Converged Core Networks Increase Sustainability

As the foundation for any organization's communication strategy, Core Networks have traditionally been architected with one primary goal: moving traffic from point A to point B.  With the advent of packet and optical network convergence, a new objective is becoming increasingly critical: architecting the core network with long-term sustainability.

Packet and optical network convergence is the blending of what have traditionally been two separate network functions into one combined layer.  Historically, packet-based routers and optical DWDM transponders have been developed in parallel to one another, and different engineering teams have often operated them.

Today, converged technology allows organizations to combine optical and packet layers by moving the DWDM transponder function from dedicated equipment to a compact pluggable optic inserted directly into a router's port.  This convergence allows organizations to retire dedicated transponders, leading to a reduction in chassis equipment as well as power and cooling infrastructure.

The primary benefit of this convergence is a significant simplification of core networks, improving their ability to move traffic from point A to point B at scale.  But another benefit is quickly gaining traction: power savings that align with sustainability strategies such as WWT's Environmental, Social and Governance (ESG) initiative.

For example, modeling of the Cisco Routed Optical Networking (RON) solution shows up to 45 percent power reduction and up to 70 percent real estate savings.  The enhanced programmability of the network through automation and new packaging of optics and other platforms to use less material can help organizations lower emissions and achieve their overall sustainability goals.

An example

Let's consider a simple use-case of an organization looking to expand its network core to 400G links.

In a traditional architecture where the optical and routing layers are kept separate, this could mean implementing the 400 Gbps XPonder line card in the NCS 2000 chassis, to provide 400G of bandwidth across the WAN and a matching 400G of bandwidth to the routed layer:

If the same organization instead adopted a Converged architecture, they would forego the XPonder line card and instead place a DWDM-capable pluggable optic into a Modular Port Adaptor (MPA) in their routers to provide 400G of WAN bandwidth directly out of the router.  This is possible because of recent advancements in Digital Coherent Optics (DCO) which allow higher bandwidth to be pushed over greater distances without frequent regeneration.  All of this through smaller form factors such as CFP2 and QSFP-DD.

In this scenario, the Converged option is simpler to manage and better equipped to scale up and out in the future--and these are the benefits leading many organizations to move towards Converged architectures.  However, the benefit of improved sustainability can also be demonstrated using simple napkin math.

The traditional solution that leverages an Xponder card inside an NCS 2000 requires approximately 330 Watts of power.  The converged solution that leverages an MPA in the router requires about 75-85 Watts.  That's a power reduction of over 77% in this one function alone.  Over the course of an entire year, this represents a reduction of over 4,000 kilowatt-hours per 400G core link.

As if the power savings aren't enough, additional efficiencies stack up when you consider the smaller form factor of the MPA (meaning less material packaging, shipping, storage, etc.) and the fact that configuration now occurs on a single device rather than two.

If the organization can fully retire its NCS 2000 chassis systems in favor of a simplified optical line system (such as NCS 1000 amplifiers and filters), then even more significant energy savings can be realized.  This option won't be suitable for every organization as certain DWDM functions like ROADM and OTN still serve a purpose in many architectures.  But as the transponder function has been collapsed into DCO pluggable form factor, the efficiencies described above continue to become more and more appealing.

The bottom line

Convergence of the network core will continue to grow in popularity as bandwidth standards move from 400 Gbps to 800 Gbps today and from 800 Gbps to multiple Tbps tomorrow.  As this growth occurs, it will be critical that we build the network of the future with long-term sustainability in mind.  What we once thought of as moving bits from point A to point B must now be thought of as enabling robust communications in an environmentally friendly way.  Converged packet & optical architectures already offer significant benefits in scaling network performance, and soon they will become critical to organizations' long-term sustainability efforts.