TECHNICAL
In addition to the protection mechanisms described above, transport networks often employed restoration mechanisms at the DWDM and/or OTN layers to protect against multiple simultaneous failures. Those restoration mechanisms are costly in the way they’re commonly implemented by deploying regenerators throughout the network and mathematically challenging in finding optimum placement for those regenerators. Conversely, a properly engineered IP network using TI-LFA outperforms any such restoration mechanisms with respect to the switching times. Furthermore, well-designed IP networks can provide massive fibre savings where a sizable percentage of restoration fibre routes can be eliminated through proper IP network planning or used to carry paying services instead of sitting idle most of the time. Another common requirement of transport networks is path predictability. Transport network operators require the ability to co-route traffic, which means map upstream and downstream traffic over a congruent, well-defined path in the network. This applies to the active/protection paths, and it’s the way synchronous optical network (SONET) and synchronous digital hierarchy (SDH) networks operated with unidirectional path switched ring (UPSR) and subnetwork connection protection (SNC-P). Electrical OTN and DWDM use similar techniques. Thanks again to segment routing, IP/ MPLS networks provide those transport capabilities by leveraging the new circuit- style segment routing (CS-SR) solution. CS-SR leverages network controllers to configure congruent upstream/ downstream active/protection paths with sub-50ms switching times. When CS-SR is combined with private line emulation, which provides bit-level transparency and predictable bandwidth consumption, the network behaviour is fully predictable to meet transport network operator requirements. Besides meeting required transport switching times, IP/MPLS networks have additional benefits in creating rich SLAs for more advanced services. Segment routing provides additional SLA metrics and advanced capabilities that are implemented through segment routing policies. Those policies can include latency limits, secure paths and diverse paths, among others. Segment routing makes the definition of such policies, which translate to SLAs, much
simpler, is intent based, and automates traffic steering and policy enforcement by the network, which will honour those SLAs whenever it’s possible, even when topology changes or failures happen in the network. Another key aspect of providing high SLAs is the ability to monitor and report the performance of the service across the network using operations, administration and maintenance (OAM) tools. Once again, IP/ MPLS networks have never been so well equipped to provide those capabilities. Besides the rich set of OAM tools available for classic IP/MPLS networks, segment routing adds additional tools for performance management (PM) and data-plane monitoring and PLE is also adding additional functions to monitor the network performance. In summary, IP/MPLS networks can be designed to meet strict SLAs required by transport services. In addition, segment routing–based IP/MPLS can provide unique capabilities that support richer and even more-strict SLAs, considering additional network metrics and criteria including latency, path diversity, path security and possibly others. Conclusion IP and optical integration is a fundamental part of routed optical networking given the significant economic benefits provided by the current 400Gbps digital coherent optics pluggable transceiver technology. However, routed optical networking goes far beyond that, and when deployed with modern IP/MPLS technology, it brings network optimisations and efficiencies to another level. In summary, IP/MPLS provides the following key benefits to routed optical networking:
n More efficient use of scarce DWDM wavelengths through statistical multiplexing and traffic aggregation leveraging direct router-to-router designs that better align with fibre topology, plus optional centralised traffic engineering. n Full services convergence: IP/MPLS is the de facto multiservice technology and the only networking technology capable of supporting L1 (emulated TDM circuits), L2 (point-to-point and multipoint Ethernet), and L3 services (internet, IP VPNs). The addition of PLE technology enabled by routed optical networking expands the IP/ MPLS capabilities further to support bit-transparent services for high-speed circuits, including OTN, Ethernet and storage protocols as clients. n Optimal traffic forwarding, improving network efficiencies, application performance, and user experience while providing a flexible, future-proof infrastructure that can deal with any changes in application placement or internet peering strategies. n Simpler network architecture, with higher focus on delayering the network using an IP/MPLS-centric architecture. IP/MPLS technologies are fully capable of meeting the most stringent service requirements including network resiliency and advanced SLAs. It’s also truly multiservice. As a result, the network can be designed without overlapping functions like protection at multiple switching layers, which simplifies the requirements to the DWDM network and results in a network with fewer touchpoints that’s simpler to operate and automate.
80
Volume 46 No.1 March 2024
Made with FlippingBook Online newsletter maker