Definitions of Managed Objects for ATM Management Version 8.0 using SMIv2
obsoleted by
- rfc-2515 — Definitions of Managed Objects for ATM Management
Extracted elements (30)
AAL5 management in an ATM switch uses a proprietary virtual internal interface (ifType=53) rather than exposing the UNI-facing interface directly, so that per-entity performance statistics can be reported via the standard ifTable without conflating them with ATM cell layer statistics.
An ATM network may be modeled as a single large distributed switch by hiding all internal connectivity, enabling Customer Network Management (CNM) without exposing internal topology. This justifies implementing both link and cross-connect groups in carrier networks.
The negotiated VPL/VCL establishment procedure (createAndWait, then active) was provided alongside one-shot (createAndGo) to enable detailed step-wise error checking, linking set errors to specific resource acquisition failures that are not distinguishable in a single-operation create.
VCCs (and VPCs) are defined as bi-directional, but uni-directional traffic is achieved by assigning zero bandwidth in one direction. Even the zero-bandwidth direction requires bandwidth for OAM cell flows.
For the subset of management information shared between the ILMI MIB (ATM Forum UNI specification) and this memo, identical semantics and syntax are retained even though different OBJECT IDENTIFIERs are used. Table 1 enumerates which functions are covered by each.
The ifPhysAddress for an ATM interface is the ATM address that would be used as the Called Party Address IE for connections terminating at or routed through this interface; for interfaces without signalling support, it is the address that would be used if signalling were supported, or a zero-length string if none exists.
The ILMI MIB lacks ATM address type, ATM administrative address, VPC/VCC administrative status, last change status, and all VCC AAL information; these gaps are filled by this MIB's groups 1, 4, and 6.
At an ATM UNI, atmInterfaceMaxVpcs and atmInterfaceConfVpcs are constrained to range from 0 to 256 only (not the full 0–4096 range allowed at NNI interfaces).
atmVplRowStatus (and the analogous VCL object) MUST NOT be set to active(1) unless atmVplReceiveTrafficDescrIndex and atmVplTransmitTrafficDescrIndex are present in the same row.
For ATM switches and networks, the MIB II sysServices object MUST have the value 2, reflecting ATM's role as a data link layer protocol.
If the neighbor system is manageable via SNMP and supports ifName, then atmInterfaceMyNeighborIfName MUST be identical to the ifName value of the lowest-level physical interface for that port on the neighbor.
The agent MUST deny a request to destroy a row in atmTrafficDescrParamTable (by setting atmTrafficDescrRowStatus to destroy(6)) if that row is still referenced by any entry in atmVplTable or atmVclTable.
The VPI value 0 MUST NOT be used for a VPL entry that is not associated with a VCL. The maximum VPI value for any VPL entry cannot exceed the value allowed by atmInterfaceMaxVpiBits.
Seven ATM traffic descriptor type OIDs are defined: atmNoTrafficDescriptor, atmNoClpNoScr, atmClpNoTaggingNoScr, atmClpTaggingNoScr, atmNoClpScr, atmClpNoTaggingScr, and atmClpTaggingScr, corresponding to ATM Forum UNI traffic descriptor types 1–7.
The AAL5 connection performance statistics group (group 6, atmAal5VccTable) tracks per-VCC AAL5 CPCS PDUs discarded due to CRC-32 errors, reassembly timeouts, and oversized SDUs for connections terminated at an AAL5 entity in a switch or host.
The atmInterfaceConfTable contains per-port ATM cell layer configuration, including maximum VPCs/VCCs, active VPI/VCI bits, ILMI VPI/VCI, address type, administrative address, and neighbor IP/interface name.
The atmInterfaceDs3PlcpTable provides DS3 PLCP performance counters (SEFSs, UASs) and alarm state (noAlarm, receivedFarEndAlarm, incomingLOF) for ATM interfaces using DS3 PLCP framing.
The atmInterfaceTCTable provides TC sublayer state for SONET/DS3 ATM interfaces, including an OCD event counter (triggered when 7 consecutive HEC-errored cells occur) and a TC alarm state (noAlarm or lcdFailure).
The atmTrafficDescrParamTable defines ATM traffic descriptors as rows indexed by atmTrafficDescrParamIndex, each specifying a descriptor type OID and up to five integer parameters (e.g., peak cell rate, sustained cell rate, burst size) plus a QoS class.
The atmVclTable models bi-directional Virtual Channel Links (VCLs) indexed by ifIndex, VPI, and VCI. Entries include admin/oper status, traffic descriptor indices, AAL type, AAL5 SDU sizes, encapsulation type, and row status.
The atmVpCrossConnectTable and atmVcCrossConnectTable manage VP and VC cross-connections in ATM switches and networks, identifying pairs of VPLs (or VCLs) and their combined operational/administrative status.
The atmVplTable models bi-directional Virtual Path Links (VPLs) indexed by ifIndex and VPI. Each entry carries admin/oper status, last change timestamp, receive and transmit traffic descriptor indices, a cross-connect identifier, and row status.
The ATM-MIB module is registered at OID { mib-2 37 }, establishing the root for all ATM managed objects defined in this document.
Several objects in this MIB (e.g., atmVplRowStatus, atmVclRowStatus, atmTrafficDescrParamTable entries) have MAX-ACCESS read-create, allowing authorized managers to create, modify, or destroy virtual links and traffic parameters. Unauthorized write access could disrupt ATM service; SNMPv2 administrative security mechanisms should be used to restrict such access.
DS3 PLCP alarm state transitions among noAlarm, receivedFarEndAlarm (Yellow Signal received), and incomingLOF (LOF failure declared). Transition from failure to noAlarm requires no defects for more than 10 seconds.
TC sublayer alarm transitions between noAlarm and lcdFailure (Loss of Cell Delineation). Recovery from lcdFailure requires 6 consecutive valid-HEC cells followed by approximately 10 seconds of acceptable signal.
VPL/VCL row creation follows two paths: negotiated establishment (createAndWait, configure traffic descriptors, set active) or one-shot (createAndGo with all parameters). Retirement is via destroy(6); the agent releases associated resources.
AAL5 CPCS layer entities are represented in ifTable with ifType=49. ifInErrors counts CRC-32, SAR timeout, and oversized SDU errors. ifSpeed and ifHighSpeed are set to 0; ifPhysAddress is zero-length.
ATM cell layer interfaces are represented in ifTable with ifType=37. ifInOctets and ifOutOctets count received/transmitted assigned cells multiplied by 53 (the ATM cell size). ifInErrors counts cells dropped due to uncorrectable HEC errors.
Proprietary virtual internal interfaces associated with AAL entities in an ATM switch use ifType=53. These pseudo-ATM interfaces link the AAL5 entity to the ATM switching fabric and are used for AAL5 performance management in switches.