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Versions: (draft-banks-bmwg-issu-meth) 00 01 02 RFC 7654

Benchmarking Working Group                                  Sarah Banks
Internet Draft                                           VSS Monitoring
Intended status: Informational                        Fernando Calabria
Expires: February 10, 2016                                Cisco Systems
                                                           Gery Czirjak
                                                          Ramdas Machat
                                                       Juniper Networks
                                                            Aug 8, 2015

                       ISSU Benchmarking Methodology


   Modern forwarding devices attempt to minimize any control and data
   plane disruptions while performing planned software changes, by
   implementing a technique commonly known as In Service Software
   Upgrade (ISSU) This document specifies a set of common methodologies
   and procedures designed to characterize the overall behavior of a
   Device Under Test (DUT), subject to an ISSU event.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   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-

   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

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on February 10, 2016.

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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document. Code Components extracted from this
   document must include Simplified BSD License text as described in
   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.

Table of Contents

   1. Introduction...................................................3
   2. Conventions used in this document..............................4
   3. Generic ISSU Process, phased approach..........................5
      3.1. Software Download.........................................5
      3.2. Software Staging..........................................6
      3.3. Upgrade Run...............................................6
      3.4. Upgrade Acceptance........................................7
   4. Test Methodology...............................................7
      4.1. Test Topology.............................................7
      4.2. Load Model................................................8
   5. ISSU Test Methodology..........................................9
      5.1. Pre-ISSU recommended verifications........................9
      5.2. Software Staging.........................................10

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      5.3. Upgrade Run..............................................11
      5.4. Post ISSU verification...................................11
      5.5. ISSU under negative stimuli..............................12
   6. ISSU Abort and Rollback.......................................12
   7. Final Report - Data Presentation - Analysis...................13
      7.1. Data collection considerations...........................15
   8. Security Considerations.......................................15
   9. IANA Considerations...........................................16
   10. References...................................................16
      10.1. Normative References....................................16
      10.2. Informative References..................................16
   11. Acknowledgments..............................................16

1. Introduction

        As required by most Service Provider (SP) network operators, ISSU
   functionality has been implemented by modern forwarding devices to
   upgrade or downgrade from one software version to another with a
   goal of eliminating the downtime of the router and/or the outage
   of service. However, it is noted that while most operators desire
   complete elimination of downtime, minimization of downtime and
   service degradation is often the expectation.

   The ISSU operation may apply in terms of an atomic version change of
   the entire system software or it may be applied in a more modular
   sense such as for a patch or maintenance upgrade. The procedure
   described herein may be used to verify either approach, as may be
   supported by the vendor hardware and software.

   In support of this document, the desired behavior for an ISSU
   operation can be summarized as follows:

   - The software is successfully migrated, from one version to a
   successive version or vice versa.

   - There are no control plane interruptions throughout the process.
  That is, the upgrade/downgrade could be accomplished while the device
  remains "in service". It is noted however, that most service
  providers will still undertake such actions in a maintenance window
  (even in redundant environments) to minimize any risk.

   - Interruptions to the forwarding plane are minimal to none.

   - The total time to accomplish the upgrade is minimized, again to
   reduce potential network outage exposure (e.g. an external failure

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   event might impact the network as it operates with reduced

   This document provides a set of procedures to characterize a given
   forwarding device's ISSU behavior quantitatively, from the
   perspective of meeting the above expectations.

   Different hardware configurations may be expected to be benchmarked,
   but a typical configuration for a forwarding device that supports
   ISSU consists of at least one pair of Routing Processors (RP's) that
   operate in a redundant fashion, and single or multiple Forwarding
   Engines (Line Cards) that may or may not be redundant, as well as
   fabric cards or other components as applicable. This does not
   preclude the possibility that a device in question can perform ISSU
   functions through the operation of independent process components,
   which may be upgraded without impact to the overall operation of the
   device. As an example, perhaps the software module involved in SNMP
   functions can be upgraded without impacting other operations.

   The concept of a multi-chassis deployment may also be characterized
   by the current set of proposed methodologies, but the implementation
   specific details (i.e. process placement and others) are beyond the
   scope of the current document.

   Since most modern forwarding devices, where ISSU would be
   applicable, do consist of redundant RP's and hardware-separated
   control plane and data plane functionality, this document will focus
   on methodologies which would be directly applicable to those
   platforms. It is anticipated that the concepts and approaches
   described herein may be readily extended to accommodate other device
   architectures as well.

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 [RFC 2119].

   In this document, these words will appear with that interpretation
   only when in ALL CAPS. Lower case uses of these words are not to be
   interpreted as carrying RFC-2119 significance.

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3. Generic ISSU Process, phased approach

   ISSU may be viewed as the behavior of a device when exposed to a
   planned change in its software functionality. This may mean changes
   to the core operating system, separate processes or daemons or even
   of firmware logic in programmable hardware devices (e.g. CPLD/FPGA).
   The goal of an ISSU implementation is to permit such actions with
   minimal or no disruption to the primary operation of the device in

   ISSU may be user initiated through direct interaction with the
   device or activated through some automated process on a management
   system or even on the device itself. For the purposes of this
   document, we will focus on the model where the ISSU action is
   initiated by direct user intervention.

   The ISSU process can be viewed as a series of different phases or
   activities, as defined below. For each of these phases, the test
   operator must record the outcome as well as any relevant
   observations (defined further in the present document). Note that, a
   given vendor implementation may or may not permit the abortion of
   the in-progress ISSU at particular stages. There may also be certain
   restrictions as to ISSU availability given certain functional
   configurations (for example, ISSU in the presence of Bidirectional
   Failure Detection (BFD) [RFC 5880] may not be supported). It is
   incumbent upon the test operator to ensure that the DUT is
   appropriately configured to provide the appropriate test
   environment. As with any properly orchestrated test effort, the test
   plan document should reflect these and other relevant details and
   should be written with close attention to the expected production-
   operating environment. The combined analysis of the results of each
   phase will characterize the overall ISSU process with the main goal
   of being able to identify and quantify any disruption in service
   (from the data and control plane perspective) allowing operators to
   plan their maintenance activities with greater precision.

3.1. Software Download

   In this first phase, the requested software package may be
   downloaded to the router and is typically stored onto a device. The
   downloading of software may be performed automatically by the device
   as part of the upgrade process, or it may be initiated separately.
   Such separation allows an administrator to download the new code
   inside or outside of a maintenance window; it is anticipated that
   downloading new code and saving it to disk on the router will not
   impact operations. In the case where the software can be downloaded
   outside of the actual upgrade process, the administrator should do

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   so; downloading software can skew timing results based on factors
   that are often not comparative in nature. Internal compatibility
   verification may be performed by the software running on the DUT, to
   verify the checksum of the files downloaded as well as any other
   pertinent checks. Depending upon vendor implementation, these
   mechanisms may extend to include verification that the downloaded
   module(s) meet a set of identified pre-requisites such as (but not
   limited to) hardware or firmware compatibility, minimum software
   requirements or even ensure that device is "authorized" to run the
   target software.
   Where such mechanisms are made available by the product, they
   should be verified, by the tester, with the perspective of avoiding
   operational issues in production. Verification should include both
   positive verification (ensuring that an ISSU action should be
   permitted) as well as negative tests (creation of scenarios where
   the verification mechanisms would report exceptions).

3.2. Software Staging

   In this second phase, the requested software package is loaded in
   the pertinent components of a given forwarding device (typically the
   RP in standby state).  Internal compatibility verification may be
   performed by the software running on the DUT, as part of the upgrade
   process itself, to verify the checksum of the files downloaded as
   well as any other pertinent checks. Depending upon vendor
   implementation, these mechanisms may extend to include verification
   that the downloaded module(s) meet a set of identified pre-
   requisites such as hardware or firmware compatibility or minimum
   software requirements. Where such mechanisms are made available by
   the product, they should be verified, by the tester (again with the
   perspective of avoiding operational issues in production). In this
   case, the execution of these checks is within scope of the upgrade
   time, and should be included in the testing results. Once the new
   software is downloaded to the pertinent components of the DUT, the
   upgrade begins and the DUT begins to prepare itself for upgrade.
   Depending on the vendor implementation, it is expected that
   redundant hardware pieces within the DUT are upgraded, including the
   backup or secondary RP.

3.3. Upgrade Run

   In this phase, a switchover of RPs may take place, where one RP is
   now upgraded with the new version of software. More importantly, the
   "Upgrade Run" phase is where the internal changes made to
   information and state stored on the router, on disk and in memory,
   are either migrated to the "new" version of code, or
   transformed/rebuilt to meet the standards of the new version of
   code, and pushed onto the appropriate pieces of hardware. It is
   within this phase that any outage(s) on the control or forwarding

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   plane may be expected to be observed. This is the critical phase of
   the ISSU, where the control plane should not be impacted and any
   interruptions to the forwarding plane should be minimal to none. For
   some implementations, the above two steps may be concatenated into
   one monolithic operation. In such case, the calculation of the
   respective ISSU time intervals may need to be adapted accordingly.

   If any control or data plane interruptions are observed within this
   stage, they should be recorded as part of the results document.

3.4. Upgrade Acceptance

   In this phase, the new version of software must be running in all
   the physical nodes of the logical forwarding device. (RP's and LC's
   as applicable). At this point, configuration control is returned to
   the operator and normal device operation i.e. outside of ISSU-
   oriented operation, is resumed.

4. Test Methodology

   As stated by [RFC 6815], the Test Topology Setup must be part
   of an ITE (Isolated Test Environment)

   The reporting of results must take into account the repeatability
   considerations from Section 4 of [RFC 2544].  It is RECOMMENDED to
   perform multiple trials and report average results. The results are
   reported in a simple statement including the measured frame loss and
   ISSU impact times.

4.1. Test Topology

   The hardware configuration of the DUT (Device Under test) should be
   identical to the one expected to be or currently deployed in
   production in order for the benchmark to have relevance. This would
   include the number of RP's, hardware version, memory and initial
   software release, any common chassis components, such as fabric
   hardware in the case of a fabric-switching platform and the specific
   LC's (version, memory, interfaces type, rate etc.)

   For the Control and Data plane, differing configuration approached
   may be utilized. The recommended approach relies on "mimicking" the
   existing production data and control plane information, in order to
   emulate all the necessary Layer1 through Layer3 communications and,
   if appropriate, the upper layer characteristics of the network, as
   well as end to end traffic/communication pairs. In other words,

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   design a representative load model of the production environment and
   deploy a collapsed topology utilizing test tools and/or external
   devices, where the DUT will be tested. Note that, the negative
   impact of ISSU operations is likely to impact scaled, dynamic
   topologies to a greater extent than simpler, static environments. As
   such, this methodology (based upon production configuration) is
   advised for most test scenarios.

   The second, more simplistic approach is to deploy an ITE
   "Isolated test Environment" in which end-points are "directly"
   connected to the DUT. In this manner, control plane information is
   kept to a minimum (only connected interfaces) and only a basic data
   plane only a basic data plane of sources and destinations is applied.
   If this methodology is selected, care must be taken to understand
   that the systemic behavior of the ITE may not be identical to that
   experienced by a device in a production network role. That is,
   control plane validation may be minimal to none with this
   methodology. Consequently, if this approach is chosen, comparison
   with at least one production configuration is recommended in order
   to understand the direct relevance and limitations of the
   test exercise.

4.2. Load Model

   In consideration of the defined test topology, a load model must be
   developed to exercise the DUT while the ISSU event is introduced.
   This applied load should be defined in such a manner as to provide a
   granular, repeatable verification of the ISSU impact on transit
   traffic. Sufficient traffic load (rate) should be applied to permit
   timing extrapolations at a minimum granularity of 100 milliseconds
   e.g. 100Mbps for a 10Gbps interface. The use of steady traffic
   streams rather than bursty loads is preferred to simplify analysis.

   The traffic should be patterned to provide a broad range of source
   and destination pairs, which resolve to a variety of FIB (forwarding
   information base) prefix lengths. If the production network
   environment includes multicast traffic or VPN's (L2, L3 or IPSec) it
   is critical to include these in the model.

   For mixed protocol environments (e.g. IPv4 and IPv6), frames should
   be distributed between the different protocols.  The distribution
   should approximate the network conditions of deployment.  In all
   cases, the details of the mixed protocol distribution must be
   included in the reporting.

   The feature, protocol timing and other relevant configurations
   should be matched to the expected production environment. Deviations
   from the production templates may be deemed necessary by the test
   operator (for example, certain features may not support ISSU or the
   test bed may not be able to accommodate such). However, the impact

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   of any such divergence should be clearly understood and the
   differences must be recorded in the results documentation. It is
   recommended that an NMS system be deployed, preferably similar to
   that utilized in production. This will allow for monitoring of the
   DUT while it is being tested both in terms of supporting the system
   resource impact analysis as well as from the perspective of
   detecting interference with non-transit (management) traffic as a
   result of the ISSU operation. Additionally, a DUT management session
   other than snmp-based, typical of usage in production, should be
   established to the DUT and monitored for any disruption. It is
   suggested that the actual test exercise be managed utilizing direct
   console access to the DUT, if at all possible to avoid the
   possibility that a network interruption impairs execution of the
   test exercise.

   All in all, the load model should attempt to simulate the production
   network environment to the greatest extent possible in order to
   maximize the applicability of the results generated.

5. ISSU Test Methodology

   As previously described, for the purposes of this test document, the
   ISSU process is divided into three main phases. The following
   methodology assumes that a suitable test topology has been
   constructed per section 4. A description of the methodology to be
   applied for each of the above phases follows:

5.1. Pre-ISSU recommended verifications

   1. Verify that enough hardware and software resources are available
   to complete the Load operation (enough disk space).

   2. Verify that the redundancy states between RPs and other nodes are
   as expected (e.g. redundancy on, RP's synchronized).

   3. Verify that the device, if running NSR (Non Stop Routing)
    capable routing protocols, is in a "ready" state; that is,
    that the sync between RPs is complete and the system is ready
    for failover, if necessary.

   4. Gather a configuration snapshot of the device and all of its
   applicable components.

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   5. Verify that the node is operating in a "steady" state (that is,
   no critical or maintenance function is being currently performed).

   6. Note any other operational characteristics that the tester may
   deem applicable to the specific implementation deployed.

5.2. Software Staging

   1. Establish all relevant protocol adjacencies and stabilize routing
   within the test topology. In particular, ensure that the scaled
   levels of the dynamic protocols are dimensioned as specified by the
   test topology plan.

   2. Clear relevant logs and interface counters to simplify analysis.
   If possible, set logging timestamps to a highly granular mode. If
   the topology includes management systems, ensure that the
   appropriate polling levels have been applied, sessions established
   and that the responses are per expectation.

   3. Apply the traffic loads as specified in the load model previously
   developed for this exercise.

   4. Document an operational baseline for the test bed with relevant
   data supporting the above steps (include all relevant load
   characteristics of interest in the topology e.g. routing load,
   traffic volumes, memory and CPU utilization)

   5. Note the start time (T0) and begin the code change process
   utilizing the appropriate mechanisms as expected to be used in
   production (e.g. active download with TFTP/FTP/SCP/etc. or direct
   install from local or external storage facility). In order to ensure
   that ISSU process timings are not skewed by the lack of a network
   wide synchronization source, the use of a network NTP source is

   6. Take note of any logging information and command line interface
   (CLI) prompts as needed (this detail will be vendor-specific)
   Respond to any DUT prompts in a timely manner.

   7. Monitor the DUT for the reload of secondary RP to the new
   software level. Once the secondary has stabilized on the new code,
   note the completion time. The duration of these steps will be
   recorded as "T1".

   8. Review system logs for any anomalies, check that relevant dynamic
   protocols have remained stable and note traffic loss if any. Verify

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   that deployed management systems have not identified any unexpected

5.3. Upgrade Run

   The following assumes that the software load step and upgrade step
   are discretely controllable. If not, maintain the afore-mentioned
   timer and monitor for completion of the ISSU as described below.

   1. Note the start time and initiate the actual upgrade procedure

   2. Monitor the operation of the secondary route processor while it
   initializes with the new software and assumes mastership of the DUT.
   At this point, pay particular attention to any indications of
   control plane disruption, traffic impact or other anomalous
   behavior. Once the DUT has converged upon the new code and returned
   to normal operation note the completion time and log the duration of
   this step as T2.

   3. Review the syslog data in the DUT and neighboring devices for any
   behavior, which would be disruptive in a production environment
   (linecard reloads, control plane flaps etc.). Examine the traffic
   generators for any indication of traffic loss over this interval. If
   the Test Set reported any traffic loss, note the number of frames
   lost as "TP_frames". If the test set also provides outage duration,
   note this as TP_time (alternatively this may be calculated as
   TP/offered pps (packets per second) load).

   4. Verify the DUT status observations as per any NMS systems
   managing the DUT and its neighboring devices. Document the observed
   CPU and memory statistics both during the ISSU upgrade event and
   after and ensure that memory and CPU have returned to an expected
   (previously baselined) level.

5.4. Post ISSU verification

   The following describes a set of post-ISSU verification tasks that
   are not directly part of the ISSU process, but are recommended for
   execution in order to validate a successful upgrade:

   1. Configuration delta analysis

     Examine the post-ISSU configurations to determine if any changes
     have occurred either through process error or due to differences
     in the implementation of the upgraded code.

   2. Exhaustive control plane analysis

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      Review the details of the RIB and FIB to assess whether any
      unexpected changes have been introduced in the forwarding paths.

   3. Verify that both RPs are up and that the redundancy mechanism for
   the control plane is enabled and fully synchronized.

   4. Verify that no control plane (protocol) events or flaps were

   5. Verify that no L1 and or L2 interface flaps were observed.

   6. Document the hitless operation or presence of an outage based
   upon the counter values provided by the Test Set.

5.5. ISSU under negative stimuli

   As an OPTIONAL Test Case, the operator may want to perform an ISSU
   test while the DUT is under stress by introducing route churn to any
   or all of the involved phases of the ISSU process.

   One approach relies on the operator to gather statistical
   information from the production environment and determine a specific
   number of routes to flap every 'fixed' or 'variable' interval.
   Alternatively, the operator may wish to simply pre-select a fixed
   number of prefixes to flap. As an example, an operator may decide to
   flap 1% of all the BGP routes every minute and restore them 1 minute
   afterwards. The tester may wish to apply this negative stimulus
   throughout the entire ISSU process or most importantly, during the
   run phase. It is important to ensure that these routes, which are
   introduced solely for stress proposes, must not overlap the ones
   (per the Load Model) specifically leveraged to calculate the TP
   (recorded outage). Furthermore, there should NOT be 'operator
   induced' control plane - protocol adjacency flaps for the duration
   of the test process as it may adversely affect the characterization
   of the entire test exercise. For example, triggering IGP adjacency
   events may force re-computation of underlying routing tables with
   attendant impact to the perceived ISSU timings. While not
   recommended, if such trigger events are desired by the test
   operator, care should be taken to avoid the introduction of
   unexpected anomalies within the test harness.

6. ISSU Abort and Rollback

   Where a vendor provides such support, the ISSU process could be
   aborted for any reason by the operator. However, the end results and
   behavior may depend on the specific phase where the process was
   aborted. While this is implementation dependent, as a general

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   recommendation, if the process is aborted during the "Software
   Download" or "Software Staging" phases, no impact to service or
   device functionality should be observed. In contrast, if the process
   is aborted during the "Upgrade Run" or "Upgrade Accept" phases, the
   system may reload and revert back to the previous software release
   and as such, this operation may be service affecting. Where vendor
   support is available, the abort/rollback functionality should be
   verified and the impact, if any, quantified generally following the
   procedures provided above.

7. Final Report - Data Presentation - Analysis

   All ISSU impact results are summarized in a simple statement
   describing the "ISSU Disruption Impact" including the measured frame
   loss and impact time, where impact time is defined as the time frame
   determined per the TP reported outage. These are considered to be
   the primary data points of interest.

   However, the entire ISSU operational impact should also be
   considered in support of planning for maintenance and as such
   additional reporting points are included.

   Software download/secondary update        T1

   Upgrade/Run                               T2

   ISSU Traffic Disruption (Frame Loss)      TP_frames

   ISSU Traffic Impact Time (milliseconds)   TP Time

   ISSU Housekeeping Interval                T

   (Time for both RP's up on new code and fully synced - Redundancy

   Total ISSU Maintenance Window            T4 (sum of T1+T2+T3)

   The results reporting must provide the following information:

   DUT hardware and software detail

   Test Topology definition and diagram (especially as related to the
   ISSU operation)

   Load Model description including protocol mixes and any divergence
   from the production environment

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   Time Results as per above

   Anomalies Observed during ISSU

   Anomalies Observed in post-ISSU analysis

   It is RECOMMENDED that the following parameters be reported
   as outlined below:

     Parameter                Units or Examples

     Traffic Load             Frames per second and bits per Second

     Disruption (average)     Frames

     Impact Time (average)    Milliseconds

     Number of trials         Integer count

     Protocols                IPv4, IPv6, MPLS, etc.

     Frame Size               Octets

     Port Media               Ethernet, Gigabit Ethernet (GbE),

                              Packet over SONET (POS), etc.

     Port Speed               10 Gbps, 1 Gbps, 100 Mbps, etc.

     Interface Encaps         Ethernet, Ethernet VLAN,

                              PPP, High-Level Data Link


     Number of Prefixes       Integer count

     flapped (ON Interval)    (Optional   # of prefixes  / Time

     flapped (OFF Interval)   (Optional   # of prefixes  / Time

     Document any configuration deltas, which are observed after the
     ISSU upgrade has taken effect. Note differences, which are driven
     by changes in the patch or release level as well as items, which

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     are aberrant changes due to software faults. In either of these
     cases, any unexpected behavioral changes should be analyzed and a
     determination made as to the impact of the change (be it
     functional variances or operational impacts to existing scripts or
     management mechanisms.

7.1. Data collection considerations

   When a DUT is undergoing an ISSU operation, it's worth noting that
   the DUT's data collection and reporting of data, such as counters,
   interface statistics, log messages, etc., may not be accurate. As
   such, one should NOT rely on the DUTs data collection methods, but
   rather, should use the test tools and equipment to collect data used
   for reporting in Section 7. Care and consideration should be paid in
   testing or adding new test cases, such that the desired data can be
   collected from the test tools themselves, or other external
   equipment, outside of the DUT itself.

8. Security Considerations

   All BMWG memos are limited to testing in a laboratory Isolated Test
   Environment (ITE), thus avoiding accidental interruption to
   production networks due to test activities.

   All benchmarking activities are limited to technology
   characterization using controlled stimuli in a laboratory
   environment with dedicated address space and the other constraints
   [RFC 2544]

   The benchmarking network topology will be an independent test setup
   and must NOT be connected to devices that may forward the test
   traffic into a production network or misroute traffic to the test
   management network.

   Further, benchmarking is performed on a "black-box" basis, relying
   solely on measurements observable external to the device under test/
   system under test (DUT/SUT).

   Special capabilities should NOT exist in the DUT/SUT specifically
   for benchmarking purposes.  Any implications for network security
   arising from the DUT/SUT should be identical in the lab and in
   production networks.

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9. IANA Considerations

   There are no IANA actions required by this memo.

10. References

10.1. Normative References

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

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

10.2. Informative References

   [RFC 5880]  D. Katz, D. Ward  "Bidirectional Forwarding Detection
               (BFD)" RFC 5880 , June 2010

   [RFC 6815]  S. Bradner, K. Dubray , J. McQuaid,  A. Morton
              ?Applicability Statement for RFC 2544:
               Use on Production Networks Considered Harmful?
               RFC 6815 , November 2012

11. Acknowledgments

   The authors wish to thank Vibin Thomas for his valued review and

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Authors' Addresses

   Sarah Banks
   VSS Monitoring
   Email: sbanks@encrypted.net

   Fernando Calabria
   Cisco Systems
   Email: fcalabri@cisco.com

   Gery Czirjak
   Juniper Networks
   Email: gczirjak@juniper.net

   Ramdas Machat
   Juniper Networks
   Email: rmachat@juniper.net

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