Home · Documentation · Technology · MPLS-TE

MPLS Traffic Engineering: RSVP-TE, FRR, Bandwidth Constraints

MPLS Traffic Engineering (MPLS-TE) forwards traffic along bandwidth-reserved, explicitly routed label-switched paths instead of the IGP shortest path. RSVP-TE signals each LSP, CSPF computes a path that meets the constraints, and Fast Reroute pre-programs a backup bypass tunnel at every point of local repair. OcNOS implements RSVP-TE (CSPF, FRR link/node protection, DS-TE class-types, and auto-bandwidth) alongside SR-MPLS, on the same chassis.

RSVP-TE LSP with FRR Backup

A four-router ring carrying a primary RSVP-TE LSP from PE-1 to PE-3. The primary path (solid) is the CSPF-computed shortest path that meets the 1G bandwidth constraint; the FRR backup (dashed) protects the primary against a P-A link or node failure.

MPLS-TE topology: four-router ring with a primary RSVP-TE LSP and a Fast Reroute backup path with bandwidth labels
MPLS-TE: four-router ring with a primary RSVP-TE LSP, an FRR backup path, and bandwidth reservations.

Where MPLS-TE still wins

Segment Routing handles most modern transport with less state in the network, but RSVP-TE still does one thing better: strict bandwidth admission control across the network, because it reserves bandwidth per LSP at every hop. For carriers with strict SLA contracts, capacity-managed wholesale services, or per-class-type DiffServ guarantees, OcNOS delivers RSVP-TE that runs alongside (or instead of) SR-MPLS on the same hardware.

The OcNOS MPLS-TE implementation

Path / Resv signalling

Full RSVP-TE signalling with explicit-route (ERO), record-route (RRO), graceful restart, hello-based detection, and refresh reduction.

Constraint-based path

CSPF using IGP-TE extensions (OSPF-TE / IS-IS-TE): bandwidth, affinity, hop-count, SRLG-disjoint, and admin-group constraints.

Link / node protection

Facility-mode FRR with bypass tunnels at every PLR, for link, node, or SRLG failure.

Class-types

Diffserv-aware TE (RFC 4124) protocol extensions, in the OcNOS-SP CSR, MPLS and PLUS SKUs.

DS-TE

Adaptive reservation

Auto-bandwidth resizing based on observed utilization with configurable adjust-interval and overflow / underflow thresholds.

What you get with OcNOS MPLS-TE

  • Coexists with SR-MPLS. Run RSVP-TE for legacy services and SR-MPLS for new ones on the same router: same IGP, same forwarding plane.
  • PCE-ready. PCEP support for stateful PCE deployments, including PCInitiate for controller-driven LSP placement.
SR-MPLS BGP-LU OcNOS-SP Segment Routing over IPv6 (SRv6) IS-IS SR with TI-LFA

Frequently asked questions

What is MPLS Traffic Engineering?
MPLS-TE forwards traffic along bandwidth-reserved, explicitly routed label-switched paths rather than the IGP shortest path. RSVP-TE signals each LSP and CSPF computes a path that meets bandwidth, affinity, hop-count, and SRLG-disjoint constraints, giving carriers strict admission control across the network.
What is RSVP-TE Fast Reroute (FRR)?
Fast Reroute pre-programs a backup bypass tunnel at every point of local repair, so traffic switches to a detour when a protected link or node fails. OcNOS supports facility-mode FRR for link, node, and SRLG protection.
When should I use MPLS-TE instead of Segment Routing?
Segment Routing handles most modern transport with less state in the network, but RSVP-TE still reserves bandwidth per LSP at every hop, which gives strict network-wide bandwidth admission control. It suits carriers with strict SLAs, capacity-managed wholesale services, or per-class DiffServ guarantees.
Can OcNOS run MPLS-TE and SR-MPLS together?
Yes. OcNOS runs RSVP-TE alongside SR-MPLS on the same router, sharing the same IGP and forwarding plane. Operators can keep RSVP-TE for legacy bandwidth-reserved services while moving new services to SR-MPLS, with no separate hardware.
What is DS-TE in OcNOS?
DS-TE (Diffserv-aware MPLS-TE, RFC 4124) extends traffic engineering with per-class-type bandwidth pools. OcNOS-SP supports the RFC 4124 protocol extensions in its CSR, MPLS and PLUS SKUs.

Go deeper. Take it with you.

The product datasheet plus short, technical downloads that go further than this page.

Datasheet

OcNOS-SP Datasheet

Full OcNOS-SP specification: the access, cell site and aggregation feature set, software SKUs, supported hardware platforms, and the solution ordering guide.

Get the datasheet
Solution Brief

SR-MPLS Upgrade with OcNOS

Migrate SR-MPLS onto OcNOS on open hardware: Flex-Algo, TI-LFA, and a node-by-node cutover path.

Get the brief
Solution Brief

Cloud & Service Provider WAN Transport

Cloud and service-provider WAN transport on open hardware: SR-MPLS, EVPN, and scale-tested forwarding.

Get the brief

Designing a TE-managed transport core?

Request a Technical Demo →