Network Working Group
   Expires in: December 2003 April 2004
                                                   Scott Poretsky
                                                   Avici Systems

                                                   Quarry Technologies

                                                   October 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
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   This draft describes the applicability of IGP Route Convergence
   benchmarking methodology [1] and IGP Route Convergence bechmarking 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].

   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
           	       IGP Data Plane Route Convergence

     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 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

   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 contributing to the
   measured Router IGP Convergence Time, as described Time.   As discussed in [5], [6],
   [7], [8] and [9].
   These [9], these categories are Event Detection, SPF
   Processing, IGP Advertisement, and FIB Update.  Each of these factors has  These have numerous
   components to that 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
           	       IGP Data Plane Route Convergence
	-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 the each of these factors listed above will have a varying amount of
   influence on the convergence result 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, 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 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 removal, failure, line card failure, and route change
   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 time.

   5. Use of Data Plane for IGP Route Convergence Benchmarking

   Customers of service providers use packet loss as the metric for 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].

   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 measured to measure 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 harnasses harnesses for the DUT.

           	       IGP Data Plane Route Convergence

   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 to the correct path. 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. 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, draft-ietf-bmwg-igp-dataplane-conv-meth-01,
	    work in progress, June October 2003.

      [2]   Poretsky, S., "Benchmarking Terminology for IGP Data Plane
	    Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-term-00, draft-ietf-bmwg-igp-dataplane-conv-term-01,
	    work in progress, June October 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 October 2002.

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

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

           	       IGP Data Plane Route Convergence

      [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.

   9. Author's Address

     	Scott Poretsky
        Avici Systems, Inc.
        101 Billerica Avenue
        N. Billerica,
   	Quarry Technologies
  	8 New England Executive Park
   	Burlington, MA 01862 01803

    	Phone: + 1 978 964 2287 781 395 5090

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