Definitions of Managed Objects for IEEE 802.12 Repeater Devices
Extracted elements (30)
For large octet counters (readable, unreadable, high-priority, normal-priority octets), the MIB provides both a 32-bit Counter32 with a paired rollover Counter32 and a 64-bit Counter64. The dual mechanism supports SNMPv1, which lacks 64-bit counters, though retrieval of the two 32-bit counters in the same PDU is not guaranteed to be atomic.
Port grouping within a repeater is recommended but optional. An implementor may place all ports in a single group or use groups to mirror field-replaceable units. Groups and ports may be sparsely numbered, and the numbering method is implementation-specific.
Several IEEE 802.12 managed objects were deliberately omitted: aGroupMap and aPortMap (derivable via GetNext sweeps), aRepeaterGroupCapacity (ambiguous semantics in chassis/stackable implementations), aRepeaterHealthData/Text (implementation-specific, non-interoperable), and aMediaType (deferred to a future 802.12 PMD MIB).
The MIB counters are defined to be identical to those in IEEE Standard 802.12-1995 so that the same hardware instrumentation can satisfy both the IEEE and IETF management standards without duplicating counter logic.
IEEE 802.12 uses the Demand Priority Access Method (DPAM), not 802.3 CSMA/CD or 802.5 token ring media access. Although 802.12 can carry 802.3 or 802.5 frame formats, it is incompatible with the 802.3 Repeater MIB's media-access-specific objects; only the topology-mapping OBJECT-GROUP (snmpRptrGrpRptrAddrSearch) from that MIB is encouraged for reuse.
The MIB-II 'interfaces' group has NO specific relationship to 802.12 repeater ports. The interfaces group applies only to the network interface(s) over which management traffic flows; repeater ports are physical-layer entities and are not represented as MIB-II interfaces.
vgRptrPortPriorityEnable has no effect on cascade ports or ports connected to cascaded repeaters; in both cases the port behaves as if the value is always true(1). The object only affects localInternal or localExternal ports connected to end nodes.
A port that is disabled (vgRptrPortAdminStatus = disabled) when power is lost or a reset is exerted shall remain disabled when normal operation resumes. The value of vgRptrPortAdminStatus should be preserved across repeater resets and power failures.
All MAC address representations in this MIB are in canonical (least-significant-bit-first) order as defined by 802.1a, even when the repeater operates in token ring framing mode (which transmits MSB-first on the wire).
Link training requires 24 consecutive error-free training frames to be exchanged before vgRptrPortOperStatus transitions to active(1). This requirement, combined with the training frame length (594–675 octets), ensures marginal links will not complete training.
The agent MUST reject a SET of vgRptrPortAllowedTrainType if the requested value includes no capabilities supported by the port hardware, ensuring that the intersection of allowed and supported training configurations is non-empty.
The SNMP response to a vgRptrInfoReset SET must be transmitted before or concurrently with the reset taking effect; the agent may delay the reset for this purpose but must not suppress the response.
vgRptrPortDesiredFramingType and other persistent configuration objects (vgRptrGroupCablesBundled, vgRptrPortAllowedTrainType, vgRptrPortPriorityEnable) should be preserved across repeater resets and power failures.
The DOT12-RPTR-MIB MODULE-IDENTITY is assigned OID mib-2.53 (1.3.6.1.2.1.53). The MIB is organized into vgRptrBasic (repeater, group, port tables), vgRptrMonitor (repeater and port statistics), and vgRptrAddrTracking (MAC address tracking) subtrees under vgRptrObjects.
vgRptrBasicGroupTable (OID mib-2.53.1.1.2) contains per-group entries with vendor OID, operational status (other/operational/malfunctioning/notPresent/underTest/resetInProgress), port capacity, and the cablesBundled flag that controls store-and-forward behavior for broadcast/multicast frames.
vgRptrBasicPortTable (OID mib-2.53.1.1.3) is indexed by {vgRptrGroupIndex, vgRptrPortIndex} and holds port type (cascadeExternal/cascadeInternal/localExternal/localInternal), admin/oper status, supported promisc/cascade modes, allowed training type, last training config, training result, priority enable, and repeater mapping.
vgRptrInfoLastChange (TimeStamp) records the sysUpTime of the most recent significant event for a repeater: agent restart, repeater creation, vgRptrInfoOperStatus change, port membership change, or counter discontinuity. Management stations should use this object to detect counter discontinuities in the associated monitor tables.
vgRptrInfoReset (read-write) causes the repeater to transition to its initial state per IEEE 802.12 clause 12. The agent may delay the reset to allow the SNMP response to be transmitted first; the response MUST be transmitted. The reset does not clear management counters or vgRptrPortAdminStatus values.
vgRptrInfoTable (OID mib-2.53.1.1.1) is a table of per-repeater information indexed by vgRptrInfoIndex, containing MAC address, current/desired/capability framing type, training version, operational status, reset control, and last-change timestamp.
vgRptrMonitorTable provides per-repeater aggregate counters: vgRptrMonTotalReadableFrames (Counter32), vgRptrMonTotalReadableOctets (Counter32) with rollover counter, vgRptrMonHCTotalReadableOctets (Counter64), and vgRptrMonTotalErrors (Counter32). Counter discontinuities are flagged via vgRptrInfoLastChange.
vgRptrMonPortTable provides per-port counters including readable frames/octets, unreadable octets, high-priority frames/octets, normal-priority frames/octets, broadcast frames, multicast frames, null-addressed frames, IPM frames, oversize frames, data error frames, priority promotions, and transitions into training. Each counter is available as Counter32 plus rollover and as Counter64.
vgRptrPortAllowedTrainType is an explicit security object (read-write) that restricts which device types may train on a port: allowEndNodesOnly, allowPromiscuousEndNodes, allowEndNodesOrRepeaters, or allowAnything. The effective policy is the intersection of this object and hardware capability reported by vgRptrPortSupportedPromiscMode/CascadeMode.
Several MIB objects are read-write and can disrupt network operation if set by unauthorized parties: vgRptrInfoReset (triggers repeater reset), vgRptrPortAdminStatus (disables ports), vgRptrPortAllowedTrainType (changes access policy), and vgRptrGroupCablesBundled (alters forwarding behavior). Implementors should apply appropriate community string or access-control protection.
vgRptrPortAllowedTrainType is the primary access-control mechanism, allowing a network manager to restrict each port to specific device types (end nodes only, promiscuous end nodes, repeaters, or any combination). The N-bit in the allowed configuration field during training can explicitly deny access due to security restrictions.
vgRptrPortOperStatus defines three states: inactive(2) during initialization or link warning; training(3) when Training_Up is received on a local port or Training_Down on a cascade port; active(1) after 24 consecutive good FCS packets are exchanged and configuration bits are acceptable. A disabled port always reports inactive(2).
IEEE 802.12 training frames consist of: DA (6 octets), SA (6 octets), Req Config (2 octets), Allow Config (2 octets), Data (594–675 octets), and FCS (4 octets). They are used exclusively during link initialization and are always sent with a null destination address.
The allowed configuration field (2 octets) encodes: vvv (version), D (duplicate address detected), C (configuration incompatible), N (access denied by security), FF (granted frame type), PP (granted address mode), and R (granted device type). The slave device sets this field to all zeros in its training request.
The requested configuration field (2 octets) encodes: vvv (3-bit 802.12 training version, current=100b), reserved bits, FF (2-bit frame type: 00=88023, 01=88025, 11=either), PP (2-bit address mode: 00=single, 01=promiscuous), and R (1-bit: 0=end node, 1=repeater).
vgRptrPortLastTrainConfig is a 16-bit OCTET STRING (SIZE 2) holding the requested configuration field from the most recent error-free training request (local ports) or the allowed configuration field from the most recent training response (cascade ports).
vgRptrPortTrainingResult is an 18-bit OCTET STRING (SIZE 3): the first octet holds 6 reserved bits plus V (Valid: at least one error-free training frame received) and G (LinkGood: 24 consecutive error-free training packets exchanged); the second and third octets hold the 16-bit allowed configuration field.