IEEE 802.5 MIB using SMIv2
Extracted elements (25)
dot5RingSpeed specifies the ring speed at next insertion rather than the current speed (given by ifSpeed), because a management station may want to pre-configure the speed for when the station next joins the ring. When set to unknown(1), the interface adopts the ring's actual speed at insertion time.
The dot5TimerTable has been designated obsolete in RFC 1748, but its definition is retained for backward compatibility. The timer values it contained are now considered implementation-specific and not necessary for interoperability at the management layer.
The setting of dot5Commands (open/close) and ifAdminStatus are interdependent: setting one affects the other. This bidirectional coupling was explicitly clarified in RFC 1748 to resolve ambiguity present in RFC 1231, ensuring consistent interface state management.
For functional addresses in the ifRcvAddressTable, only one entry is required per 802.5 interface: the entry for the address whose functional address bit is ANDed with the bitmask of all accepted functional addresses. Address format in ifRcvAddressAddress matches ifPhysAddress canonical order.
When used with the pre-RFC 1573 interfaces group, the relationship between an 802.5 interface and an RFC 1213 interface is one-to-one: the ifIndex value for an 802.5 interface directly identifies corresponding instances in this MIB. This MIB applies only to interfaces with ifType value iso88025-tokenRing(9).
If an interface's hardware maintains statistics in 16-bit counters, the agent MUST read the hardware counters frequently enough to prevent loss of significance in order to maintain the required 32-bit Counter32 values in software.
Systems having 802.5 interfaces MUST implement both the dot5Table and dot5StatsTable in addition to the ifTable defined in RFC 1213 and RFC 1573. These two groups are the mandatory conformance groups per dot5Compliance.
The dot5Compliance MODULE-COMPLIANCE statement requires that conforming SNMPv2 entities implement dot5StateGroup and dot5StatsGroup as mandatory groups. Write access to dot5ActMonParticipate and dot5Functional is explicitly optional (MIN-ACCESS read-only).
dot5ActMonParticipate is a read-write INTEGER (true(1)/false(2)) controlling whether the interface participates in active monitor selection. Changes do not take effect until the next Active Monitor election and possibly not until the interface is next opened. Write access is not required for conformance.
dot5Commands is a read-write INTEGER controlling interface ring membership: noop(1), open(2), reset(3), close(4). Setting open(2) corresponds to ifAdminStatus up(1); setting close(4) corresponds to ifAdminStatus down(2). When read, always returns noop(1).
dot5Functional is a read-write MacAddress object representing a bitmask of all Token Ring functional addresses for which the interface will accept frames. Write access is not required for conformance.
dot5LastBeaconSent is a read-only TimeStamp recording the value of sysUpTime at which the local system last transmitted a Beacon frame on the interface. This object was newly added in RFC 1748 (not present in RFC 1231).
dot5RingOpenStatus is a read-only INTEGER indicating the result of the station's most recent ring-entry attempt, with values: noOpen(1), badParam(2), lobeFailed(3), signalLoss(4), insertionTimeout(5), ringFailed(6), beaconing(7), duplicateMAC(8), requestFailed(9), removeReceived(10), open(11).
dot5RingSpeed is a read-write INTEGER specifying the ring speed at the next insertion: unknown(1), oneMegabit(2), fourMegabit(3), sixteenMegabit(4). This indicates the speed at next insertion, not the current operational speed (which is given by MIB-II's ifSpeed). Interfaces that do not support changing ring-speed may only be set to their current value.
dot5RingStatus is a read-only INTEGER (0..262143) representing a bitmask of currently active ring conditions including Ring Recovery (32), Single Station (64), Remove Received (256), Auto-Removal Error (1024), Lobe Wire Fault (2048), Transmit Beacon (4096), Soft Error (8192), Hard Error (16384), Signal Loss (32768), and no status/open not completed (131072).
dot5StatsACErrors counts frames where a station receives an AMP or SMP frame with A=C=0 followed immediately by another SMP frame with A=C=0 without an intervening AMP frame, indicating a station that cannot set AC bits properly.
dot5StatsLostFrameErrors is incremented when a transmitting station's TRR timer expires in strip mode — meaning the station did not receive the trailer of its own frame before the timer elapsed. This detects a class of ring failure distinct from other error counters.
dot5UpStream is a read-only MacAddress object containing the MAC address of the upstream neighbor station in the ring.
The dot5StatsTable defines 18 Counter32 error counters per interface: LineErrors, BurstErrors, ACErrors, AbortTransErrors, InternalErrors, LostFrameErrors, ReceiveCongestions, FrameCopiedErrors, TokenErrors, SoftErrors, HardErrors, SignalLoss, TransmitBeacons, Recoverys, LobeWires, Removes, Singles, and FreqErrors.
The TOKENRING-MIB defines three tables for IEEE 802.5 management: the 802.5 Interface Table (dot5Table) for state and parameters, the 802.5 Statistics Table (dot5StatsTable) for error counters, and the 802.5 Timer Table (dot5TimerTable, now obsolete). Each 802.5 interface has one entry in the Interface and Statistics tables.
Three chip set identifiers are defined under dot5ChipSets for backward compatibility with RFC 1229's ifExtnsChipSet: dot5ChipSetIBM16 (IBM 16/4 Mbs), dot5ChipSetTItms380 (TI TMS 380 4Mbs), and dot5ChipSetTItms380c16 (TI TMS 380C16 16/4 Mbs). These are retained for backward compatibility only, as RFC 1573 obsoletes ifExtnsChipSet.
Two interface tests are defined via OBJECT-IDENTITY under dot5Tests: dot5TestInsertFunc (tests the insert ring logic by actually inserting the station into the network) and dot5TestFullDuplexLoopBack (tests the memory-through-chipset-back-to-memory path). Implementation of these tests is not required.
The RFC explicitly states that security issues are not discussed in this memo. No access controls, authentication, or authorization mechanisms are defined for the MIB objects, some of which (dot5Commands, dot5RingSpeed, dot5ActMonParticipate, dot5Functional) have read-write access and could disrupt ring operation if misused.
dot5RingState captures the interface's state with respect to ring membership: opened(1), closed(2), opening(3), closing(4), openFailure(5), ringFailure(6). Transitions are triggered by writing dot5Commands (open/close/reset) and by ring-level error conditions.
All MAC addresses in this MIB use the MacAddress textual convention in IEEE 802.1a 'canonical' order (least-significant-bit first), even though 802.5 transmits MAC addresses most-significant-bit first. ifPhysAddress is a 6-octet string with the Group Bit as the low-order bit (0x01) of the first octet. 16-bit addresses are represented by padding the upper 4 octets with zeros.