Comcast Taps 'Trellis' Open Fabric for Distributed Access ArchitectureComcast Taps 'Trellis' Open Fabric for Distributed Access Architecture

SANTA CLARA, Calif. -- Comcast has deployed an open-source Ethernet fabric in multiple markets as part of its Distributed Access Architecture (DAA) buildout, taking a chance on an emerging technology it hopes will provide greater scalability, efficiency and flexibility.

The cable operator said last week it is already using the Trellis Open Source Network Fabric from the Open Networking Foundation on its production network. It is part of infrastructure delivering Xfinity TV, Internet and video-on-demand services on a scale of tens of thousands of subscribers, with the deployment continuing to grow. That makes it the first network operator to put an ONF technology to work on a large scale, according to ONF.

The open-source approach allows Comcast to tap into an ecosystem of white-box hardware vendors and open-source developers that could give it more equipment options -- and less expensive ones -- as it evolves its access and edge architecture. It could also make new software features easier to implement. But open networking technologies are just beginning to enter commercial use, while traditional equipment still makes up the lion's share of network rollouts.

Trellis is a virtualized control plane, running on standard servers in the cloud, for white-box switches that make up the data plane. In the DAA architecture, Comcast is using Trellis as the Converged Interconnect Network (CIN), an Ethernet fabric that links its Remote PHY units near customers' homes with the cable modem termination system (CMTS) infrastructure that manages subscribers. Trellis controls the data plane through the Open Network Operating System (ONOS) SDN operating system, using ONF's OpenFlow protocol.

With Trellis, Comcast is centralizing intelligence instead of having to run embedded switching and routing protocols on individual switches. The open approach is also expected to make designing, debugging and upgrading the network easier.

Figure 1: Photo by Mike Mozart (CC BY 2.0)