Due to a ransomware attack, the wiki was reverted to a July 2022 version. . We apologize for the lack of a more recent valid backup.
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Overview
In order to manage the infrastructure, ONOS must keep track of information about the infrastructure (topology, installed flows, etc) in a form available to its applications. Importantly, the applications must be shielded from protocol-specifics, even if network state information is collected in protocol-specific ways.
As a solution, ONOS maintains protocol-agnostic and protocol-specific network element and state representations that can be translated from one to the other. The former are constructs of the core tier, referred to as Model Objects, and the latter are constructs of the appropriate provider. For example, DeviceStore (and consequently the DeviceManager and DeviceListeners) sees a network device as a Device, whereas the OpenFlowDeviceProvider will see the device as an OpenFlowSwitch. Recall that these two representations are bridged across the provider and core layers by the intermediate transcription into a DeviceDescription. Model Objects are what ONOS exposes to its applications.
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The interface definitions and implementations of these objects can be found across several packages under [org.onlab.onosonosproject.net.*]. While not formal, implicit object classifications fall out of the organization of these packages.Note that the following list is not comprehensive.
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- OutboundPacket - Protocol agnostic representation of a synthetic packet to be emitted on the network. This includes information about where to emit this packet.
- InboundPacket - Protocol agnostic representation of a packet sent to the controller by a device. This enables reactive packet processing by making PacketIns available to providers and applications to use as needed, e.g. host tracking, link detection.
Model Object Dependencies
Some entities rely on the existence of other entities, as in the case of Ports, which cannot exist without a Device. Similarly, Links, and by extension, Topologies, cannot exist without Ports serving as endpoints to the Link. We therefore consider Devices to be a first-class entity in ONOS's network representations.
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