Radio Frequency (RF) Interface Management Information Base for MCNS/DOCSIS compliant RF interfaces
obsoleted by
- rfc-4546 — Radio Frequency (RF) Interface Management Information Base for Data over Cable Service Interface Specifications (DOCSIS) 2.0 Compliant RF Interfaces
Extracted elements (28)
docsIfCmRangingRespTimeout (TimeTicks) and docsIfCmtsInsertionInterval (TimeTicks) were obsoleted and replaced by docsIfCmRangingTimeout and docsIfCmtsInsertInterval (both TimeInterval) because the original SYNTAX type was incorrect for the intended semantics. New implementations must use the replacement objects.
docsIfQosProfileTable is maintained as a separate table rather than inlining service-class parameters into docsIfCmServiceTable/docsIfCmtsServiceTable, avoiding redundant storage when multiple service queues share the same class of service profile.
The MIB is divided into three groups (docsIfBaseObjects, docsIfCmObjects, docsIfCmtsObjects) to separate objects common to both CM and CMTS from device-specific objects, reducing implementation burden on devices that implement only one role.
At the CMTS, the downstream interface is output-only: all ifIn* counters MUST return zero. At the CM, the downstream interface is input-only: all ifOut* counters MUST return zero. The reverse applies for upstream interfaces. Implementations that conflate these roles will report incorrect interface statistics.
Telco Return systems (cable modem or CMTS with no upstream RF channel) are accommodated by the layering model without modification; upstream Telco Return channels are managed by PPP or modem MIBs, while the DOCSIS RF MIB only covers the downstream RF channel in such deployments.
The ifTestTable and ifRcvAddressTable from the Interfaces MIB are explicitly not supported by this MIB. Virtual circuits are also not applicable to the DOCSIS RF medium.
A translated SMIv1 MIB MUST be semantically equivalent to the SMIv2 original, except where objects are omitted because no translation is possible (e.g., Counter64). Loss of machine-readable information during translation is not considered a semantic change.
QoS profile parameters (priority, bandwidth limits, max TX burst, baseline privacy) MUST NOT be changed while the docsIfQosProfileEntry row is active and referenced by a service table entry.
The docsIfQosProfStatus object MUST NOT be changed from active while the row is referenced by any entry in docsIfCmServiceTable (CM) or docsIfCmtsServiceTable (CMTS), preventing deletion of in-use service class profiles.
The ifStackTable MUST be implemented to identify relationships among sub-interfaces, specifically to express the layering of the RF MAC interface on top of downstream and upstream channel interfaces.
docsIfCmMacTable extends ifEntry for CM MAC interfaces (ifType docsCableMaclayer(127)), exposing the CMTS MAC address (source of SYNC/MAP messages), capability bits (atmCells, concatenation), and ranging response timeout (docsIfCmRangingTimeout, TimeInterval).
docsIfCmServiceTable describes upstream service queues at the CM, indexed by ifIndex and Service ID (1–16383). Tracks mini-slots used in immediate (contention) and dedicated modes, transmission retries/failures, and bandwidth request retries/failures — all Counter32.
docsIfCmStatusTable provides CM-only operational counters: resets, lost downstream synchronizations, invalid MAP/UCD/ranging-response/registration-response message counts, T1–T4 timer expiry counts, and ranging-aborted counts. All are read-only Counter32 objects.
docsIfCmtsMacTable extends ifEntry for CMTS MAC interfaces, providing capabilities bits, configurable SYNC message interval (1–200 ms), UCD message interval (1–2000 ms), maximum simultaneous service IDs, and the broadcast station maintenance grant interval (docsIfCmtsInsertInterval, max 2 s).
docsIfCmtsMacToCmTable provides a MAC-address-keyed index into docsIfCmtsCmStatusTable, enabling fast CM lookup by MAC address without a full table scan.
docsIfCmtsModulationTable controls modulation profiles for upstream RF channels at the CMTS. Each row specifies an interval usage code and associated modulation parameters, allowing the CMTS operator to configure per-channel modulation profiles referenced by docsIfUpChannelModulationProfile.
docsIfCmtsStatusTable aggregates CMTS MAC-layer error counters: invalid range requests, aborted rangings, invalid/failed registration requests, invalid data requests, and T5 timeout count. One entry per MAC layer ifEntry.
docsIfDownstreamChannelTable describes active downstream channels for a CMTS and the received downstream channel for a CM. Fields include channel ID (0–255), center frequency (Hz), bandwidth (Hz), modulation (QAM64/QAM256), FEC interleaving depth, and power level (TenthdBmV). Indexed by ifIndex with ifType docsCableDownstream(128).
docsIfQosProfileTable defines service class profiles shared between CM and CMTS, comprising priority (0–7), max/guaranteed upstream bandwidth, max downstream bandwidth, max TX burst (mini-slots), and a baseline privacy flag. Entries may be created by management station or automatically from REG-REQ/TFTP option file.
docsIfSignalQualityTable monitors PHY signal quality: unerrored/corrected/uncorrectable codeword counters (Counter32), SNR in tenths of dB, microreflections in dBc (0–255), and equalization data (OCTET STRING). At CM it covers the downstream channel; at CMTS it covers upstream channels and may exclude contention intervals.
docsIfUpstreamChannelTable describes attached upstream channels with fields for channel ID, center frequency, bandwidth, modulation profile reference, mini-slot size (in 6.25 µs ticks), TX timing offset, and four backoff window parameters (ranging start/end, TX start/end) expressed as powers of 2 in range 0–16.
DOCS-IF-MIB is assigned OID { transmission 127 }. Three IANA ifType values are used: docsCableMaclayer(127) for the RF MAC layer, docsCableDownstream(128) for downstream interfaces, and docsCableUpstream(129) for upstream interfaces. These OID/ifType assignments are normative for all DOCSIS-compliant implementations.
Several objects in this MIB are read-write (e.g., downstream/upstream channel frequency, power, modulation, QoS profile parameters, and CMTS timing intervals). Unauthorized writes could disrupt RF channel operation or alter service-class enforcement; implementors should apply SNMPv3 authentication and access control (VACM) to restrict write access to these objects.
docsIfCmStatusValue tracks CM connectivity state through 13 states: other(1), notReady(2), notSynchronized(3), phySynchronized(4), usParametersAcquired(5), rangingComplete(6), ipComplete(7), todEstablished(8), securityEstablished(9), paramTransferComplete(10), registrationComplete(11), operational(12), accessDenied(13). Transitions follow the DOCSIS RF Interface Specification Chapter 7.2 registration flow.
docsIfCmStatusCode is an OCTET STRING encoding a CM status code defined in the DOCSIS RF Interface Specification: a single ASCII character indicating the error group followed by a two- or three-digit decimal number indicating the specific status condition.
docsIfUpChannelTxTimingOffset is a Unsigned32 encoding round-trip timing in units of (6.25 µs / 64), i.e., approximately 97.66 nanoseconds per unit. At the CM it reflects current round-trip time; at the CMTS it reflects the maximum seen, used to synchronize upstream transmissions.
TenthdB is a textual convention (Integer32) for signal-quality ratios normally expressed in dB. Units are tenths of a dB; for example, 5.1 dB is encoded as 51. Used in docsIfSigQSignalNoise.
TenthdBmV is a textual convention (Integer32) for RF power levels normally expressed in dBmV. Units are tenths of a dBmV; for example, 5.1 dBmV is encoded as 51. Used in docsIfDownChannelPower and docsIfCmStatusTxPower.