DDC – Distributed Disaggregated Chassis

Distributed Disaggregated Chassis (DDC)

Today’s routing infrastructure is still hardware centric, complex, monolithic, and proprietary.
However, there is an alternative DDC, or distributed disaggregated chassis, a new architecture for building flexible and simple to operate networking
infrastructure.

DDC provides the high performance of a chassis with the high scalability and flexibility of Clos. Breaking up the traditional chassis, DDC
disaggregates hardware from software. With DDC, chassis modules are distributed into an array of standard white box units.

Components such as line cards, fabric cards, or controllers are transformed into white box building blocks with optical cables replacing the chassis backplane. In this way, DDC functions as a virtual chassis that’s connected in a physical Clos topology.

DDC components are distributed into several standalone devices that act as line cards and fabric cards. These standalone devices can be purchased
as standard white boxes separate from the software that runs them. While this looks like a typical Clos, DDC offers two key differences.

• First, even though it can seamlessly scale out using the same white boxes to grow to various cluster sizes, it is still managed as a single network device.
• Second, unlike Ethernet, which is a lossy technology interconnecting Clos, DDC has a lossless and a predictable fabric thanks to a scheduled cell based fabric.

Just as in a chassis, DDC spreads the traffic evenly across all the multiple spines. When a packet enters the system, it’s segmented into fabric cells before being
sent to the fabric, ensuring equal distribution. These cells are evenly distributed across all links of the white box fabric. This near perfect traffic distribution
method is independent of the quantity and sizes of flows and their entropy.A credit- based mechanism ensures there is no packet loss.

DDC also employs an end to end virtual output queuing or VoQ mechanism to eliminate head of line blocking bottlenecks. Both service providers and hyperscalers
use DDC to build their networking infrastructure.

• For service providers, DDC supports multiple network use cases from core and peering to metroedge and aggregation with the same two white box building blocks
  but in different sizes of network router clusters. DDC simplifies operations and warehousing, flattening the network hierarchy.
• For hyperscalers, using DDC for AI backend networks to support AI infrastructure, DDC offers a predictable, lossless backend cluster connectivity and improves the performance of high scale AI workloads by 10 to 30% in job completion time.

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