the time for the Route Controller to update the FIB on
   the forwarding engine of the hardware.  A router is not fully
   converged until all components are updated and traffic is
   rerouted along the correct path.  As long as there is packet
   loss, routes have not converged.  It is possible to send diverse
   traffic flows to destinations matching every route in the FIB
   so that the time it takes for the router to converge an entire
   route table can be benchmarked.

   6. Security Considerations

        Documents of this type do not directly effect the security of
        the Internet or of corporate networks as long as benchmarking
        is not performed on devices or systems connected to operating

   7. Acknowledgements
        Thanks to Curtis Villamizar for sharing so much of his
        knowledge and experience through the years. Also, special
        thanks to the many Network Engineers and Network Architects
        at the Service Providers who are always eager to discuss
        Route Convergence.

   8. References

      [1]   Poretsky, S., "Benchmarking Methodology for IGP Data Plane
            Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-00,
            work in progress, June 2003.

      [2]   Poretsky, S., "Benchmarking Terminology for IGP Data Plane
            Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-00,
            work in progress, June 2003.

      [3]   Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
            Environments", RFC 1195, December 1990.

      [4]   Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.

      [5]   Villamizar, C., "Convergence and Restoration Techniques for
            ISP Interior Routing", NANOG 25, June 2002.

      [6]   Katz, D., "Why are we Scared of SPF?  IGP Scaling and
            Stability", NANOG 25, June 2002.

      [7]   Filsfils, C., "Deploying Tight-SLA Services on an Internet
            Backbone: ISIS Fast Convergence and Differentiated Services
            Design (tutorial)", NANOG 25, June 2002.

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      [8]   Alaettinoglu, C. and Casner, S., "ISIS Routing on the Qwest
            Backbone: a Recipe for Subsecond ISIS Convergence", NANOG 24,
            June 2002.

      [9]   Alaettinoglu, C., Jacobson, V., and Yu, H., "Towards
            Millisecond IGP Convergence", NANOG 20, October 2000.

   9. Author's Address

        Scott Poretsky
        Avici Systems, Inc.
        101 Billerica Avenue
        N. Billerica, MA 01862

        Phone: + 1 978 964 2287

   10.  Full Copyright Statement

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