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 Network Working Group                         S. Poretsky
 Internet Draft                                Allot Communications
 Expires: September 08, 2009
 Intended Status: Informational                Brent Imhoff
                                               Juniper Networks

                                               March 08, 2009

                        Terminology for Benchmarking
                 Link-State IGP Data Plane Route Convergence

               <draft-ietf-bmwg-igp-dataplane-conv-term-17.txt>

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ABSTRACT
   This document describes the terminology for benchmarking Interior
   Gateway Protocol (IGP) Route Convergence.   The terminology is to
   be used for benchmarking IGP convergence time through externally
   observable (black box) data plane measurements.  The terminology
   can be applied to any link-state IGP, such as ISIS and OSPF.

Poretsky, Imhoff                                                [Page 1]


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Table of Contents
     1. Introduction and Scope........................................3
     2. Existing Definitions .........................................4
     3. Term Definitions..............................................4
        3.1 States
           3.1.1 Route Convergence....................................4
           3.1.2 Full Convergence.....................................5
           3.1.3 Network Convergence..................................5
           3.1.4 Route-Specific Convergence...........................6
           3.1.5 Stale Forwarding.....................................6
        3.2 Events
           3.2.1 Convergence Event....................................7
           3.2.2 Convergence Event Trigger............................7
           3.2.3 Convergence Event Instant............................8
           3.2.4 Convergence Recovery Instant.........................8
           3.2.5 First Route Convergence Instant......................9
           3.2.6 Convergence Event Transition.........................9
           3.2.7 Convergence Recovery Transition......................10
           3.2.8 Nested Convergence Events............................10
        3.3 Interfaces
           3.3.1 Local Interface......................................11
           3.3.2 Neighbor Interface...................................11
           3.3.3 Remote Interface.....................................11
           3.3.4 Preferred Egress Interface...........................12
           3.3.5 Next-Best Egress Interface...........................12
        3.4 Benchmarking Method
           3.4.1 Packet Loss..........................................13
           3.4.2 Convergence Packet Loss..............................13
           3.4.3 Rate-Derived Convergence Method......................14
           3.4.4 Loss-Derived Convergence Method......................14
           3.4.5 Packet Sampling Interval.............................15
        3.5 Benchmarks
           3.5.1 Full Convergence Time................................17
           3.5.2 First Route Convergence Time.........................17
           3.5.3 Route-Specific Convergence Time......................17
           3.5.4 Sustained Convergence Validation Time................18
           3.5.5 Reversion Convergence Time...........................19
     4. IANA Considerations...........................................19
     5. Security Considerations.......................................19
     6. Acknowledgements..............................................20
     7. References....................................................20
     8. Author's Address..............................................21






Poretsky, Imhoff                                                [Page 2]


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1. Introduction and Scope

   This draft describes the terminology for benchmarking Interior
   Gateway Protocol (IGP) Route Convergence.  The motivation and
   applicability for this benchmarking is provided in [Po07a].  The
   methodology to be used for this benchmarking is described in [Po07m].
   The purpose of this document is to introduce new terms required to
   complete execution of the IGP Route Convergence Methodology [Po07m].
   These terms apply to IPv4 and IPv6 traffic and IGPs.

   Convergence times are measured at the Tester on the data plane by
   observing packet loss through the DUT.  The methodology and
   terminology to be used for benchmarking Route Convergence can be
   applied to any link-state IGP such as ISIS [Ca90] and OSPF [Mo98].
   The data plane is measured to obtain black-box (externally
   observable) convergence benchmarking metrics.  When there is no
   packer loss observed in the data plane, the convergence time
   SHALL be reported as zero.

   An example of Route Convergence as observed and measured from the
   data plane is shown in Figure 1.  The graph in Figure 1 shows
   Forwarding Rate versus Time.  Time 0 on the X-axis is on the far
   right of the graph.  The Offered Load to the ingress interface of
   the DUT SHOULD equal the measured Throughput [Ba99][Ma98] of the DUT
   and the Forwarding Rate [Ma98] and Convergence Packet Loss is
   measured at the Preferred and Next-Best Egress interfaces of the DUT
   befire, during, and after a Convergence Event Trigger.  These
   components of the graph are defined in the Term Definitions section.

  Full Convergence-> Convergence     Convergence
                     Recovery       Event   Event    Time=
                     Instant        Instant Trigger  0sec
  Forwarding Rate=         ^              ^    ^     ^     Offered Load=
     Offered Load --> ------\    Packet   /----------- <--Max Throughput
                             \    Loss   /<----Convergence
           Convergence------->\         /      Event Transition
        Recovery Transition    \       /
                                \_____/<------Maximum Packet Loss
                                ^
                          First Route
                      Convergence Instant

        Y-axis = Forwarding Rate
        X-axis = Time (increases right to left to match commercial test
                       equipment displays)

                        Figure 1. Convergence Graph


Poretsky, Imhoff                                                [Page 3]


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2.  Existing Definitions
   This document uses existing terminology defined in other BMWG
   work.  Examples include, but are not limited to:

             Latency                   [Ref.[Ba91], section 3.8]
             Frame Loss Rate           [Ref.[Ba91], section 3.6]
             Throughput                [Ref.[Ba91], section 3.17]
             Device Under Test (DUT)   [Ref.[Ma98], section 3.1.1]
             System Under Test (SUT)   [Ref.[Ma98], section 3.1.2]
             Out-of-order Packet       [Ref.[Po06], section 3.3.2]
             Duplicate Packet          [Ref.[Po06], section 3.3.3]
             Packet Reordering         [Ref.[Mo06], section 3.3]

   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 BCP 14, RFC 2119
   [Br97].  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. Term Definitions

 3.1 States
   3.1.1 Route Convergence

        Definition:
        The action to update all components of the router with the
        most recent route change(s) including the Routing
        Information Base (RIB) and Forwarding Information Base (FIB),
        along with software and hardware tables, such that forwarding
        is successful for one or more route entries.

        Discussion:
        Route Convergence MUST occur after a Convergence Event.
        Route Convergence can be observed externally by the rerouting
        of data traffic to the Next-best Egress Interface.  Also,
        completion of Route Convergence may or may not be sustained
        over time.

        Measurement Units: N/A

        Issues: None

        See Also:
        Network Convergence
        Full Convergence
        Convergence Event

Poretsky, Imhoff                                                [Page 4]


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   3.1.2 Full Convergence

        Definition:
        Route Convergence for an entire FIB in which complete recovery
        from the Convergence Event is indicated by the DUT throughput
        equal to the offered load.

        Discussion:
        When benchmarking convergence, it is useful to measure
        the time to converge an entire FIB.  For example,
        a Convergence Event can be produced for an OSPF table of
        5000 routes so that the time to converge routes 1 through
        5000 is measured.  Completion of Full Convergence is externally
        observable from the data plane when the Throughput of the data
        plane traffic on the Next-Best Egress Interface equals the
        offered load.

        Full Convergence MAY be measured using Rate-Derived Convergence
        Method or calculated using Loss-Derived Convergence Method.
        Full Convergence may or may not be sustained over time.  The
        Sustained Convergence Validation Time MUST be applied.

        Measurement Units: N/A

        Issues: None

        See Also:
        Network Convergence
        Route Convergence
        Convergence Event

   3.1.3 Network Convergence

        Definition:
        The process of updating of all routing tables, including
        distributed FIBs, in all routers throughout the network.

        Discussion:
        Network Convergence requires completion of all Route
        Convergence operations for all routers in the network following
        a Convergence Event.  Completion of Network Convergence can be
        observed by recovery of System Under Test (SUT) Throughput to
        equal the offered load, with no Stale Forwarding, and no
        Blenders [Ca01][Ci03].

        Measurement Units: N/A

        Issues: None

Poretsky, Imhoff                                                [Page 5]


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        See Also:
        Route Convergence
        Stale Forwarding

  3.1.4 Route-Specific Convergence
        Definition:
        Route Convergence for one or more specific route entries in
        the FIB in which recovery from the Convergence Event is
        indicated when data-plane traffic for the flow [Po06] matching
        that route entry(ies) is routed to the Next-Best Egress
        Interface.

        Discussion:
        When benchmarking convergence, it is sometimes useful to
        measure the time to converge a single flow [Po06] or group of
        flows to benchmark convergence time for one or a few route
        entries in the FIB instead of the entire FIB.  Route-Specific
        Convergence of a flow is externally observable from the data
        plane when the data plane traffic for that flow is routed to
        the Next-Best Egress Interface.

        Measurement Units: N/A

        Issues: None

        See Also:
        Full Convergence
        Route Convergence
        Convergence Event

   3.1.5 Stale Forwarding
        Definition:
        Forwarding of traffic to route entries that no longer exist
        or to route entries with next-hops that are no longer preferred.

        Discussion:
        Stale Forwarding can be caused by a Convergence Event and can
        manifest as a "black-hole" or microloop that produces packet
        loss.  Stale Forwarding can exist until Network Convergence is
        completed.  Stale Forwarding cannot be observed with a single
        DUT.

        Measurement Units: N/A

        Issues: None

        See Also:
        Network Convergence

Poretsky, Imhoff                                                [Page 6]


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 3.2 Events

   3.2.1 Convergence Event

        Definition:
        The occurrence of a planned or unplanned event in the network
        that results in a change in the egress interface of the Device
        Under Test (DUT) for routed packets.

        Discussion:
        Convergence Events include link loss, routing protocol session
        loss, router failure, configuration change, and better next-hop
        learned via a routing protocol.

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Convergence Packet Loss
        Convergence Event Instant

   3.2.2 Convergence Event Trigger

        Definition:
        An action taken by the Tester to produce a Convergence Event.

        Discussion:
        The Convergence Event Trigger is introduced by the Tester and
        may be indicated by link loss, routing protocol session loss,
        router failure, configuration change, or a better next-hop
        learned via a routing protocol introduced by the Tester.

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Convergence Event
        Convergence Packet Loss
        Convergence Recovery Instant



Poretsky, Imhoff                                                [Page 7]


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   3.2.3 Convergence Event Instant

        Definition:
        The time instant that a Convergence Event becomes observable in
        the data plane.

        Discussion:
        Convergence Event Instant is observable from the data
        plane as the precise time that the device under test begins
        to exhibit packet loss.  The Convergence Event Instant is
        produced by the Convergence Event Trigger.  The Convergence
        Event Instant always occurs concurrent or subsequent to the
        Tester introducing the Convergence Event Trigger.

        Measurement Units:
        hh:mm:ss:nnn:uuu,
           where 'nnn' is milliseconds and 'uuu' is microseconds.

        Issues: None

        See Also:
        Convergence Event
        Convergence Packet Loss
        Convergence Recovery Instant

   3.2.4 Convergence Recovery Instant

        Definition:
        The time instant that Full Convergence completion is
        observed.

        Discussion:
        Convergence Recovery Instant is measurable from the data
        plane as the precise time that the device under test completes
        Full Convergence.  The Convergence Recovery Instant MUST be
        maintained for an interval of duration equal to the Sustained
        Convergence Validation Time.

        Measurement Units:
        hh:mm:ss:nnn:uuu,
           where 'nnn' is milliseconds and 'uuu' is microseconds.

        Issues:
        None

        See Also:
        Sustained Convergence Validation Time
        Convergence Packet Loss
        Convergence Event Instant

Poretsky, Imhoff                                                [Page 8]


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   3.2.5 First Route Convergence Instant
        Definition:
        The time instant a first route entry has converged
        following a Convergence Event, as observed by receipt of
        the first packet from the Next-Best Egress Interface.

        Discussion:
        The First Route Convergence Instant is an indication that the
        process to achieve Full Convergence has begun.  Any route may
        be the first to converge for First Route Convergence Instant.
        Measurement on the data-plane enables the First Route
        Convergence Instant to be observed without any white-box
        information from the DUT.

        Measurement Units:
           hh:mm:ss:nnn:uuu,
             where 'nnn' is milliseconds and 'uuu' is microseconds.

        Issues:
        None

        See Also:
        Route Convergence
        Full Convergence
        Stale Forwarding

   3.2.6 Convergence Event Transition
        Definition:
        A time interval observed following a Convergence Event in which
        Throughput gradually reduces to a minimum value.

        Discussion:
        The Convergence Event Transition is best observed for Full
        Convergence.  The egress packet rate observed during a
        Convergence Event Transition may not decrease linearly and may
        not decrease to zero.  Both the offered load and the Packet
        Sampling Interval influence the observations of the Convergence
        Event Transition.  For example, it is possible that if the
        Convergence Event were to cause the Throughput [Ba91] to drop
        to zero then this may not be observed if the Packet Sampling
        Interval is set too high.  This is further discussed with the
        term "Packet Sampling Interval".

        Measurement Units:
          seconds

        Issues: None

Poretsky, Imhoff                                                [Page 9]


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        See Also:
        Convergence Event
        Full Convergence
        Packet Sampling Interval

   3.2.7 Convergence Recovery Transition

        Definition:
        The characteristic of the DUT in which Throughput gradually
        increases to equal the offered load.

        Discussion:
        The Convergence Recovery Transition is best observed for
        Full Convergence.  The egress packet rate observed during
        a Convergence Recovery Transition may not increase linearly.
        Both the offered load and the Packet Sampling Interval
        influence the observations of the Convergence Recovery
        Transition.  This is further discussed with the term
        "Packet Sampling Interval".

        Measurement Units:
        seconds

        Issues: None

        See Also:
        Full Convergence
        Packet Sampling Interval

   3.2.8 Nested Convergence Events

        Definition:
        The occurrence of a Convergence Event while the route
        table is converging from a prior Convergence Event.

        Discussion:
        The Convergence Events for a Nested Convergence Event
        MUST occur with different neighbors.  A common
        observation from a Nested Convergence Event will be
        the withdrawal of routes from one neighbor while the
        routes of another neighbor are being installed.

        Measurement Units: N/A

        Issues: None

        See Also:
        Convergence Event

Poretsky, Imhoff                                               [Page 10]


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 3.3 Interfaces

   3.3.1 Local Interface

        Definition:
        An interface on the DUT.

        Discussion:
        A failure of the Local Interface indicates that the failure
        occurred directly on the DUT.

        Measurement Units: N/A

        Issues: None

        See Also:
        Neighbor Interface
        Remote Interface

   3.3.2 Neighbor Interface

        Definition:
        The interface on the neighbor router or tester that is
        directly linked to the DUT's Local Interface.

        Discussion:
        A failure of a Neighbor Interface indicates that a
        failure occurred on a neighbor router's interface that
        directly links the neighbor router to the DUT.

        Measurement Units: N/A

        Issues: None

        See Also:
        Local Interface
        Remote Interface

   3.3.3 Remote Interface

        Definition:
        An interface on a neighboring router that is not directly
        connected to any interface on the DUT.

        Discussion:
        A failure of a Remote Interface indicates that the failure
        occurred on a neighbor router's interface that is not
        directly connected to the DUT.

Poretsky, Imhoff                                               [Page 11]


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        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Local Interface
        Neighbor Interface

   3.3.4 Preferred Egress Interface

        Definition:
        The outbound interface from the DUT for traffic routed to the
        preferred next-hop.

        Discussion:
        The Preferred Egress Interface is the egress interface prior
        to a Convergence Event.

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Next-Best Egress Interface

   3.3.5 Next-Best Egress Interface

        Definition:
        The outbound interface from the DUT for traffic routed to the
        second-best next-hop.  It is the same media type and link speed
        as the Preferred Egress Interface

        Discussion:
        The Next-Best Egress Interface becomes the egress interface
        after a Convergence Event.

        Measurement Units:
        N/A

        Issues: None

        See Also:
        Preferred Egress Interface

Poretsky, Imhoff                                               [Page 12]


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 3.4 Benchmarking Methods

   3.4.1  Packet Loss

        Definition:
        The number of packets that should have been forwarded
        by a DUT under a constant offered load that were
        not forwarded due to lack of resources.

        Discussion:
        Packet Loss is a modified version of the term "Frame Loss Rate"
        as defined in [Ba91].  The term "Frame Loss" is intended for
        Ethernet Frames while "Packet Loss" is intended for IP packets.
        Packet Loss can be measured as a reduction in forwarded traffic
        from the Throughput [Ba91] of the DUT.

        Measurement units:
        Number of offered packets that are not forwarded.

        Issues:  None

        See Also:
        Convergence Packet Loss

   3.4.2 Convergence Packet Loss

        Definition:
        The number of packets lost due to a Convergence Event
        until Full Convergence completes.

        Discussion:
        Convergence Packet Loss includes packets that were lost and
        packets that were delayed due to buffering.  The Convergence
        Packet Loss observed in a Packet Sampling Interval may or may
        not be equal to the number of packets in the offered load
        during the interval following a Convergence Event (see Figure
        1).

        Measurement Units:
        number of packets

        Issues: None

        See Also:
        Packet Loss
        Route Convergence
        Convergence Event
        Packet Sampling Interval

Poretsky, Imhoff                                               [Page 13]


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   3.4.3 Rate-Derived Convergence Method
        Definition:
        The method to calculate convergence time benchmarks from the
        amount of time that Convergence Packet Loss persists upon
        occurrence of a Convergence Event.

        Rate-Derived Convergence Method can be calculated as the time
        difference from the Convergence Event Instant to the
        Convergence Recovery Instant, as shown with Equation 1.

        (Equation 1)
          Rate-Derived Convergence Method =
              Convergence Recovery Instant - Convergence Event Instant.

        Discussion:
        It is RECOMMENDED that the Rate-Derived Convergence Method be
        measured when benchmarking convergence times.  The Rate-Derived
        Convergence Method SHOULD be measured with an Offered Load at
        the Throughput of the DUT.  At least one packet per route
        in the FIB for all routes in the FIB MUST be offered to the DUT
        within the Packet Sampling Interval.

        It is possible to measure no packet loss, which results in a
        Rate-Derived Convergence Time benchmark of zero.  Failure to
        achieve Full Convergence results in a Rate-Derived Convergence
        Time benchmark of infinity.

        Measurement Units:
        seconds

        Issues: None

        See Also:
        Convergence Packet Loss
        Convergence Recovery Instant
        Convergence Event Instant
        Full Convergence

   3.4.4 Loss-Derived Convergence Method
        Definition:
        The method to calculate convergence time benchmarks from the
        amount of Convergence Packet Loss.  Loss-Derived Convergence
        Method can be calculated from Convergence Packet Loss as shown
        with Equation 2.

        Equation 2 -
          Loss-Derived Convergence Method =
                Convergence Packets Loss / Offered Load
          where units are packets / packets/second = seconds

Poretsky, Imhoff                                               [Page 14]


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        Discussion:
        Ideally, the Convergence Event Transition and Convergence
        Recovery Transition are instantaneous so that the Rate-Derived
        Convergence Method = Loss-Derived Convergence Method.  However,
        router implementations are less than ideal.  Loss-Derived
        Convergence Method gives a better than actual result when
        converging many routes simultaneously because it ignores the
        transitions.  The Rate-Derived Convergence Method takes the
        transitions into account.

        Equation 2 calculates the average convergence time over all
        routes to which packets have been sent. The average convergence
        time is often lower than the maximum convergence time
        over all routes, so it can produce a result that is faster than
        the actual convergence time..  Therefore, Loss-Derived
        Convergence Method is not the preferred method to measure
        convergence benchmarks.  For these reasons the RECOMMENDED
        method to obtain a benchmark metric for convergence time is the
        Rate-Derived Convergence Method.

        Measurement Units:
        seconds

        Issues: None

        See Also:
        Convergence Packet Loss
        Rate-Derived Convergence Method
        Route-Specific Convergence
        Convergence Event Transition
        Convergence Recovery Transition

   3.4.5 Packet Sampling Interval
        Definition:
        The interval at which the tester (test equipment) polls to make
        measurements for arriving packet flows.

        Discussion:
        At least one packet per route in the FIB for all routes in the
        FIB MUST be offered to the DUT within the Packet Sampling
        Interval.  Metrics measured at the Packet Sampling Interval
        MUST include Forwarding Rate and Convergence Packet Loss.

        Packet Sampling Interval can influence the Convergence Graph.
        This is particularly true when implementations complete Full
        Convergence in less time than the Packet Sampling Interval.  The
        Convergence Event Transition and Convergence Recovery Transition

Poretsky, Imhoff                                               [Page 15]


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        can become exaggerated when the Packet Sampling Interval is too
        long.  In this condition, the Rate-Derived Convergence Method
        may produce a larger than actual convergence time.  In such
        cases the Loss-Derived Convergence Method may produce a more
        accurate result.  The recommended value for configuration of
        the Packet Sampling Interval is provided in [Po07m].

        Measurement Units: seconds

        Issues: None

        See Also:
        Convergence Packet Loss
        Convergence Event Transition
        Convergence Recovery Transition

3.5 Benchmarks

   3.5.1 Full Convergence Time

        Definition:
        The amount of time it takes for Full Convergence to occur.

        Discussion:
        Full Convergence Time can be determined using the Rate-Derived
        Convergence Method or Loss-Derived Convergence Method.  The
        Rate-Derived Convergence Method is RECOMMENDED.  When
        measuring Route-Specific Convergence Time, there may be
        conditions in which the maximum Route Specific Convergence Time
        can be reported as the Full Convergence Time.  Full Convergence
        may or may not be sustained over time.  The Sustained
        Convergence Validation Time MUST be applied.

        Measurement Units:
        seconds

        Issues: None

        See Also:
        Full Convergence
        Rate-Derived Convergence Method
        Loss-Derived Convergence Method

   3.5.2 First Route Convergence Time

        Definition:
        The amount of time for Convergence Packet Loss until the
        convergence of a first route entry on the Next-Best Egress
        Interface, as indicated by the First Route Convergence
        Instant.

Poretsky, Imhoff                                               [Page 16]


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        Discussion:
        The First Route Convergence Time benchmarking metric can be
        measured when benchmarking either Full Convergence or
        Route-Specific Convergence.  When benchmarking Full Convergence,
        First Route Convergence Time can be measured as the time
        difference from the Convergence Event Instant and the First
        Route Convergence Instant, as shown with Equation 4a.

        (Equation 4a)
        First Route Convergence Time =
        First Route Convergence Instant - Convergence Event Instant

        First Route Convergence Time should be measured at the maximum
        Throughput of the DUT.  At least one packet per route in the FIB
        for all routes in the FIB MUST be offered to the DUT within the
        Packet Sampling Interval.  Failure to achieve the First Route
        Convergence Instant results in a First Route Convergence Time
        benchmark of infinity.

        Measurement Units:
        seconds

        Issues: None

        See Also:
        Convergence Packet Loss
        First Route Convergence Instant

   3.5.3 Route-Specific Convergence Time

        Definition:
        The amount of time it takes for Route-Specific Convergence to
        be completed as calculated from the amount of Convergence
        Packet Loss for the flow associated to a specific route.

        Route-Specific Convergence Time can be calculated from
        Convergence Packet Loss as shown with Equation 3.

        (Equation 3) Route-Specific Convergence Time =
                           Convergence Packets Loss / Offered Load
          where units are packets / packets/second = seconds

Poretsky, Imhoff                                               [Page 17]


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                 Link-State IGP Data Plane Route Convergence

        Discussion:
        It is possible to provide an offered load that has flows
        matching every route entry in the FIB and benchmarking
        Route-Specific Convergence Time for all route entries.  The
        number of flows that can be measured is dependent upon the flow
        measurement capabilities of the Tester.  When benchmarking
        Route-Specific Convergence, Convergence Packet Loss is measured
        for specific flow(s) and Equation 3 is applied for each flow.
        Each flow has a single destination address matching a different
        route entry.  The fastest measurable convergence time is equal
        to the time between two consecutive packets of a flow offered
        by the Tester.  In practice, the fastest measurable
        convergence time is the Packet Sampling Interval of the Tester.

        The Route-Specific Convergence Time benchmarks enable minimum,
        maximum, average, and median convergence time measurements to be
        reported by comparing the results for the different route
        entries.  It also enables benchmarking of convergence time when
        configuring a priority value for route entry(ies).  Since
        multiple Route-Specific Convergence Times can be measured it is
        possible to have an array of results.  The format for reporting
        Route-Specific Convergence Time is provided in [Po07m].

        Measurement Units:
        seconds

        Issues:
        None

        See Also:
        Convergence Event
        Convergence Packet Loss
        Route-Specific Convergence

   3.5.4 Sustained Convergence Validation Time
        Definition:
        The amount of time for which the completion of Full
        Convergence is maintained without additional packet loss.

        Discussion:
        The purpose of the Sustained Convergence Validation Time is to
        produce Convergence benchmarks protected against fluctuation
        in Throughput after the completion of Full Convergence is
        observed.  The RECOMMENDED Sustained Convergence Validation
        Time to be used is 5 seconds.  The BMWG selected 5 seconds
        based upon RFC 2544 [Ba99] which recommends waiting 2 seconds
        for residual frames to arrive and 5 seconds for DUT
        restabilization.

Poretsky, Imhoff                                               [Page 18]


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        Measurement Units:
        seconds

        Issues: None

        See Also:
        Full Convergence
        Convergence Recovery Instant

   3.5.5 Reversion Convergence Time

        Definition:
        The amount of time for the DUT to complete Full Convergence
        to the Preferred Egress Interface, instead of the Next-Best
        Egress Interface, upon recovery from a Convergence Event.

        Discussion:
        Reversion Convergence Time is the amount of time for Full
        Convergence to the original egress interface.  This is
        achieved by recovering from the Convergence Event, such as
        restoring the failed link.  Reversion Convergence Time
        can be measured using the Rate-Derived Convergence Method
        or Loss-Derived Convergence Method.  The Rate-Derived
        Convergence Method is RECOMMENDED.  It is possible to have
        the Reversion Convergence Time differ from the Full
        Convergence Time.

        Measurement Units: seconds

        Issues: None

        See Also:
        Preferred Egress Interface
        Convergence Event
        Rate-Derived Convergence Method


4. IANA Considerations

   This document requires no IANA considerations.

5. Security Considerations

   Documents of this type do not directly affect the security of
   Internet or corporate networks as long as benchmarking is not
   performed on devices or systems connected to production networks.
   Security threats and how to counter these in SIP and the media
   layer is discussed in RFC3261, RFC3550, and RFC3711 and various
   other drafts.  This document attempts to formalize a set of
   common terminology for benchmarking IGP convergence performance
   in a lab environment.

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6. Acknowledgements
   Thanks to Sue Hares, Al Morton, Kevin Dubray, Ron Bonica, David Ward,
   Kris Michielsen and the BMWG for their contributions to this work.

7. References
 7.1 Normative References
   [Ba91] Bradner, S. "Benchmarking Terminology for Network
         Interconnection Devices", RFC1242, July 1991.

   [Ba99] Bradner, S. and McQuaid, J., "Benchmarking
         Methodology for Network Interconnect Devices",
         RFC 2544, March 1999.

   [Br97] Bradner, S., "Key words for use in RFCs to Indicate
          Requirement Levels", RFC 2119, March 1997

   [Ca90] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual
         Environments", RFC 1195, December 1990.

   [Ma98] Mandeville, R., "Benchmarking Terminology for LAN
         Switching Devices", RFC 2285, February 1998.

   [Mo98] Moy, J., "OSPF Version 2", RFC 2328, IETF, April 1998.

   [Mo06] Morton, A., et al, "Packet Reordering Metrics", RFC 4737,
          November 2006.

   [Po06] Poretsky, S., et al., "Terminology for Benchmarking
         Network-layer Traffic Control Mechanisms", RFC 4689,
         November 2006.

   [Po07a] Poretsky, S., "Benchmarking Applicability for Link-State
         IGP Data Plane Route Convergence",
         draft-ietf-bmwg-igp-dataplane-conv-app-17, work in progress,
         March 2009.

   [Po07m] Poretsky, S. and Imhoff, B., "Benchmarking Methodology for
         Link-State IGP Data Plane Route Convergence",
         draft-ietf-bmwg-igp-dataplane-conv-meth-17, work in progress,
         March 2009.

 7.2 Informative References
   [Ca01] S. Casner, C. Alaettinoglu, and C. Kuan, "A Fine-Grained View
         of High Performance Networking", NANOG 22, June 2001.

   [Ci03] L. Ciavattone, A. Morton, and G. Ramachandran, "Standardized
         Active Measurements on a Tier 1 IP Backbone", IEEE
         Communications Magazine, pp90-97, May 2003.

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8. Author's Address

      Scott Poretsky
      Allot Communications
      67 South Bedford Street, Suite 400
      Burlington, MA 01803
      USA
      Phone: + 1 508 309 2179
      Email: sporetsky@allot.com

      Brent Imhoff
      Juniper Networks
      1194 North Mathilda Ave
      Sunnyvale, CA 94089
      USA
      Phone: + 1 314 378 2571
      EMail: bimhoff@planetspork.com































Poretsky, Imhoff                                               [Page 21]


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