Glossary

This page defines the terms used across the Prelude Topology Engine documentation. Definitions are intentionally short. For worked examples, see the surrounding documentation.

Core objects

Peer : A BGP-LS speaker Prelude TE maintains a session with — typically a router or a route reflector. Peer configuration lives in the database, so you can add, disable, or reconfigure peers at runtime without restarting the engine.

Domain : A single IGP scope inside the topology — typically an ISIS area, an OSPF area, or a routing realm you keep separate. Each domain has its own graph and its own NATS publish topic.

Node : A network element — usually a router — that one of your peers reports. Carries router IDs, AS number, area identifiers, and any SR-MPLS / SRv6 / Flex-Algo information the network advertises.

Link : A directed adjacency between two nodes. Carries metrics (IGP, TE, delay), bandwidth, admin groups, SRLGs, and Segment Routing adjacency information.

Prefix : An IP prefix attached to a node, IPv4 or IPv6. Carries the route type, IGP metric, and any SR-MPLS Prefix SID or SRv6 locator metadata.

Source peer : A peer that contributed a given node, link, or prefix. Every graph entity tracks the set of peers reporting it, so losing one peer only withdraws the elements unique to that peer.

Topology change : The event published when an entity is added, updated, or withdrawn from the graph. Tagged with the domain, the entity type, and a timestamp.

Segment Routing

SR-MPLS : Segment Routing with an MPLS data plane (RFC 8667). The engine surfaces SR capabilities, Node SIDs, Adjacency SIDs, and Prefix SIDs as first-class attributes on nodes, links, and prefixes.

SRv6 : Segment Routing with an IPv6 data plane (RFC 8986). The engine surfaces SRv6 capabilities, locators, End.X SIDs, and named endpoint behaviors. See Topology / Links for the exposed fields.

SID : Segment Identifier. A label (in SR-MPLS) or an IPv6 address (in SRv6) used by Segment Routing.

Flex-Algo

Flex-Algo : IGP Flexible Algorithm (RFC 9350). An IGP-level mechanism that lets operators define custom routing algorithms based on constraints. Flex-Algo identifiers are in the range 128–255 and are independent of the data plane (SR-MPLS or SRv6).

FAD : Flexible Algorithm Definition — the advertisement carried by a node that wants to participate in a Flex-Algo. Carries the metric type, the calculation type, the priority, and the admin-group and SRLG constraints.

Admin group : A 32-bit bitmask that tags a link with up to 32 "colors". Flex-Algo constraints reference admin groups through include-any, include-all, and exclude-any rules. The engine exposes both the raw bitmask and the decoded list of bit positions.

SRLG : Shared Risk Link Group. A label shared by links that fail together (e.g. fibers in the same conduit). Flex-Algo can exclude links carrying any of a configured list of SRLGs.

Operations

Output : A connected backend that receives topology changes. NATS is the only output type today. Outputs are configured through the UI or the API.

API token : The credential the REST API uses to authenticate requests. You create tokens with prelude-te user token or through the UI and pass them as a Bearer header on every API call.

License : The entitlement that controls how many peers, domains, and nodes a Prelude TE instance can manage. Three tiers ship today — community, standard, premium — see Licensing.

Deployment

OCI image : The container image format used to distribute Prelude TE. The same image runs under Docker, Podman, or any other OCI-compliant runtime.

systemd unit : A native Linux service definition you can use to run Prelude TE outside of a container, managed alongside other services on the host.