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How to Do IPoDWDM Right

portrait of Teresa Monteiro

November 9, 2023
By Teresa Monteiro
Director of Solutions, Software and Automation

Meet Host-independent Management

Previously, I wrote a blog on the challenges of managing IP over DWDM (IPoDWDM) networks. I described how the demarcation between the IP and optical domains gets blurred when coherent pluggable transceivers are deployed directly into routers, and how this disrupts the operational practices of many communication service providers (CSPs), where the IP and optical domains are managed separately and by different teams. The blog debated alternative IPoDWDM management frameworks, including an approach specified by the Open XR Optics Forum.

In this blog, I dive into the Open XR Optics Forum proposal and look at how it reestablishes the demarcation of the packet and optical domains in an IPoDWDM network by replacing physical demarcation (based on hardware) with virtual demarcation (supported by software). By doing so, CSPs are able to maintain mature operational practices and organizational responsibilities, while having uniform management across disaggregated networks where coherent optical pluggables coexist with traditional transponders. But there are more advantages – if you’re curious, read on and watch the video below.

Why is the Open XR Optics Forum management approach so powerful? The Open XR Optics Forum specifies an approach for dual management of coherent pluggables in which two complementary management paths are supported simultaneously for the same module.

Option 1: Relying on the Host Operating System for the Management of Pluggables

In a deployment in a Layer 2/Layer 3 host (e.g., in a router), pluggables are managed with help from the host operating system (OS). This is what we call the “traditional management path,” where the module functions are accessed by the host’s northbound interface (NBI) or command line interface (CLI). The host OS translates each NBI/CLI management command into a specific instruction to configure and/or monitor the module. Instructions are typically passed between module and host software using Common Management Interface Specification (CMIS), based on simple read and write access to a set of registers.

But if the network operator wants to use a new-to-market pluggable with new configuration options, the management software within the host OS and the NBI, CLI, and CMIS definitions all need to be updated to cope with those changes.

While this procedure has worked fine for grey, short-reach pluggable interfaces, which only support minimal configurations and have evolved little over time, this approach will become a bottleneck when it comes to high-performance intelligent coherent pluggable optics.

QSFP-DD Intelligent Coherent PluggableFigure 1: An intelligent coherent pluggable

A new breed of intelligent coherent pluggables is available that offers a high level of programmability and supports advanced features such as optical spectrum analysis, single-fiber designs, threshold crossing alarms, and the first ever point-to-multipoint operation. This feature set is expected to evolve rapidly and be deployed broadly across multiple host types and models. So, making the management of intelligent coherent pluggables dependent on explicit support in the operating systems of all hosts in a network will dramatically slow down the adoption of pluggable innovations.

Option 2: A Host-independent Approach to Managing Pluggables

By contrast, in a host-independent management approach, the host does not need to be aware of the optical specificities of the pluggable. Instead, the pluggable is managed by a small software application called an intelligent pluggable controller that is deployed outside of the host and integrated into the network’s optical transport control system.

This requires a secure IP connection between the pluggable and the controller. This can be achieved by configuring a management virtual local area network (VLAN) or using virtual routing and forwarding (VRF) in the host, ensuring that management packets with the appropriate tag coming through the host through the data path are handed to the pluggable. Connectivity can also be established through the router data communication network (DCN) port, with the help of a communication agent (an autonomous software piece that runs in the router, independently of its OS) that transfers management packets to the module either via data path or a fast interface such as enhanced serial gigabit media-independent interface (E-SGMII).

This approach bypasses the host CMIS and avoids the inherent capacity limitations of a register-based interface, which slows down functions such as firmware upgrade and restricts the power of streaming telemetry.

The pluggables controller subsumes the handling of the optical parameters, and its pairing with the coherent pluggable optics effectively decouples the optical functionality from the host OS, recovering the demarcation between the packet and optical domains – now in a virtual manner. Following the Open XR Optics Forum’s specifications, any module vendor can bring to market innovative coherent optical pluggables and a matching controller. Infinera’s own intelligent coherent pluggables and intelligent pluggables controller are our ICE-X transceivers and Intelligent Pluggables Manager (IPM) software respectively.

The Value of a Dual-management Approach

Since the Open XR Optics Forum proposes a dual management approach, pluggables can simultaneously be managed through the host device, for example for IP-related or basic configurations during module bring-up, and in a host-independent manner for more sophisticated optical functions. As the features of transceivers evolve, network operators do not have to wait for host software developments and field upgrades that enable them.

Open XR Optics Forum dual management approachFigure 2: Open XR Optics Forum dual management approach

Wide adoption of IPoDWDM won’t be achieved without a network management framework that is robust, scalable, and well suited for mainstream operational practices. The Open XR Optics Forum dual-management approach establishes a virtual demarcation between the packet and optical domains in IPoDWDM networks, aligning with the most common operational practices of CSPs. This approach is particularly valuable when the types of coherent optical pluggables become diverse, as do the hosts they are deployed in (routers, but also servers or radio units, and from multiple vendors), avoiding combination-related challenges in IPoDWDM operation.