rfc2889.txt

来自「中、英文RFC文档大全打包下载完全版 .」· 文本 代码 · 共 1,697 行 · 第 1/5 页

   be implementing a flow control mechanism.  The type of flow control
   mechanism used is beyond the scope of this memo.

   It should be noted that some DUTs may not be able to handle the 100%
   load presented at the input port. In this case, there may be frame
   loss reported at the uncongested port which is due to the load at the
   input port rather than the congested port's load.

   If the uncongested frame loss is reported as zero, but the maximum
   forwarding rate is less than 7440 (for 10Mbps Ethernet), then this
   may be an indication of congestion control being enforced by the DUT.
   In this case, the congestion control is affecting the throughput of
   the uncongested port.

   If no congestion control is detected, the expected percentage frame
   loss for the congested port is 33% at 150% overload.  It is receiving
   100% load from 1 port, and 50% from another, and can only get 100%
   possible throughput, therefore having a frame loss rate of 33%
   (150%-50%/150%).

5.6 Forward Pressure and Maximum Forwarding Rate

5.6.1 Objective

   The Forward Pressure test overloads a DUT/SUT port and measures the
   output for forward pressure [2].  If the DUT/SUT transmits frames
   with an interframe gap less than 96 bits (section 4.2.3.2.2 [4]),
   then forward pressure is detected.

   The objective of the Maximum Forwarding Rate test is to measure the
   peak value of the Forwarding Rate when the Offered Load is varied
   between the throughput [1] and the Maximum Offered Load [2].

5.6.2 Setup Parameters

   The following parameters MUST be defined.  Each variable is
   configured with the following considerations.

      Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
      1280 and 1518 bytes, per RFC 2544 section 9 [3].  The four CRC
      bytes are included in the frame size specified.




Mandeville & Perser          Informational                     [Page 19]

RFC 2889          LAN Switch Benchmarking Methodology        August 2000


      Duplex mode - Half duplex or full duplex.

      Trial Duration - The recommended Trial Duration is 30 seconds.
      Trial duration SHOULD be adjustable between 1 and 300 seconds.

      Step Size - The minimum incremental resolution that the Iload will
      be incremented in frames per second.  The smaller the step size,
      the more accurate the measurement and the more iterations
      required.  As the Iload approaches the MOL, the minimum step size
      will increase because of gap resolution on the testing device.

5.6.3 Procedure

5.6.3.1 Maximum forwarding rate

   If the Throughput [1] and the MOL [2] are the same, then MFR [2] is
   equal to the MOL [2].

   This test MUST at a minimum be performed in a two-port configuration
   as described below.  Learning frames MUST be sent to allow the
   DUT/SUT to update its address tables properly.

   Test frames are transmitted to the first port (port 1) of the DUT/SUT
   at the Iload.  The FR [2] on the second port (port 2) of the DUT/SUT
   is measured.  The Iload is incremented for each Step Size to find the
   MFR.  The algorithm for the test is as follows:

    CONSTANT
      MOL = ... frames/sec; {Maximum Offered Load}
    VARIABLE
      MFR   := 0 frames/sec; {Maximum Forwarding Rate}
      ILOAD := starting throughput in frames/sec; {offered load}
      STEP  := ... frames/sec; {Step Size}
    BEGIN
      ILOAD := ILOAD - STEP;
      DO
      BEGIN
        ILOAD := ILOAD + STEP
        IF (ILOAD > MOL) THEN
        BEGIN
          ILOAD := MOL
        END
        AddressLearning; {Port 2 broadcasts with its source address}
        Transmit(ILOAD); {Port 1 sends frames to Port 2 at Offered load}
        IF (Port 2 Forwarding Rate > MFR) THEN
        BEGIN
           MFR := Port 2 Forwarding Rate; {A higher value than before}
        END



Mandeville & Perser          Informational                     [Page 20]

RFC 2889          LAN Switch Benchmarking Methodology        August 2000


    END
    WHILE (ILOAD < MOL); {ILOAD has reached the MOL value}
    DONE

5.6.3.2 Minimum Interframe Gap

   The Minimum Interframe gap test SHOULD, at a minimum, be performed in
   a two-port configuration as described below.  Learning frames MUST be
   sent to allow the DUT/SUT to update its address tables properly.

   Test frames SHOULD be transmitted to the first port (port 1) of the
   DUT/SUT with an interframe gap of 88 bits.  This will apply forward
   pressure to the DUT/SUT and overload it at a rate of one byte per
   frame.  The test frames MUST be constructed with a source address of
   port 1 and a destination address of port 2.

   The FR on the second port (port 2) of the DUT/SUT is measured.  The
   measured Forwarding Rate should not exceed the medium's maximum
   theoretical utilization (MOL).

5.6.4 Measurements

   Port 2 MUST categorize, then count the frames into one of two groups:

      1.) Received Frames: received frames MUST have the correct
          destination MAC address and SHOULD match a signature field.

      2.) Flood count [2].

   Any frame originating from the DUT/SUT MUST not be counted as a
   received frame.  Frames originating from the DUT/SUT MAY be counted
   as flooded frames or not counted at all.

5.6.5 Reporting format

   MFR MUST be reported as the highest forwarding rate of a DUT/SUT
   taken from an iterative set of forwarding rate measurements. The
   Iload applied to the device MUST also be cited.

   Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
   of frames per second that the device is observed to successfully
   transmit to the correct destination interface in response to a
   specified Oload. The Iload MUST be cited and the Oload MAY be
   recorded.

   If the FR exceeds the MOL during the Minimum Interframe gap test,
   this MUST be highlighted with the expression "Forward Pressure
   detected".



Mandeville & Perser          Informational                     [Page 21]

RFC 2889          LAN Switch Benchmarking Methodology        August 2000


5.7 Address Caching Capacity

5.7.1 Objective

   To determine the address caching capacity of a LAN switching device
   as defined in RFC 2285, section 3.8.1 [2].

5.7.2 Setup Parameters

   The following parameters MUST be defined.  Each variable is
   configured with the following considerations.

      Age Time - The maximum time that a DUT/SUT will keep a learned
      address in its forwarding table.

      Addresses Learning Rate - The rate at which new addresses are
      offered to the DUT/SUT to be learned.  The rate at which address
      learning frames are offered may have to be adjusted to be as low
      as 50 frames per second or even less, to guarantee successful
      learning.

      Initial Addresses - The initial number of addresses to start the
      test with.  The number MUST be between 1 and the maximum number
      supported by the implementation.

5.7.3 Procedure

   The aging time of the DUT/SUT MUST be known.  The aging time MUST be
   longer than the time necessary to produce frames at the specified
   rate.  If a low frame rate is used for the test, then it may be
   possible that sending a large amount of frames may actually take
   longer than the aging time.

   This test MUST at a minimum be performed in a three-port
   configuration described below.  The test MAY be expanded to fully
   utilized the DUT/SUT in increments of two or three ports.  An
   increment of two would include an additional Learning port and Test
   port.  An increment of three would include an additional Learning
   port, Test port, and Monitoring port.

   The Learning port (Lport) transmits learning frames to the DUT/SUT
   with varying source addresses and a fixed destination address
   corresponding to the address of the device connected to the Test port
   (Tport) of the DUT/SUT.  By receiving frames with varying source
   addresses, the DUT/SUT should learn these new addresses.  The source
   addresses MAY be in sequential order.





Mandeville & Perser          Informational                     [Page 22]

RFC 2889          LAN Switch Benchmarking Methodology        August 2000


   The Test port (Tport) of the DUT/SUT acts as the receiving port for
   the learning frames.  Test frames will be transmitted back to the
   addresses learned on the Learning port.  The algorithm for this is
   explained below.

   The Monitoring port (Mport) on the DUT/SUT acts as a monitoring port
   to listen for flooded or mis-forwarded frames.  If the test spans
   multiple broadcast domains (VLANs), each broadcast domain REQUIRES a
   Monitoring port.

   It is highly recommended that SNMP, Spanning Tree, and any other
   frames originating from the DUT/SUT be disabled when running this
   test.  If such protocols cannot be turned off, the flood count MUST
   be modified only to count test frame originating from Lport and MUST
   NOT count frames originating from the DUT/SUT.

   The algorithm for the test is as follows:

   CONSTANT
      AGE = ...;  {value greater that DUT aging time}
      MAX = ...;  {maximum address support by implementation}
    VARIABLE
      LOW  := 0;    {Highest passed valve}
      HIGH := MAX;  {Lowest failed value}
      N    := ...;  {user specified initial starting point}
    BEGIN
      DO
        BEGIN
        PAUSE(AGE);   {Age out any learned addresses}
          AddressLearning(TPort); {broadcast a frame with its source
                                  Address and broadcast destination}
          AddressLearning(LPort); {N frames with varying source addresses
                                  to Test Port}
        Transmit(TPort); {N frames with varying destination addresses
                           corresponding to Learning Port}
        IF (MPort receive frame != 0) OR
           (LPort receive frames < TPort transmit) THEN
          BEGIN  {Address Table of DUT/SUT was full}
            HIGH := N;
          END
        ELSE
          BEGIN  {Address Table of DUT/SUT was NOT full}
            LOW := N;
          END
        N := LOW + (HIGH - LOW)/2;
      END WHILE (HIGH - LOW >= 2);
    END {Value of N equals number of addresses supported by DUT/SUT}




Mandeville & Perser          Informational                     [Page 23]

RFC 2889          LAN Switch Benchmarking Methodology        August 2000


   Using a binary search approach, the test targets the exact number of
   addresses supported per port with consistent test iterations.  Due to
   the aging time of DUT/SUT address tables, each iteration may take
   some time during the waiting period for the addresses to clear.  If
   possible, configure the DUT/SUT for a low value for the aging time.

   Once the high and low values of N meet, then the threshold of address
   handling has been found.

5.7.4 Measurements

   Whether the offered addresses per port was successful forwarded
   without flooding.

5.7.5 Reporting format

   After the test is run, results for each iteration SHOULD be displayed
   in a table to include:

      The number of addresses used for each test iteration (varied).

      The intended load used for each test iteration (fixed).

      Number of test frames that were offered to Tport of the DUT/SUT.
      This SHOULD match the number of addresses used for the test
      iteration.  Test frames are the frames sent with varying
      destination addresses to confirm that the DUT/SUT has learned all
      of the addresses for each test iteration.

      The flood count on Tport during the test portion of each test.  If
      the number is non-zero, this is an indication of the DUT/SUT
      flooding a frame in which the destination address is not in the
      address table.

      The number of frames correctly forwarded to test Lport during the
      test portion of the test.  Received frames MUST have the correct
      destination MAC address and SHOULD match a signature field.  For a
      passing test iteration, this number should be equal to the number
      of frames transmitted by Tport.

      The flood count on Lport during the test portion of each test.  If
      the number is non-zero, this is an indication of the DUT/SUT
      flooding a frame in which the destination address is not in the
      address table.







Mandeville & Perser          Informational                     [Page 24]

RFC 2889          LAN Switch Benchmarking Methodology        August 2000


      The flood count on Mport.  If the value is not zero, then this
      indicates that for that test iteration, the DUT/SUT could not
      determine the proper destination port for that many frames.  In
      other words, the DUT/SUT flooded the frame to all ports since its
      address table was full.

5.8 Address Learning Rate

5.8.1 Objective