Definitions of Managed Objects for Monitoring and Controlling the UNI/NNI Multilink Frame Relay Function
updated by
- rfc-9141 — Updating References to the IETF FTP Service
Extracted elements (25)
mfrBundleIndex is kept separate from ifIndex because the manager must choose mfrBundleIndex during row creation while the agent must be free to choose ifIndex values. This follows the pattern of RFC 2494 and RFC 2863 and mirrors the ATM LAN-Emulation and IMA MIBs, which also use dual indices.
The mfrBundleIfIndexMappingTable exists to enable efficient lookup of mfrBundleIndex given an ifIndex, since the mfrBundleTable is indexed by mfrBundleIndex (not ifIndex) and a reverse mapping cannot otherwise be performed without a full table scan.
Bundles and bundle links must appear in the ifStackTable (RFC 2863). Each bundle link appears as a lower layer beneath its owner bundle; the bundle itself appears as a lower layer to a frame relay service or UNI. This layering is required for correct integration with the interfaces group.
The MFR bundle has a one-to-one correspondence with a DLCMI/UNI in the Frame Relay DTE MIB (RFC 2115) and a one-to-one relationship with the frame relay service logical port defined in RFC 1604. These relationships must be maintained for consistent cross-MIB management.
mfrBundleIfIndex must match an entry in the ifTable whose ifType is set to frf16MfrBundle(163). The MIB compliance statement makes all three groups (mfrMibBundleGroup, mfrMibBundleLinkGroup, mfrMibTrapGroup) mandatory.
Several objects (mfrBundleFragmentation, mfrBundleMaxFragSize, mfrBundleThreshold, mfrBundleMaxDiffDelay, mfrBundleSeqNumSize) have MIN-ACCESS read-only in the compliance statement, meaning write access is not required but the value in use must be reported.
The mfrBundleLinkRowStatus create operation must fail if no physical interface is associated with the bundle link. Additionally, the bundle identified by mfrBundleIndex must exist at the time of bundle link creation.
When a bundle is created via createAndGo(4) on mfrBundleRowStatus, the agent must create a new interface in the ifTable. The ifIndex chosen by the agent for this new interface is stored as mfrBundleIfIndex.
mfrBundleActivationClass controls when a bundle becomes active: ClassA requires at least one link up, ClassB requires all links up, ClassC requires a threshold number of links (mfrBundleThreshold) up, and ClassD is implementation-specific. Default is ClassA.
mfrBundleIfIndexMappingTable provides a reverse-lookup from ifIndex to mfrBundleIndex. It is indexed by ifIndex and contains a single column mfrBundleIfIndexMappingIndex giving the corresponding mfrBundleIndex.
mfrBundleLinkLoopbackSuspected counts the number of times a loopback has been suspected based on magic number detection as defined in FRF.16 section 4.3.7.
mfrBundleLinkTable provides configuration and monitoring for MFR bundle links, indexed by ifIndex. It tracks per-link state (MfrBundleLinkState), round-trip delay, control frame counters, timer expiration events, loopback detection events, unexpected sequence frames, and bundle name mismatch events.
mfrBundleLinkUnexpectedSequence counts data MFR frames discarded because the sequence number was less than (delayed) or equal to (duplicate) the expected value for a DLCI, implementing the duplicate/delayed frame detection logic from FRF.16 section 4.2.3.2.
mfrBundleMaxFragSize specifies the maximum fragment size in octets (range -1..8184). A value of -1 is returned by bundles that do not support fragmentation; zero is not a valid fragment size. Only meaningful when mfrBundleFragmentation is enabled.
mfrBundleNextIndex is a TestAndIncr scalar used to assist managers in selecting a unique mfrBundleIndex for row creation in mfrBundleTable and to avoid race conditions when multiple managers attempt simultaneous row creation.
mfrBundleResequencingErrors counts resequencing error events on a bundle; each event may correspond to multiple lost frames. One event is counted per gap detection regardless of how many frames were lost in that gap.
mfrBundleSeqNumSize selects between the standard FRF.12 12-bit sequence number (default) and the optional 24-bit sequence number, controlling the sequence space for fragment reordering across bundle links.
mfrBundleTable provides configuration and monitoring for MFR bundles, indexed by mfrBundleIndex. Key columns include mfrBundleFragmentation, mfrBundleTimerHello, mfrBundleTimerAck, mfrBundleCountMaxRetry, mfrBundleActivationClass, mfrBundleThreshold, mfrBundleMaxDiffDelay, mfrBundleSeqNumSize, and mfrBundleResequencingErrors.
mfrBundleTimerHello (default 10 seconds, range 1–180) and mfrBundleTimerAck (default 4 seconds, range 1–10) configure the FRF.16 hello and acknowledgment timers. mfrBundleCountMaxRetry (default 2, range 1–5) sets N_MAX_RETRY.
mfrMibTrapBundleLinkMismatch notification is sent when a bundle link mismatch is detected, reporting the near-end bundle name, far-end bundle name (previously known), near-end link name, far-end link name, and currently reported far-end bundle name. The mfrBundleLinkMismatch counter is incremented concurrently.
The MFR Bundle is a grouping of one or more physical links (bundle links) that operates as a logical interface emulating a single physical interface to the Q.922 data link layer. Each bundle appears as an interface in the ifTable with ifType frf16MfrBundle(163).
Read-write and read-create objects in this MIB can negatively affect network operations if SET operations are performed without proper access control. No managed objects contain sensitive information, but SNMPv3 with User-based Security Model (RFC 2574) and View-based Access Control Model (RFC 2575) is recommended to restrict GET/SET access to authorized principals.
SNMPv1 alone is not a secure environment. Even when the underlying network uses IPsec, SNMPv1 provides no control over which principals on the secure network may access or modify MIB objects. Operators must configure the SNMP entity to enforce access restrictions.
Bundle linkUp trap fires when ifOperStatus transitions from down to up, triggered when a sufficient number of links (per mfrBundleActivationClass and mfrBundleThreshold) reach operational up state. Bundle linkDown fires on the reverse transition.
MfrBundleLinkState textual convention defines 8 states for a bundle link as specified in FRF.16 Annex A: AddSent(1), AddRx(2), AddAckRx(3), Up(4), IdlePending(5), Idle(6), Down(7), DownIdle(8). Transitions drive linkUp and linkDown SNMP traps.