The adoption of OTN switching as a network underlay for IP and private line services has seen rapid acceleration. Tim Doiron, Vice President of Solutions Marketing at Infinera, shared three key insights from the "Beyond OTN Core Switching: Transport Network Evolution" whitepaper.
OTN Switching Background
Originally introduced in the late 2000s, OTN switching provided network operators with a higher-capacity alternative to SONET/SDH cross-connects. It effectively integrated TDM and packet traffic into a unified technology, gaining momentum alongside the adoption of 100G coherent technology in the early 2010s.
Initially deployed primarily as an underlay, OTN switching ensured end-to-end transport connectivity for various network traffic types, including internet, IP VPN, Ethernet services, and private lines. However, significant changes have occurred over the past nearly two decades.
The landscape has evolved dramatically, marked by an 80-fold increase in Ethernet switching and IP routing silicon capacities, now capable of delivering up to 51.2 Tb/s and 28.8 Tb/s respectively using readily available merchant chips. Coherent optics have also progressed from 100 Gb/s per wave to the terabit era, offering enhanced reach and reduced power consumption per bit.
Moreover, modern network traffic patterns predominantly feature IP traffic over wavelengths, driven largely by connectivity to cloud data centers. This shift has transformed traffic dynamics from a decentralized "any to any" model to a more centralized "hub and spoke" architecture.
OTN Switching Trends
According to Doiron, research indicates that high-speed private line services are increasingly bypassing centralized OTN switching. With the shift from low-speed to high-speed services and the introduction of ultra-high-speed services like 400G, this trend is expected to accelerate even further.
Service providers also described the biggest challenges they face with their current OTN switching infrastructure: lack of high-speed coherent line interfaces and high capital costs.
“With centralized OTN switching, it’s not just a new higher-speed line interface that is needed. The switching fabric must also scale to support the increased capacity of the line cards and line interfaces,” explained Doiron. “This process and the dependencies among the line interfaces, backplane connectivity speeds, and switch fabric capacity add complexity and cost.”
When service providers were asked about their network architecture plan, 82% of respondents expect to cap their centralized OTN switching investments by the end of 2025, while 67% expect to remove their centralized OTN switching in the same year.
Doiron stated that a shift to a distributed OTN architecture could be the next step for network operators, helping them transition from centralized OTN switching while supporting legacy services and reducing space, power, and costs.
Infinera's analysis of four real-world networks showed that switchponder-based distributed OTN solutions could achieve up to 45% CapEx savings, 44% power savings, and 68% space savings compared to traditional OTN switches. Additional benefits included higher availability, lower latency, and reduced high vendor support fees typically associated with legacy OTN switches.
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