Software-Defined Networking (SDN)
Network programmability refers to the trend toward SDN.
SDN decouples the data, control, and management planes from the physical device, virtualizes them, and defines the networking functions in software.
A traditional networking device contains two planes. The data plane is responsible for forwarding data as quickly as possible. To do so, it relies on tables built by the control plane.
Controllers:
In SDN, the functions of the control plane can be completely removed from the physical networking devices, and placed in a centralized application called a controller.
Centralized Controller and Distributed Data Plane
The connections to the networking devices are called the southbound interface (SBI).
A northbound interface (NBI) also exists between the SDN controller and the applications that are installed on the controller.
These applications are what enable network programmability.
Open SDN and OpenFlow:
The Open Networking Foundation (ONF) model of SDN uses an SBI called
OpenFlow, which is a protocol used between the controller and the networking
devices to manage traffic flows.
ONF’s controller, OpenDaylight, is the result of a collaborative effort
among many vendors, including Cisco.
The controller has SBIs for other activities, such as configuring network devices (NetConf), managing routing (BGP-LS and PCEP), and switching traffic between VMs (OVSDB).
NBIs typically include Java APIs for applications and the RESTful API. REST (Representational State Transfer) uses HTTP messages to transfer data to other applications that are not running on the controller.
The Cisco Application Centric Infrastructure (ACI):
The Cisco in-house SDN solution for data centers is ACI
The Cisco Application Policy Infrastructure Controller (APIC) uses the endpoint topology and policies to direct the network regarding what needs to be in the forwarding tables and how to easily react to VM changes.
ACI uses a partially centralized control plane, RESTful and native APIs, and OpFlex as an SBI
Cisco ACI for Data Centers
Spine and Leaf:
Cisco ACI uses a spine and leaf design. Spine and leaf switches are connected using the following design guidelines:
■ Each leaf switch must connect to every spine switch.
■ Each spine switch must connect to every leaf switch.
■ Leaf switches cannot connect to each other.
■ Spine switches cannot connect to each other.
■ Endpoints connect only to the leaf switches.
Spine and Leaf Network Design
The Cisco APIC Enterprise Module (APIC-EM)
APIC-EM is the Cisco SDN offering for enterprises. The APIC-EM solution
uses a controller to manage existing network devices but also attempts to
support new generations of Cisco enterprise routers and switches by using SBIs
that are familiar to network administrators, such as remote access to the CLI
(Telnet and SSH) and SNMP support.
APIC-EM Controller
Comparing Characteristics of Three SDN Controllers
Post a Comment