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

                                                Brent Imhoff
                                                Wiltel Communications

                                                June 2003

                   Benchmarking Methodology for
                IGP Data Plane Route Convergence

        <draft-ietf-bmwg-igp-dataplane-conv-meth-00.txt>


   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
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
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   documents at any time.  It is inappropriate to use Internet-Drafts
   as reference material or to cite them other than as "work in
   progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


   Table of Contents
     1. Introduction ...............................................2
     2. Existing definitions .......................................2
     3. Test Setup..................................................2
     3.1 Test Topologies............................................2
     3.2 Test Considerations........................................3
     4. Test Cases..................................................4
     4.1 Local Events...............................................4
     4.1.1 Convergence Due to SONET Link Failure....................4
     4.1.2 Convergence Due to PPP Session Failure...................5
     4.1.3 Convergence Due to IGP Adjacency Failure.................5
     4.1.4 Convergence Due to Route Withdrawal......................6
     4.1.5 Convergence Due to Cost Change...........................7
     4.2 Remote Events..............................................7
     4.2.1 Convergence Due to Remote SONET Link Failure.............7

Poretsky, Imhoff                                                [Page 1]


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     5. Measuring Convergence Times.................................8
     5.1 Measuring Peak-to-Peak Convergence Time....................8
     5.2 Measuring Impact of Components for Convergence.............8
     6. Security Considerations.....................................9
     7. Acknowledgements............................................9
     8. References..................................................9
     9. Author's Address............................................9
     10. Full Copyright Statement...................................10


   1. Introduction
   This draft describes the methodology for benchmarking IGP Route
   Convergence.  The applicability of this testing is described in
   [1] and the new terminology that it introduces is defined in [2].
   Service Providers use IGP Convergence time as a key metric of
   router design and architecture.  Customers of Service Providers
   observe convergence time by packet loss.  IGP Route Convergence
   is a Direct Measure of Quality (DMOQ) when benchmarking the data
   plane and not the control plane.  The test cases in this document
   are black-box tests that emulate the network events that cause
   route convergence, as described in [1].  Black-box test design
   accounts for all of the factors for route convergence time, as
   provided in [1].  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].

   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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in RFC 2119.

   3.  Test Setup
   3.1 Test Topologies


        ---------    Ingress Traffic Path       ---------
        |       |<------------------------------|       |
        |       |                               |       |
        |       |    Preferred Egress Path      |       |
        |  DUT  |------------------------------>|Tester |
        |       |                               |       |
        |       |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~>|       |
        |       |    Backup Egress Path         |       |
        ---------                               ---------

        Figure 1.  IGP Route Convergence Test Topology
                        for Local Changes

Poretsky, Imhoff                                                [Page 2]


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   Figure 1 shows the test topology to measure IGP Route Convergence due
   to local changes such as SONET Link Failure, PPP Session Failure, IGP
   Adjacency Failure, Route Withdrawal, and Route cost change.  These
   test cases are described in section 4.1.  These test cases provide
   IGP Route Convergence times that consider the Event Detection time,
   SPF Processing time, and FIB Update time.  These times are measured
   by observing packet loss in the data plane.  Physical Links may be of
   any type, such as Sonet or Ethernet, and any speed.

   Figure 2 shows the test topology to measure IGP Route Convergence
   time due to remote changes in the network topology.  These times are
   measured by observing packet loss in the data plane.  Physical Links
   may be of any type, such as Sonet or Ethernet, and any speed. In this
   topology, the three routers are considered a System Under Test (SUT).
   Application of this topology and test cases described in section 4.2
   account for the impact of IGP Advertisement on Route Convergence, as
   described in [1].

                  -----              -----------
                  |   |  Preferred   |         |
        -----     |R2 |------------->|         |
        |   |---->|   | Egress Path  |         |
        |   |     -----              |         |
        |R1 |                        |  Tester |
        |   |     -----              |         |
        |   |---->|   |   Backup     |         |
        -----     |R3 |~~~~~~~~~~~~~>|         |
          ^       |   | Egress Path  |         |
          |       -----              -----------
          |                               |
          |--------------------------------
                Ingress Traffic Path

        Figure 2.  IGP Route Convergence Test Topology
                        for Remote Changes

   3.2 Test Considerations

   3.2.1 IGP Selection
   The test cases described in section 4 can be used for ISIS or
   OSPF.  The Route Convergence test methodology for both is
   identical.  The IGP adjacencies are established on the Preferred
   Egress Path and Backup Egress Path.

   3.2.2 BGP Configuration
   The obtained results for IGP Route Convergence may vary if
   BGP routes are installed.  For results similar to those that
   would be observed in an operational network it is recommended
   that a BGP session be established on the Ingress Traffic Path
   with routes installed.



Poretsky, Imhoff                                                [Page 3]


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   3.2.3 IGP Route Scaling
   The number of IGP routes will impact the measured IGP Route
   Convergence because convergence for the entire IGP route table is
   measured.   For results similar to those that would be observed in
   an operational network it is recommended that the number of
   installed routes closely approximate that for routers in the
   network.

   3.2.4 BGP Route Scaling
   The number of installed BGP routes may impact the IGP Convergence
   time.  For results similar to those that would be observed in an
   operational Network it is recommended that the number of installed
   routes closely approximate that for routers in the network.

   3.2.5 Timers
   There are some timers that will impact the measured IGP Convergence
   time. The following timers should be configured to the minimum value
   prior to beginning execution of the test cases:
        SONET Failure Indication Delay
        IGP Hello Timer
        IGP Dead-Interval
        LSA Generation Delay
        LSA Flood Packet Pacing
        LSA Retransmission Packet Pacing
        SPF Delay

   4. Test Cases
   4.1 Local Events
   The test cases in this section use the test topology shown in
   Figure 1.

   4.1.1 Convergence Due to Local SONET Link Failure
        Objective
        To obtain the IGP Route Convergence due to a Local SONET Link
        failure event.

        Procedure
1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
        2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
         Egress Path is the preferred next-hop.
3. Send traffic at maximum forwarding rate to destinations
         matching all IGP routes from Tester to DUT on Ingress Traffic
         Path.
        4. Verify traffic routed over Preferred Egress Path.
        5. Remove SONET on Tester Interface connected to Preferred Egress
           Path.
        6. Measure Peak-to-Peak Convergence Time [2] as DUT detects
           the link down event and converges all IGP routes and
           traffic over the Backup Egress Path.

Poretsky, Imhoff                                                [Page 4]


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        Results
        The measured IGP Convergence time is influenced by the Local
        SONET indication, SPF delay, SPF Holdtime, SPF Execution
        Time, Tree Build Time, and Hardware Update Time.

   4.1.2 Convergence Due to PPP Session Failure

        Objective
        To obtain the IGP Route Convergence due to a Local PPP Session
        failure event.

        Procedure
        1. Advertise IGP routes from Tester to DUT on Ingress Traffic
           Path.
        2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
           Egress Path is the preferred next-hop.
        3. Send traffic at maximum forwarding rate to destinations
           matching all IGP routes from Tester to DUT on Ingress
           Traffic Path.
        4. Verify traffic routed over Preferred Egress Path.
        5. Remove PPP session from Tester Interface connected to
           Preferred Egress Path.
        6. Measure Peak-to-Peak Convergence Time as DUT detects the
           PPP session down event and converges all IGP routes and
           traffic over the Backup Egress Path.

        Results
        The measured IGP Convergence time is influenced by the Local
      PPP failure indication, SPF delay, SPF Holdtime, SPF Execution
      Time, Tree Build Time, and Hardware Update Time.

   4.1.3 Convergence Due to IGP Adjacency Failure

        Objective
        To obtain the IGP Route Convergence due to a Local IGP Adjacency
        failure event.

        Procedure
        1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
        2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
         Egress Path is the preferred next-hop.
        3. Send traffic at maximum forwarding rate to destinations
           matching all IGP routes from Tester to DUT on Ingress
           Traffic Path.
        4. Verify traffic routed over Preferred Egress Path.
        5. Remove IGP adjacency from Tester interface connected to
           Preferred Egress Path.

Poretsky, Imhoff                                                [Page 5]


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        6. Measure Peak-to-Peak Convergence Time as DUT detects the
           IGP session failure event and converges all IGP routes and
           traffic over the Backup Egress Path.

        Results
        The measured IGP Convergence time is influenced by the IGP
        Hello Interval, IGP Dead Interval, SPF delay, SPF Holdtime,
        SPF Execution Time, Tree Build Time, and Hardware Update
        Time.

   4.1.4 Convergence Due to Route Withdrawal

        Objective
        To obtain the IGP Route Convergence due to Route Withdrawal.

        Procedure
        1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
        2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
         Egress Path is the preferred next-hop.
        3. Send traffic at maximum forwarding rate to destinations
           matching all IGP routes from Tester to DUT on Ingress
           Traffic Path.
        4. Verify traffic routed over Preferred Egress Path.
        5. Tester withdraws all IGP routes from DUT's Local Interface
           on Preferred Egress Path.
        6. Measure Peak-to-Peak Convergence Time as DUT processes the
           route withdrawal event and converges all IGP routes and
           traffic over the Backup Egress Path.

        Results
        The measured IGP Convergence time is the SPF Processing and FIB
        Update time as influenced by the SPF delay, SPF Holdtime,
        SPF Execution Time, Tree Build Time, and Hardware Update Time.

   4.1.5 Convergence Due to Cost Change

        Objective
        To obtain the IGP Route Convergence due to route cost change.

        Procedure
        1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
        2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
         Egress Path is the preferred next-hop.
        3. Send traffic at maximum forwarding rate to destinations
           matching all IGP routes from Tester to DUT on Ingress
           Traffic Path.

Poretsky, Imhoff                                                [Page 6]


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        4. Verify traffic routed over Preferred Egress Path.
        5. Tester increases cost for all IGP routes at DUT's Local
           Interface on Preferred Egress Path so that Backup Egress
           Path have lower cost and becomes preferred path.
        6. Measure Reroute Convergence Time [2] as DUT detects the
           cost change event and converges all IGP routes and
           traffic over the Backup Egress Path.

        Results
        The measured IGP Convergence time is the SPF Processing and FIB
        Update time as influenced by the SPF delay, SPF Holdtime,
        SPF Execution Time, Tree Build Time, and Hardware Update Time.
        There should be no packet loss for this case.

   4.2 Remote Events

   The test cases in this section use the test topology shown in
   Figure 2.

   4.2.1 Convergence Due to Remote SONET Link Failure

        Objective
        To obtain the IGP Route Convergence due to a Remote
        SONET Link failure event.

        Procedure
        1. Advertise IGP routes from Tester to DUT on Ingress Traffic
         Path.
        2. Advertise matching IGP routes from Tester to DUT on
         Preferred Egress Path and Backup Egress Path.  Set the cost
         of the routes so that the IGP routes along the Preferred
         Egress Path is the preferred next-hop.
        3. Send traffic at maximum forwarding rate to destinations
           matching all IGP routes from Tester to DUT on Ingress
           Traffic Path.
        4. Verify traffic routed over Preferred Egress Path.
        5. Remove SONET on Neighbor Interface connected to
           Preferred Egress Path.
        6. Measure Peak-to-Peak Convergence time as DUT detects the
           link down event and converges all IGP routes and traffic
           over the Backup Egress Path.

        Results
        The measured IGP Convergence time is influenced by the
        SONET failure indication, LSA/LSP Flood Packet Pacing,
        LSA/LSP Retransmission Packet Pacing, LSA/LSP Generation
        time, SPF delay, SPF Holdtime, SPF Execution Time, Tree
        Build Time, and Hardware Update Time.





Poretsky, Imhoff                                                [Page 7]


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   5. Measuring Convergence Times
   5.1 Measuring Full Convergence Time

        Figure 3 shows a graph model of Convergence Time as measured
        from the data plane.  Refer to [2] for definitions of the terms
        used.  IGP Route Convergence Time is the amount of time for the
        Forwarding Rate to begin its downward slope upon occurrence of
        a network event and then fully recover to the Maximum
        Forwarding Rate.

                        Forwarding Rate versus Time

                   Time=Recovery    Time=Network Event  Time = 0sec
        Maximum               ^              ^          ^
        Forwarding Rate--> ----\             /-----------
                                \           /<----Route Convergence
        Route Convergence------->\         /      Event Slope
        Recovery Slope            \_______/<------100% Packet Loss

        X-axis = Time
        Y-axis = Forwarding Rate

                        Figure 3. Convergence Graph

        Maximum forwarding rate at a fixed packet size without packet
        loss is required for accurate measurement.  The test duration
        must be greater than the convergence time. Full Convergence
        Time is obtained directly from the graph in Figure 3 using
        equation 1.

        (eq 1) Convergence Time(Full)=Time(Recovery)-Time(Network Event).

        Given a known constant rate of offered load in units packet per
        second (pps), the Average Convergence Time can be obtained
        using equation 2 or equation 3.

      (eq 2) Convergence Time(Average)=Number Packets Lost/pps(Offered)

        (eq 3) Convergence Time(Average)= (Number Packets Offered -
                Number of Packets Received)/pps(Offered)

        As discussed in [1], Full Convergence Time is the more accurate
        measurement.  Average Convergence Time does not account for the
        angle of the Route Convergence Recovery Slope, so Full Convergence
        Time > Average Convergence Time.  Ideally, the Recovery Slope has
        no angle so that it is vertical and Average Convergence Time =
        Full Convergence Time.

   5.2 Measuring Impact of Components for Convergence
        The factors for IGP Route Convergence Time are provided in [1].
        The results of the test cases in section 4 above can be used to
        calculate the impact each factor has on the Convergence

Poretsky, Imhoff                                                [Page 8]


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        results, as follow:

        SPF Processing and FIB Update time = Result (4.1.4)

        SONET failure indication time = Result(4.1.1) - Result(4.1.4)

        PPP failure indication time = Result(4.1.2) - Result(4.1.4)

        IGP failure indication time = Result(4.1.3) - Result(4.1.4)

        IGP Advertisement time = Result(4.1.1) - Result(4.2.1)

   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
        networks.

   7. Acknowledgements
        Thanks to Jayant Kulkarni for doing as most Test Engineers
        do - working beyond the call of duty to help advance
        technology.  Especially 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 Applicability for IGP
            Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-00, work
            in progress, June 2003.

      [2] Poretsky, S., "Benchmarking Terminology for IGP 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.

   9. Author's Address

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

        Phone: + 1 978 964 2287
        EMail: sporetsky@avici.com


Poretsky, Imhoff                                                [Page 9]


INTERNET-DRAFT          Benchmarking Methodology for            June 2003
                      IGP Data Plane Route Convergence

        Brent Imhoff
        WilTel Communications
        3180 Rider Trail South
        Bridgeton, MO 63045
        USA

        Phone: +1 314 595 6853
        EMail: brent.imhoff@wcg.com


   10.  Full Copyright Statement

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        The limited permissions granted above are perpetual and will
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Poretsky, Imhoff                                                [Page 10]


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