Network Working Group                                     Vishwas Manral
Internet Draft                                     Sinett Semiconductors                                          Netplane Systems
                                                              Russ White
                                                           Cisco Systems
                                                             Aman Shaikh
Expiration Date: May Novemeber 2004                 University of California
File Name: draft-ietf-bmwg-ospfconv-intraarea-07.txt       November 2003 draft-bmwg-ospfconv-intraarea-08.txt                 May 2004

    Benchmarking Basic OSPF Single Router Control Plane Convergence
                 draft-ietf-bmwg-ospfconv-intraarea-07.txt
                 draft-ietf-bmwg-ospfconv-intraarea-08.txt

1. 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.

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   http://www.ietf.org/ietf/1id-abstracts.txt

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   http://www.ietf.org/shadow.html.

2.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This draft provides suggestions for measuring OSPF single router
   control plane convergence. Its initial emphasis is on the control
   plane of single OSPF routers.  We do not address forwarding plane
   performance.

   NOTE: Within this document, the word convergence relates to single
   router control plane convergence only.

3. Motivation

2. Introduction

   There is a growing interest in routing protocol convergence testing,
   with many people looking at various tests to determine how long it
   takes for a network to converge after various conditions occur. The
   major problem with this sort of testing is that the framework of the
   tests has a major impact on the results; for instance, determining
   when a network is converged, what parts of the router's operation are
   considered within the testing, and other such things will have a
   major impact on what apparent performance routing protocols provide.

   This document attempts to provide a framework within which Open
   Shortest Path First [OSPF] performance testing can be placed, and
   provide some tests with which some aspects of OSPF performance can be
   measured. The motivation of the draft is to provide a set of tests
   that can provide the user comparable data from various vendors with
   which to evaluate the OSPF protocol performance on the devices.

3. Specification of Requirements

   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 [RFC2119].

4. Overview & Scope

   While this document describes a specific set of tests aimed at
   characterizing the single router control plane convergence
   performance of OSPF processes in routers or other boxes that
   incorporate OSPF functionality, a key objective is to propose
   methodologies that will prdouce directly comparable convergence
   related measurements.

   Things which are outside the scope of this document include:

   o    The interactions of convergence and forwarding; testing is
           restricted res-
        tricted to events occurring within the control plane. For-
           warding Forwarding
        performance is the primary focus in [INTERCONNECT] and it is
        expected to be dealt with in work that ensues from [FIB-TERM].

   o    Inter-area route generation, AS-external route generation, and
        simultaneous traffic on the control and data paths within the
        DUT. While the tests outlined in this document measure SPF time,
        flooding times, and other aspects of all OSPF con-
           vergence performance, convergence per-
        formance, it does not provide tests for measuring external or
        summary route generation, route translation, or other OSPF
        inter-area and external routing performance. These are expected
        to be dealt with in a later draft.

   Other drafts in the future may cover some of the items noted as not
   covered in the scope of this draft. For a discussion of the
   terminology terminol-
   ogy used in this draft (in relation to the tests themselves), refer
   to [TERM]. For a discussion of the applicability of this draft, refer
   to [APPLICABILITY].

   While this draft assumes OSPFv2, which only carries routing informa-
   tion for IPv4 destinations, nothing the tests described in this draft precludes it from
   use with document
   apply to OSPFv3, which carries IPv6 destinations.

5. Test Conditions

   In all tests, the following test conditions will be assumed:

   o    The link speed should be high enough so that does not become a
        bottleneck. Link speeds of 10MBps or higher are recom-
           mended. recommended. The
        link speed between routers should be specified in the test
        report.

   o    For all point-to-point links, it is assumed that a link failure
        results in an immediate notification to the operating system,
        and thus to the OSPF process; this is explained thoroughly in
        [MILLISEC].

   o    No data traffic will be running between the routers during these
        tests.

   o    Optional capabilities which can reduce performance, such as
        authentication, should be noted in the test results if they are
        enabled.

   o    Optional changes in the default timer values, such as the SPF,
        hello, router dead, and other intervals, should be noted in the
        test results.

   o    All places where injecting a set of LSAs is referenced, the set
        can include varying numbers of LSAs of varying types
           representing represent-
        ing a varying number of reachable destinations. See [TERM] for
        further information about issues with LSA sets and network topologies. topo-
        logies.

        Tests should be run more than once, since a single test run
        cannot be relied on to produce statistically sound results. The
        number of test runs and any variations between the tests should
        be recorded in the test results (see [TERM] for more information
        on what items should be recorded in the test results).

6. Reference Topologies

   Several reference topologies will be used throughout the tests
   described in the remainder of this document. Rather than repeating
   these topologies, we've gathered them all in one section.

   o    Reference Topology 1 (Emulated Topology)

                             (                   )
        DUT----Generator----(  emulated topology  )
                             (                   )

        A simple back-to-back configuration. It's assumed that the link
        between the generator and the DUT is a point-to-point link,
        while the connections within the generator represent some emulated emu-
        lated topology.

   o    Reference Topology 2 (Generator and Collector)

                                          (                   )
        Collector-----DUT-----Generator--(  emulated topology  )
               \              /          (                   )
                \------------/

        All routers are connected through point-to-point links. The cost
        of all links is assumed to be the same unless otherwise noted.

   o    Reference Topology 3 (Broadcast Network)

        DUT     R1     R2
         |      |      |
        -+------+------+-----.....

        Any number of routers could be included on the common broad-
           cast broadcast
        network.

   o    Reference Topology 4 (Parallel Links)

          /--(link 1)-----\           (                   )
        DUT               Generator--(  emulated topology  )
          \--(link 2)-----/           (                   )
   In all cases the tests and topologies are designed to allow perfor-
   mance measurements to be taken all on a single device, whether the
   DUT or some other device in the network. This eliminates the need for
   syncronized clocks within the test networks.

7. Basic Process Performance Tests

   These tests will measure aspects of the OSPF implementation as a pro-
   cess on the device under test, including:

   o    Time required to process an LSA

   o    Flooding time

   o    Shortest Path First computation

7.1. Time required to process an LSA

   o    Using reference topology 1 (Emulated Topology), begin with all
        links up and a full adjacency established between the DUT and
        the generator.

        Note: The generator does not have direct knowledge of the state
        of the adjacency on the DUT. The fact the adjacency may be in
        Full on the generator does not mean that the DUT is ready. It
        may still (and is likely to) be requesting LSAs from the genera-
        tor. This process, involving processing of requested LSAs, will
        affect the results of the test. The generator should either wait
        until it sees the DUT's router-LSA listing the adjacency with
        the generator or introduce a configurable delay before starting
        the test.

   o    Send an LSA that is already there in the DUT (a duplicate LSA),
        note the time difference between when the LSA is sent to when
        the ack is received. This measures the time to pro-
           pagate propagate the LSA
        and the ack, as well as processing time of the duplicate LSA.
        This is dupLSAprocTime.

   o    Send a new LSA from the generator to the DUT, followed
           immediately immedi-
        ately by a duplicate LSA (LSA that already resides in the database data-
        base of DUT, but not the same as the one just sent).

   o    The DUT will acknowledge this second LSA immediately; note the
        time of this acknowledgement. This is newLSAprocTime.

        The amount of time required for an OSPF implementation to
           process pro-
        cess the new LSA can be computed by subtracting dupLSAprocTime
        from newLSAprocTime.

        Note: The duplicate LSA cannot be the same as the one just sent
        because of the MinLSInterval restriction.[RFC2328] This test is
        taken from [BLACKBOX].

7.2. Flooding Time

   o    Using reference topology 2 (Generator and Collector), enable
        OSPF on all links and allow the devices to build full adjacencies. adjacen-
        cies. Configure the collector so it will block all flooding
        towards the DUT, although it continues receiving advertisements
        from the DUT.

   o    Inject a new set of LSAs from the generator towards the
              collector collec-
        tor and the DUT.

   o    On the collector, note the time the flooding is complete across
        the link to the generator. Also note the time the flooding is
        complete across the link from the DUT.

           Two measurements can be taken from this test:

         o

   The time between the last LSA is received on the collector from the
   generator and the time the last LSA is received on the collector from
   the DUT.

         o    The DUT should be measured during this test.  This time between the last LSA is received on the collector
              from the generator and important
   in link state protocols, since the time loop free nature of the first LSA network is received
   reliant on the collector from the DUT. speed at which revised topology information is
   flooded.

   Depending on the number of LSAs flooded, the sizes of the LSAs, the
   number of LSUs, and the rate of flooding, these numbers could vary by
   some amount. The settings and variances of these numbers should be
   reported with the test results.

           This time is important in link state protocols, since the
           loop free nature of the network is reliant on the speed at
           which revised topology information is flooded.

7.3. Shortest Path First Computation Time

   o    Use reference topology 1 (Emulated Toplogy), beginning with the
        DUT and the generator fully adjacent.

   o    The default SPF timer on the DUT should be set to 0, so that any
        new LSA that arrives, immediately results in the SPF calculation
        [BLACKBOX].

   o    The generator should inject a set of LSAs towards the DUT; the
        DUT should be allowed to converge and install all best paths in
        the local routing table, etc..

   o    Send an LSA that is already there in the DUT (a duplicate LSA),
        note the time difference between when the LSA is sent to when
        the ack is received. This measures the time to propagate the LSA
        and the ack, as well as processing time of the duplicate LSA.
        This is dupLSAprocTime.

   o    Change the link cost between the generator and the emu-
              lated network emulated net-
        work it is advertising. advertising, and transmit the new LSA to the DUT.

   o    Immediately inject another LSA which is a duplicate of some
        other LSA the generator has previously injected (preferrably a
        stub network someplace within the emulated network).

        Note: The generator should make sure that outbound LSA packing
        is not performed for the duplicate LSAs and they are always sent
        in a separate Link-state Update packet. Otherwise, if the LSA
        carrying the topo change and the duplicate LSA are in the same
        packet, the SPF will be started the duplicate LSA is acked.

   o    Measure the time between transmitting the second (dupli-
              cate) (duplicate) LSA
        and the acknowledgement for that LSA; this is the totalSPFtime.
        The total time required to run SPF can be computed by subtracting subtract-
        ing dupLSAprocTime from totalSPF-
              time. totalSPFtime.

   The accuracy of this test is crucially dependant on the amount of
   time between the transmission of the first and second LSAs. If there
   is too much time between them, the test is meaningless because the
   SPF run will complete before the second (duplicate) LSA is received.
   If there is too little time between the LSAs being generated, then
   they will both be handled before the SPF run is scheduled and
   started, and thus the measurement would only be for the handling of
   the dupli-
           cate duplicate LSA.

   This test is also specified in [BLACKBOX].

   Note: This test may not be accurate on systems which implement OSPF
   as a multithreaded process, where the flooding takes place in a
   separate process (or on a dif-
              ferent different processor) than shortest path
   first computations.

   It is also possible to measure the SPF time using white box tests
   (using output supplied by the OSPF software impelem-
           tor). impelemtor). For
   instance:

   o    Using reference topology 1 (Emulated Topology), establish a full
        adjacency between the generator and the DUT.

   o    Inject a set of LSAs from the generator towards the DUT. Allow
        the DUT to stabilize and install all best paths in the routing
        table, etc.

   o    Change the link cost between the DUT and the generator (or the
        link between the generator and the emulated network it is
        advertising), such that a full SPF is required to run, although
        only one piece of information is changed.

   o    Measure the amount of time required for the DUT to compute new
        shortest path tree as a result of the topology changes injected
        by the generator. These measurements should be taken using
        available show and debug information on the DUT.

   Several caveats must MUST be mentioned when using a white box method of
   measuring SPF time; for instance, such white box tests are only
   applicable when testing various versions or variations within a single sin-
   gle implementation of the OSPF proto-
           col. protocol. Futher, the same set of commands must com-
   mands MUST be used in each iteration of such a test, to ensure consistent con-
   sistent results.

   There is some interesting relationship between the SPF times reported
   by white box (internal) testing, and black box (external) testing;
   these two types of tests may be used as a "sanity check" on the other
   type of tests, by comparing the results of the two tests.

   See [APPLICABILITY] for further discussion.

8. Basic Intra-Area OSPF tests

   These tests measure the performance of an OSPF implementation for
   basic intra-area tasks, including:

   o    Forming Adjacencies on Point-to-Point Link (Initialization)

   o    Forming Adjacencies on Point-to-Point Links

   o    Link Up with Information Already in the Database
   o    Initial convergence Time on a Designated Router Electing (Broad-
        cast) Network

   o    Link Down with Layer 2 Detection

   o    Link Down with Layer 3 Detection

   o    Designated Router Election Time on A Broadcast Network

8.1. Forming Adjacencies on Point-to-Point Link (Initialization)

   This test measures the time required to form an OSPF adjacency from
   the time a layer two (data link) connection is formed between two
   devices running OSPF.

   o    Use reference topology 1 (Emulated Topology), beginning with the
        link between the generator and DUT disabled on the DUT. OSPF
        should be configured and operating on both devices.

   o    Inject a set of LSAs from the generator towards the DUT.

   o    Bring the link up at the DUT, noting the time that the link carrier car-
        rier is established on the generator.

   o    Note the time the acknowledgement for the last LSA transmitted
        from the DUT is received on the generator.

   The time between the carrier establishment and the ack-
           nowledgement acknowledgement
   for the last LSA transmitted by the generator should be taken as the
   total amount of time required for the OSPF process on the DUT to
   react to a link up event with the set of LSAs injected, including the
   time required for the operating system to notify the OSPF process
   about the link up, etc.. The acknowledgement for the last LSA
   transmitted is used instead of the last acknowledgement received in
   order to prevent timing skews due to retransmitted acknowledgements
   or LSAs.

8.2. Forming Adjacencies on Point-to-Point Links

   This test measures the time required to form an adjacency from the
   time the first communication occurs between two devices running OSPF.

   o    Using reference topology 1 (Emulated Topology), configure the
        DUT and the generator so traffic can be passed along the link
        between them.

   o    Configure the generator so OSPF is running on the point-
              to-point point-to-point
        link towards the DUT, and inject a set of LSAs.

   o    Configure the DUT so OSPF is initialized, but not running on the
        point-to-point link between the DUT and the genera-
              tor. generator.

   o    Enable OSPF on the interface between the DUT and the gen-
              erator generator
        on the DUT.

   o    Note the time of the first hello received from the DUT on the
        generator.

   o    Note the time of the acknowledgement from the DUT for the last
        LSA transmitted on the generator.

   The time between the first hello received and the ack-
           nowledgement acknowledgement for
   the last LSA transmitted by the generator should be taken as the
   total amount of time required for the OSPF process on the DUT to
   build a FULL neighbor adjacency with the set of LSAs injected. The
   acknowledgement for the last LSA transmitted is used instead of the
   last acknowledge-
           ment acknowledgement received in order to prevent timing skews due to
   retransmitted acknowledgements or LSAs.

8.3. Forming adjacencies with Information Already in the Database

   o    Using reference topology 2 (Generator and Collector), con-
              figure configure
        all three devices to run OSPF.

   o    Configure the DUT so the link between the DUT and the gen-
              erator generator
        is disabled .

   o    Inject a set of LSAs into the network from the generator; the
        DUT should receive these LSAs through normal flooding from the
        collector.

   o    Enable the link between the DUT and the generator.

   o    Note the time of the first hello received from the DUT on the
        generator.

   o    Note the time of the last DBD received on the generator.

   o    Note the time of the acknowledgement from the DUT for the last
        LSA transmitted on the generator.

   The time between the hello received from the DUT by the gen-
           erator generator and
   the acknowledgement for the last LSA transmitted by the generator
   should be taken as the total amount of time required for the OSPF
   process on the DUT to build a FULL neighbor adjacency with the set of
   LSAs injected. In this test, the DUT is already aware of the entire
   network topol-
           ogy, topology, so the time required should only include the processing pro-
   cessing of each DBDs exchanged when in EXCHANGE state, the time to build a
   new router LSA from containing the generator new connection information, and transmitting an
           acknowledgement. the
   time required to flood and acknowledge this new router LSA.

   The acknowledgement for the last LSA transmitted is used instead of
   the last acknowledgement received in order to prevent timing skews
   due to retransmit-
           ted retransmitted acknowledgements or LSAs.

8.4. Designated Router Election Time on A Broadcast Network

   o    Using reference topology 3 (Broadcast Network), configure R1 to
        be the designated router on the link, and the DUT to be the
        backup designated router.

   o    Enable OSPF on the common broadcast link on all the routers in
        the test bed.

   o    Disble the broadcast link on R1.

   o    Note the time of the last hello received from R1 on R2.

   o    Note the time of the first network LSA generated by the DUT as
        received on R2.

   The time between the last hello received on R2 and the first network
   LSA generated by the DUT should be taken as the amount of time
   required for the DUT to complete a designated router election computation. compu-
   tation. Note this test includes the dead interval timer at the DUT,
   so this time may be factored out, or the hello and dead intervals
   reduced to make these timers impact the overall test times less. All
   changed timers, the number of routers connected to the link, and
   other variable factors should be noted in the test results.

   Note: If R1 sends a "goodbye hello," typically a hello with its
   neighbor list empty, in the process of shutting down its interface,
   using the time this hello is received instead of the time of the last
   hello received would provide a more accurate measurement.

8.5. Initial Convergence Time on a Broadcast Network, Test 1

   o    Using reference topology 3 (Broadcast Network), begin with the
        DUT connected to the network with OSPF enabled. OSPF should be
        enabled on R1, but the broadcast link should be disabled.

   o    Enable the broadcast link between R1 and the DUT. Note the time
        of the first hello received by R1.

   o    Note the time the first network LSA is flooded by the DUT at R1.

   o    The differential between the first hello and the first network
        LSA is the time required by the DUT to converge on this new
        topology.

   This test assumes that the DUT will be the designated router on the
   broadcast link. A similar test could be designed to test the convergence conver-
   gence time when the DUT is not the designated router as well.

   This test may be performed with varying numbers of devices attached
   to the broadcast network, and varying sets of LSAs being advertised
   to the DUT from the routers attached to the broadcast network. Variations Varia-
   tions in the LSA sets and other fac-
           tors factors should be noted in the test
   results.

   The time required to elect a designated router, as measured in Designated Desig-
   nated Router Election Time on A Broadcast Network, above, may be subtracted sub-
   tracted from the results of this test to provide just the convergence
   time across a broadcast network.

   Note all the other tests in the document include route calculation
   time in the conergence time, as described in [TERM], this test may
   not include route calculation time in the resulting measured conver-
   gence time, because initial route calculation may occur after the
   first network LSA is flooded.

8.6. Initial Convergence Time on a Broadcast Network, Test 2

   o    Using reference topology 3 (Broadcast Network), begin with the
        DUT connected to the network with OSPF enabled. OSPF should be
        enabled on R1, but the broadcast link should be disabled.

   o    Enable the broadcast link between R1 and the DUT. Note the time
        of the first hello transmitted by the DUT with a designated
        router listed.

   o    Note the time the first network LSA is flooded by the DUT at R1.

   o    The differential between the first hello with a designated
        router lists and the first network LSA is the time required by
        the DUT to converge on this new topology.

8.7. Link Down with Layer 2 Detection

   o    Using reference topology 4 (Parallel Links), begin with OSPF in
        the full state between the generator and the DUT. Both links
        should be point-to-point links with the ability to notify the
        operating system immediately upon link failure.

   o    Disable link 1; this should be done in such a way that the
        keepalive timers at the data link layer will have no impact on
        the DUT recognizing the link failure (the operating system in
        the DUT should recognize this link failure immediately). Disconnecting Discon-
        necting the cable on the gen-
              erator generator end would be one possibility,
        or shutting the link down.

   o    Note the time of the link failure on the generator.

   o    At the generator, note the time of the receipt of the new router
        LSA from the DUT notifying the generator of the link 2 failure.

        The difference in the time between the initial link failure and
        the receipt of the LSA on the generator across link 2 should be
        taken as the time required for an OSPF implementa-
           tion implementation to recognize recog-
        nize and process a link failure. failure, including the time required to
        generate and flood an LSA describing the link down event to an
        adjacent neighbor.

8.8. Link Down with Layer 3 Detection

   o    Using reference topology 4 (Parallel Links), begin with OSPF in
        the full state between the generator and the DUT.

   o    Disable OSPF processing on link 1 from the generator. This
        should be done in such a way so it does not affect link status;
        the DUT must MUST note the failure of the adjacency through the dead
        interval.

   o    At the generator, note the time of the receipt of the new router
        LSA from the DUT notifying the generator of the link 2 failure.

   The difference in the time between the initial link failure and the
   receipt of the LSA on the generator across link 2 should be taken as
   the time required for an OSPF implementa-
           tion implementation to recognize and process
   an adjacency failure.

9. Security Considerations

   This draft adds no new security considerations nor doecument does it resolve
   any not modify the underlying security considerations from the protocols tested.
   in [OSPF].

10. Acknowledgements

   Thanks to Howard Berkowitz, (hcb@clark.net), for his encouragement
   and support. Thanks also to Alex Zinin (zinin@psg.net), Gurpreet
   Singh
   (Gurpreet.Singh@SpirentCom.COM) (Gurpreet.Singh@SpirentCom.COM), and Yasuhiro Ohara
   (yasu@sfc.wide.ad.jp) for their comments as well.

11. Normative References

 [OSPF]Moy,

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

   [TERM]Manral, V., "OSPF Convergence Testing Terminiology and Concepts",
      draft-ietf-bmwg-ospfconv-term-04, March 2003 Con-
        cepts", draft-ietf-bmwg-ospfconv-term-08, May 2004

   [APPLICABILITY]
        Manral, V., "Benchmarking Applicability for Basic OSPF Conver-
        gence", draft-ietf-bmwg-ospfconv-applicability-03, draft-ietf-bmwg-ospfconv-applicability-05, May

   [RFC2119]
        Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 2003 1997

12. Informative References

   [INTERCONNECT]
        Bradner, S., McQuaid, J., "Benchmarking Methodology for Network
        Interconnect Devices", RFC2544, March 1999.

   [MILLISEC]
        Alaettinoglu C., et al., "Towards Milli-Second IGP Convergence"
        draft-alaettinoglu-isis-convergence

   [FIB-TERM]
        Trotter, G., "Terminology for Forwarding Information Base (FIB)
        based Router Performance", RFC3222, October 2001.

   [BLACKBOX]
        Shaikh, Aman, Greenberg, Albert, "Experience in Black-Box OSPF
        measurement"

13. Authors' Addresses

        Vishwas Manral
      Sinett Semiconductors
      1st floor, Embassy Icon Annex, 2/1 Infantry Road,
      Bangalore,
        Netplane Systems
        189 Prashasan Nagar
        Road number 72
        Jubilee Hills
        Hyderabad, India

      email: vishwas@sinett.com

        vmanral@netplane.com

        Russ White
        Cisco Systems, Inc.
        7025 Kit Creek Rd.
        Research Triangle Park, NC 27709

        riw@cisco.com

        Aman Shaikh
        AT&T Labs (Research)
        180, Park Av
        Florham Park, NJ 07932

        ashaikh@research.att.com

Network Working Group                                     Vishwas Manral
Internet Draft                                          Netplane Systems
                                                              Russ White
                                                           Cisco Systems
                                                             Aman Shaikh
Expiration Date: November 2004                  University of California
File Name: draft-ietf-bmwg-ospfconv-applicability-05.txt        May 2004

         Benchmarking Applicability for Basic OSPF Convergence
             draft-ietf-bmwg-ospfconv-applicability-05.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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   Drafts as reference material or to cite them other than as a "working
   draft" or "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.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document discusses the applicability of various tests for
   measuring single router control plane convergence, specifically in
   regards to the Open Shortest First (OSPF) protocol. There are two
   general sections in this document, the first discussing specific
   advantages and limitations of specific OSPF convergence tests, and
   the second discussing more general pitfalls to be considered when
   testing routing protocols convergence testing.

1. Introduction

   There is a growing interest in testing single router control plane
   convergence for routing protocols, with many people looking at
   testing methodologies which can provide information on how long it
   takes for a network to converge after various network events occur.
   It is important to consider the framework within which any given
   convergence test is executed when attempting to apply the results of
   the testing, since the framework can have a major impact on the
   results. For instance, determining when a network is converged, what
   parts of the router's operation are considered within the testing,
   and other such things will have a major impact on what apparent
   performance routing protocols provide.

   This document describes in detail the various benefits and pitfalls
   of tests described in [BENCHMARK]. It also explains how such
   measurements can be useful for providers and the research community.

   NOTE: The word convergence within this document refers to single
   router control plane convergence [TERM].

2. Advantages of Such Measurement

   o    To be able to compare the iterations of a protocol implementa-
        tion. It is often useful to be able to compare the performance
        of two iterations of a given implementation of a protocol to
        determine where improvements have been made and where further
        improvements can be made.

   o    To understand, given a set of parameters (network conditions),
        how a particular implementation on a particular device is going
        to perform. For instance, if you were trying to decide the pro-
        cessing power (size of device) required in a certain location
        within a network, you can emulate the conditions which are going
        to exist at that point in the network and use the test described
        to measure the perfomance of several different routers. The
        results of these tests can provide one possible data point for
        an intelligent decision.

        If the device being tested is to be deployed in a running net-
        work, using routes taken from the network where the equipment is
        to be deployed rather than some generated topology in these
        tests will give results which are closer to the real preformance
        of the device. Care should be taken to emulate or take routes
        from the actual location in the network where the device will be
        (or would be) deployed. For instance, one set of routes may be
        taken from an ABR, one set from an area 0 only router, various
        sets from stub area, another set from various normal areas, etc.

   o    To measure the performance of an OSPF implementation in a wide
        variety of scenarios.

   o    To be used as parameters in OSPF simulations by researchers. It
        may some times be required for certain kinds of research to
        measure the individual delays of each parameter within an OSPF
        implementation. These delays can be measured using the methods
        defined in [BENCHMARK].

   o    To help optimize certain configurable parameters. It may some
        times be helpful for operators to know the delay required for
        individual tasks so as to optimize the resource usage in the
        network i.e. if it is found that the processing time is x
        seconds on an router, it would be helpful to determine the rate
        at which to flood LSA's to that router so as to not overload the
        network.

3. Assumptions Made and Limitations of such measurements

   o    The interactions of convergence and forwarding; testing is res-
        tricted to events occurring within the control plane. Forwarding
        performance is the primary focus in [INTERCONNECT] and it is
        expected to be dealt with in work that ensues from [FIB-TERM].

   o    Duplicate LSAs are Acknowledged Immediately. A few tests rely on
        the property that duplicate LSA Acknowledgements are not delayed
        but are done immediately. However if some implementation does
        not acknowledge duplicate LSAs immediately on receipt, the test-
        ing methods presented in [BENCHMARK] could give inaccurate meas-
        urements.

   o    It is assumed that SPF is non-preemptive. If SPF is implemented
        so that it can (and will be) preempted, the SPF measurements
        taken in [BENCHMARK] would include the times that the SPF pro-
        cess is not running ([BENCHMARK] measures the total time taken
        for SPF to run, not the amount of time that SPF actually spends
        on the device's processor), thus giving inaccurate measurements.

   o    Some implementations may be multithreaded or use a
        multiprocess/multirouter model of OSPF. If because of this any
        of the assumptions taken in measurement are violated in such a
        model, it could lead to inaccurate measurements.

   o    The measurements resulting from the tests in [BENCHMARK] may not
        provide the information required to deploy a device in a large
        scale network. The tests described focus on individual com-
        ponents of an OSPF implementation's performance, and it may be
        difficult to combine the measurements in a way which accurately
        depicts a device's performance in a large scale network. Further
        research is required in this area.

   o    The measurements described in [BENCHMARK] should be used with
        great care when comparing two different implementations of OSPF
        from two different vendors. For instance, there are many other
        factors than convergence speed that need to be taken into con-
        sideration when comparing different vendor's products, and it's
        difficult to align the resources available on one device to the
        resources available on another device.

4. Observations on the Tests Described in [BENCHMARK]

   Some observations taken while implementing the tests described in
   [BENCHMARK] are noted in this section.

4.1. Measuring the SPF Processing Time Externally

   The most difficult test to perform is the external measurement of the
   time required to perform an SPF calculation, since the amount of time
   between the first LSA which indicates a topology change and the
   duplicate LSA is critical. If the duplicate LSA is sent too quickly,
   it may be received before the device under test actually begins run-
   ning SPF on the network change information. If the delay between the
   two LSAs is too long, the device under test may finish SPF processing
   before receiving the duplicate LSA. It is important to closely inves-
   tigate any delays between the receipt of an LSA and the beginning of
   an SPF calculation in the device under test; multiple tests with
   various delays might be required to determine what delay needs to be
   used to accurately measure the SPF calculation time.

   Some implementations may force two intervals, the SPF hold time and
   the SPF delay, between successive SPF calculations. If an SPF hold
   time exists, it should be subtracted from the total SPF execution
   time. If an SPF delay exists, it should be noted in the test results.

4.2. Noise in the Measurement Device

   The device on which measurements are taken (not the device under
   test) also adds noise to the test results, primarily in the form of
   delay in packet processing and measurement output. The largest source
   of noise is generally the delay between the receipt of packets by the
   measuring device and the information about the packet reaching the
   device's output, where the event can be measured. The following steps
   may be taken to reduce this sampling noise:

   o    Increasing the number of samples taken will generally improve
        the tester's ability to determine what is noise, and remove it
        from the results.

   o    Try to take time-stamp for a packet as early as possible.
        Depending on the operating system being used on the box, one can
        instrument the kernel to take the time-stamp when the interrupt
        is processed. This does not eliminate the noise completely, but
        at least reduces it.

   o    Keep the measurement box as lightly loaded as possible.

   o    Having an estimate of noise can also be useful.

        The DUT also adds noise to the measurement. Points (a) and (c)
        apply to the DUT as well.

4.3. Gaining an Understanding of the Implementation Improves Measure-
   ments

   While the tester will (generally) not have access to internal infor-
   mation about the OSPF implementation being tested using [BENCHMARK],
   the more thorough the tester's knowledge of the implementation is,
   the more accurate the results of the tests will be. For instance, in
   some implementations, the installation of routes in local routing
   tables may occur while the SPF is being calculated, dramatically
   impacting the time required to calculate the SPF.

4.4. Gaining an Understanding of the Tests Improves Measurements

   One method which can be used to become familiar with the tests
   described in [BENCHMARK] is to perform the tests on an OSPF implemen-
   tation for which all the internal details are available, such as
   [GATED]. While there is no assurance that any two implementations
   will be similar, this will provide a better understanding of the
   tests themselves.

5. LSA and Destination mix

   In many OSPF benchmark tests, a generator injecting a number of LSAs
   is called for. There are several areas in which injected LSAs can be
   varied in testing:

   o    The number of destinations represented by the injected LSAs

        Each destination represents a single reachable IP network; these
        will be leaf nodes on the shortest path tree. The primary impact
        to performance should be the time required to insert destina-
        tions in the local routing table and handling the memory
        required to store the data.

   o    The types of LSAs injected

        There are several types of LSAs which would be acceptable under
        different situations; within an area, for instance, type 1, 2,
        3, 4, and 5 are likely to be received by a router. Within a
        not-so-stubby area, however, type 7 LSAs would replace the type
        5 LSAs received. These sorts of characterizations are important
        to note in any test results.

   o    The Number of LSAs injected

        Within any injected set of information, the number of each type
        of LSA injected is also important. This will impact the shortest
        path algorithms ability to handle large numbers of nodes, large
        shortest path first trees, etc.

   o    The Order of LSA Injection

        The order in which LSAs are injected should not favor any given
        data structure used for storing the LSA database on the device
        under test. For instance, AS-External LSA's have AS wide flood-
        ing scope; any Type-5 LSA originated is immediately flooded to
        all neighbors. However the Type-4 LSA which announces the ASBR
        as a border router is originated in an area at SPF time (by ABRs
        on the edge of the area in which the ASBR is). If SPF isn't
        scheduled immediately on the ABRs originating the type 4 LSA,
        the type-4 LSA is sent after the type-5 LSA's reach a router in
        the adjacent area. So routes to the external destinations aren't
        immediately added to the routers in the other areas. When the
        routers which already have the type 5's receive the type-4 LSA,
        all the external routes are added to the tree at the same time.
        This timing could produce different results than a router
        receiving a type 4 indicating the presence of a border router,
        followed by the type 5's originated by that border router.

        The ordering can be changed in various tests to provide insight
        on the efficiency of storage within the DUT. Any such changes in
        ordering should be noted in test results.

6. Tree Shape and the SPF Algorithm

   The complexity of Dijkstra's algorithm depends on the data structure
   used for storing vertices with their current minimum distances from
   the source, with the simplest structure being a list of vertices
   currently reachable from the source. In a simple list of vertices,
   finding the minimum cost vertex then would take O(size of the list).
   There will be O(n) such operations if we assume that all the vertices
   are ultimately reachable from the source. Moreover, after the vertex
   with min cost is found, the algorithm iterates thru all the edges of
   the vertex and updates cost of other vertices. With an adjacency list
   representation, this step when iterated over all the vertices, would
   take O(E) time, with E being the number of edges in the graph. Thus,
   overall running time is:

   O(sum(i:1, n)(size(list at level i) + E).

   So, everything boils down to the size (list at level i).

   If the graph is linear:

      root
       |
       1
       |
       2
       |
       3
       |
       4
       |
       5
       |
       6
      and source is a vertex on the end, then size(list at level i) = 1
      for all i. Moreover, E = n - 1. Therefore, running time is O(n).

      If graph is a balanced binary tree:

          root
         /    \
        1      2
       / \    / \
      3   4  5   6

      size(list at level i) is a little complicated. First it increases
      by 1 at each level upto a certain number, and then goes down by 1.
      If we assumed that tree is a complete tree (like the one in the
      draft) with k levels (1 to k), then size(list) goes on like this:
      1, 2, 3,

      Then the number of edges E is still n - 1. It then turns out that
      the run-time is O(n^2) for such a tree.

      If graph is a complete graph (fully-connected mesh), then
      size(list at level i) = n - i.  Number of edges E = O(n^2). There-
      fore, run-time is O(n^2).

      So, the performance of the shortest path first algorithm used to
      compute the best paths through the network is dependant o the con-
      struction of the tree The best practice would be to try and make
      any emulated network look as much like a real network as possible,
      especially in the area of the tree depth, the meshiness of the
      network, the number of stub links versus transit links, and the
      number of connections and nodes to process at each level within
      the original tree.

7. Topology Generation

   As the size of networks grows, it becomes more and more difficult to
   actually create a large scale network on which to test the properties
   of routing protocols and their implementations. In general, network
   emulators are used to provide emulated topologies which can be adver-
   tised to a device with varying conditions. Route generators either
   tend to be a specialized device, a piece of software which runs on a
   router, or a process that runs on another operating system, such as
   Linux or another variant of Unix.

   Some of the characteristics of this device should be:

   o    The ability to connect to the several devices using both point-
        to-point and broadcast high speed media. Point-to-point links
        can be emulated with high speed Ethernet as long as there is no
        hub or other device in between the DUT and the route generator,
        and the link is configured as a point-to-point link within OSPF
        [BROADCAST-P2P].

   o    The ability to create a set of LSAs which appear to be a logi-
        cal, realistic topology. For instance, the generator should be
        able to mix the number of point-to-point and broadcast links
        within the emulated topology, and should be able to inject vary-
        ing numbers of externally reachable destinations.

   o    The ability to withdraw and add routing information into and
        from the emulated topology to emulate links flapping.

   o    The ability to randomly order the LSAs representing the emulated
        topology as they are advertised.

   o    The ability to log or otherwise measure the time between packets
        transmitted and received.

   o    The ability to change the rate at which OSPF LSAs are transmit-
        ted.

   o    The generator and the collector should be fast enough so that
        they are not bottle necks. The devices should also have a degree
        of granularity of measurement atleast as small as desired from
        the test results.

8. Security Considerations

   This doecument does not modify the underlying security considerations
   in [OSPF].

9. Acknowledgements

    Thanks to Howard Berkowitz, (hcb@clark.net) and the rest of the BGP
   benchmarking team for their support and to Kevin
   Dubray(kdubray@juniper.net) who realized the need of this draft.

10. Normative References

   [BENCHMARK]
        Manral, V., "Benchmarking Basic OSPF Single Router Control Plane
        Convergence", draft-bmwg-ospfconv-intraarea-08, May 2004

   [TERM]Manral, V., "OSPF Convergence Testing Terminiology and Con-
        cepts", draft-bmwg-ospfconv-term-08, May 2004

   [RFC2119]
        Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997

11. Informative References

   [INTERCONNECT]
        Bradner, S., McQuaid, J., "Benchmarking Methodology for Network
        Interconnect Devices", RFC2544, March 1999.

   [FIB-TERM]
        Trotter, G., "Terminology for Forwarding Information Base (FIB)
        based Router Performance", RFC3222, October 2001.

   [BROADCAST-P2P]
        Shen, Naiming, et al., "Point-to-point operation over LAN in
        link-state routing protocols", draft-ietf-isis-igp-p2p-over-
        lan-03.txt, August, 2003.

   [GATED]
        http://www.gated.org

12. Authors' Addresses
   Vishwas Manral
   Netplane Systems
   189 Prashasan Nagar
   Road number 72
   Jubilee Hills
   Hyderabad, India

   vmanral@netplane.com

   Russ White
   Cisco Systems, Inc.
   7025 Kit Creek Rd.
   Research Triangle Park, NC 27709

   riw@cisco.com

   Aman Shaikh
   University of California
   School of Engineering
   1156 High Street
   Santa Cruz, CA  95064

   aman@soe.ucsc.edu

Network Working Group                                     Vishwas Manral
Internet Draft                                          Netplane Systems
                                                              Russ White
                                                           Cisco Systems
                                                             Aman Shaikh
Expiration Date: November 2004                  University of California
File Name: draft-bmwg-ospfconv-term-08.txt                      May 2004

               OSPF Benchmarking Terminology and Concepts
                    draft-bmwg-ospfconv-term-06.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
   months.  Internet Drafts may be updated, replaced, or obsoleted by
   other documents at any time. It is not appropriate to use Internet
   Drafts as reference material or to cite them other than as a "working
   draft" or "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.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This draft explains the terminology and concepts used in OSPF
   benchmarking. While some of these terms may be defined elsewhere, and
   we will refer the reader to those definitions in some cases, we also
   include discussions concerning these terms as they relate
   specifically to the tasks involved in benchmarking the OSPF protocol.

1. Specification of Requirements

   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 [RFC2119].

2. Motivation

   This draft is a companion to [BENCHMARK], which describes basic Open
   Shortest Path First [OSPF] testing methods. This draft explains
   terminology and concepts used in OSPF Testing Framework Drafts, such
   as [BENCHMARK].

3. Common Definitions

   Definitions in this section are well known industry and benchmarking
   terms which may be defined elsewhere.

   o    White Box (Internal) Measurements

        -    Definition

             White Box measurements are measurements reported and col-
             lected on the Device Under Test (DUT) itself.

        -    Discussion

             These measurement rely on output and event recording, along
             with the clocking and timestamping available on the DUT
             itself. Taking measurements on the DUT may impact the
             actual outcome of the test, since it can increase processor
             loading, memory utilization, and timing factors. Some dev-
             ices may not have the required output readily available for
             taking internal measurements, as well.

             Note: White box measurements can be influenced by the
             vendor's implementation of the various timers and process-
             ing models. Whenever possible, internal measurements should
             be compared to external measurements to verify and validate
             them.

             Because of the potential for variations in collection and
             presentation methods across different DUTs, white box
             measurements MUST NOT be used as a basis of comparison in
             benchmarks.  This has been a guiding principal of Bench-
             marking Methodology Working Group.

   o    Black Box (External) Measurements

        -    Definition

             Black Box measurements infer the performance of the DUT
             through observation of its communications with other dev-
             ices.

        -    Discussion

             One example of a black box measurement is when a downstream
             device receives complete routing information from the DUT,
             it can be inferred that the DUT has transmitted all the
             routing information available. External measurements of
             internal operations may suffer in that they include not
             just the protocol action times, but also propagation
             delays, queuing delays, and other such factors.

             For the purposes of [BENCHMARK], external techniques are
             more readily applicable.

   o    Multi-device Measurements

        -    Measurements assessing communications (usually in combina-
             tion with internal operations) between two or more DUTs.
             Multi-device measurements may be internal or external.

4. Terms Defined Elsewhere

   Terms in this section are defined elsewhere, and included only to
   include a discussion of those terms in reference to [BENCHMARK].

   o    Point-to-Point links

        -    Definition

             See [OSPF], Section 1.2.

        -    Discussion

             A point-to-point link can take lesser time to converge than
             a broadcast link of the same speed because it does not have
             the overhead of DR election. Point-to-point links can be
             either numbered or unnumbered. However in the context of
             [BENCHMARK] and [OSPF], the two can be regarded the same.

   o    Broadcast Link

        -    Definition

             See [OSPF], Section 1.2.

        -    Discussion

             The adjacency formation time on a broadcast link can be
             more than that on a point-to-point link of the same speed,
             because DR election has to take place. All routers on a
             broadcast network form adjacency with the DR and BDR.

             Async flooding also takes place thru the DR. In context of
             convergence, it may take more time for an LSA to be flooded
             from one DR-other router to another DR-other router,
             because the LSA has to be first processed at the DR.

   o    Shortest Path First Execution Time

        -    Definition
             The time taken by a router to complete the SPF process, as
             described in [OSPF].

        -    Discussion

             This does not include the time taken by the router to give
             routes to the forwarding engine.

             Some implementations may force two intervals, the SPF hold
             time and the SPF delay, between successive SPF calcula-
             tions. If an SPF hold time exists, it should be subtracted
             from the total SPF execution time. If an SPF delay exists,
             it should be noted in the test results.

        -    Measurement Units

             The SPF time is generally measured in milliseconds.

   o    Hello Interval

        -    Definition

             See [OSPF], Section 7.1.

        -    Discussion

             The hello interval should be the same for all routers on a
             network.

             Decreasing the hello interval can allow the router dead
             interval (below) to be reduced, thus reducing convergence
             times in those situations where the router dead interval
             timing out causes an OSPF process to notice an adjacency
             failure. Further discussion on small hello intervals is
             given in [OSPF-SCALING].

   o    Router Dead interval

   -    Definition

        See [OSPF], Section 7.1.

   -    Discussion

        This is advertised in the router's Hello Packets in the Router-
        DeadInterval field. The router dead interval should be some mul-
        tiple of the HelloInterval (say 4 times the hello interval), and
        must be the same for all routers attached to a common network.

5. Concepts

5.1. The Meaning of Single Router Control Plane Convergence

   A network is termed to be converged when all of the devices within
   the network have a loop free path to each possible destination. Since
   we are not testing network convergence, but performance for a partic-
   ular device within a network, however, this definition needs to be
   narrowed somewhat to fit within a single device view.

   In this case, convergence will mean the point in time when the DUT
   has performed all actions needed to react to the change in topology
   represented by the test condition; for instance, an OSPF device must
   flood any new information it has received, rebuild its shortest path
   first (SPF) tree, and install any new paths or destinations in the
   local routing information base (RIB, or routing table).

   Note that the word convergence has two distinct meanings; the process
   of a group of individuals meeting the same place, and the process of
   a single individual meeting in the same place as an existing group.
   This work focuses on the second meaning of the word, so we consider
   the time required for a single device to adapt to a network change to
   be Single Router Convergence.

   This concept does not include the time required for the control plane
   of the device to transfer the information required to forward packets
   to the data plane, nor the amount of time between the data plane
   receiving that information and being able to actually forward
   traffic.

5.2. Measuring Convergence

   Obviously, there are several elements to convergence, even under the
   definition given above for a single device, including (but not lim-
   ited to):

   o    The time it takes for the DUT to pass the information about a
        network event on to its neighbors.

   o    The time it takes for the DUT to process information about a
        network event and calculate a new Shortest Path Tree (SPT).

   o    The time it takes for the DUT to make changes in its local rib
        reflecting the new shortest path tree.

5.3. Types of Network Events

   A network event is an event which causes a change in the network
   topology.

   o    Link or Neighbor Device Up

        The time needed for an OSPF implementation to recoginize a new
        link coming up on the device, build any necessarily adjacencies,
        synchronize its database, and perform all other needed actions
        to converge.

   o    Initialization

        The time needed for an OSPF implementation to be initialized,
        recognize any links across which OSPF must run, build any needed
        adjacencies, synchronize its database, and perform other actions
        needed to converge.

   o    Adjacency Down

        The time needed for an OSPF implementation to recognize a link
        down/adjacency loss based on hello timers alone, propogate any
        information as necessary to its remaining adjacencies, and per-
        form other actions needed to converge.

   o    Link Down

        The time needed for an OSPF implementation to recognize a link
        down based on layer 2 provided information, propogate any infor-
        mation as needed to its remaining adjacencies, and perform other
        actions needed to converge.

6. Security Considerations

   This doecument does not modify the underlying security considerations
   in [OSPF].

7. Acknowedgements

   The authors would like to thank Howard Berkowitz (hcb@clark.net),
   Kevin Dubray, (kdubray@juniper.net), Scott Poretsky
   (sporetsky@avici.com), and Randy Bush (randy@psg.com) for their dis-
   cussion, ideas, and support.

8. Normative References

   [BENCHMARK]
        Manral, V., "Benchmarking Basic OSPF Single Router Control Plane
        Convergence", draft-bmwg-ospfconv-intraarea-08, May 2004.

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

9. Informative References

   [OSPF-SCALING]
        Choudhury, Gagan L., Editor, "Prioritized Treatment of Specific
        OSPF Packets and Congestion Avoidance", draft-ietf-ospf-
        scalability-06.txt, August 2003.

10. Authors' Addresses

      Vishwas Manral,
      Netplane Systems,
      189 Prashasan Nagar,
      Road number 72,
      Jubilee Hills,
      Hyderabad.

      vmanral@netplane.com

      Russ White
      Cisco Systems, Inc.
      7025 Kit Creek Rd.

      Research Triangle Park, NC 27709

      riw@cisco.com

      Aman Shaikh
      University of California
      School of Engineering
      1156 High Street
      Santa Cruz, CA  95064

      aman@soe.ucsc.edu