RFC 4319
Definitions of Managed Objects for High Bit-Rate DSL - 2nd generation (HDSL2) and Single-Pair High-Speed Digital Subscriber Line (SHDSL) Lines
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.
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 ....................................731. 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.
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
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 Objects2.2. 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.
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
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.
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
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
- 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.
<-- 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 Line2.6. 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
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.
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
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
encountered during span discovery, additional table entries are to be created using the default span configuration profile.
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