Network Working Group                                     Vishwas Manral
Internet Draft                                          Netplane Systems
                                                              Russ White
                                                           Cisco Systems
                                                             Aman Shaikh
Expiration Date: July November 2004                  University of California
File Name: draft-bmwg-ospfconv-term-07.txt                  January draft-bmwg-ospfconv-term-08.txt                      May 2004

               OSPF Benchmarking Terminology and Concepts


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

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


   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",
   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 proces-
              sor processor
             loading, memory utilization, and timing factors. Some
              devices 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

             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-

        -    Discussion

             One example of a black box measurement is when a down-
              stream downstream
             device receives complete routing information from the DUT,
             it can be inferred that the DUT has transmitted all the
             routing information available. External measure-
              ments measurements of
             internal operations may suffer in that they include not
             just the protocol action times, but also pro-
              pagation 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 con-
              text 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

             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
              RouterDeadInterval Router-
        DeadInterval field. The router dead interval should be some multiple 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


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

   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 adja-
           cencies, 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, propo-
           gate propogate any
        information as necessary to its remaining adjacen-
           cies, adjacencies, and perform 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 information 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 (,
   Kevin Dubray, (, Scott Poretsky
   (, and Randy Bush ( for their dis-
   cussion, ideas, and support.

8. Normative References

        Manral, V., "Benchmarking Basic OSPF Single Router Control Plane
        Convergence", draft-bmwg-ospfconv-intraarea-05, March 2003 draft-bmwg-ospfconv-intraarea-08, May 2004.

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

9. Informative References

        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,

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

      Research Triangle Park, NC 27709

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