IPoDWDM & Optical

Evolving from Legacy P-OTN to SR-MPLS Based IPoDWDM Networks with OcNOS

IP Infusion Team · · 2 min read

Networks built on 2nd-generation Packet-Optical Transport Network (P-OTN) technology face a structural refresh challenge. Many OTN platforms are at or approaching end-of-life, spare parts are becoming scarce, and the technology itself predates modern SR-MPLS and coherent optical standards that offer dramatically better scalability, flexibility, and economics.

The migration path from P-OTN to SR-MPLS based IPoDWDM is not a single cutover event — it is a phased architectural evolution that can be executed without service disruption. OcNOS 7.0 provides the migration platform with full SR-TE, SR-MPLS, and IPoDWDM support on a single NOS.

Why P-OTN Networks Need to Evolve

Factor Legacy P-OTN SR-MPLS + IPoDWDM
Circuit flexibility Fixed OTN timeslots (ODU0–ODU4) Any bandwidth, packet-switched flexibility
Protection model ODU path protection (50ms) SR-TE + TI-LFA (<50ms, topology-independent)
Management Separate IP and optical NMS Unified OcNOS CLI + IP Maestro
Capacity 10G/100G OTN channels 400G/800G per wavelength (ZR+)
Traffic engineering Static OTN circuits Dynamic SR-TE, Flex-Algo network slicing
Hardware longevity Proprietary chassis, EOL risk Open white-box, multi-ODM sourcing

Migration Architecture: Three Phases

Phase 1 SR-MPLS overlay Phase 2 Introduce IPoDWDM Phase 3 OTN decommission • Enable IS-IS SR on all nodes • OTN circuits remain as transport • SR-TE policies replace RSVP-TE • TI-LFA replaces OTN protection • No traffic disruption • Add OcNOS IPoDWDM nodes • 400G ZR+ alongside OTN • Migrate services node by node • Validate SR+optical integration • Parallel operation • All traffic on SR-MPLS + IPoDWDM • Decommission OTN hardware • Unified OcNOS management • Flex-Algo network slicing active • Full TCO benefits realized Months 1–6 Months 7–18 Months 19+
Three-phase P-OTN to SR-MPLS IPoDWDM migration. Phase 1 introduces SR-MPLS as an overlay while OTN circuits remain. Phase 2 adds IPoDWDM nodes in parallel. Phase 3 decommissions OTN after full traffic migration.

Phase 1: SR-MPLS Overlay on Existing Infrastructure

! OcNOS 7.0 -- Phase 1: Enable IS-IS SR on existing nodes
! OTN circuits remain as transport; SR-MPLS operates as overlay
!
router isis TRANSPORT
  net 49.0003.0000.0000.0001.00
  is-type level-2-only
  segment-routing mpls
  !
  ! BGP-Free Core: remove BGP from transit nodes
  ! PE nodes retain BGP; P nodes use SR labels only
  !
  fast-reroute per-prefix level-2 ti-lfa    ! Replace OTN 1+1 protection
  !
  address-family ipv4 unicast
    segment-routing mpls
  exit-address-family
!
interface lo
  ip address 10.100.0.1/32
  ip router isis TRANSPORT
  isis segment-routing prefix-sid index 1
!
! Verify SR is active (OTN circuits still carrying traffic):
show isis segment-routing prefix-sids
show mpls forwarding-table

IP Infusion Engineering Team

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Tags IPoDWDM Migration OcNOS OTN P-OTN ROADM SR-MPLS Transport

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