rsvp te

Pre-Alpha. This page describes behavior that may change.

RSVP-TE (RFC 3209, on top of RFC 2205 RSVP) signals explicitly-routed MPLS LSP tunnels with bandwidth reservation. It runs directly over IP as protocol 46 and requires CAP_NET_RAW.

Status

The control plane (signaling, admission, reroute) and the dataplane wiring are implemented and unit-tested: the engine emits push/swap/pop forwarding entries on the mpls-fib event bus and fib-kernel programs them into the kernel (IP route plus label for push, AF_MPLS routes for swap/pop). End-to-end and FRR interop validation on a live kernel is still pending. Use for evaluation, not production forwarding.

Configuration

rsvp-te {
    router-id 10.0.0.1

    interface eth0 {
        max-bandwidth            10e9
        max-reservable-bandwidth 8e9
        address                  10.0.0.4/30
    }

    tunnel to-egress {
        destination 10.0.0.9
        tunnel-id   1
        bandwidth   1e9
        explicit-route 1 {
            address 10.0.0.5/32
        }
        explicit-route 2 {
            address 10.0.0.9/32
        }
    }
}

Field	Meaning
router-id	This LSR's address; also the raw-socket source and the SESSION extended-tunnel-id.
interface	Per-link max-bandwidth / max-reservable-bandwidth used by admission control.
address	The local link prefix (e.g. 10.0.0.4/30). Lets admission map an LSP to this interface when more than one is configured: the neighbor's address is matched against each interface's prefix. Optional with a single interface. An interface without it is not admission-enforced in a multi-interface config (a startup warning lists how many).
tunnel	An ingress (head-end) LSP. Each explicit-route <index> names a hop address (IPv4 prefix) from this node toward the destination (the egress tunnel endpoint); type strict|loose defaults to strict.

How signaling works

1. Ingress sends a PATH along the ERO toward the egress.
2. Transit nodes consume their own ERO hop, relay the PATH downstream, and on the returning RESV allocate a local label, program a swap, and relay the RESV upstream.
3. Egress allocates a label and returns a RESV.
4. Ingress records the downstream label and the LSP comes up.
5. Soft-state is maintained by periodic PATH refresh; PathTear removes it.

Admission control reserves the requested bandwidth per interface; an oversubscribed link is rejected with a PathErr (admission-control failure). Make-before-break reroute signals a replacement LSP (new LSP-ID, SHARED-EXPLICIT style) and tears the old one down only once the new one is up.

Dataplane

The signaling engine does not touch the kernel directly. It emits push/swap/pop forwarding entries on the mpls-fib event bus, and fib-kernel programs them (IP route plus label for push, AF_MPLS routes for swap/pop), keeping fib-kernel the single kernel-FIB owner.

Inspecting LSPs

The RSVP-TE component exposes three introspection commands that report LSP, interface, and tunnel state as JSON, available both under the top-level show grammar and as direct plugin commands. The show forms proxy to the plugin commands through the dispatcher.

Command	Plugin command	Reports
show rsvp-te lsp	rsvp-te show-session	All LSPs: state, role, bandwidth, in/out labels.
show rsvp-te interface	rsvp-te show-interface	Per-interface reserved / available / max bandwidth.
show rsvp-te tunnel	rsvp-te show-tunnel	Configured tunnels and their state.

Metrics

ze_rsvpte_lsps_active, ze_rsvpte_lsps_total, ze_rsvpte_path_sent_total, ze_rsvpte_path_recv_total, ze_rsvpte_resv_sent_total, ze_rsvpte_resv_recv_total, ze_rsvpte_patherr_recv_total, ze_rsvpte_admission_denied_total.

See also

• MPLS for the kernel MPLS FIB and LDP.
• FIB for the route-installation pipeline.
• Kernel FIB for the netlink backend that owns the kernel FIB.

Adapted from main/docs/guide/rsvp-te.md.