LAUSR

What is “software-defined”? Software-defined has become one of the hottest buzzwords in the information technology (IT) community. It is used to describe a family of technologies, including software-defined networking (SDN), softwaredefined storage (SDS), and software-defined data centers (SDDC). These are part of a broader trend that is referred to as software-defined everything (SDX). The movement toward software-defined infrastructure is focused on decoupling hardware layers that execute data transactions and computations from the software layers that manage them. The term “software-defined” originated from software-defined networking (SDN), which became popular after the release of OpenFlow [1]. As one of the most important research outcomes of POMI 2020, an NSF Expedition project led by Stanford University that began in 2009, OpenFlow has been widely adopted in the cloud and in data centers. Although the term SDN has been frequently linked to OpenFlow, the technical essence of SDN can be traced back to as early as the 1990s, where early software-defined prototypes, including AT&T’s GeoPlex, emerged. The core technologies of software-defined can be summarized by two concepts [2]. The first is the virtualization of hardware resources, meaning that all hardware resources can be abstracted as virtual resources, which can be managed by OS routines or the control plane. The second core technology is the programmability of management functionalities, meaning that users can write programs to access the services provided by virtualized resources. The functionality of virtualized hardware resources should be programmable, such that it can be managed by software. From the perspective of programming, this means that one can use software to define the functionality of a system, thereby allowing it to be called a “software-defined system”. Software is far more flexible than hardware and can be changed much more easily. Although firmware can also be updated in legacy devices, it is still much less flexible than today’s softwaredefined environments. With SDN, SDS, and software-defined servers, we can construct large software-defined environments, such as SDDC, which can be controlled, managed, and maintained much more flexibly. The technical and economic benefits brought about by using software-defined technology have been overwhelming. Softwaredefined is not only changing technology and products, but also changing the entire technological infrastructure and ecosystem.