Cisco worked with T-Mobile to build a virtualized packet core throughout the mobile operator’s nationwide footprint. Cisco’s software-defined network (SDN) architecture now supports T-Mobile’s more than 70 million customers.

The two companies have also signed a five-year agreement in which Cisco will continue to provide the virtualized packet core part of the network as T-Mobile migrates to 5G. The deal includes hardware, software, and other services.

The virtualized packet core is considered the “brains” of the network. In all-IP networks like LTE, the packet core is the smarts of the network where quality of service, policy enforcement, security, and other services converge. Moving to a virtualized packet core means that operators can deploy new services more quickly and in a more automated way than before. The packet core is separate from the RAN, but often traditional RAN vendors bundle the mobile packet core into their service offerings.

Because Cisco is not a RAN vendor, it has offered its virtualized packet core as a standalone product.

Neville Ray, T-Mobile’s CTO, said that deploying the virtualized core architecture was a significant undertaking for the company because it had to shift from a centralized architecture to a distributed architecture. “We couldn’t have achieved that without virtualization,” Ray said in a statement.

Ray added that moving to a virtualized core will set the company up to be able to deploy 5G with more flexibility and deliver new services to customers more quickly.

Cisco said that T-Mobile’s virtualized packet core deployment is the largest one operating today.