Page 157 - 5G Basics - Core Network Aspects

Core network aspects 1

I.6 Multiple-level of programmability

In conventional networks, each resource in multiple open system interconnection (OSI) layers [b-ITU-T X.200]
is managed by different management entities. This makes it difficult to orchestrate total performance and to
recover from network failures quickly. SDN is desirable to provide control and management programming
interfaces to network resources, e.g., for coordination and status monitoring purposes. In addition, the
demands of SDN applications can be diverse and may be related to multiple OSI layers.

The interfaces need to span multiple OSI layers and work in a unified manner: multiple-level of
programmability that spans L1-L7 OSI layers is an important issue to be addressed for SDN.
One example for such multi-level programmability is cut-through optical path computation. In this example,
some SDN components may dynamically change the target OSI layer to allocate a path, depending on traffic
characteristics. For example, SDN components may first allocate a path in the OSI layer 3, namely an IP route.
After checking OSI layer 3 header and its applicability, SDN intelligence may then decide instead to allocate
an optical path, e.g., to provide additional bandwidth.

I.7 Programmatic extension in resource layer
In order to improve network programmability, it is desirable to extend the functions of the resource layer on
demand in a programmable manner [b-SDN-WS Nakao]. This ability can dynamically add or remove additional
functions for data transport and processing (such as packet caching, header/payload compression, regular
expression matching, data transcoding, or even handling newly developed protocols) as per SDN application
requirements or can dynamically update the control support function, thereby avoiding hardware
replacement.
Thus, rapid development, deployment, and replacement of resource layer functionalities and resource-
control interfaces leads to timely and tailored service solutions aligned with requirements of applications and
operator policies.
I.8 Management
The following management functionalities specific to one of the layers need to be further considered:

– Management of the underlying physical and virtual network resources, providing support for
programmatically extendable SDN data transport and processing functions, which is described in
clause I.7;
– Management of the software and hardware platform of an SDN controller which includes lifecycle
management of dynamically upgradable functions of the SDN controller and FCAPS.
The multi-layer management functions should interoperate with 3rd party management functions, for
example, for billing, customer care, statistics collection or dynamic service provisioning.
Another issue to be considered is how the multi-layer management functions are deployed. Possible
approaches include the use of a centralized management model or a hybrid model. In the hybrid model, some
management functions are distributed, while others are implemented in centralized management systems.
With such an approach, network resources support management functions that may improve network
robustness and scalability as well as shorten the management system response time. In both models, there
is an SDN management system that performs all centralized management operations.

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