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Comcast Taps 'Trellis' Open Fabric for Distributed Access Architecture

Light Reading
News Analysis
Light Reading
9/16/2019

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.


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The production rollout of Trellis, which is now accelerating across Comcast's network, comes after years of design work and field trials, Comcast said.

ONF highlighted Comcast's open-source rollout at its ONF Connect conference on Friday.

"This is a confirmation and validation of our strategy," said Timon Sloane, ONF's vice president of standards and membership. He played up the opportunity for industry collaboration that comes along with open networking. "The team that built this has multiple supply-chain vendors working together," Sloane said.

ONF expects Comcast's to be the first of many such announcements. Service providers that have been discussing production deployments of open networking systems, such as AT&T and Deutsche Telekom, have been talking about 2020 time frames. Several other operators, including AT&T, Sprint, NTT, China Unicom, Turk Telecom, Telefonica and T-Mobile Poland, are also active supporters of ONF.

Why this matters
Comcast is keeping its options open in rolling out DAA by using open-source software for a major piece of its architecture in multiple markets. Its decision to deploy the open Trellis fabric, and be public about it, should give other network operators more confidence in open networking, and additional big rollouts like Comcast's could expand the ecosystem around these technologies so Comcast has more suppliers and developers to tap into in the future.

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Stephen Lawson, special to Light Reading. Follow him on Twitter @sdlawsonmedia

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