AT&T isn’t just working to beef up its residential fiber infrastructure. The operator’s VP of Network Core Infrastructure Services Mike Satterlee and AVP of Network Infrastructure Services John Gibbons told Fierce its 400G-based fiber backbone currently carries 453 petabytes of domestic traffic each day and noted plans are in place to ensure its core architecture can scale as bandwidth demand rises.
The fiber backbone serves both AT&T's fiber broadband and 5G networks. The operator has openly been working over the past several years to transition to a white box-based architecture, but Gibbons noted it recently crossed the halfway point in its shift. Today, 52% of the aforementioned traffic runs on its new disaggregated infrastructure powered by Broadcom silicon and Drivenets’ network operating system. By the end of 2023, it is looking to push that figure to 65%, he said. Satterlee explained AT&T currently uses 400G technology for its core backbone and 100G uplinks to connect edge nodes to the core. But the latter are already beginning to shift to 400G and AT&T has its eye on pushing the core to 800G as costs come down, he added.
“Once we need more than a single hundred gig link [at the edge] – which often we do – it’s cheaper to go right to 400[G] than doing two hundreds. So, the economics of 400[G] is really coming into play right now,” Gibbons said. “Eventually we feel 800[G] will as well, but that’s probably two to three years out.” There’s another reason AT&T isn’t moving to 800G just yet that goes beyond cost. Gibbons noted the operator is also waiting for the standards to mature to ensure the technology is fully open, just like the rest of its revamped network.
Coherent optics and Open ROADM The move to white box architecture gave AT&T the flexibility to deploy infrastructure using a building block approach. That means it can roll out one “pizza box” in a central office to support something like a small business network or as many as 48 in a cluster for a core switching node, Satterlee said.
Gibbons noted white boxes offer AT&T a capital savings of about 10X compared to traditional chassis and line card architecture. But AT&T is also looking at other ways it can tweak its network to save money using coherent optics and Open ROADM.
Satterlee explained transponders account for around 70% of the cost of optical infrastructure. In the past, operators were locked in to deploying optical equipment from the same vendor on both ends of a line. Open ROADM, however, allows it to mix and match and therefore save money.
AT&T began integrating Open ROADM into its network a few years back. Thus far, the operator has deployed over 100 nodes and has production traffic flowing over a 100G connection, Gibbons said. “We’re going to move to 400-gig this year,” he added. “So, it’s for real.” As far as transponders go, AT&T is also looking at coherent optics as a way to cut costs. Gibbons explained coherent optics would allow allow AT&T to put the optics in a router instead of using a transponder.
He added it’s doing “a lot of trials on that now” but deployments are “probably a year or two out.”