Management Information Base for the Differentiated Services Architecture
Extracted elements (27)
diffServDscpMarkActTable uses the DSCP value as both the sole index and the sole data column; the OID of any instance fully conveys the action. This unusual design avoids a separate value column and allows the table to serve as an array of OBJECT-IDENTIFIER conventions.
RowPointer is used as the universal connector between functional data path elements rather than typed foreign keys, so that new element types defined in other MIB modules (proprietary or standards-track) can be integrated into a DiffServ data path without modifying this MIB. This provides open-ended extensibility analogous to class inheritance.
The Meter Table uses three RowPointers (succeedNext, failNext, specific) rather than a richer N-rate structure because of SNMP modeling constraints. Multi-rate meters such as trTCM are expressed by chaining multiple meter entries through the failNext link, with diffServTBParamType in the first entry indicating the overall algorithm.
The MIB separates structural elements (data path linkage tables) from parameter elements (parameterization tables) so that a single parameter block such as a token bucket specification can be configured once and reused across many interfaces. Reuse of structural elements is explicitly discouraged because it would share counters, losing per-path monitoring information.
The MIB is specified as SMIv2-compliant. An SMIv1-conformant translation is possible but objects using Counter64 syntax must be omitted as there is no SMIv1 equivalent, and some machine-readable SMIv2 information is converted to textual descriptions.
For algorithmic drop entries using Active Queue Management (randomDrop and similar), additional parameters via diffServRandomDropTable are REQUIRED; tail-drop and head-drop algorithms do not require the extra parameter table.
For multi-rate token bucket meters, rates in chained diffServMeterTable entries MUST be specified in monotonically increasing order (most-committed to most-excess), passing through diffServMeterFailNext from lower to higher rates.
If diffServClfrElementSpecific is zeroDotZero, the device is misconfigured and the classifier element MUST be operationally treated as if it were not present.
When a RowPointer is written and the row it points to does not exist, the SNMP SET MUST return an inconsistentValue error. When a RowStatus is set to 'destroy' but the usage counter is non-zero, the SET returns no error and the row is left intact; the agent removes the row only when the usage counter reaches zero.
diffServActionTable chains sequences of actions via diffServActionNext, terminating in zeroDotZero, a pointer to a queue, or another functional data path element. Successive actions such as count, mark, and drop are linked through this table.
diffServAlgDropTable identifies a packet-dropping algorithm (alwaysDrop, headDrop, tailDrop, or Active Queue Management) and counts drops. It references a diffServQEntry via diffServAlgDropQMeasure to determine current queue depth, and for AQM algorithms requires a diffServRandomDropEntry via diffServAlgDropSpecific.
diffServClfrElementTable defines classifier elements, each with a precedence value, a 'specific' RowPointer to the matching rule, and a 'next' RowPointer directing matched traffic to the next functional data path element. Multiple elements within a classifier are evaluated at each precedence level as if in parallel.
diffServCountActTable accumulates per-path packet and byte counters along with a discontinuity timestamp. It is intended for usage-based billing, statistical analysis, and policy behavior monitoring.
diffServDataPathTable provides a starting point for DiffServ processing, indexed by interface and direction (ingress/egress). Each entry contains a single RowPointer (diffServDataPathStart) pointing to the first functional data path element to apply.
diffServDscpMarkActTable is an unusual table where the index (the DSCP value to mark packets with) is both the sole column and is read-only; the OID of a diffServDscpMarkActDscp instance fully encodes the action.
diffServMaxRateTable caps the output rate of a queue or scheduler input. A multi-rate shaper requires multiple diffServMaxRateEntries, shaping traffic to the lowest specified rate that exceeds the arrival rate at any given time.
diffServMeterTable is a structural table with three RowPointers: 'succeedNext' for conforming traffic, 'failNext' for non-conforming traffic, and 'specific' pointing to the meter parameters. Multiple meter entries chained via failNext implement multi-rate meters such as trTCM.
diffServMinRateTable assigns a minimum service rate or priority to a queue or scheduler input. Rates may be expressed as absolute (diffServMinRateAbsolute) or relative as a fraction of ifSpeed (diffServMinRateRelative); the two are inter-related and changes to one may update the other.
diffServMultiFieldClfrTable defines the Multi-field Classifier parameter, matching on IP source/destination address prefix, IPv6 Flow ID, IP protocol, TCP/UDP/SCTP source and destination port ranges, and DSCP. A Behavior Aggregate classifier is a degenerate case specifying only the DSCP field.
diffServQTable models simple FIFO queues. Multiple upstream elements (e.g., diffServAlgDropNext pointers for AF11, AF12, AF13) may direct traffic to the same queue entry. Minimum and maximum service rates are associated with the queue via diffServMinRateTable and diffServMaxRateTable.
diffServRandomDropTable provides AQM parameters: minimum threshold (Qmin), maximum threshold (Qmax), maximum drop probability inverse (Pmax), exponentially weighted moving average coefficient (weight as numerator over 65536 denominator), and sampling rate. These correspond to the classic RED parameter set.
diffServSchedulerTable models scheduling elements that accept inputs from queues or preceding schedulers. The scheduling method is identified by an OBJECT-IDENTITY OID (diffServSchedulerMethod), allowing new scheduling algorithms to be defined in other MIBs.
diffServTBParamTable defines Token Bucket meter parameters including diffServTBParamType (algorithm OID), diffServTBParamRate, diffServTBParamBurstSize, and diffServTBParamInterval. Multi-rate meters list rates in monotonically increasing order from most-committed to most-excess.
The DIFFSERV-DSCP-TC module is assigned OID mib-2 96 (diffServDSCPTC). The DIFFSERV-MIB module is assigned OID mib-2 97 (diffServMib). Both are defined under the mib-2 subtree registered with IANA.
The DIFFSERV-MIB provides read-write access to objects that control traffic classification, metering, marking, dropping, and queuing. Unauthorized write access could allow an adversary to alter QoS policies, disrupt service guarantees, or redirect traffic, making SNMPv3 with authentication and privacy strongly advisable for any write-capable access.
The Dscp textual convention encodes a Differentiated Services Code Point as Integer32 in the range 0..63, displayed as a decimal integer. Used wherever a DSCP marks a traffic stream.
The DscpOrAny textual convention extends Dscp with the sentinel value -1 to indicate a wildcard ('any DSCP'). Encoded as Integer32 (-1 | 0..63) and used in classifier filter fields.