The Open Broadband-Broadband Access Abstraction (OB-BAA) is an open source project that specifies the Northbound Interfaces (NBI), Core Components and Southbound Adapter Interfaces (SAI) for functions associated with the access network devices (e.g., configuration, reporting, alarms) that have been virtualized. Inherent in the OB-BAA project is the ability to pull differing access device types, including legacy implementations, together under a single network and service management &control umbrella to be exposed to management elements such as the SDN Management and/or Control and Element Management Systems. The OB-BAA project is designed to be deployed as as one or more virtualized network functions (VNFs) that provide a reference implementation of the BBF's Cloud CO BAA layer. Because the NBI and SAI utilize standardized data models and the Core components of the OB-BAA project are designed as virtualized micro-services with specified interfaces, the components of the OB-BAA project can also be adapted and deployed in other virtualized or non-virtualized environments.
The high level functional diagram for the BAA layer is shown in the figure below.
The BAA Core provides functions needed manage and control Access PNFs, either legacy or hardware disaggregated. These functions are defined independent of the protocols used to communicate with the network elements to the south or with the management and control elements to the north. This independence is achieved by using standardized network abstraction interfaces at the northbound and device adaptation interfaces at the southbound edge of the BAA Core.
The Northbound Abstraction Interface (NAI) and SAI are combined with protocol‑specific adapters and, in the case of SAI, also device‑specific adapters to express the BAA NBIs and Soutbound Interfaces (SBI), i.e. the external interfaces that allow the interaction with the SDN Manager and Controller and the Access Nodes respectively.
The combination of the NBI/NAI–Core–SAI/SBI converts generic messages from the SDN Management and Control (SDN M&C) elements into protocol-specific/device-specific messages used to communicate with external access devices and vice versa.
Southbound (SB) layer
The Southbound layer (SB) contains device adapters that support communication with the access devices in the network. These adapters may be device‑specific in that they provide a low-level interface to device hardware or accommodate vendor variations between devices. Alternatively, they may be a generic device adapter designed to interface with devices from multiple vendors. In either case, the device adapter must comply with the SAI API which is the standards‑based interface between the BAA Core and the access devices. This interface is specified via the required data models and procedures, which in turn govern the interworking between systems from different sources. Since communication with specific a Access Node relies on device adapter, the interface between the adapter and the Access Node is device‑specific and is not considered a point of interworking. Device adapters may use southbound protocol libraries provided as common resources, or they can embed their own protocols as needed.
Southbound Adaptation Interface (SAI)
The SAI is specified via the required data models and procedures, which in turn provide a first degree of adaptation between the Core and the Access Nodes to the south.
Northbound (NB) layer
Northbound the BAA layer communicates with one or more management and control systems which may include access network managers, SDN managers and controllers, and potentially directly with other management entities such as the CloudCO's Domain Orchestrators. These systems may use different protocols to communicate with functions in the BAA Core. The BAA’s NB layer exposes one or more NBIs with the appropriate protocol(s) by applying protocol adapters at the NAI, the systems to the north can be redefined and interfaces can be updated to use a different protocol (e.g., RESTCONF or NETCONF) with minimum redesign.
Since the NBI relies on common protocol adapters, there is no analogy to the device-specific interfaces at the SBI, and the behavior of the protocol adapters should be defined by standards per each of the applicable protocols. However, the data carried by the protocols is specified at the abstraction interface.
Northbound Abstraction Interface (NAI)
The NAI is specified via the required data models and procedures. It exposes a standardized abstract representation of access resources that allows the interworking between the Core and the SDN Management and Control elements to the north. For some deployment options it also exposes standardized technology-specific interfaces to manage physical layer and other AN specific attributes.
BAA layer Deployed as an Actuator
When deployed as an Actuator, the BAA layer acts as an aggregating entity that provides actuation capabilities of control and management functions expressed by northbound SDN M&C elements where the BAA layer can be deployed as an executes the inputs received from the SDN M&C element(s) and may act as a proxy of the data (flow information, PM and alarm reports) received from the ANs.
The benefits of deploying BAA layer as an actuator is that the BAA layer aggregates the connectivity of the ANs toward the SDN M&C and acts as the authoritative source of truth and provides an always-on digital representation for the ANs. In addition to providing the digital representation of the AN, the BAA layer does proxy/relay selected data from the ANs toward management elements (e.g., control, PM and alarms). The determination of what data is relayed toward the SDN M&C elements is dependent on the capabilities and characteristics of the BAA layer with respect to the management and control architecture in which it is deployed.
The figures below depicts the BAA layer deployed as an Actuator: the Minf_L1 interface that provides a vendor agnostic representation of L1 management plane while the Minf_L2-3 and Mfc_L2-3 interfaces provide an abstract (i.e. vendor and technology agnostic) representation of the L2-3 management and control plane. The distinction between Minf_L2-3/Mfc_L2-3 and Minf_L1 interfaces enables the separation of Service Provisioning tasks from Network Operation tasks. The functionalities exposed by these interfaces are configurable with out-of-the-box configurations that map to standardized Data Models (e.g., TR-385 OLT, TR-301 DPU, TR-383 Firmware Management and TR-383 forwarding module).
In addition, both the Minf and Mfc interfaces provide the capability to transmit data from the AN toward the SDN M&C element. In some cases, the BAA layer uses the data as it provides the AN digital representations (e.g., operation states, current alarms, current PM) while other times BAA layer acts as a relay encapsulating the data without acting on the data in any way (e.g. DHCP snooping, IGMP control). In all cases the data is presented in a vendor and technology agnostic way toward the management systems for the type of access node. Note that the proxy and relay capability is not part of this release.