MPLS and Backbone VPN

MPLS is what lets you sell transparent L2 circuits to corporate customers, isolate traffic per VRF and do real traffic engineering — without end-to-end VLAN hacks.

What MPLS is

Multiprotocol Label Switching forwards packets based on short labels instead of full IP headers. This allows creating predefined paths (LSPs) across the backbone, separating multiple customers' traffic on the same physical link, and applying differentiated treatment by SLA.

In ISPs, MPLS shows up mostly to sell transparent L2 (customer wants "virtual dark fiber" between HQ and branch) and to create segregated L3 VPNs (each customer sees only its own routes).

What RASYS does with MPLS

  • L2 VPN (VPLS / EVPN) — point-to-point or multipoint Ethernet between customer sites. EVPN is the modern standard, with BGP in the control plane (vs. VPLS's classic LDP).
  • L3 VPN (BGP/MPLS VPN, RFC 4364) — VRF per customer, route exchange via MP-BGP, total isolation between VPNs on the same PE.
  • Traffic Engineering (RSVP-TE / SR-TE) — explicit paths to optimize expensive link usage, avoid congested links.
  • Fast Reroute (FRR) — LSP failover in <50ms via pre-computed backup paths. Customer never notices the link failure.
  • Backbone QoS — DSCP-to-EXP mapping, traffic-class queues, bandwidth guarantee for VoIP/video on the same backbone.
  • Segment Routing (SR-MPLS) — modern alternative to LDP/RSVP-TE, simpler control plane and programmable PCE.

Equipment we work with

Huawei NE40/NE80, Juniper MX series, Cisco ASR/IOS XR, Datacom DM. On CE (customer edge), MikroTik with limited MPLS.

When it makes sense to talk to us

You want to sell corporate L2 circuits and are using brute-force VLAN trunking cross-PoP; have multi-PoP and need to separate customer traffic; growing without criteria on the expensive link and need TE; want to migrate from LDP/RSVP to Segment Routing.

Talk to us. See also: BGP, OSPF, MPLS in glossary.

FREQUENTLY ASKED QUESTIONS

MPLS L2VPN or L3VPN — which to choose?

L2VPN (VPLS, EVPN) delivers end-to-end Ethernet — a corporate client sees a single LAN across branches. L3VPN (VPRN/VRF) delivers separate IP routing per client. For corporate clients: L2VPN wins on simplicity. For segmenting internal traffic (management, NOC, finance): L3VPN.

Is it worth deploying MPLS with only 2 PoPs?

Marginally. 2 PoPs with a simple IGP and point-to-point tunneling is enough. MPLS starts paying off from 3-4 PoPs or when there is a clear need for L2VPN for corporate clients. Do not deploy MPLS just for the technology — deploy it when there is a concrete use case.

MPLS traffic engineering (MPLS-TE / Segment Routing) — when does it make sense?

When the backbone has links of different capacity and the IGP shortest path saturates the preferred path while others sit idle. Also for critical services that need an explicit path (premium client, voice). In a regional ISP with a symmetric backbone, the operational overhead rarely pays off.

How do you migrate from pure IP routing to MPLS without downtime?

Enable LDP in parallel on the existing IGP without changing any client service. Create an L2VPN/L3VPN pilot for a new service. Migrate existing clients in a scheduled maintenance window per VPN — each one takes minutes. The pure IP backbone keeps running as fallback until confidence in MPLS is established.