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   Network Working Group
   INTERNET-DRAFT
   Expires in: January 2005
                                                   Scott Poretsky
                                                   Quarry Technologies

                                                   Brent Imhoff


                                                   July 2004

                        Terminology for Benchmarking
                      IGP Data Plane Route Convergence

                <draft-ietf-bmwg-igp-dataplane-conv-term-03.txt>

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in accordance with RFC 3668.

   Status of this Memo

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   ABSTRACT
   This draft describes the terminology for benchmarking IGP Route
   Convergence as described in Applicability document [1] and
   Methodology document [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 [2].




Poretsky, Imhoff                                                                [Page 1]


INTERNET-DRAFT          Benchmarking Terminology for            July 2004
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   Table of Contents

     1. Introduction .................................................2
     2. Existing definitions .........................................3
     3. Term definitions..............................................3
        3.1 Convergence Event.........................................3
        3.2 Route Convergence.........................................4
        3.3 Network Convergence.......................................4
        3.4 Full Convergence..........................................5
        3.5 Convergence Packet Loss...................................5
        3.6 Convergence Event Instant.................................6
        3.7 Convergence Recovery Instant..............................6
        3.8 Rate-Derived Convergence Time.............................7
        3.9 Convergence Event Transition..............................7
        3.10 Convergence Recovery Transition..........................8
        3.11 Loss-Derived Convergence Time............................8
        3.12 Sustained Forwarding Convergence Time....................9
        3.13 Restoration Convergence Time.............................9
        3.14 Packet Sampling Interval.................................10
        3.15 Local Interface..........................................10
        3.16 Neighbor Interface.......................................11
        3.17  Remote Interface........................................11
        3.18 Preferred Egress Interface...............................11
        3.19  Next-Best Egress Interface..............................12
        3.20 Stale Forwarding.........................................12
     4. Security Considerations.......................................13
     5. References....................................................13
     6. Author's Address..............................................13

   1. Introduction
   This draft describes the terminology for benchmarking IGP Route
   Convergence.  The motivation and applicability for this
   benchmarking is provided in [1].  The methodology to be used for
   this benchmarking is described in [2].  The methodology and
   terminology to be used for benchmarking Route Convergence can be
   applied to any link-state IGP such as ISIS [3] and OSPF [4].  The
   data plane is measured to obtain black-box (externally observable)
   convergence benchmarking metrics.  The purpose of this document is
   to introduce new terms required to complete execution of the IGP
   Route Convergence Methodology [2].

   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 components of the graph and metrics are
   defined in the Term Definitions section.






Poretsky, Imhoff                                                                [Page 2]


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                           Convergence    Convergence
                           Recovery         Event
                           Instant         Instant      Time = 0sec
        Maximum                ^              ^             ^
        Forwarding Rate--> ----\    Packet   /---------------
                                \    Loss   /<----Convergence
              Convergence------->\         /      Event Transition
        Recovery Transition       \       /
                                   \_____/<------100% Packet Loss

        X-axis = Time
        Y-axis = Forwarding Rate
                        Figure 1. Convergence Graph

   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. Term Definitions

   3.1 Convergence Event

        Definition:
        The occurrence of a planned or unplanned action in the network
        that results in a change in the egress interface of the 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






Poretsky, Imhoff                                                                [Page 3]


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   3.2 Route Convergence

        Definition:
        Recovery from a Convergence Event indicated by the DUT
        forwarding rate equal to the offered load.

        Discussion:
        Route Convergence is the action of all components of the router
        being updated with the most recent route change(s) including the
        RIB and FIB, along with software and hardware tables. Route
        Convergence can be observed externally by the rerouting of data
        Traffic to a new egress interface.

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Network Convergence
        Full Convergence
        Convergence Event


   3.3 Network Convergence

        Definition:
        The completion of updating of all routing tables, including the
        FIB, in all routers throughout the network.

        Discussion:
        Network Convergence is bounded by the sum of Route Convergence
        for all routers in the network.  Network Convergence can be
        determined by recovery of the forwarding rate to equal the offered
        load, no Stale Forwarding, and no blenders[5][6].

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Route Convergence
        Stale Forwarding






Poretsky, Imhoff                                                                [Page 4]


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   3.4 Full Convergence
        Definition:
        Route Convergence for an entire FIB.

        Discussion:
        When benchmarking convergence it is useful to measure
        the time to converge an entire route table.  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.

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Network Convergence
        Route Convergence
        Convergence Event

   3.5 Convergence Packet Loss

        Definition:
        The amount of packet loss produced by a Convergence Event
        until Route Convergence occurs.

        Discussion:
        Packet loss can be observed as a reduction of forwarded traffic from
        the maximum forwarding rate.  Convergence Packet Loss include packets
        that were lost and packets that were delayed due to buffering.

        Measurement Units:
        number of packets

        Issues:
        None

        See Also:
        Route Convergence
        Convergence Event
        Rate-Derived Convergence Time
        Loss-Derived Convergence Time







Poretsky, Imhoff                                                                [Page 5]


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   3.6 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.

        Measurement Units:
        hh:mm:ss:uuu

        Issues:
        None

        See Also:
        Convergence Event
        Convergence Packet Loss
        Convergence Recovery Instant

   3.7 Convergence Recovery Instant

        Definition:
        The time instant that Full Convergence is measured
        and maintained for at least an additional five seconds.

        Discussion:
        Convergence Recovery Instant is measurable from the data
        plane as the precise time that the device under test
        achieves Full Convergence.  Convergence Recovery Instant
        is externally observable from the data plane when the
        forwarding rate on the Next-Best Egress Interface equals
        the offered rate.

        Measurement Units:
        hh:mm:ss:uuu

        Issues:
        None

        See Also:
        Convergence Packet Loss
        Convergence Event Instant







Poretsky, Imhoff                                                                [Page 6]


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   3.8 Rate-Derived Convergence Time
        Definition:
        The amount of time for Convergence Packet Loss to
        persist upon occurrence of a Convergence Event until
        occurrence of Route Convergence.

        Discussion:

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

        (eq 1)  Rate-Derived Convergence Time =
                Convergence Recovery Instant - Convergence Event Instant.

        Rate-Derived Convergence Time should be measured at the maximum
        forwarding rate.  Failure to achieve Full Convergence results in
        a Rate-Derived Convergence Time benchmark of infinity.

        Measurement Units:
        seconds/milliseconds

        Issues:
        None

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

   3.9 Convergence Event Transition
        Definition:
        The characteristic of a router in which forwarding rate
        gradually reduces to zero after a Convergence Event.

        Discussion:
        The Convergence Event Transition is best observed for
        Full Convergence.

        Measurement Units:
        seconds/milliseconds

        Issues:
        None

        See Also:
        Convergence Event
        Rate-Derived Convergence Time
        Convergence Packet Loss
        Convergence Recovery Transition

Poretsky, Imhoff                                                                [Page 7]


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   3.10 Convergence Recovery Transition

        Definition:
        The characteristic of a router in which forwarding rate
        gradually increases to equal the offered load.

        Discussion:
        The Convergence Recovery Transition is best observed for
        Full Convergence.

        Measurement Units:
        seconds/milliseconds

        Issues:
        None

        See Also:
        Full Convergence
        Rate-Derived Convergence Time
        Convergence Packet Loss
        Convergence Event Transition

   3.11 Loss-Derived Convergence Time

        Definition:
        The amount of time it takes for Route Convergence to
        to be achieved as calculated from the Convergence Packet
        Loss.

        Discussion:
        Loss-Derived Convergence Time can be calculated from
        Convergence Packet Loss that occurs due to a Convergence Event
        and Route Convergence, as shown with Equation 2.

        (eq 2) Loss-Derived Convergence Time =
                Convergence Packets Loss / Forwarding Rate

                NOTE: Units for this measurement are
                packets / packets/second = seconds

        Measurement Units:
        seconds/milliseconds

        Issues:
        Loss-Derived Convergence Time gives a better than
        actual result when converging many routes simultaneously.
        Rate-Derived Convergence Time takes the Convergence Recovery
        Transition into account, but Loss-Derived Convergence Time
        ignores the Route Convergence Recovery Transition because
        it is obtained from the measured Convergence Packet Loss.
        Ideally, the Convergence Event Transition and Convergence

Poretsky, Imhoff                                                                [Page 8]


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        Recovery Transition are instantaneous so that the
        Rate-Derived Convergence Time = Loss-Derived Convergence Time.
        However, router implementations are less than ideal.
        For these reasons the preferred reporting benchmark for IGP
        Route Convergence is the Rate-Derived Convergence Time.
        Guidelines for reporting Loss-Derived Convergence Time are
        provided in [2].

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

   3.12 Sustained Forwarding Convergence Time

        Definition:
        The amount of time for Route Convergence to be achieved for
        cases in which there is no packet loss.

        Discussion:
        Sustained Forwarding Convergence Time is the IGP Route Convergence
        benchmark to be used for Convergence Events that produce
        a change in next-hop without packet loss.

        Measurement Units:
        seconds/milliseconds

        Issues:
        None

        See Also:
        Route Convergence
        Rate-Derived Convergence Time
        Loss-Derived Convergence Time

   3.13 Restoration Convergence Time

        Definition:
        The amount of time for the router under test to restore
        traffic to the original outbound port after recovery from
        a Convergence Event.

        Discussion:
        Restoration Convergence Time is the amount of time to
        Converge back to the original outbound port.  This is achieved
        by recovering from the Convergence Event, such as restoring
        the failed link.  Restoration Convergence Time is measured
        using the Rate-Derived Convergence Time calculation technique,
        as provided in Equation 1.  It is possible, but not desired

Poretsky, Imhoff                                                                [Page 9]


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        to have the Restoration Convergence Time differ from the
        Rate-Derived Convergence Time.

        Measurement Units:
        seconds or milliseconds

        Issues:
        None

        See Also:
        Convergence Event
        Rate-Derived Convergence Time


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

        Discussion:
        Metrics measured at the Packet Sampling Interval may include
        Forwarding Rate and Convergence Packet Loss.

        Measurement Units:
        seconds or milliseconds

        Issues:
        Packet Sampling Interval can influence the Convergence Graph.
        This is particularly true as implementations achieve Full
        Convergence in less than 1 second.  The Convergence Event
        Transition and Convergence Recovery Transition can become
        exaggerated when the Packet Sampling Interval is too long.
        This will produce a larger than actual Rate-Derived
        Convergence Time.  The recommended value for configuration
        of the Packet Sampling Interval is provided in [2].

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


   3.15 Local Interface
        Definition:
        An interface on the DUT.

        Discussion:
        None

        Measurement Units:
        N/A

Poretsky, Imhoff                                                                [Page 10]


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        Issues:
        None

        See Also:
        Neighbor Interface
         Remote Interface

   3.16 Neighbor Interface

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

        Discussion:
        None

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Local Interface
         Remote Interface

   3.17  Remote Interface

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

        Discussion:
        None

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Local Interface
        Neighbor Interface

   3.18 Preferred Egress Interface

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


Poretsky, Imhoff                                                                [Page 11]


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

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
         Next-Best Egress Interface


   3.19  Next-Best Egress Interface

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

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

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Preferred Egress Interface

   3.20 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 is
        also known as a "black-hole" since it may produce packet loss.
        Stale Forwarding exists until Network Convergence is achieved.

        Measurement Units:
        N/A

        Issues:
        None

        See Also:
        Network Convergence

Poretsky, Imhoff                                                                [Page 12]


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   4. 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 operating
        networks.

   5. References

   [1]   Poretsky, S., "Benchmarking Applicability for IGP Data Plane
         Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-app-03,
         work in progress, July 2004.

   [2]   Poretsky, S., "Benchmarking Methodology for IGP Data Plane
         Route Convergence", draft-ietf-bmwg-igp-dataplane-conv-meth-03,
         work in progress, July 2004.

   [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]   S. Casner, C. Alaettinoglu, and C. Kuan, "A Fine-Grained View
         of High Performance Networking", NANOG 22, May 2001.

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


  6. Author's Address

        Scott Poretsky
        Quarry Technologies
        8 New England Executive Park
        Burlington, MA 01803
        USA
        Phone: + 1 781 395 5090
        EMail: sporetsky@quarrytech.com

        Brent Imhoff
        USA
        EMail: bimhoff@planetspork.com








Poretsky, Imhoff                                                                [Page 13]


INTERNET-DRAFT          Benchmarking Terminology for            July 2004
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Poretsky, Imhoff                                                                [Page 14]


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