Page 149 - 5G Basics - Core Network Aspects

Core network aspects 1

5 Conventions

This Recommendation uses the following conventions:
The term "is required to" indicates a requirement which must be strictly followed, and from which no
deviation is permitted, if conformance to this Recommendation is to be claimed.
The term "is recommended" indicates a requirement which is recommended, but which is not absolutely
required. Thus, this requirement need not be present to claim conformance.

6 Introduction
Due to the great success of communication technologies, diverse applications are realized on networks, and
the requirements that they bring are diverging. To support these diverging requirements, it is necessary to
make networks even more controllable and manageable. The necessity to treat different traffic in different
manners, and to make networks more application- and service-oriented is also increasing.

Technologies that enable more direct and lower-level (e.g., flow-level) control methods of data packet
forwarding are emerging. These technologies can simplify the reaction of network resources (e.g., switches
or routers) to operations, and significantly increase the controllability of networks for operators. With
modeling and programing of network resources, networks can be controlled in an automated manner, which
enables more agile operations of the networks.

This change of control method can also provide a chance to redesign control functionalities by introducing
logically centralized and programmable control of network resources through standardized interfaces and
protocols.

This approach allows for:
– logically centralized network control, which decreases the number of points to control and manage;
– supporting network virtualization as one important feature of the network architecture;
– defining, controlling and managing network resources using software; thus, allowing network
services to be provided in a deterministic manner in accordance with the requested behaviour; and
– network customization, which is necessary for efficient and effective network deployment and
operations.
In order to realize the aforementioned features, this Recommendation provides the framework of software-
defined networking (SDN) by specifying the fundamentals of SDN with its definitions, objectives, high-level
capabilities, requirements and high-level architecture.
While there have been various efforts to develop SDN-related technologies and standards (see
[ITU-T Y.3001], [ITU-T Y.3011], [b-ITU-T Y.2622], [b-ETSI NFV], [b-IETF I2RS] [b-IETF RFC 3746], [b-ONF] and
[b-OpenDayLight]) with different approaches and different focuses, they all share the same objective of
providing the programmability of network resources as described above, which is a core technology for the
networks of the future.

7 Overview
SDN is a set of techniques that enables users to directly program, orchestrate, control and manage network
resources, which facilitates the design, delivery and operation of network services in a dynamic and scalable
manner.
Figure 7-1 depicts the basic concept of SDN.

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