Network Working Group
   Expires in: January April 2006
                                                   Scott Poretsky
                                                   Reef Point Systems


                                                   October 2005

                   Considerations for Benchmarking
                   IGP Data Plane Route Convergence



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Copyright Notice
   Copyright (C) The Internet Society (2005).  All Rights Reserved.

   This draft provides considerations for IGP Route Convergence
   benchmarking methodology [1] and IGP Route Convergence benchmarking
   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].

                      IGP Data Plane Route Convergence

   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 Plane for IGP Route Convergence Benchmarking....3
     6. IANA Considerations.........................................4
     7. Security Considerations.....................................4
     7. Acknowledgements............................................4
     8. Acknowledgements............................................4
     9. Normative References........................................5
     10. Author's Address............................................5 Address...........................................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 network users and operators 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
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in BCP 14, RFC 2119
   2119.  RFC 2119 defines the use of these key words to help make the
   intent of standards track documents as clear as possible.  While
   this document uses these keywords, this document is not a standards
   track document.

3. Factors for IGP Route Convergence Time

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

                      IGP Data Plane Route Convergence

      -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

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

      -FIB Update-
        Tree Build time
        Hardware Update time

   The contribution of each of these factors listed above will vary
   with each router vendors' architecture and IGP implementation.
   It is therefore necessary to design a convergence test that
   considers all of these components, not just one or a few 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 convergence 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 failure, line card failure, and route
   changes 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

5. Use of Data Plane for IGP Route Convergence Benchmarking
   Customers of service providers use packet loss as the metric to
   calculate 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].

                      IGP Data Plane Route Convergence

   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 to the
   device under test (DUT), an emulated network event can be forced
   to occur, and packet loss can be externally measured to calculate
   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 harnesses for the DUT.

   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 to the correct egress interface.  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. IANA Considerations

   This document requires no IANA considerations.

7. 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 production networks.


8. 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 benchmarking.

                      IGP Data Plane Route Convergence


9. Normative References
      [1] Poretsky, S., "Benchmarking Methodology for IGP Data Plane
          Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-07, draft-ietf-bmwg-igp-dataplane-conv-meth-08,
          work in progress, July October 2005.

      [2] Poretsky, S., "Benchmarking Terminology for IGP Data Plane
          Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-07, draft-ietf-bmwg-igp-dataplane-conv-term-08,
          work in progress, July October 2005.

      [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, October 2002.

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

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

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

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


10. Author's Address

      Scott Poretsky
      Reef Point Systems
      8 New England Executive Park
      Burlington, MA 01803

      Phone: + 1 781 395 5090 508 439 9008
                      IGP Data Plane Route Convergence

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