MPLS Transport Profile Linear Protection MIB
Extracted elements (25)
SNMP SET is no longer recommended for configuring MPLS networks (per RFC 3812), but certain objects are specified with MAX-ACCESS read-write or read-create to maintain consistency with the base tables in RFC 3812 and RFC 7697 that this MIB is designed to work alongside.
The mplsLpsMeConfigTable extends mplsOamIdMeTable (RFC 7697) via sparse augmentation, sharing the same index triple. Each time an entry is created in mplsOamIdMeTable for an LER supporting MPLS-TP linear protection, a row is automatically created in mplsLpsMeConfigTable.
If an ME participates in protection switching, an entry in the mplsLpsMeConfigTable MUST be created with objects indicating which protection domain it belongs to and whether it is for the working or protection path.
Implementations claiming compliance to SNMPv3 MUST include full support for authentication and privacy via the User-based Security Model (USM) with the AES cipher algorithm. Deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED; instead SNMPv3 with cryptographic security is RECOMMENDED.
Implementations SHOULD provide the security features described by the SNMPv3 framework, and MAY also provide support for the Transport Security Model (TSM) in combination with SSH or TLS/DTLS secure transports.
Two Maintenance Entities (MEs) MUST be defined for each protection domain: one for the working path and one for the protection path, resulting in two entries in mplsLpsMeConfigTable associated with one entry in mplsLpsConfigTable.
When changing mplsLpsConfigMode during operation, the protection processes in both LERs MUST be restarted with the same new value.
mplsLpsConfigContinualTxInterval (1–20 seconds, default 5) sets the interval for sending continual PSC packets based on current state. mplsLpsConfigRapidTxInterval (1000–20000 microseconds, default 3300) sets the interval for sending PSC packets when there is a local state change.
mplsLpsStatusFopNoResponses counts protocol failure occurrences where no PSC message with the matching Path value is received within 50 ms of a traffic switchover request. mplsLpsStatusFopTimeouts counts occurrences where no PSC message is received during at least 3.5 times the long PSC message interval with no defect on the protection path.
Seven SNMP notifications are defined: mplsLpsEventSwitchover (active path switchover), mplsLpsEventRevertiveMismatch, mplsLpsEventProtecTypeMismatch, mplsLpsEventCapabilitiesMismatch, mplsLpsEventPathConfigMismatch, mplsLpsEventFopNoResponse (no response within 50 ms), and mplsLpsEventFopTimeout (no PSC message for ≥3.5× long PSC message interval).
Signal Degrade (SD) detection uses packet loss measurement per second. The SD defect is detected after mplsLpsConfigSdBadSeconds (2–10, default 10) consecutive Bad Seconds where packet loss ratio exceeds mplsLpsConfigSdThreshold (0–100%, default 30%), and cleared after mplsLpsConfigSdGoodSeconds (2–10, default 10) consecutive Good Seconds.
The MPLS-LPS-MIB module defines four tables: mplsLpsConfigTable (protection domain configuration), mplsLpsStatusTable (domain status, AUGMENTS ConfigTable), mplsLpsMeConfigTable (ME-to-domain associations), and mplsLpsMeStatusTable (ME protection status, AUGMENTS MeConfigTable). The module is rooted under mplsStdMIB at OID decimal 22.
The MplsLpsCommand textual convention allows operator commands over a protection domain: noCmd(1), clear(2), lockoutOfProtection(3), forcedSwitch(4), manualSwitchToWork(5), manualSwitchToProtect(6), exercise(7), freeze(8), clearfreeze(9). The exercise, freeze, and clearfreeze commands are not applicable to PSC mode.
The mplsLpsConfigHoldOff object (0–100 deciseconds, default 0, in 100 ms intervals) delays declaration of SF/SD requests to the protection switching logic after defect detection. It applies only to defects on the active path; defects on the standby path do not start the hold-off timer.
The mplsLpsConfigMode object selects PSC mode (RFC 6378) or APS mode (RFC 7271). Changing this value during operation causes the LER to generate PSC packets with a new Capabilities TLV, resulting in mplsLpsEventCapabilitiesMismatch notifications at both LERs. Both LERs MUST be restarted with the same new value when changing mode.
The mplsLpsConfigTable configures MPLS-TP linear protection domains, indexed by mplsLpsConfigDomainIndex. Key objects include mplsLpsConfigMode (psc/aps), mplsLpsConfigProtectionType (1+1 unidirectional, 1:1 bidirectional, 1+1 bidirectional), mplsLpsConfigRevertive (revertive/nonrevertive), timer parameters, and mplsLpsConfigCommand for operator actions.
The mplsLpsConfigWaitToRestore object sets the WTR timer (5–12 minutes, default 5) in 1-minute intervals. It delays reversion from the protection path back to the working path after failure recovery in revertive mode.
The MplsLpsFpathPath textual convention encodes the FPath and Path fields of PSC control packets as a 2-octet OCTET STRING (DISPLAY-HINT '1x:'). FPath (first octet) indicates whether the anomaly is on the working (1) or protection (0) path; Path (second octet) indicates whether the protection path is transporting user data (1) or not (0). Values 2-255 are reserved for future extensions.
The mplsLpsMeConfigTable associates Maintenance Entities with protection domains, using the same index triple (mplsOamIdMegIndex, mplsOamIdMeIndex, mplsOamIdMeMpIndex) as mplsOamIdMeTable. Each entry specifies mplsLpsMeConfigDomain (which protection domain) and mplsLpsMeConfigPath (working or protection).
The mplsLpsMeStatusTable (AUGMENTS mplsLpsMeConfigTable) provides per-ME status: mplsLpsMeStatusCurrent (BITS: localSelectTraffic, localSD, localSF), mplsLpsMeStatusSignalDegrades (Counter32), mplsLpsMeStatusSignalFailures (Counter32), mplsLpsMeStatusSwitchovers (Counter32), mplsLpsMeStatusLastSwitchover (TimeStamp), and mplsLpsMeStatusSwitchoverSeconds (cumulative PSD in seconds).
The MplsLpsReq textual convention encodes the PSC Request field of PSC control packets, with values: noRequest(0), doNotRevert(1), reverseRequest(2), exercise(3), waitToRestore(4), manualSwitch(5), signalDegrade(7), signalFail(10), forcedSwitch(12), lockoutOfProtection(14).
IANA assigned OID decimal 22 for the MPLS-LPS-MIB module (MPLS-LPS-MIB) in the 'MIB Transmission Group - MPLS STD MIB' subregistry of the 'Internet-standard MIB - Transmission Group' registry, rooted at mplsStdMIB.
Read-write/read-create objects in mplsLpsConfigTable are sensitive: improper manipulation can delay traffic switching (mplsLpsConfigHoldOff), delay/accelerate reversion (mplsLpsConfigWaitToRestore), cause unexpected traffic switching (mplsLpsConfigCommand), or discontinue protection switching (mplsLpsConfigMode, mplsLpsConfigProtectionType). Manipulation of mplsLpsMeConfigTable can also discontinue protection switching, and compromise of mplsLpsNotificationEnable can prevent operator notification of failures.
The mplsLpsStatusTable and mplsLpsMeStatusTable expose history and current status of MPLS-TP linear protection domains, enabling performance estimation of the network. These tables should be considered sensitive/vulnerable if operators do not wish to reveal network performance information, and GET/NOTIFY access should be controlled and values possibly encrypted.
The MplsLpsState textual convention defines 21 PSC state machine states: normal(1), unavLOlocal(2), unavSFPlocal(3), unavSDPlocal(4), unavLOremote(5), unavSFPremote(6), unavSDPremote(7), protfailSFWlocal(8), protfailSDWlocal(9), protfailSFWremote(10), protfailSDWremote(11), switadmFSlocal(12), switadmMSWlocal(13), switadmMSPlocal(14), switadmFSremote(15), switadmMSWremote(16), switadmMSPremote(17), wtr(18), dnr(19), exerLocal(20), exerRemote(21). Triggers are local/remote commands (LO, FS, MS) and defect conditions (SF-W, SF-P, SD-W, SD-P).