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, RFC 4090 fast 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
        }
        fast-reroute {
            backup          facility
            node-protection false
        }
    }

    bypass around-eth0 {
        merge-point 10.0.0.5
        explicit-route 1 {
            address 10.1.0.5/32
        }
    }
}

Field	Meaning
router-id	This LSR's address; also the raw-socket source and the SESSION extended-tunnel-id. A reload that changes it is rejected (restart-class) and the running value is kept.
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.
fast-reroute (on a tunnel)	Request RFC 4090 local protection. backup is facility (one bypass protects many LSPs, the default) or one-to-one; node-protection true asks for a backup around the next node (not just the next link); bandwidth-protection and hop-limit (default 16) tune the backup. Presence of the container enables protection.
bypass	A facility-backup bypass LSP from this node (a Point of Local Repair) to a merge-point along an explicit-route that avoids the protected resource. ze has no IGP/CSPF, so bypass paths are explicit. node-protection true marks a bypass that merges at a next-next hop.
refresh-period / refresh-multiplier	Optional soft-state timers (defaults 30s / 3 missed refreshes).
setup-priority / hold-priority (on a tunnel)	RSVP setup/hold priority (0 = highest, default 7).

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.

Fast Reroute (RFC 4090)

Fast Reroute pre-signals a backup so an LSP survives a link or node failure with local repair instead of waiting for the head-end to re-signal from scratch. ze implements facility backup (one bypass LSP protects every LSP crossing a resource):

1. A tunnel with fast-reroute sends a PATH carrying a FAST_REROUTE object and a SESSION_ATTRIBUTE with "local protection desired" set.
2. A transit node that can protect the next resource (a Point of Local Repair) selects a configured bypass whose merge-point is the next hop (link protection) or the next-next hop (node protection), arms it, and records "local protection available" in its RESV RECORD_ROUTE.
3. On a link failure the PLR redirects the protected LSP onto the bypass by pushing the bypass label over the protected label (a 2-label stack) and forwarding via the bypass next hop, within the link-down event handling and with no re-signaling round trip. It records "local protection in use".
4. The PLR sends a PathErr "Notify" (code 25, value 3 "Tunnel locally repaired") toward the head-end and keeps the LSP up (it does not tear it down). For node protection it pushes the next-next hop's recorded label (label recording is requested automatically).
5. The head-end re-optimizes onto a fresh path (make-before-break) and tears the locally-repaired LSP once the replacement is up.

An LSP with no matching bypass keeps the base behavior (tear down plus PathErr on a link failure). One-to-one (detour) backup is tracked separately and not yet implemented.

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.

Reload semantics

rsvp-te reconciles its tunnel set on reload without restarting the engine:

Change	Reload behaviour
Added tunnel	Signaled (PATH sent along its ERO).
Changed ERO / bandwidth	Rerouted make-before-break (new LSP-ID, old torn down once the new one is up).
Removed tunnel	Torn down with PathTear.
Interface bandwidth	Hot-applied to admission; live reservations are preserved (the link is not opened past max-reservable-bandwidth until pre-reload LSPs drain).
Bypass set	Reloaded; FRR re-arms against the new bypasses.
router-id	Restart-class. A configured change is rejected with a WARN and the running value is kept (no split-brain).

Inspecting LSPs

The RSVP-TE component exposes four introspection commands that report LSP, interface, tunnel, and protection 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	Reports
show rsvp-te lsp (= show rsvp-te session)	All LSPs: state, role, bandwidth, in/out labels.
show rsvp-te interface	Per-interface reserved / available / max bandwidth.
show rsvp-te tunnel	Configured tunnels and their state.
show rsvp-te fast-reroute	RFC 4090 protection state: each configured bypass LSP and each protected LSP with its armed bypass and whether protection is available / in use.

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, ze_rsvpte_local_repairs_total, ze_rsvpte_protected_lsps, ze_rsvpte_bypass_lsps.

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.