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GMPLS Control Plane for G.709 OTN

The Optical Transport Network (OTN), defined by the ITU-T G.709 and G.872 specifications, creates a transparent, hierarchical network designed for use on both Time Division Multiplexed (TDM) and Wavelength Switched Optical Network (WSON) devices. It provides an efficient way to carry both next-generation packet services (for example any of the MPLS services described in MPLS Services) and legacy circuit services.

OTN uses GMPLS for the control plane - and OTN extensions to GMPLS are defined by the IETF in RFC 4328.

Metaswitch is heavily involved in the development of GMPLS standards including those for OTN. Metaswitch's MPLS solution, DC-MPLS, fully supports the OTN extensions, and in combination with DC-OSPF and DC-ISIS, provides a complete control plane solution that can be used in G.709 compliant OTN devices.

G.709 OTN Model

G.709 OTN model

OTN is a flexible way of carrying different types of digital signal across an optical core using Time Division Multiplexing (TDM) and/or Wavelength Division Multiplexing (WDM).

In more detail, OTN uses an optical fiber network which provides optical channels to carry digital client signals independent of the client signals' characteristics. To each channel, it provides the functions of transport, multiplexing, routing, management, supervision and survivability. The OTN control plane automates many of these functions, with corresponding operational benefits relative to a statically provisioned OTN network.

  • The control plane automatically calculates an optimal path for each client connection when the connection is established.
  • It can also automatically calculate a path for a diversely routed protecting connection, on which resources can either be held in reserve or preempted when required.
  • When resources are added to or removed from the network, the control plane can automatically recalculate optimal routes for all existing connections to make best use of the newly available resources.

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