Page 1364 - 5G Basics - Core Network Aspects

3 Signalling aspects

Sma
Application entities Application plane
Sa
Smo
Management plane Smc SDN control Sew SDN control Control plane
Orchestration entities
Sn

entities
entities
Ss Ss

Smn Network Network Transport plane
entities entities

Q Suppl.67(15)_F7-1

Figure 7-1 – The signalling model of SDN framework

Figure 7-1 depicts the basic signalling model of SDN framework which consists of three horizontal planes and
one vertical plane. These are the: Application plane, control plane, transport plane and management plane.
In the application plane, the application entities, i.e., SDN-enabled applications, communicate their network
needs/policies/requirements/hints to the orchestration entities in the control plane.

The orchestration entities in the control plane provide network service open API and service control, e.g.,
service provision, service composition/encapsulation/exposure and negotiation between different SDN
control entities. These also provide middlebox management functions such as checking their availability,
monitoring resource status and providing connection information (e.g., IP address, port, etc.).
The SDN control entities (CE) in the control plane perform logically centralized control of network entities
(NEs), translating the intention communicated with orchestration entities to detailed instructions that are
sent to the underlying, low-level SDN data paths, and offering an abstraction of the SDN data paths to provide
a logical view of the network. There will also be interactions between SDN control entities if they are in
different administrative domains.
In the transport plane, the NEs perform forwarding and processing capabilities.

The management plane provides functionalities for traditional fault management, configuration
management, accounting management, performance management and security management (FCAPS), as
described in [ITU-T M.3400]. The management plane interacts with all the horizontal planes.

8 Description of interfaces in the signalling model

8.1 Sa

The Sa interface permits application entities, e.g., SDN-aware network services, applications, or other users
of SDN to interact with the orchestration entities. HTTP (such as RESTful web API) or other protocols may run
over this interface. Applications' explicit requirements and network state, stats and events can be exchanged
between application entities and orchestration entities via this interface.

8.2 Sn
The Sn interface permits interactions between orchestration entities and SDN control entities, providing the
generation of detailed or abstracted views of the networks to permit the orchestration entities to configure/
manage/control the SDN CEs by interacting with the view. This interface translates the applications'
requirements and enforces behaviours of orchestration entities. The functions of this interface include:

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