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Meriton Networks AON - Meriton's Agile Optical Networking
Carrier Ethernet Transport (CET)

Comparing Alternative Approaches for Ethernet-Optical Transport Networks

There are three approaches that vendors are advocating for an NGN transport infrastructure optimized to handle Ethernet services.

IP over WDM
(Intelligent Packet over Optical Transport)

  • Transport layer comprises OADMs from the access networks, and some optical switches in the core
  • Keeps the optical layer as "dumb fat pipes" and extends MPLS to the edge
  • No real separation of services and transport layer
  • Generates proliferation of ports on layer 2/3 routers as traffic traverses to service layers for switching
  • Added complexity

Carrier Ethernet Overlay
(Intelligent Ethernet over Optical Transport)

  • Transport layer comprises OADMs from the access networks, and some optical switches in the core
  • This model aims to deal with scalability issues by putting an end-to-end layer 2 layer between service and transport layers
  • Adds complexity by forcing fixed correlation between service nodes and the transport network
  • Blurs boundary between service and transport layers

Carrier Ethernet Transport

(Integrated Optical & Ethernet Tunnel Networking)

  • The transport layer incorporates flexibility by using switches instead of OADMs to become a switched architecture
  • Manages wavelengths, sub-wavelengths and Ethernet tunnels
  • Adds "just enough" layer 2 functionality to the optical layer to provide end-to-end Ethernet connection without burdening the optical layer with standard layer 2 functionality and cost
  • Clear delineation of service layer and transport layer, thus delivering scalability and flexibility
  • Keeps traffic in the optical domain, sending traffic to the service layer only when necessary
  • Switching in optical layer enables deterministic, end-to-end connections that can support SLAs
  • Reduces metro head-end Gig E port consumption and reduces requirement for separate aggregation system between packet and optical layers
  • Very comfortable model for transport organizations, as paths are set-up through the network like you would with SDH or ATM