Page 680 - Cloud computing: From paradigm to operation

3 XaaS

the NaaS CSC. This representation avoids the direct communication and interaction between the NaaS CSC
and these NaaS resources (e.g., network elements of the NaaS CSP infrastructure) and masks implementation
specific aspects of NaaS resources used in the context of the NaaS service instance. This abstract view
presented to the NaaS CSC also allows real-time configuration change demands from the NaaS CSC to be
reflected by the NaaS CSP on its own resources. Therefore, a hierarchical and extensible framework, which
can be realised by a set of information models, needs to be designed to hide the protocol specific and/or
vendor specific details of the resources being used by the NaaS CSP. The modelled objects being part of these
NaaS information models can be grouped as NaaS resource model, NaaS service model, and NaaS service
operational policy model.
NaaS resource models reflect in an abstract manner NaaS CSP's resources including their associated
topological view across different layers (e.g., layer 2 (L2) and layer 3 (L3)). NaaS resource models designed by
the NaaS CSP or cloud service partners (CSNs) (e.g., service developer) are used by the NaaS CSP to represent
NaaS CSP's resources at a conceptual level, including physical and/or virtualized network functions as well as
connectivity links. NaaS resource models are not exposed to the NaaS CSC.
A NaaS service model is service specific, i.e., specific to the NaaS service being offered to the NaaS CSC by the
NaaS CSP but rely on underlying NaaS resource models. Once a NaaS service is instantiated for a NaaS CSC,
the corresponding NaaS service model designed by the NaaS CSP is exposed to the NaaS CSC.
A NaaS service operational policy model is service specific, i.e., are specific to the NaaS service being offered
to the NaaS CSC. This model defines NaaS CSP-wide policies applicable for the corresponding NaaS service
and is designed by the NaaS CSP or CSN (e.g., service developer). During the instantiation of a NaaS service,
the NaaS service operational policy model is combined with the NaaS service model and mapped into a target
configuration of NaaS CSP's resources (e.g., network elements), according to NaaS resource models.
NOTE – The usage example of modelling is provided in Appendix II.

7.3 Functionalities for NaaS service orchestration
The NaaS service orchestration functionalities are responsible for cross-domain service orchestration within
the NaaS CSP, e.g., for a NaaS connectivity service, the functionality will be capable to orchestrate NaaS
resources (including network services, network functions and resources) in multiple NaaS CSP domains
(including legacy domains and virtualized network domains).
Upon receipt of a NaaS service request from the NaaS CSC, these functionalities are responsible for
decomposing, as necessary, the request into several independent requests and for distributing each of the
resulting requests to the relevant control functions of the NaaS CSP. An example of a composite NaaS service
is a service chain path, i.e., an ordered list of connection points forming a chain of network functions (PNFs
and/or VNFs), along with policies associated to the list.
The NaaS service orchestration functionalities interact with the NaaS service instantiation functionalities to
address NaaS service decomposition and configuration of requests received from NaaS service instantiation
functionalities (see clause 7.2.1).

In case of a non-composite NaaS service request received from the NaaS CSC, the NaaS service orchestration
functionalities can transfer this request to the relevant domain control function.
The NaaS orchestration functionalities are also responsible for ensuring that NaaS resources (e.g., NSs, NFs,
connectivity) are appropriately instantiated throughout the different NaaS CSP domains (e.g., across one or
network domains that can be using different networking connectivity technologies).

7.4 Functionalities for network analytics
Functionalities for network analytics are responsible for data collection from the NaaS CSP's network
environment (such as network jitter, delay, packet loss rate, round-trip time, domain name system (DNS)
resolution time) and events listening to continuously monitor NaaS services during their lifecycle. These
functionalities help to provide customized analytical network applications and provide the analysed results
to the related functional components (such as resource abstraction and control) for further action, including
healing the service, appropriately scale up or scale down the service, dynamically adjust routing, etc.

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