Integrated Services Management Information Base Guaranteed Service Extensions using SMIv2
Extracted elements (15)
The Backlog parameter captures implementation-specific deviations from a strict bit-by-bit service model; for example, packetized weighted fair queueing sets Backlog to the Maximum Packet Size. This separates idealized fluid-model analysis from real scheduler behavior.
The Slack term allows intermediate network elements to lower resource allocations for flows whose required end-to-end delay exceeds the fluid-model minimum. An RCSD scheduler can increase its local delay bound by s ≤ S (setting Sout = Sin - s), and a WFQ scheduler can reduce its rate reservation from Rin to Rout using equivalent transformation rules.
The MIB imports intSrv from INTEGRATED-SERVICES-MIB and ifIndex from IF-MIB, extending the base Integrated Services MIB with Guaranteed Service-specific interface attributes rather than defining a standalone MIB.
If a network element uses slack Si to reduce resources reserved for flow i, it MUST store Si and subsequently use the same slack Si without any further computation when reservation refreshes are received, to guarantee consistency in the reservation process.
Should the sum of Backlog or Delay terms across all elements exceed (2^32)-1, the end-to-end error or delay term MUST be reported as (2^32)-1 (saturating arithmetic).
Systems supporting the Guaranteed Service of the Integrated Services Architecture MUST implement the intSrvGuaranteedIfAttribGroup, which includes intSrvGuaranteedIfBacklog, intSrvGuaranteedIfDelay, intSrvGuaranteedIfSlack, and intSrvGuaranteedIfStatus.
intSrvGuaranteedIfBacklog is an INTEGER (0 to 0x0FFFFFFF) measured in bytes representing the data backlog caused by implementation deviation from strict bit-by-bit service (e.g., Maximum Packet Size for packetized WFQ). Individual element values range up to 2^28; the end-to-end sum saturates at (2^32)-1.
intSrvGuaranteedIfDelay is an INTEGER (0 to 0x0FFFFFFF) measured in microseconds representing the maximum packet transfer delay through a service element independent of bucket size. Individual values range up to 2^28 (over two minutes); the end-to-end aggregate saturates at (2^32)-1.
intSrvGuaranteedIfSlack is an INTEGER (0 to 0x0FFFFFFF) representing the slack Si that a network element uses to reduce resource reservations for a flow. It is computed as S = Dreq - (b/r + Ctot/r + Dtot) when the required end-to-end delay exceeds the maximum fluid flow delay.
intSrvGuaranteedIfStatus is a RowStatus object (read-create) that is 'valid' on interfaces configured for the Guaranteed Service, used to manage table row lifecycle.
intSrvGuaranteedIfTable is a table of Guaranteed Service interface attributes indexed by ifIndex. Each row (IntSrvGuaranteedIfEntry) contains Backlog, Delay, Slack, and Status objects representing per-interface Guaranteed Service parameters.
The INTEGRATED-SERVICES-GUARANTEED-MIB module (OID intSrv 5) defines managed objects for the Guaranteed Service of the Integrated Services Protocol, organized under intSrvGuaranteedObjects, intSrvGuaranteedNotifications, and intSrvGuaranteedConformance sub-trees.
Using an SNMP SET on this MIB results in an RSVP or Integrated Services reservation created under rules different from those applied when reservations are negotiated using RSVP directly. No additional security considerations beyond those imposed by SNMP itself are identified.
intSrvGuaranteedIfBacklog is encoded as INTEGER (0..'0FFFFFFF'h), units bytes, MAX-ACCESS read-create. Individual element range is 1 to 2^28; aggregate end-to-end sum capped at (2^32)-1.
intSrvGuaranteedIfDelay is encoded as INTEGER (0..'0FFFFFFF'h), units microseconds, MAX-ACCESS read-create. Per-element range 1 to 2^28; end-to-end sum capped at (2^32)-1.