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RFC 4319

 Errata 
Proposed STD
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Definitions of Managed Objects for High Bit-Rate DSL - 2nd generation (HDSL2) and Single-Pair High-Speed Digital Subscriber Line (SHDSL) Lines

Part 1 of 3, p. 1 to 14
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Obsoletes:    3276


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Network Working Group                                           C. Sikes
Request for Comments: 4319                      Zhone Technologies, Inc.
Obsoletes: 3276                                                   B. Ray
Category: Standards Track                   PESA Switching Systems, Inc.
                                                                 R. Abbi
                                                             Alcatel USA
                                                           December 2005


                  Definitions of Managed Objects for
            High Bit-Rate DSL - 2nd generation (HDSL2) and
      Single-Pair High-Speed Digital Subscriber Line (SHDSL) Lines

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document defines a Management Information Base (MIB) module for
   use with network management protocols in the Internet community.  In
   particular, it describes objects used for managing High Bit-Rate
   Digital Subscriber Line (DSL) - 2nd generation (HDSL2) and
   Single-Pair High-Speed Digital Subscriber Line (SHDSL) interfaces.
   This document introduces extensions to several objects and textual
   conventions defined in HDSL2-SHDSL-Line MIB (RFC 3276).  This
   document obsoletes RFC 3276.

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Table of Contents

   1. The Internet-Standard Management Framework ......................2
   2. Overview ........................................................2
      2.1. Relationship to Other MIBs .................................3
           2.1.1. General IF-MIB Integration (RFC 2863) ...............3
           2.1.2. Usage of ifTable ....................................3
      2.2. IANA Considerations ........................................4
      2.3. Conventions Used in the MIB Module .........................5
           2.3.1. Naming Conventions ..................................5
           2.3.2. Textual Conventions .................................5
      2.4. Structure ..................................................7
      2.5. Line Topology ..............................................9
      2.6. Counters, Interval Buckets, and Thresholds ................10
      2.7. Profiles ..................................................11
      2.8. Notifications .............................................12
   3. Definitions ....................................................14
   4. Implementation Analysis ........................................66
   5. Security Considerations ........................................66
   6. Acknowledgements ...............................................71
   7. References .....................................................72
      7.1. Normative References ......................................72
      7.2. Informative References ....................................73

1.  The Internet-Standard Management Framework

   For a detailed overview of the documents that describe the current
   Internet-Standard Management Framework, please refer to Section 7 of
   RFC 3410 [RFC3410].

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  MIB objects are generally
   accessed through the Simple Network Management Protocol (SNMP).
   Objects in the MIB are defined using the mechanisms defined in the
   Structure of Management Information (SMI).  This memo specifies a MIB
   module that is compliant to the SMIv2, which is described in STD 58,
   RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
   [RFC2580].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Overview

   This document defines a Management Information Base (MIB) module for
   use with network management protocols in the Internet community for
   the purpose of managing HDSL2/SHDSL lines.

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   The MIB module described in RFC 3276 [RFC3276] describes objects used
   for managing High Bit-Rate DSL - 2nd generation (HDSL2) [T1E1.4] and
   Single-Pair High-Speed Digital Subscriber Line (SHDSL) interfaces
   [G.991.2].  These object descriptions are based upon the
   specifications for the HDSL2 and SHDSL Embedded Operations Channel
   (EOC), as defined in the American National Standards Institute (ANSI)
   T1E1.4/2000-006 [T1E1.4] and International Telecommunication Union
   (ITU) G.991.2 [G.991.2].

   This document obsoletes RFC 3276 [RFC3276], which supports G.shdsl in
   that the MIB module described herein supports G.shdsl.bis as
   described in the G.991.2 [G.991.2].  In addition, objects have been
   added to improve the management of SHDSL lines.

   The MIB module is located in the MIB tree under MIB 2 transmission,
   as discussed in the MIB-2 Integration (RFC 2863 [RFC2863]) section of
   this document.

2.1.  Relationship to Other MIBs

   This section outlines the relationship of this MIB module with other
   MIB modules described in RFCs.  Specifically, the IF-MIB, as
   presented in RFC 2863 [RFC2863], is discussed.

2.1.1.  General IF-MIB Integration (RFC 2863)

   The HDSL2/SHDSL line MIB specifies the detailed attributes of a data
   interface.  As such, it needs to integrate with RFC 2863 [RFC2863].
   The IANA has assigned the following ifTypes to HDSL2 and SHDSL:

      IANAifType ::= TEXTUAL-CONVENTION
          ...
      SYNTAX INTEGER {
          ...
          hdsl2 (168), -- High Bit-Rate DSL, 2nd generation
          shdsl (169), -- Multirate HDSL2
          ...
          }

   Note that the ifFixedLengthGroup from RFC 2863 [RFC2863] MUST be
   supported and that the ifRcvAddressGroup does not apply to this MIB
   module.

2.1.2.  Usage of ifTable

   The MIB branch identified by this ifType contains tables appropriate
   for this interface type.  Most such tables extend the ifEntry table
   and are indexed by ifIndex.  For interfaces in systems implementing

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   this MIB module, those table entries indexed by ifIndex MUST be
   persistent.

   The following attributes are part of the mandatory
   ifGeneralInformationGroup in RFC 2863 [RFC2863] and are not
   duplicated in the HDSL2/SHDSL line MIB.

   ===================================================================

      ifIndex                  Interface index.

      ifDescr                  See interfaces MIB [RFC2863].

      ifType                   hdsl2(168) or shdsl(169).

      ifSpeed                  Set as appropriate.
                               (This is fixed at 1552000 for HDSL2
                               lines)

      ifPhysAddress            This object MUST have an octet string
                               with zero length.

      ifAdminStatus            See interfaces MIB [RFC2863].

      ifOperStatus             See interfaces MIB [RFC2863].

      ifLastChange             See interfaces MIB [RFC2863].

      ifName                   See interfaces MIB [RFC2863].

      ifAlias                  See interfaces MIB [RFC2863].

      ifLinkUpDownTrapEnable   Default to enabled(1).

      ifHighSpeed              Set as appropriate.
                               (For HDSL2 lines, this is fixed at 2)

      ifConnectorPresent       Set as appropriate.

   ===================================================================
                     Figure 1: Use of ifTable Objects

2.2.  IANA Considerations

   The HDSL2-SHDSL-LINE-MIB module requires the allocation of a single
   object identifier for its MODULE-IDENTITY.  The IANA has allocated
   this object identifier in the transmission subtree (48), defined in
   the SNMPv2-SMI MIB module.

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   The assignment was in fact done when RFC 3276 was published, and this
   revision of the RFC does not require any new action from IANA.

2.3.  Conventions Used in the MIB Module

2.3.1.  Naming Conventions

   A.  xtuC refers to a central site terminal unit;
       H2TU-C for HDSL2, or STU-C for SHDSL.
   B.  xtuR refers to a remote site terminal unit;
       H2TU-R for HDSL2, or STU-R for SHDSL.
   C.  xtu refers to a terminal unit; either an xtuC or xtuR.
   D.  xru refer to a regenerator unit;
       H2RU for HDSL2, or SRU for SHDSL.
   E.  xU refers to any HDSL2/SHDSL unit; either an xtu or xru.
   F.  CRC is Cyclic Redundancy Check [G.991.2].
   G.  ES means Errored Second [G.991.2].
   J.  LOSW means Loss of Sync Word [G.991.2].
   I.  LOSWS means LOSW Seconds [G.991.2].
   J.  SES means Severely Errored Second [G.991.2].
   K.  SNR means Signal-to-Noise Ratio [G.991.2].
   L.  UAS means Unavailable Second [G.991.2].

2.3.2.  Textual Conventions

   The following textual conventions are defined to reflect the line
   topology in the MIB module (further discussed in the following
   section) and to define the behavior of the statistics to be
   maintained by an agent.

   o  Hdsl2ShdslUnitId:

      Attributes with this syntax uniquely identify each unit in an
      HDSL2/SHDSL span.  It mirrors the EOC addressing mechanism:

         xtuC(1)                - central office (CO) terminal unit
         xtuR(2)                - customer premises equipment (CPE)
                                  terminal unit
         xru1(3) .. xru8(10)    - regenerators, numbered from
                                  central office side

   o  Hdsl2ShdslUnitSide:

      Attributes with this syntax reference the two sides of a unit:

         networkSide(1)   - N in figure 2, below
         customerSide(2)  - C in figure 2, below

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   o  Hdsl2ShdslWirePair:

      Attributes with this syntax reference the wire pairs connecting
      the units:

         wirePair1(1)   - First pair for HDSL2/SHDSL.
         wirePair2(2)   - Optional second pair for SHDSL only.
         wirePair3(3)   - Optional third pair for SHDSL.bis only.
         wirePair4(4)   - Optional fourth pair for SHDSL.bis only.

   o  Hdsl2ShdslTransmissionModeType:

      Attributes with this syntax specify the regional setting for an
      SHDSL line.  Specified as a BITS construct, the two mode types
      are:

         region1   - ITU-T G.991.2 Annex A
         region2   - ITU-T G.991.2 Annex B

   o  Hdsl2ShdslPerfCurrDayCount:

      Attributes with this syntax define the behavior of the 1-day (24
      hour) gauges found in the MIB module.

   o  Hdsl2Shdsl1DayIntervalCount:

      Attributes with this syntax define the behavior of the 1-day (24
      hour) interval counters found in the MIB module.

   o  Hdsl2ShdslPerfTimeElapsed:

      Attributes with this syntax define the behavior of the elapsed
      time counters found in the MIB module.

   o  Hdsl2ShdslPerfIntervalThreshold:

      Attributes with this syntax define the behavior of the alarm
      thresholds found in the MIB module.

   o  Hdsl2ShdslClockReferenceType:

      Attributes with this syntax define the clock references for the
      HDSL2/SHDSL span.

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2.4.  Structure

   The MIB module is structured into the following MIB groups:

   o  Span Configuration Group:

      This group supports MIB objects for configuring parameters for the
      HDSL2/SHDSL span.  It contains the following table:

         - hdsl2ShdslSpanConfTable

   o  Span Status Group:

      This group supports MIB objects for retrieving span status
      information.  It contains the following table:

         - hdsl2ShdslSpanStatusTable

   o  Unit Inventory Group:

      This group supports MIB objects for retrieving unit inventory
      information about units in HDSL2/SHDSL lines via the EOC.  It
      contains the following table:

         - hdsl2ShdslInventoryTable

   o  Segment Endpoint Configuration Group:

      This group supports MIB objects for configuring parameters for the
      HDSL2/SHDSL segment endpoints.  It contains the following table:

         - hdsl2ShdslEndpointConfTable

   o  Segment Endpoint Current Status/Performance Group:

      This group supports MIB objects that provide the current status/
      performance information relating to segment endpoints.  It
      contains the following table:

         - hdsl2ShdslEndpointCurrTable

   o  Segment Endpoint 15-Minute Interval Status/Performance Group:

      This group supports MIB objects that provide historic status/
      performance information relating to segment endpoints in 15-minute
      intervals.  It contains the following table:

         - hdsl2Shdsl15MinIntervalTable

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   o  Segment Endpoint 1-Day Interval Status/Performance Group:

      This group supports MIB objects that provide historic status/
      performance information relating to segment endpoints in 1-day
      intervals.  It contains the following table:

         - hdsl2Shdsl1DayIntervalTable

   o  Maintenance Group:

      This group supports MIB objects for performing maintenance
      operations such as loopbacks for HDSL2/SHDSL lines.  It contains
      the following table(s):

         - hdsl2ShdslEndpointMaintTable
         - hdsl2ShdslUnitMaintTable

   o  Span Configuration Profile Group:

      This group supports MIB objects for defining configuration
      profiles for HDSL2/SHDSL spans.  It contains the following table:

         - hdsl2ShdslSpanConfProfileTable

   o  Segment Endpoint Alarm Configuration Profile Group:

      This group supports MIB objects for defining alarm configuration
      profiles for HDSL2/SHDSL segment endpoints.  It contains the
      following table:

         - hdsl2ShdslEndpointAlarmConfProfileTable

   o  Notifications Group:

      This group defines the notifications supported for HDSL2/SHDSL
      lines:

            - hdsl2ShdslLoopAttenCrossing
            - hdsl2ShdslSNRMarginCrossing
            - hdsl2ShdslPerfESThresh
            - hdsl2ShdslPerfSESThresh
            - hdsl2ShdslPerfCRCanomaliesThresh
            - hdsl2ShdslPerfLOSWSThresh
            - hdsl2ShdslPerfUASThresh
            - hdsl2ShdslSpanInvalidNumRepeaters
            - hdsl2ShdslLoopbackFailure
            - hdsl2ShdslpowerBackoff
            - hdsl2ShdsldeviceFault

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            - hdsl2ShdsldcContinuityFault
            - hdsl2ShdslconfigInitFailure
            - hdsl2ShdslprotocolInitFailure
            - hdsl2ShdslnoNeighborPresent
            - hdsl2ShdslLocalPowerLoss

   o  SHDSL Wire Pair Group:

      This group supports MIB objects that provide status of the SHDSL-
      specific wire pairs.

            - hdsl2ShdslEndpointCurrTipRingReversal
            - hdsl2ShdslEndpointCurrActivationState

   o  Payload Group:

      This group supports MIB objects for retrieving payload rates that
      exclude any framing overhead.

            - hdsl2ShdslStatusMaxAttainablePayloadRate
            - hdsl2ShdslStatusActualPayloadRate

2.5.  Line Topology

   An HDSL2/SHDSL line consists of a minimum of two units: xtuC (the
   central termination unit) and an xtuR (the remote termination unit).
   The line may optionally support up to 8 repeater/regenerator units
   (xru) as shown in the figure below.

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       <-- Network Side                            Customer Side -->

       |</////////////////// HDSL2/SHDSL Span ////////////////////>|

               <~~~>       <~~~> HDSL2/SHDSL Segments  <~~~>

       +-------+   +-------+   +-------+       +-------+   +-------+
       +       C=1=N       C=1=N       C=..1..=N       C=1=N       +
       | xtuC  |   |  xru1 |   |  xru2 |       |  xru8 |   |  xtuR |
       +       C=2=N       C=2=N       C=..2..=N       C=2=N       +
       +-------+   +-------+   +-------+       +-------+   +-------+

       Key:  <////> HDSL2/SHDSL span
             <~~~~> HDSL2/SHDSL segment
             =1=    HDSL2/SHDSL wire-pair-1
             =2=    SHDSL optional wire-pair-2 (Not applicable to HDSL2)
             C      Customer side segment endpoint (modem)
             N      Network side segment endpoint (modem)

            Figure 2: General Topology for an HDSL2/SHDSL Line

2.6.  Counters, Interval Buckets, and Thresholds

   For SNR Margin, Loop Attenuation, ES, SES, CRC anomalies, LOSW, and
   UAS, there are event counters, current 15-minute and 0 to 96 15-
   minute history bucket(s) of "interval-counters", as well as current
   and 0 to 30 previous 1-day interval-counter(s).  Each current 15-
   minute event bucket has an associated threshold notification.

   Unlike RFC 3593 [RFC3593] and RFC 2662 [RFC2662], there is no
   representation in the MIB module for invalid buckets.  In those cases
   where the data for an interval is suspect or known to be invalid, the
   agent MUST NOT report the interval.  If the current 15-minute event
   bucket is determined to be invalid, notifications based upon the
   value of the event bucket MUST NOT be generated.

   Not reporting an interval will result in holes in the associated
   table.  For example, the table hdsl2Shdsl15MinIntervalTable is
   indexed by { ifIndex, hdsl2ShdslInvIndex, hdsl2ShdslEndpointSide,
   hdsl2ShdslEndpointWirePair, hdsl2Shdsl15MinIntervalNumber}.  If
   interval 12 is determined to be invalid but intervals 11 and 13 are
   valid, a Get Next operation on the indices .1.1.1.1.11 would return
   indices .1.1.1.1.13.

   There is no requirement for an agent to ensure a fixed relationship
   between the start of a 15-minute interval and any wall clock;
   however, some implementations may align the 15-minute intervals with

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   quarter hours.  Likewise, an implementation may choose to align 1-day
   intervals with the start of a day.

   Counters are not reset when an xU is reinitialized, only when the
   agent is reset or reinitialized (or under specific request outside
   the scope of this MIB module).

2.7.  Profiles

   As a managed node can handle a large number of xUs (e.g., hundreds or
   perhaps thousands of lines), provisioning every parameter on every xU
   may become burdensome.  Moreover, most lines are provisioned
   identically with the same set of parameters.  To simplify the
   provisioning process, this MIB module makes use of profiles.  A
   profile is a set of parameters that can be shared by multiple lines
   using the same configuration.

   The following profiles are used in this MIB module:

   o  Span Configuration Profiles - Span configuration profiles contain
      parameters for configuring HDSL2/SHDSL spans.  They are defined in
      the hdsl2ShdslSpanConfProfileTable.  Since span configuration
      parameters are only applicable for SHDSL, the support for span
      configuration profiles is optional for HDSL2 interfaces.

      Note that the configuration of the span dictates the behavior for
      each individual segment endpoint in the span.  If a different
      configuration is provisioned for any given segment endpoint within
      the span, the new configuration for this segment endpoint will
      override the span configuration for this segment endpoint only.

   o  Segment Endpoint Alarm Configuration Profiles - These profiles
      contain parameters for configuring alarm thresholds for HDSL2/
      SHDSL segment endpoints.  These profiles are defined in the
      hdsl2ShdslEndpointAlarmConfProfileTable.

      The index value for this profile is a locally-unique
      administratively-assigned name for the profile having the textual
      convention 'SnmpAdminString' (RFC 3411 [RFC3411]).

   One or more lines may be configured to share parameters of a single
   profile (e.g., hdsl2ShdslEndpointAlarmConfProfile = 'silver') by
   setting its hdsl2ShdslEndpointAlarmConfProfile objects to the value
   of this profile.  If a change is made to the profile, all lines that
   refer to it will be reconfigured to the changed parameters.  Before a
   profile can be deleted or taken out of service, it must be first
   unreferenced from all associated lines.

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   Implementations MUST provide a default profile whose name is 'DEFVAL'
   for each profile type.  The values of the associated parameters will
   be vendor specific unless otherwise indicated in this document.
   Before a line's profiles have been set, these profiles will be
   automatically used by setting hdsl2ShdslEndpointAlarmConfProfile and
   hdsl2ShdslSpanConfProfile to 'DEFVAL' where appropriate.  This
   default profile name, 'DEFVAL', is considered reserved in the context
   of profiles defined in this MIB module.

   Profiles are created, assigned, and deleted dynamically using the
   profile name and profile row status in each of the four profile
   tables.

   Profile changes MUST take effect immediately.  These changes MAY
   result in a restart (hard reset or soft restart) of the units on the
   line.

2.8.  Notifications

   The ability to generate the SNMP notifications coldStart/warmStart
   (per [RFC3418]), which are per agent (e.g., per Digital Subscriber
   Line Access Multiplexer, or DSLAM, in such a device), and linkUp/
   linkDown (per [RFC2863]), which are per interface (i.e., HDSL2/SHDSL
   line) is required.

   A linkDown notification MAY be generated whenever any ES, SES, CRC
   anomaly, LOSW, or UAS event occurs.  The corresponding linkUp
   notification MAY be sent when all link failure conditions are
   cleared.

   The notifications defined in this MIB module are for initialization
   failure and for the threshold crossings associated with the following
   events: ES, SES, CRC anomaly, LOSW, and UAS.  Each threshold has its
   own enable/threshold value.  When that value is 0, the notification
   is disabled.

   The hdsl2ShdslEndpointCurrStatus is a bitmask representing all
   outstanding error conditions associated with a particular segment
   endpoint.  Note that since the status of remote endpoints is obtained
   via the EOC, this information may be unavailable for units that are
   unreachable via EOC during a line error condition.  Therefore, not
   all conditions may always be included in its current status.
   Notifications corresponding to the bit fields in this object are
   defined.

   Two alarm conditions, SNR Margin Alarm and Loop Attenuation Alarm,
   are organized in a manner slightly different from that implied in the
   EOC specifications.  In the MIB module, these alarm conditions are

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   tied to the two thresholds, hdsl2ShdslEndpointThreshSNRMargin and
   hdsl2ShdslEndpointThreshLoopAttenuation, found in the
   hdsl2ShdslEndpointAlarmConfProfileTable.  In the EOC, the alarm
   conditions associated with these thresholds are per unit.  In the MIB
   module, these alarm conditions are per endpoint.  For terminal units,
   this has no impact.  For repeaters, this implies an implementation
   variance where the agent in the terminal unit is responsible for
   detecting a threshold crossing.  As the reporting of a repeater
   detected alarm condition to the polling terminal unit occurs in the
   same EOC message as the reporting of the current SNR Margin and Loop
   Attenuation values, it is anticipated that this will have very little
   impact on agent implementation.

   A threshold notification occurs whenever the corresponding current
   15-minute interval error counter becomes equal to, or exceeds, the
   threshold value.  Only one notification SHOULD be sent per interval
   per interface.  Since the current 15-minute counter is reset to 0
   every 15 minutes, and if the condition persists, the notification may
   recur as often as every 15 minutes.  For example, to get a
   notification whenever a "loss of" event occurs (but at most once
   every 15 minutes), set the corresponding threshold to 1.  The agent
   will generate a notification when the event originally occurs.

   Notifications, other than the threshold notifications listed above,
   SHOULD be rate limited (throttled) such that there is at least a
   1-minute gap between the generation of consecutive notifications of
   the same event.  When notifications are rate limited, they are
   dropped and not queued for sending at a future time.  This is
   intended to be a general rate-limiting statement for notifications
   that have no explicit rate-limiting assertions in this document
   otherwise.

   Note that the Network Management System, or NMS, may receive a
   linkDown notification as well, if enabled (via ifLinkUpDownTrapEnable
   [RFC2863]).  At the beginning of the next 15-minute interval, the
   counter is reset.  When the first second goes by and the event
   occurs, the current interval bucket will be 1, which equals the
   threshold, and the notification will be sent again.

   An hdsl2ShdslSpanInvalidNumRepeaters notification may be generated
   following completion of the discovery phase if the number of
   repeaters discovered on the line differs from the number of repeaters
   specified in hdsl2ShdslSpanConfNumRepeaters.  For those conditions
   where the number of provisioned repeaters is greater than those
   encountered during span discovery, all table entries associated with
   the nonexistent repeaters are to be discarded.  For those conditions
   where the number of provisioned repeaters is less than those

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   encountered during span discovery, additional table entries are to be
   created using the default span configuration profile.



(page 14 continued on part 2)

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