Azure | Cloud, Computing, Chaos

Introduction

I have mostly worked in systems technologies, building things like operating system, hypervisor, networking protocols and other virtualization related technologies. I love building system software due to simplicity of the overall software stack, programming languages (C and assembly) and tools to build this software. During my work on Windows Network Controller, I spent some time building WCF services in C#. I really liked coding in C# as it is a very well designed high level language and makes coding some of things much faster. However, at times I felt lost in the myriad of abstractions, frameworks and tools. Fortunately, for the service I was building, all the framework details were handled by a core framework team, and that allowed me to focus on writing the core business logic for my service without getting bogged down in all the other details. Even though I was able to build my service faster; I continued to feel lost at the magic, framework components performed; to do things like cross machine API invocation, associated security handling etc. (more…)

Hyper-V Virtual Switch (referred also as VMSWITCH) is the foundational component of network device virtualization in Hyper-V. It powers some of the largest data centers in the world, including Windows Azure. In this post, I would talk about its high level architecture.

Standards Compliant Virtual Switch

As I mentioned in my previous post, the main goal in building VMSWITCH was to build a standards compliant, high performance virtual switch. There are many ways to interpret standards compliant because there are many standards. So to be specific, our goal was to build packet forwarding based on 802.1q and mimic physical network semantics (such as link up/down) as much as possible. This was to make sure that whatever works in a physical network, works in the virtual environment as well. We defined three main objects in VMSWITCH, vSwitch, vPort and NIC. A vSwitch is an instance of a virtual switch that provides packet forwarding and various other features provided by a switch such as QoS, ACL etc. A vPort is analogous to a physical switch port and has configuration associated with it for various features. And finally, a NIC objects, that acts as the endpoint connecting to a vPort. This is similar to the physical network, where a host has a physical NIC that connects to a physical port on a physical switch. (more…)