VOLTHA provides a layer of abstraction over vendor-specific and white-box PON hardware devices. On its northbound interface, VOLTHA abstracts the PON network to appear as a programmable Ethernet switch to an SDN controller. On its southbound side, VOLTHA communicates with PON devices through vendor or device specific OLT and ONU adapters. VOLTHA has adapters contributed by OEM vendors and the community for both proprietary and white box devices. Contrary to what one might expect - the adapters are not just a translation layers; they are fairly complex, state-full modules that implement the core of PON device management. Adding support for a new hardware device entails a fairly good understanding VOLTHA internals which can be daunting especially for smaller white-box vendors with limited software development resources. One of the objectives of the current VOLTHA 2.0 release is to introduce a common OLT adapter that enables rapid onboarding of new white-box and proprietary OLT devices. This new adapter, called OpenOLT, exposes a well-defined protobuf-based, vendor-agnostic gRPC interface on the southbound side. OLT OEM/ODM device vendors are now able to re-use the OpenOLT adapter and focus on implementing the gRPC OpenOLT agent on their device. OpenOLT is actively being developed with code contributions from ONF, AT&T Foundry and members of the VOLTHA community and currently has support for OLT devices from EdgeCore, CIG and Iskratel. This paper presents the motivation, design, interfaces, current status and future development of OpenOLT.
