TECHNICAL
the mid-2000s, legacy SONET/SDH networks started to become obsolete with the emergence of Ethernet services that demanded packet-based networks to support the full spectrum of services required by the market (e.g., MEF E-Line, E-LAN, and E-Tree services). Despite industry attempts to extend the life of SONET/SDH systems by integrating Ethernet services, eventually packet- based carrier Ethernet solutions became ubiquitous given their superior economic benefits and technical advantages. At the time, the industry also went through a major debate about people skills, as carrier Ethernet was very different from legacy time-division multiplexing (TDM) technologies. Eventually the business drivers pushed the industry to find a solution— transport network operators became fluent in carrier Ethernet technologies at the same time as traditional IP network engineers. Most network operators embraced the new technologies introduced to deliver Ethernet services over IP/MPLS, and today few in the industry would argue there’s a lack of technical expertise to operate IP/MPLS-based carrier Ethernet networks in any major equipment vendor or service provider. With routed optical networking, we’re at the start of a similar transition. The new technology components push network engineers from both transport and IP organisations out of their comfort zones. However, there’s a major difference this time. With very few exceptions—like private line emulation (PLE) that’s truly a new industry development—most components of routed optical networking are optimisations of well-established technologies. DCO pluggable transceivers are compact implementations of DWDM transponders. DWDM line systems are based on the same reconfigurable optical add-drop multiplexer (ROADM) technologies currently used, just with a bigger focus on operational simplicity, automation, and provisioning of “alien” wavelengths (i.e., DWDM signals generated directly by a client of the network). IP/MPLS networks can be simplified by adopting segment routing when possible, while reuse of classical routing paradigms based on IP/MPLS with label distribution protocol (LDP) or resource reservation protocol (RSVP) is also an option, even though it provides less optimal results. Both approaches are well known and widely deployed in the industry. Lastly, at the network operations level, automation
optical networking and a key source of the dramatic economic savings of the solution, and the fact that 400Gbps DCO has been standardised and embraced by the optics industry (e.g., through Open ROADM and OpenZR+) adds to the vast list of benefits provided by the technology. However, the value of the solution goes well beyond that. Arguably, the biggest benefit of routed optical networking is the full services convergence and the network efficiencies enabled by packet switching with the intelligence, efficiency, and operational simplicity of a modern, end-to-end routed IP/MPLS network. This paper discusses in greater detail those additional network efficiency gains enabled by the optimised routing layer and other relevant aspects of routed optical networking that aim to bridge the gap between packet and transport networks. But before we talk about technology, let’s address another common topic related to any network transformation. Are people skills a real problem for routed optical networking adoption? The technology components of routed optical networking are full of innovations in silicon, optics, network protocols, and software tools. That raises questions about the technical skills required by operators who will run day-to-day network tasks. Let’s remember that this isn’t the first time the traditional transport industry has undergone a major transformation. During
Figure 1: Routed optical networking architecture: A simplified end-to-end, fully converged IP/MPLS network tightly integrated with the DWDM layer built for cost efficiency and business agility.
MARCH 2024 Volume 46 No.1
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