and WAN. That research resulted in Cisco’s current SDN offerings of ACI in the data center,
Software-Defined Access (SDA) in the enterprise campus, and Software-Defined WAN (SD-
WAN) in the enterprise WAN.
When reimagining networking for the data center, the designers of SCI focused on the applications
that run in a data center and what they need. As a result, they built networking concepts around
application architectures. Cisco made the network infrastructure become application centric, hence
the name of the Cisco data center SDN solution: Application
Centric Infrastructure, or ACI.
Cisco APIC Enterprise Module
Cisco came up with a couple of approaches, with one of those being APIC-EM, which Cisco
released to the public around 2015.
APIC-EM assumes the use of the same traditional switches and routers with their familiar
distributed data and control planes. Cisco rejected the idea that its initial enterprise-wide SDN
(network programmability) solution could begin by requiring customers to replace all hardware.
Instead, Cisco looked for ways to add the benefits of network programmability with a centralized
controller while keeping the same traditional switches and routers in place. That approach could
certainly change over time (and it has), but Cisco APIC-EM does just that: offer enterprise SDN
using the same switches and routers already installed in
networks.
REST-Based APIs
Applications use application programming interfaces (APIs) to communicate. To do so, one
program can learn the variables and data structures used by another program, making logic choices
based on those values, changing the values of those variables, creating new variables, and deleting