Definitions of Managed Objects for the Ethernet-like Interface Types
obsoleted by
- rfc-1398 — Definitions of Managed Objects for the Ethernet-Like Interface Types
Extracted elements (26)
Attributes already represented in MIB-II (RFC 1213) or the generic interface extensions MIB (RFC 1229) — such as octet counts, frame counts, promiscuous status, MAC address, and multicast information — are deliberately not duplicated in this MIB. The relationship between an ethernet-like interface and an ifIndex instance is one-to-one.
Some counters in the Statistics group may be difficult or impossible to implement due to chipset or driver limitations. The design explicitly permits undercount (value equals detections, not true occurrences, down to zero) rather than requiring perfect accuracy, but vendors are strongly encouraged to document conditions under which underestimation occurs.
dot3StatsOutOfRangeLengthFields (dot3StatsEntry 15) counts frames where the length field exceeds the maximum allowed LLC data size. This counter is NOT incremented in implementations that observe Ethernet encapsulation conventions, where the IEEE 802.3 length field is interpreted as the Ethernet Type field.
The testFullDuplexLoopBack test defined in RFC 1229 (ifExtnsTestTable) for ethernet-like interfaces can only be executed while the interface is offline. After test completion the MAC chip should be reinitialized for network operation but must remain offline.
Implementation of the Ethernet-like Collision Statistics group (dot3CollTable) is optional; it is appropriate for systems that have the necessary metering hardware.
Implementation of the Ethernet-like Statistics group (dot3StatsTable) is mandatory. Where counters are difficult or impossible to implement due to chipset or driver restrictions, implementors should apply best effort; the value must always equal the number actually detected, which is less than or equal to actual occurrences.
Implementation of the Generic Ethernet-like group (dot3Table) is mandatory for all systems that attach to an ethernet-like medium, including ethernet-csmacd(6), iso88023-csmacd(7), and starLan(11) interface types.
dot3ChipSets (dot3 8) provides a hierarchy of OBJECT IDENTIFIERs identifying specific 802.3 MAC hardware chipsets: AMD 7990/79900, Intel 82586/82596, Seeq 8003, National 8390/SONIC, and Fujitsu 86950. These OIDs are used as values for ifExtnsChipSet defined in RFC 1229.
dot3CollTable (dot3 5) is the optional Ethernet-like Collision Statistics group providing a per-interface collision histogram. Each entry, indexed by (dot3CollIndex, dot3CollCount), holds dot3CollFrequencies — a count of MAC frames accompanied by exactly dot3CollCount (1–16) collisions.
dot3InitializeMac (dot3Entry 2) is a read-write INTEGER with values initialized(1) or uninitialized(2). Any write to either value invokes the initializeMAC action: all MAC/PLS counters reset to zero, receive and transmit are enabled, promiscuous receive is disabled, and multicast reception is disabled.
dot3MacSubLayerStatus (dot3Entry 3) is a read-write INTEGER controlling the MAC sublayer operational state: enabled(1) starts normal transmit/receive from idle and resets the PLS; disabled(2) terminates transmit/receive after completing any in-progress operations.
dot3MulticastReceiveStatus (dot3Entry 4) is a read-write INTEGER controlling multicast frame reception. Actual multicast reception requires both dot3MulticastReceiveStatus and dot3MacSubLayerStatus to be enabled(1).
dot3StatsAlignmentErrors (dot3StatsEntry 2) counts received frames that are not an integral number of octets in length and do not pass the FCS check. Frames with multiple error conditions are counted exclusively per the error status presented to the LLC, per IEEE 802.3 conventions.
dot3StatsCarrierSenseErrors (dot3StatsEntry 11) counts times the carrier sense condition was lost or never asserted during a transmission attempt. The counter is incremented at most once per transmission attempt even if carrier sense fluctuates multiple times.
dot3StatsFCSErrors (dot3StatsEntry 3) counts received frames that are an integral number of octets in length but fail the FCS check (frameCheckError). Distinct from alignment errors; frames with multiple errors are counted by their primary error status.
dot3StatsInRangeLengthErrors (dot3StatsEntry 14) counts received frames whose length field falls between the minimum unpadded LLC data size and maximum LLC data size inclusive but does not match the actual number of LLC data octets received; also includes frames with length field below the minimum.
dot3StatsInternalMacReceiveErrors (dot3StatsEntry 16) counts receive failures due to internal MAC errors not already counted by dot3StatsFrameTooLongs, dot3StatsAlignmentErrors, dot3StatsFCSErrors, dot3StatsInRangeLengthErrors, or dot3StatsOutOfRangeLengthFields. Its precise meaning is implementation-specific.
dot3StatsInternalMacTransmitErrors (dot3StatsEntry 10) counts transmission failures due to internal MAC sublayer errors not already counted by dot3StatsLateCollisions, dot3StatsExcessiveCollisions, dot3StatsCarrierSenseErrors, or dot3StatsExcessiveDeferrals. Its precise meaning is implementation-specific.
dot3StatsLateCollisions (dot3StatsEntry 8) counts collisions detected later than 512 bit-times (51.2 microseconds on 10 Mbit/s) into a packet transmission. Late collisions are also counted in generic collision statistics.
dot3StatsSingleCollisionFrames (dot3StatsEntry 4) and dot3StatsMultipleCollisionFrames (dot3StatsEntry 5) count successfully transmitted frames inhibited by exactly one or more than one collision, respectively. A frame is counted in at most one of these two objects and is also counted in ifOutUcastPkts or ifOutNUcastPkts.
dot3StatsTable (dot3 2) is the Ethernet-like Statistics group, a mandatory table of per-interface error and collision counters. It includes 16 Counter objects covering alignment errors, FCS errors, collision types, carrier sense errors, frame size errors, and internal MAC errors.
dot3Table (dot3 1) is the Generic Ethernet-like group providing status information and control variables for ethernet-like interfaces, indexed by dot3Index which maps directly to ifIndex. Implementation is mandatory for all systems attached to an ethernet-like medium.
dot3TestTdr (dot3Tests 1, OID dot3 6 1) defines the Time-domain Reflectometry test for ethernet-like interfaces. On completion the result (10 MHz tick interval to collision) is stored in dot3TestTdrValue, and the OID of that instance is stored in ifExtnsTestResult.
dot3TestTdrValue (dot3Entry 6) is a read-only Gauge holding the number of 10 MHz ticks elapsed between the start of a TDR measurement and the collision that ended it. Value is 0 if no TDR test has been executed or the last value is unavailable.
dot3TxEnabled (dot3Entry 5) is a read-write INTEGER representing the transmitEnabled layer management state variable per IEEE 802.3 [9]. Its value is false(2) whenever dot3MacSubLayerStatus is disabled(2); any transmissions in progress are completed before transmission is inhibited.
Security issues are not discussed in this memo.