Nokia VPLS key terms

Virtual Private LAN Service: a Layer 2 multipoint service that emulates an Ethernet LAN across an MPLS provider network, so customer sites share one bridged broadcast domain regardless of location.

Virtual Switch Instance: the Nokia SR OS construct that holds the bridge logic for one VPLS, including its SAPs, SDP bindings, MAC table, and forwarding state.

The numeric identifier that names a VPLS instance in the service manager; it scopes the VSI and must be unique on the router, with a matching service ID usually configured on peer PEs.

Service Access Point: the local customer-facing attachment on a PE, formed by a port and an encapsulation value (such as a VLAN tag) that maps customer traffic into the VPLS.

Service Distribution Point: a Nokia object that identifies a unidirectional tunnel to a far-end PE and carries service traffic to it; SDPs are bound into services to create pseudowires.

The association of an SDP with a VPLS instance, which creates the pseudowire toward the remote PE and appears as a spoke in the VSI for forwarding and MAC learning.

A VPLS SDP binding that follows split-horizon rules: traffic received from one spoke SDP is not forwarded to another spoke SDP, preventing loops in the full-mesh topology.

A VPLS SDP binding that may forward traffic to and from other SDP bindings, used in hub-and-spoke designs where the hub needs to relay between spokes.

The forwarding rule that blocks traffic from leaving the VSI on the same type of interface it arrived on, stopping pseudowire loops without running a spanning-tree protocol over the core.

The standard VPLS core topology in which every PE has a pseudowire to every other PE in the same VPLS, giving one hop between any pair of sites.

A VPLS topology where spoke sites connect only to a central hub PE, which uses mesh SDP bindings to relay traffic between them, reducing pseudowire count at the cost of tromboning.

The process by which a VSI records the source MAC address of received frames against the SAP or SDP binding they arrived on, building the table used for forwarding.

The per-VSI forwarding database that maps learned MAC addresses to SAPs and SDP bindings, populated by source learning and consulted for every frame's destination lookup.

The timer-driven removal of idle MAC entries from a VSI table so that stations that move or disappear are relearned rather than blackholed by stale forwarding information.

A control message or operational action that clears learned MAC addresses in a VPLS, typically after a topology change, so traffic is relearned over the new path.

Forwarding of frames whose destination MAC is not in the VSI table out of every eligible SAP and SDP binding except the ingress one, until the destination replies and is learned.

Replication of broadcast, multicast, and unknown unicast frames to all ports in the VPLS bridge domain, subject to split-horizon rules on spoke SDPs.

A point-to-point emulated Layer 2 circuit carried over MPLS between two PEs, transporting customer Ethernet frames encapsulated for the VPLS in a tunnel LSP.

The MPLS label that identifies a specific pseudowire at the egress PE, pushed below the tunnel label so the receiver can map the packet to the correct service.

The inner label allocated per service or SDP binding that lets the egress PE demultiplex received frames into the right VSI and pseudowire context.

An optional 4-byte field inserted between the VC label and the payload to carry sequence numbers and preserve padding, helping order detection and payload alignment on pseudowires.

The maximum frame size a service will forward, negotiated between VPLS peers; a mismatch between local and far-end values prevents the SDP binding from coming up.

The maximum transmission unit configured on a physical or logical port, which must be at least the service MTU plus encapsulation overhead for VPLS traffic to pass.

A SAP configuration where all untagged traffic on the port maps into the service, typically used when the customer hands off a single untagged Ethernet connection.

A SAP configuration that matches a single 802.1Q VLAN tag on the port, mapping only frames with that VLAN ID into the VPLS instance.

A SAP configuration matching a stacked 802.1Q tag (outer and inner VLAN IDs), used to give each customer a distinct outer tag while preserving their inner VLANs.

A traffic-engineered MPLS tunnel signaled with RSVP that can carry VPLS pseudowires, supporting bandwidth reservation, fast reroute, and explicit paths across the core.

An MPLS label-switched path built by the Label Distribution Protocol along IGP shortest paths, commonly used as the tunnel beneath VPLS SDPs in simpler core designs.

Fast Reroute: pre-signaled backup paths that redirect MPLS traffic within tens of milliseconds after a link or node failure, protecting VPLS pseudowires carried in the tunnel.

Multi-chassis Link Aggregation: two PE routers present one logical LAG to a dual-homed customer device, giving redundant access into a VPLS without running STP toward the customer.

Inter-Chassis Link: the direct link between MC-LAG peers that carries synchronization and, in some designs, data traffic between the two chassis.

Connecting a customer site to two PEs so service survives one PE or access link failing; in VPLS it is commonly built with MC-LAG or with a redundant SAP.

A SAP configuration in which a primary and standby interface are defined for a service, with only the active one forwarding and the other taking over on failure.

An event such as a pseudowire or SAP going down that alters the VSI forwarding graph and triggers MAC flushing and relearning to restore connectivity.

BGP Auto-Discovery: using BGP to signal VPLS membership and endpoint information so PEs automatically build pseudowires to the correct peers without manual SDP configuration.

Operations, Administration, and Maintenance: the tools and protocols used to test, monitor, and isolate faults in services, such as service-level ping and trace for VPLS.

An on-demand test that sends OAM packets through a service to a far-end PE to verify reachability and measure round-trip delay and loss for a VPLS.

An OAM operation that follows the path of a given MAC address through the VPLS, identifying which PE and port learned it and where forwarding breaks.