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  Network Working Group                                     Debra Stopp
                                                            Hardev Soor
  INTERNET-DRAFT                                                   IXIA
  Expires in:  November 2002



                Methodology for IP Multicast Benchmarking
                     <draft-ietf-bmwg-mcastm-08.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 and may be updated, replaced, or obsoleted by other
     documents at any time.  It is inappropriate to use Internet-Drafts
     as reference material or to cite them other than as "work in
     progress."

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

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


  Copyright Notice

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


  Abstract

     The purpose of this draft is to describe methodology specific to
     the benchmarking of multicast IP forwarding devices. It builds upon
     the tenets set forth in RFC 2544, RFC 2432 and other IETF
     Benchmarking Methodology Working Group (BMWG) efforts.  This
     document seeks to extend these efforts to the multicast paradigm.

     The BMWG produces two major classes of documents: Benchmarking
     Terminology documents and Benchmarking Methodology documents. The
     Terminology documents present the benchmarks and other related
     terms. The Methodology documents define the procedures required to
     collect the benchmarks cited in the corresponding Terminology
     documents.


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  Table of Contents

  1. INTRODUCTION...................................................3

  2. KEY WORDS TO REFLECT REQUIREMENTS..............................3

  3. TEST SET UP....................................................3
  3.1. Test Considerations..........................................5
  3.1.1.  IGMP Support..............................................5
  3.1.2.  Group Addresses...........................................5
  3.1.3.  Frame Sizes...............................................5
  3.1.4.  TTL.......................................................6
  3.1.5.  Trial Duration............................................6
  3.2. Layer 2 Support..............................................6
  4. FORWARDING AND THROUGHPUT......................................6
  4.1. Mixed Class Throughput.......................................6
  4.2. Scaled Group Forwarding Matrix...............................7
  4.3. Aggregated Multicast Throughput..............................8
  4.4. Encapsulation/Decapsulation (Tunneling) Throughput...........9
  4.4.1.  Encapsulation Throughput..................................9
  4.4.2.  Decapsulation Throughput..................................9
  4.4.3.  Re-encapsulation Throughput..............................10
  5. FORWARDING LATENCY............................................10
  5.1. Multicast Latency...........................................11
  5.2. Min/Max Multicast Latency...................................13
  6. OVERHEAD......................................................14
  6.1. Group Join Delay............................................14
  6.2. Group Leave Delay...........................................15
  7. CAPACITY......................................................16
  7.1. Multicast Group Capacity....................................16
  8. INTERACTION...................................................16
  8.1. Forwarding Burdened Multicast Latency.......................17
  8.2. Forwarding Burdened Group Join Delay........................17
  9. SECURITY CONSIDERATIONS.......................................17

  10. ACKNOWLEDGEMENTS.............................................17

  11. REFERENCES...................................................18

  12. AUTHOR'S ADDRESSES...........................................19

  13. FULL COPYRIGHT STATEMENT.....................................19





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  1. Introduction

     This document defines a specific set of tests that vendors can use
     to measure  and  report  the  performance characteristics and
     forwarding capabilities of network devices that support IP
     multicast  protocols. The results of these tests will provide the
     user comparable data from different vendors with which to evaluate
     these devices.

     A previous document, " Terminology for IP Multicast Benchmarking"
     (RFC 2432), defined many of the terms that are used in this
     document. The terminology document should be consulted before
     attempting to make use of this document.

     This methodology will focus on one source to many destinations,
     although many of the tests described may be extended to use
     multiple source to multiple destination IP multicast communication.

  2. Key Words to Reflect 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.
     RFC 2119 defines the use of these key words to help make the intent
     of standards track documents as clear as possible.  While this
     document uses these keywords, this document is not a standards
     track document.

  3. Test set up

     The set of methodologies presented in this draft are for single
     ingress, multiple egress scenarios as exemplified by Figures 1 and
     2.  Methodologies for multiple ingress, multiple egress scenarios
     are beyond the scope of this document.

     Figure 1 shows a typical setup for an IP multicast test, with one
     source to multiple destinations.

















Soor & Stopp                                                  [Page 3]


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                                                     +----------------+
                             +------------+          |    Egress      |
          +--------+         |           (-)-------->| destination(E1)|
          |        |         |            |          |                |
          | source |------->(|)Ingress    |          +----------------+
          |        |         |            |          +----------------+
          +--------+         |   D U T   (-)-------->|    Egress      |
                             |            |          | destination(E2)|
                             |            |          |                |
                             |            |          +----------------+
                             |            |               . . .
                             |            |          +----------------+
                             |            |          |    Egress      |
                             |           (-)-------->| destination(En)|
                             |            |          |                |
                             +------------+          +----------------+

                                 Figure 1
                                 ---------

     If the multicast metrics are to be taken across multiple devices
     forming a System Under Test (SUT), then test packets are offered to
     a single ingress interface on a device of the SUT, subsequently
     routed across the SUT topology, and finally forwarded to the test
     apparatus' packet-receiving components by the test egress
     interface(s) of devices in the SUT. Figure 2 offers an example SUT
     test topology.  If a SUT is tested, the details of the test
     topology MUST be disclosed with the corresponding test results.


   +--------+                       +----------------+    +--------+
   |        |     +------------+    |DUT B Egress E0(-)-->|        |
   |        |     |DUT A       |--->|                |    |        |
   | Test   |     |            |    |      Egress E1(-)-->| Test   |
   | App.   |--->(-)Ingress, I |    +----------------+    | App.   |
   | Traffic|     |            |    +----------------+    | Traffic|
   | Src.   |     |            |--->|DUT C Egress E2(-)-->| Dest.  |
   |        |     +------------+    |                |    |        |
   |        |                       |      Egress En(-)-->|        |
   +--------+                       +----------------+    +--------+

                                  Figure 2
                                  ---------

     Generally, the destination ports first join the desired number of
     multicast groups by sending IGMP Join Group messages to the
     DUT/SUT. To verify that all destination ports successfully joined
     the appropriate groups, the source port MUST transmit IP multicast
     frames destined for these groups. The destination ports MAY send
     IGMP Leave Group messages after the transmission of IP Multicast
     frames to clear the IGMP table of the DUT/SUT.



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     In addition, test equipment MUST validate the correct and proper
     forwarding actions of the devices they test in order to ensure the
     receipt of only the frames that are involved in the test.


  3.1. Test Considerations

     The procedures outlined below are written without regard for
     specific physical layer or link layer protocols. The methodology
     further assumes a uniform medium topology. Issues regarding mixed
     transmission media, such as speed mismatch, headers differences,
     etc., are not specifically addressed. Flow control, QoS and other
     traffic-affecting mechanisms MUST be disabled.  Modifications to
     the specified collection procedures might need to be made to
     accommodate the transmission media actually tested.  These
     accommodations MUST be presented with the test results.

  3.1.1. IGMP Support

     Each of the destination ports should support and be able to test
     all IGMP versions 1, 2 and 3. The minimum requirement, however, is
     IGMP version 2.

     Each destination port should be able to respond to IGMP queries
     during the test.

     Each destination port should also send LEAVE (running IGMP version
     2) after each test.

  3.1.2. Group Addresses

     The Class D Group address SHOULD be changed between tests.  Many
     DUTs have memory or cache that is not cleared properly and can bias
     the results.

     The following group addresses are recommended by use in a test:

             224.0.1.27-224.0.1.255
             224.0.5.128-224.0.5.255
             224.0.6.128-224.0.6.255

     If the number of group addresses accommodated by these ranges does
     not satisfy the requirements of the test, then these ranges may be
     overlapped. The total number of configured group addresses must be
     less than or equal to the IGMP table size of the DUT/SUT.

  3.1.3. Frame Sizes

     Each test SHOULD be run with different Multicast Frame Sizes. The
     recommended frame sizes are 64, 128, 256, 512, 1024, 1280, and 1518
     byte frames.


Soor & Stopp                                                  [Page 5]


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  3.1.4. TTL

     The source frames should have a TTL value large enough to
     accommodate the DUT/SUT.

  3.1.5. Trial Duration

     The duration of the test portion of each trial SHOULD be at least
     30 seconds.  This parameter MUST be included as part of the results
     reporting for each methodology.

  3.2.  Layer 2 Support

     Each of the destination ports should support GARP/GMRP protocols to
     join groups on Layer 2 DUTs/SUTs.


  4. Forwarding and Throughput

  This section contains the description of the tests that are related
  to the characterization of the packet forwarding of a DUT/SUT in a
  multicast environment. Some metrics extend the concept of throughput
  presented in RFC 1242. The notion of Forwarding Rate is cited in RFC
  2285.

  4.1. Mixed Class Throughput

     Objective

     To determine the maximum throughput rate at which none of the
     offered frames, comprised from a unicast Class and a multicast
     Class, to be forwarded are dropped by the device across a fixed
     number of ports as defined in RFC 2432.

     Procedure

     Multicast and unicast traffic are mixed together in the same
     aggregated traffic stream in order to simulate the non-homogenous
     networking environment. The DUT/SUT MUST learn the appropriate
     unicast IP addresses, either by sending ARP frames from each
     unicast address, sending a RIP packet or by assigning static
     entries into the DUT/SUT address table.

     The mixture of multicast and unicast traffic MUST be set up in one
     of two ways:

          a) Input frame rate for each class of traffic [Br91] or as a
          percentage of media_maximum-octets [Ma98].  Frame rate should
          be specified independently for each traffic class.




Soor & Stopp                                                  [Page 6]


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          b) As an aggregate rate (given either in frames per second or
          as a percentage), with the ratio of multicast to unicast
          traffic declared.


     While the multicast traffic is transmitted from one source to
     multiple destinations, the unicast traffic MAY be evenly
     distributed across the DUT/SUT architecture. Unicast traffic
     distribution can either be non-meshed or meshed [Ma98] as specified
     in RFC2544 or RFC2289.

     Throughput measurement is defined in RFC1242 [Br91]. A search
     algorithm MUST be utilized to determine the maximum offered frame
     rate with a zero frame loss rate.


     Result

     Parameters to be measured MUST include the aggregate offered load,
     number of multicast frames offered, number of unicast frames
     offered, number multicast frames received, number of unicast frames
     received and transmit duration of offered frames.


  4.2.  Scaled Group Forwarding Matrix

     Objective

     A table that demonstrates Forwarding Rate as a function of tested
     multicast groups for a fixed number of tested DUT/SUT ports.

     Procedure

     Multicast traffic is sent at a fixed percent of maximum offered
     load with a fixed number of receive ports of the tester at a fixed
     frame length.

     On each iteration, the receive ports SHOULD incrementally join 10
     multicast groups until a user defined maximum number of groups is
     reached.

     Results

     Parameters to be measured MUST include the offered load and
     forwarding rate as a function of the total number of multicast
     groups, for each test iteration.

     The nature of the traffic stream contributing to the result MUST be
     reported, specifically number of source and destination ports
     within the multicast group.  In addition, all other reporting
     parameters of the scaled group forwarding matrix methodology MUST


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     be reflected in the results report, such as the transmitted packet
     size(s) and offered load of the packet stream for each source port.

     Result reports MUST include the following parameters for each
     iteration: the number of frames offered, number of frames received
     per each group, number of multicast groups and forwarding rate, in
     frames per second, and transmit duration of offered frames.
     Constructing a table that contains the forwarding rate vs. number
     of groups is desirable.

  4.3. Aggregated Multicast Throughput

     Objective

     The maximum rate at which none of the offered frames to be
     forwarded through N destination interfaces of the same multicast
     group is dropped.

     Procedure

     Multicast traffic is sent at a fixed percent of maximum offered
     load with a fixed number of groups at a fixed frame length for a
     fixed duration of time.

     The initial number of receive ports of the tester will join the
     group(s) and the sender will transmit to the same groups after a
     certain delay (a few seconds).

     If any frame loss is detected, one receive port MUST leave the
     group(s) and the sender will transmit again.  Continue in this
     iterative fashion until either there are no ports left joined to
     the multicast group(s) OR 0% frame loss is achieved.

     Results

     Parameters to be measured MUST include the maximum offered load at
     which no frame loss occurred (as defined by RFC 2544)

     The nature of the traffic stream contributing to the result MUST be
     reported.  All required reporting parameters of aggregated
     throughput MUST be reflected in the results report, such as the
     initial number of receive ports, the final number of receive ports,
     total number of multicast group addresses, the transmitted packet
     size(s), offered load of the packet stream and transmit duration of
     offered frames.

     Constructing a table from the measurements might be useful in
     illustrating the effect of modifying the number of active egress
     ports on the tested system.




Soor & Stopp                                                  [Page 8]


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  4.4. Encapsulation/Decapsulation (Tunneling) Throughput

     This sub-section provides the description of tests that help in
     obtaining throughput measurements when a DUT/SUT or a set of DUTs
     are acting as tunnel endpoints


  4.4.1. Encapsulation Throughput

     Objective

     The maximum rate at which frames offered a DUT/SUT are encapsulated
     and correctly forwarded by the DUT/SUT without loss.

     Procedure

     Traffic is sent through a DUT/SUT that has been configured to
     encapsulate the frames. Traffic is received on a test port prior to
     decapsulation and throughput is calculated based on RFC2544.

     Results

     Parameters to be measured SHOULD include the measured throughput
     per tunnel,

     The nature of the traffic stream contributing to the result MUST be
     reported.  All required reporting parameters of encapsulation
     throughput MUST be reflected in the results report, such as the
     transmitted packet size(s), offered load of the packet stream and
     transmit duration of offered frames.

  4.4.2. Decapsulation Throughput

     Objective

     The maximum rate at which frames offered a DUT/SUT are decapsulated
     and correctly forwarded by the DUT/SUT without loss.

     Procedure

     Encapsulated traffic is sent through a DUT/SUT that has been
     configured to decapsulate the frames. Traffic is received on a test
     port after decapsulation and throughput is calculated based on
     RFC2544.

     Results

     Parameters to be measured SHOULD include the measured throughput
     per tunnel.

     The nature of the traffic stream contributing to the result MUST be
     reported.  All required reporting parameters of decapsulation

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     throughput MUST be reflected in the results report, such as the
     transmitted packet size(s), offered load of the packet stream and
     transmit duration of offered frames.

  4.4.3. Re-encapsulation Throughput

     Objective

     The maximum rate at which frames of one encapsulated format offered
     a DUT/SUT are converted to another encapsulated format and
     correctly forwarded by the DUT/SUT without loss.

     Procedure

     Traffic is sent through a DUT/SUT that has been configured to
     encapsulate frames into one format, then re-encapsulate the frames
     into another format. Traffic is received on a test port after all
     decapsulation is complete and throughput is calculated based on
     RFC2544.

     Results

     Parameters to be measured SHOULD include the measured throughput
     per tunnel.

     The nature of the traffic stream contributing to the result MUST be
     reported.  All required reporting parameters of re-encapsulation
     throughput MUST be reflected in the results report, such as the
     transmitted packet size(s), offered load of the packet stream and
     transmit duration of offered frames.

  5. Forwarding Latency

     This section presents methodologies relating to the
     characterization of the forwarding latency of a DUT/SUT in a
     multicast environment. It extends the concept of latency
     characterization presented in RFC 2544.

     In order to lessen the effect of packet buffering in the DUT/SUT,
     the latency tests MUST be run such that the offered load is less
     than the multicast throughput of the DUT/SUT as determined in the
     previous section. The tests should also take into account the
     DUT's/SUT's need to cache the traffic in its IP cache, fastpath
     cache or shortcut tables since the initial part of the traffic will
     be utilized to build these tables.

     Lastly, RFC 1242 and RFC 2544 draw distinction between two classes
     of devices: "store and forward" and "bit-forwarding." Each class
     impacts how latency is collected and subsequently presented. See
     the related RFCs for more information.  In practice, much of the
     test equipment will collect the latency measurement for one class
     or the other, and, if needed, mathematically derive the reported
     value by the addition or subtraction of values accounting for

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     medium propagation delay of the packet, bit times to the timestamp
     trigger within the packet, etc. Test equipment vendors SHOULD
     provide documentation regarding the composition and calculation
     latency values being reported.  The user of this data SHOULD
     understand the nature of the latency values being reported,
     especially when comparing results collected from multiple test
     vendors. (E.g., If test vendor A presents a "store and forward"
     latency result and test vendor B presents a "bit-forwarding"
     latency result, the user may erroneously conclude the DUT has two
     differing sets of latency values.)

  5.1. Multicast Latency

     Objective

     To produce a set of multicast latency measurements from a single,
     multicast ingress port of a DUT or SUT through multiple, egress
     multicast ports of that same DUT or SUT as provided for by the
     metric "Multicast Latency" in RFC 2432.

     The procedures highlighted below attempt to draw from the
     collection methodology for latency in RFC 2544 to the degree
     possible.  The methodology addresses two topological scenarios: one
     for a single device (DUT) characterization; a second scenario is
     presented or multiple device (SUT) characterization.

     Procedure

     If the test trial is to characterize latency across a single Device
     Under Test (DUT), an example test topology might take the form of
     Figure 1 in section 3.  That is, a single DUT with one ingress
     interface receiving the multicast test traffic from packet-
     transmitting component of the test apparatus and n egress
     interfaces on the same DUT forwarding the multicast test traffic
     back to the packet-receiving component of the test apparatus.  Note
     that n reflects the number of TESTED egress interfaces on the DUT
     actually expected to forward the test traffic (as opposed to
     configured but untested, non-forwarding interfaces, for example).

     If the multicast latencies are to be taken across multiple devices
     forming a System Under Test (SUT), an example test topology might
     take the form of Figure 2 in section 3.

     The trial duration SHOULD be 120 seconds.  Departures to the
     suggested traffic class guidelines MUST be disclosed with the
     respective trial results.  The nature of the latency measurement,
     "store and forward" or "bit forwarding," MUST be associated with
     the related test trial(s) and disclosed in the results report.

     End-to-end reach ability of the test traffic path SHOULD be
     verified prior to the engagement of a test trial.  This implies
     that subsequent measurements are intended to characterize the

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     latency across the tested device's or devices' normal traffic
     forwarding path (e.g., faster hardware-based engines) of the
     device(s) as opposed a non-standard traffic processing path (e.g.
     slower, software-based exception handlers).  If the test trial is
     to be executed with the intent of characterizing a non-optimal,
     forwarding condition, then a description of the exception
     processing conditions being characterized MUST be included with the
     trial's results.

     A test traffic stream is presented to the DUT. At the mid-point of
     the trial's duration, the test apparatus MUST inject a uniquely
     identifiable ("tagged") packet into the test traffic packets being
     presented.  This tagged packet will be the basis for the latency
     measurements. By "uniquely identifiable," it is meant that the test
     apparatus MUST be able to discern the "tagged" packet from the
     other packets comprising the test traffic set.  A packet generation
     timestamp, Timestamp A, reflecting the completion of the
     transmission of the tagged packet by the test apparatus, MUST be
     determined.

     The test apparatus then monitors packets from the DUT's tested
     egress port(s) for the expected tagged packet(s) until the
     cessation of traffic generation at the end of the configured trial
     duration.A value of the Offered Load presented the DUT/SUT MUST be
     noted.

     The test apparatus MUST record the time of the successful detection
     of a tagged packet from a tested egress interface with a timestamp,
     Timestamp B.  A set of Timestamp B values MUST be collected for all
     tested egress interfaces of the DUT/SUT.

     A trial MUST be considered INVALID should any of the following
     conditions occur in the collection of the trial data:

       . Forwarded test packets directed to improper destinations.
       . Unexpected differences between Intended Load and Offered Load
          or unexpected differences between Offered Load and the
          resulting Forwarding Rate(s) on the DUT/SUT egress ports.
       . Forwarded test packets improperly formed or packet header
          fields improperly manipulated.
       . Failure to forward required tagged packet(s) on all expected
          egress interfaces.
       . Reception of a tagged packet by the test apparatus outside the
          configured test duration interval or 5 seconds, whichever is
          greater.

     Data from invalid trials SHOULD be considered inconclusive.  Data
     from invalid trials MUST not form the basis of comparison.






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     The set of latency measurements, M, composed from each latency
     measurement taken from every ingress/tested egress interface
     pairing MUST be determined from a valid test trial:
           M = { (Timestamp B(E0) - Timestamp A),
                 (Timestamp B(E1) - Timestamp A), ...
                 (Timestamp B(En) - Timestamp A) }

     where (E0 ... En) represents the range of all tested egress
     interfaces and Timestamp B represents a tagged packet detection
     event for a given DUT/SUT tested egress interface.

     Results

     Two types of information MUST be reported: 1) the set of latency
     measurements and 2) the significant environmental, methodological,
     or device particulars giving insight into the test or its results.

     Specifically, when reporting the results of a VALID test trial, the
     set of ALL latencies related to the tested ingress interface and
     each tested egress DUT/SUT interface of MUST be presented.  The
     time units of the presented latency MUST be uniform and with
     sufficient precision for the medium or media being tested.  Results
     MAY be offered in tabular format and SHOULD preserve the
     relationship of latency to ingress/egress interface to assist in
     trending across multiple trials.

     The Offered Load of the test traffic presented the DUT/SUT, size of
     the "tagged" packet, transmit duration of offered frames and nature
     (i.e., store-and-forward or bit-forwarding) of the trial's
     measurement MUST be associated with any reported test trial's
     result.


  5.2. Min/Max Multicast Latency

     Objective

     The difference between the maximum latency measurement and the
     minimum latency measurement from a collected set of latencies
     produced by the Multicast Latency benchmark.

     Procedure

     Collect a set of multicast latency measurements, as prescribed in
     section 5.1. This will produce a set of multicast latencies, M,
     where M is composed of individual forwarding latencies between DUT
     packet ingress and DUT packet egress port pairs. E.g.:

         M = {L(I,E1),L(I,E2), …, L(I,En)}




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     where L is the latency between a tested ingress port, I, of the
     DUT, and Ex a specific, tested multicast egress port of the DUT.
     E1 through En are unique egress ports on the DUT.

     From the collected multicast latency measurements in set M,
     identify MAX(M), where MAX is a function that yields the largest
     latency value from set M.

     Identify MIN(M), when MIN is a function that yields the smallest
     latency value from set M.

     The Max/Min value is determined from the following formula:

         Result = MAX(M) – MIN(M)

     Results

     The result MUST be represented as a single numerical value in time
     units consistent with the corresponding latency measurements.  In
     addition, the number of tested egress ports on the DUT MUST be
     reported.

     The nature of the traffic stream contributing to the result MUST be
     reported.  All required reporting parameters of multicast latency
     MUST be reflected in the min/max results report, such as the
     transmitted packet size(s), offered load of the packet stream in
     which the tagged packet was presented to the DUT and transmit
     duration of offered frames.


  6. Overhead

     This section presents methodology relating to the characterization
     of the overhead delays associated with explicit operations found in
     multicast environments.


  6.1. Group Join Delay

     Objective

     The time duration it takes a DUT/SUT to start forwarding multicast
     packets from the time a successful IGMP group membership report has
     been issued to the DUT/SUT.

     Procedure

     Traffic is sent on the source port at the same time as the IGMP
     JOIN Group message is transmitted from the destination ports.  The
     join delay is the difference in time from when the IGMP Join is
     sent (timestamp A) and the first frame is forwarded to a receiving
     member port (timestamp B).

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               Group Join delay = timestamp B - timestamp A

     One of the keys is to transmit at the fastest rate the DUT/SUT can
     handle multicast frames.  This is to get the best resolution and
     the least margin of error in the Join Delay.

     However, you do not want to transmit the frames so fast that frames
     are dropped by the DUT/SUT. Traffic should be sent at the
     throughput rate determined by the forwarding tests of section 4.

     Results

     The parameter to be measured is the join delay time for each
     multicast group address per destination port. In addition, the
     number of frames transmitted and received and percent loss may be
     reported.


  6.2. Group Leave Delay

     Objective

     The time duration it takes a DUT/SUT to cease forwarding multicast
     packets after a corresponding IGMP "Leave Group" message has been
     successfully offered to the DUT/SUT.

     Procedure

     Traffic is sent on the source port at the same time as the IGMP
     Leave Group messages are transmitted from the destination ports.
     The leave delay is the difference in time from when the IGMP leave
     is sent (timestamp A) and the last frame is forwarded to a
     receiving member port (timestamp B).

               Group Leave delay = timestamp B - timestamp A

     One of the keys is to transmit at the fastest rate the DUT/SUT can
     handle multicast frames.  This is to get the best resolution and
     least margin of error in the Leave Delay.  However, you do not want
     to transmit the frames too fast that frames are dropped by the
     DUT/SUT.  Traffic should be sent at the throughput rate determined
     by the forwarding tests of section 4.

     Results

     The parameter to be measured is the leave delay time for each
     multicast group address per destination port. In addition, the
     number of frames transmitted and received and percent loss may be
     reported.



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  7. Capacity

     This section offers terms relating to the identification of
     multicast group limits of a DUT/SUT.

  7.1. Multicast Group Capacity

     Objective

     The maximum number of multicast groups a DUT/SUT can support while
     maintaining the ability to forward multicast frames to all
     multicast groups registered to that DUT/SUT.

     Procedure

     One or more destination ports of DUT/SUT will join an initial
     number of groups.

     Then after a delay (enough time for all ports to join) the source
     port will transmit to each group at a transmission rate that the
     DUT/SUT can handle without dropping IP Multicast frames.

     If all frames sent are forwarded by the DUT/SUT and received the
     test iteration is said to pass at the current capacity.

     If the iteration passes at the capacity the test will add an user
     defined incremental value of groups to each receive port.

     The iteration is to run again at the new group level and capacity
     tested as stated above.

     Once the test fails at a capacity the capacity is stated to be the
     last Iteration that pass at a giving capacity.

     Results

     The parameter to be measured is the total number of group addresses
     that were successfully forwarded with no loss.

     In addition, the nature of the traffic stream contributing to the
     result MUST be reported.  All required reporting parameters MUST be
     reflected in the results report, such as the transmitted packet
     size(s) and offered load of the packet stream.


  8. Interaction

     Network forwarding devices are generally required to provide more
     functionality than just the forwarding of traffic.  Moreover,
     network-forwarding devices may be asked to provide those functions
     in a variety of environments.  This section offers terms to assist


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     in the characterization of DUT/SUT behavior in consideration of
     potentially interacting factors.

  8.1. Forwarding Burdened Multicast Latency

     The Multicast Latency metrics can be influenced by forcing the
     DUT/SUT to perform extra processing of packets while multicast
     traffic is being forwarded for latency measurements. In this test,
     a set of ports on the tester will be designated to be source and
     destination similar to the generic IP Multicast test setup. In
     addition to this setup, another set of ports will be selected to
     transmit some multicast traffic that is destined to multicast group
     addresses that have not been joined by these additional set of
     ports.

     For example, if ports 1,2, 3, and 4 form the burdened response
     setup (setup A) which is used to obtain the latency metrics and
     ports 5, 6, 7, and 8 form the non-burdened response setup (setup B)
     which will afflict the burdened response setup, then setup B
     traffic will join multicast group addresses not joined by the ports
     in this setup.  By sending such multicast traffic, the DUT/SUT will
     perform a lookup on the packets that will affect the processing of
     setup A traffic.

  8.2. Forwarding Burdened Group Join Delay

     The port configuration in this test is similar to the one described
     in section 8.1, but in this test, the ports in setup B do not send
     the multicast traffic. Rather, setup A traffic must be influenced
     in such a way that will affect the DUT's/SUT's ability to process
     Group Join messages. Therefore, in this test, the ports in setup B
     will send a set of IGMP Group Join messages while the ports in
     setup A are also joining its own set of group addresses. Since the
     two sets of group addresses are independent of each other, the
     group join delay for setup A may be different than in the case when
     there were no other group addresses being joined.


  9. Security Considerations

     As this document is solely for the purpose of providing metric
     methodology and describes neither a protocol nor a protocol's
     implementation, there are no security considerations associated
     with this document.


  10. Acknowledgements

     The authors would like to acknowledge the following individuals for
     their help and participation of the compilation and editing of this
     document – Ralph Daniels, Netcom Systems, who made significant


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     contributions to earlier versions of this draft, Daniel Bui, IXIA,
     and Kevin Dubray, Juniper Networks.


  11. References

  [Br91] Bradner, S., "Benchmarking Terminology for Network
         Interconnection Devices", RFC 1242, July 1991.

  [Br96] Bradner, S., and J. McQuaid, "Benchmarking Methodology for
         Network Interconnect Devices", RFC 2544, March 1999.

  [Br97] Bradner, S. "Use of Keywords in RFCs to Reflect Requirement
         Levels, RFC 2119, March 1997

  [Du98] Dubray, K., "Terminology for IP Multicast Benchmarking", RFC
         2432, October 1998.

  [Hu95] Huitema, C.  "Routing in the Internet."  Prentice-Hall, 1995.

  [Ka98] Kosiur, D., "IP Multicasting: the Complete Guide to
         Interactive Corporate Networks", John Wiley & Sons, Inc, 1998.

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

  [Mt98] Maufer, T.  "Deploying IP Multicast in the Enterprise."
         Prentice-Hall, 1998.

  [Se98] Semeria, C. and Maufer, T.  "Introduction to IP Multicast
         Routing."  http://www.3com.com/nsc/501303.html  3Com Corp.,
         1998.






















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  12. Author's Addresses

     Debra Stopp
     IXIA
     26601 W. Agoura Rd.
     Calabasas, CA  91302
     USA

     Phone: 818 871 1800
     EMail: debby@ixiacom.com


     Hardev Soor
     IXIA
     26601 W. Agoura Rd.
     Calabasas, CA  91302
     USA

     Phone: 818 871 1800
     EMail: hardev@ixiacom.com


  13. Full Copyright Statement

     "Copyright (C) The Internet Society (date). All Rights Reserved.
     This document and translations of it may be copied and furnished to
     others, and derivative works that comment on or otherwise explain
     it or assist in its implementation may be prepared, copied,
     published and distributed, in whole or in part, without restriction
     of any kind, provided that the above copyright notice and this
     paragraph are included on all such copies and derivative works.
     However, this document itself may not be modified in any way, such
     as by removing the copyright notice or references to the Internet
     Society or other Internet organizations, except as needed for the
     purpose of developing Internet standards in which case the
     procedures for copyrights defined in the Internet Standards process
     must be followed, or as required to translate it into.
















Soor & Stopp                                                 [Page 19]


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