SERGE MELLE IP-OPTICAL INTEGRATION
unnecessary router hops when these are not needed, and which otherwise add latency, consume router switch fabric capacity, space, and power, and very importantly requires additional 400G pluggable coherent ports at the ingress and egress of each transit router, simply to transit the packet traffic. ROADM-enabled optical line systems enable IP-optical deployments over complex ring or mesh fibre topologies and provide a key tool that allows network operators to optimise the overall router and IP link topology, maximises IP network scaling, ensures network resiliency and minimises TCO. OPTIMAL COHERENT OPTICS Network operators must also consider the optimal type of coherent optics needed for their application. As described above, 400ZR/ZR+ are optimal for access/metro point-point DCI applications. However, multi-node access/aggregation and metro core applications with ROADMs may require high-performance 400G pluggable DCOs that support the higher optical launch powers and signal-to-noise ratio needed in such applications. Finally, traditional transponder-based architectures will continue to be ideal to aggregate large amounts of 100GE router interfaces, and/ or in regional and long-haul applications where coherent optics optimised for maximum capacity-reach performance are needed (Figure 1). Operational and management aspects critical to IP-optical integration success: The disaggregation of transponder and optical line systems, and integration of the photonic data plane into the router, removes the traditional hard demarcation between the IP routing and optical transport layers making deployable multilayer coordination of operations a necessity. This transition will transform the relationship between IP routing and optical transport, and simultaneously restructure some operational responsibilities and practices. As IP routers integrate coherent optical transport capabilities, a focus on improved cross domain management becomes critical, and arises from the fact that routers will play an integral role in port and link management practices that were traditionally the jurisdiction of the optical transport network. Router and optical networks will jointly play important roles in discovering and identifying pluggable coherent optics equipped in router ports, managing operational parameters such as power, modulation and wavelength provisioning, optical connectivity discovery, and monitoring performance indicators such as forward error correction (FEC) and bit error rate (BER). Also important is ensuring end-to-end coordination of IP-optical parameters such as channel selection, wavelength routes, physical diversity and restoration options, and maintenance
Figure 2: Intent-based end-to-end multi-layer management, control and automation, delivered via operationalisable use cases, enables successful operationalisation of IP-optical architectures. IP-optical coordination and automation use cases. Source: Nokia.
and troubleshooting of optical links, for example.
optical experts, and allows the primary fault location to be rapidly identified and service-affecting issues resolved. Coordinated operational control can also assist with activities such as maintenance, when for example, IP traffic can be moved away from fibre links that must be taken out of service for maintenance operations. OPTIMISATION AND AUTOMATION Finally, optimisation and automation of service creation and protection provides rapid reactive and proactive engineering responses to changing network conditions. This includes coordinating elastic link aggregation (LAG), supporting variable link bandwidth needs in the IP layer, with optical bandwidth re-configuration due to distance or modulation, for example, thereby accommodating end-to- end traffic flows with correctly sized bandwidth.
OPERATIONAL MODEL The need to closely manage and
coordinate all this across converged IP- optical architectures will accelerate and intensify the need for flexible and powerful tools to operate efficiently across layers, navigating and coordinating operational activities between the IP and optical worlds. What is needed is an operational model with the tools to enable efficient, seamless multilayer, cross-domain operations. Fortunately, new technologies are appearing to support the development of these cross-domain tools, leveraging intent-based workflows and automation use cases. The visibility provided by these tools and the crucial, actionable data they bring, enables optimal decision making, and efficient and automated control of the network. These capabilities can be leveraged across all network lifecycle operations such as: configuration, maintenance, traffic engineering and service availability assurance. USE CASES The leading use cases for IP-optical coordination and automation can be placed into three categories for discussion: Discovery, Correlation and Optimisation. Discovery use cases operationalise automated cross-domain topology discovery and provide insight and visibility into cross domain topologies of networks, to reduce probability of service outages, simplify troubleshooting and tighten latency control. Automated topology management can ensure that the path diversity needed for IP links or services is replicated in the wavelength connections over line systems and fibre paths, and diversity analysis tools can perform real time analysis of any shared risks, establishing diverse paths as necessary and reducing the probability of service outages. Correlation use cases allow events and activities across layers to be synchronised and associated for operational efficiency. Coordinated and automated cross-domain troubleshooting assists with rapid root cause identification, facilitate inter- team communications between IP and
Cross-domain coordination of protection can also leverage the
efficiencies and performance of using multi-layer protection such as 1+1 or 1:N optical protection schemes, rather than relying solely on IP domain mechanisms, such as redundant traffic provisioning or fast reroute, and can reduce total network cost in the process. “What-if” analytical optimisation tools complement real- time network optimisation to provide useful predictions of network response to infrastructure failures, and enable pro- active optimisation of redundant capacity availability, and help plan where more backup resources are needed.
CONCLUSION Implementing successful IP-optical
solutions across a wide range of network use cases will be enabled by leveraging the unique capabilities of both the IP and optical layers, including high-performance pluggable DCOs deployed in routers, ROADM-enabled optical line systems, and unified cross-domain management and automation tools. When considered and deployed in synergy, the combination of these building blocks into a complete IP-optical solution provides the scalability, efficiency and simplicity needed by network operators to realize the expected benefits of IP-optical integration.
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ISSUE 30 | Q3 2022
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