4.1 SDN Overview 71
App
App
App
Network operating
system
Simple forwarding
hardware
Specialized
forwarding
hardware
S S S Speci li
i li
i li
iali d d d
zed
Control software
Simple forwarding
hardware
Simple forwarding
hardware
Simple forwarding
hardware
Specialized
forwarding
hardware
Specialized
forwarding
hardware
Specialized
forwarding
hardware
Control software
Control software
Control software
Southbound interface
Figure 4.3 SDN comparison.
will lead to highly specialized and cost-effective high-performance
packet-forwarding data plane devices and control plane servers, thus
reducing the CAPEX of service providers significantly. And finally,
since network information, applications, and services are concentrated at a centralized location in SDN, operations such as network
orchestration and monitoring become much easier and cost-effective
by avoiding individual software upgrades at multiple device locations
prevalent in current distributed networks.
4.1.2.2 Northbound Open APIs
Open APIs enable developers to exploit the centrally available network
information and the mechanisms to securely program the underlying
network resources [78]. They not only enable rapid development and
deployment of both in-house and third-party applications and services
but also provide a standard mechanism to interface with the network.
4.1.2.3 Southbound Control/Data Plane Protocol
A secure and extensible control plane signaling protocol is an important component for the success of SDN. It should enable efficient and
flexible control of network resources by the centralized control plane.
OpenFlow [13] is a well-known control plane signaling protocol that
is standardized and increasingly being made extensible and flexible.
There are other southbound protocols such as OVSDB, which is more
backward compatible with existing protocols.