Microsoft is making significant strides in software-defined networking (SDN) with its open source data center networking OS called Azure Cloud Switch (ACS). Based on Linux, this marks the official entry of the world’s largest proprietary software company into the open source SDN segment.

Microsoft and the Open Compute Project

The Open Compute Project (OCP) was initiated by Facebook in April 2011 to share the design and architecture of data center components. OCP’s founding members include Microsoft, Apple, Rackspace, Cisco, Juniper Networks, Goldman Sachs, Fidelity, and Bank of America. In January 2014, Microsoft joined Intel, Mellanox, Seagate, Geist, and Delta to drive the effort of Open Cloud Servers (OCS). Since then, Microsoft has been an active participant and contributor to OCP; its latest contribution is ACS.

What is ACS?

According to Kamala Subramaniam, principal architect of Azure networking, ACS “… is a cross-platform modular operating system for data center networking built on Linux. ACS allows us to debug, fix, and test software bugs much faster. It also allows us the flexibility to scale down the software and develop features that are required for our datacenter and our networking needs.”

What this means is that Microsoft is building a Linux-based networking OS that can talk to a disparate set of networking equipment such as routers and switches manufactured by a variety of vendors. Subramaniam explains that traditional switch software is generic, as it has to cater to a broad customer base with different use cases.

Microsoft took a different approach to building the software switch considering its experience and learning of running large data centers and the Azure cloud platform. ACS is modular, lean, and mean, which makes it easy for developers to ship an efficient piece of networking software.

Microsoft is known for its friendly interface and even for managing complex server-side operations. Unlike other open source switch software, ACS comes with a set of GUI tools that integrate with existing monitoring and management software such as System Center Operations Manager.

The power behind ACS

What lies beneath ACS is an abstraction layer called Switch Abstraction Interface (SAI) that hides the differences among various hardware implementations.

SAI is the standardized C API that programs the hardware switches based on application-specific integrated circuits (ASICs). The core premise on which it is built is to allow developers to program different chips through a standardized API. The concept is very similar to an x86 OS that abstracts Intel and AMD processors. It enables network operators to adopt a more dynamic and programmable infrastructure. Submitted in March 2015, SAI was officially accepted by OCP as the standard API. It acts as a glue, de-coupling the hardware from the software interface.

Apart from Microsoft, SAI’s contributors include Dell, Mellanox, and Big Switch Networks.

The parallel force

OCP is not the only industry consortium focused on standardizing SDN. The Linux Foundation announced in April 2013 the OpenDaylight Platform (ODL); it was formed to advance the research and development in the areas of SDN and network functions virtualization. Interestingly, Microsoft is one of the founding members, along with Cisco, Citrix, Ericsson, HP, IBM, Juniper Networks, Red Hat, VMware, and others. The significant outcome of this project is OpenFlow, which has emerged as a standard for SDN. Major OpenStack distributions integrated OpenFlow as a part of their networking stacks.

SDN for the win

The future of networking is in software. After reaping the benefits of compute and storage virtualization, the industry is focused on SDN. VMware is investing heavily in NSX, the technology it got through its acquisition of Nicira. Microsoft has chosen to contribute its SDN efforts to OCP through ACS and SAI. Cisco, Juniper Networks, Alcatel-Lucent, and other major networking vendors are heavily investing in SDN-based research and development.

ACS indicates that Microsoft is no longer the same company that was once known for fiercely competing with its open source counterparts. It is indeed a welcome change.