Ethernet Pseudowire (PW) Management Information Base (MIB)
Extracted elements (25)
The PW may optionally be modeled as an etherLike virtual interface in the ifTable (via pwEnetPwIfIndex), enabling management of the PW via the existing Etherlike-MIB for statistics gathering, status, and configuration. This is a design choice to leverage existing tooling without requiring new Ethernet-specific management infrastructure.
The pwEnetPwInstance index value MAY be set to the VLAN field value when the VLAN is known at row creation time, for better readability and backward compatibility with older versions of the MIB. Otherwise, value 1 SHOULD be used for the first row so management applications know how to access it.
The three-layer MIB architecture (service-specific / generic PW / PSN-specific) is designed to sufficiently isolate PW services from the underlying PSN, while providing a standard means to connect any supported service to any supported PSN. This allows the Ethernet PW MIB to be agnostic to the PSN type.
For VPLS services, the PW is associated to a virtual interface attached to a bridge or VPLS forwarder. The bridging function between local physical ports and virtual interfaces is out of scope for this MIB module and must be handled by other MIB modules managing the forwarder and Native Service Processing (NSP) sections.
pwEnetPwIfIndex represents the ifIndex of the Ethernet PW in the Etherlike-MIB on the PSN side, and may differ from pwIfIndex (the ifIndex for the PW itself with ifType 'pw'). Implementations that model the PW in both the generic ifTable and Etherlike-MIB must manage these two distinct ifIndex values.
When pwEnetVlanMode is removeVlan, the service-delimiting VLAN field is stripped from PW-bound packets, which causes loss of Ethernet PRI (priority) bits transparency. Implementations and operators must account for this when CoS or QoS treatment based on PRI bits is required.
An implementation MUST support at least the noChange(2) value for pwEnetVlanMode. Support for portBased, removeVlan, addVlan, other, and changeVlan is OPTIONAL.
Deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED. It is RECOMMENDED to deploy SNMPv3 and enable cryptographic security (authentication and privacy) for accessing this MIB module.
For nested VLAN (QinQ) with both provider and user VLAN as service-delimiting tags, it is RECOMMENDED that pwType equal EthernetTagged, though pwType equal to Ethernet MAY be used as well.
In port mode (1B) when adding a provider VLAN tag to outgoing PW packets using addVlan, the pwType SHOULD be set to EthernetTagged. In single VLAN one-to-one, change, and remove modes, pwType SHOULD also be EthernetTagged.
Manual entries in the pwEnetTable SHOULD be preserved after a reboot. If a row's set of entries is found to be inconsistent after reboot, the agent MUST declare the PW pwOperStatus as notPresent(5).
pwEnetPortVlan MUST equal pwEnetPwVlan when pwEnetVlanMode equals noChange, enforcing consistency between the port-side and PW-side VLAN values in pass-through mode.
SNMPv3 VACM and USM MUST be used with any v3 agent that implements this MIB module to protect read-write and read-create objects from unauthorized access.
The value 4095 MUST be used for pwEnetPwVlan when the object is not applicable (e.g., port mode where all packets from the port map to the PW). The value 0 MUST be set to indicate untagged frames when pwEnetVlanMode is noChange and pwEnetPortVlan is 0.
The PW-ENET-STD-MIB module is organized in a three-layer MIB framework: a service-specific layer (this module), a generic PW layer (PW-STD-MIB, RFC 5601), and a PSN-specific layer. Each layer is connected by common indexes, isolating Ethernet PW service management from the underlying PSN type.
The pwEnetPortIfIndex object specifies the ifIndex of the CE-bound Ethernet port (for point-to-point service) or the VPLS virtual interface ifIndex. Two rows may reference the same ifIndex only if their pwEnetPortVlan values do not overlap. Zero indicates the association is not yet known.
The pwEnetPortVlan object defines the service-delimiting VLAN on the original physical or virtual CE-bound port. Value 4095 means all port traffic maps to the same PW (port mode); value 0 means untagged frames. This object MUST equal pwEnetPwVlan when pwEnetVlanMode is noChange.
The pwEnetPwIfIndex object optionally associates the Ethernet PW with an ifIndex in the Etherlike-MIB to enable statistics and configuration via existing Ethernet management tools. This value may differ from the pwIfIndex representing the PW itself in the ifTable.
The pwEnetPwVlan object defines the service-delimiting VLAN field value on the PW side. The reserved value 4095 indicates port-mode (no VLAN applicable); value 0 indicates untagged frames when pwEnetVlanMode is noChange and pwEnetPortVlan is 0.
The pwEnetStatsTable provides per-PW counters: pwEnetStatsIllegalVlan counts packets received from the PSN with a missing, unexpected, or illegal VLAN field; pwEnetStatsIllegalLength counts packets with Ethernet length outside the advertised MTU or minimum frame size.
The pwEnetTable provides per-PW Ethernet port mapping and VLAN configuration. It is indexed by pwIndex (from PW-STD-MIB) and pwEnetPwInstance, allowing multiple VLANs or mappings to exist on the same PW. An entry is automatically created by the agent for every pwTable row with pwType 'ethernet' or 'ethernetTagged'.
The pwEnetVlanMode object specifies how VLAN tags are handled between the CE-bound port and the PW encapsulation. Defined values are: other(0), portBased(1), noChange(2), changeVlan(3), addVlan(4), removeVlan(5). The default is noChange(2).
IANA assigned the OBJECT IDENTIFIER value mib-2 180 (i.e., { mib-2 180 }) to the pwEnetStdMIB module in the SMI Numbers registry. This is the top-level OID for all objects defined in the PW-ENET-STD-MIB.
Even read access to pwEnetTable configuration (PW service layout, VLAN mappings) may be undesirable. Implementers should control GET and NOTIFY access and consider encrypting MIB values in transit via SNMPv3 cryptographic mechanisms.
The pwEnetTable contains read-write and read-create objects that provision Ethernet PWs. Unauthorized SET operations could disrupt network traffic. SNMPv3 security mechanisms should be used, and administrators should consider restricting even GET access to these objects since the PW service configuration may be sensitive.