Recently, I began a deep dive into more SDN and OpenFlow. Overall I was very happy with the process and quality of the material out there for newcomers. However, I noticed a gap when I hit my first stumbling block. I set up a mininet instance, noticed it was running Open vSwitch (OVS) v2.0. I needed a newer version of OVS, and turfed the mininet instance while the upgrading OVS. It quickly became apparent that I needed a repeatable development environment setup....
Operating Open vSwitch brings a new set of challenges. One of those challenges is managing Open vSwitch itself and making sure you’re up to date with performance and stability fixes. For example, in late 2013 there were significant performance improvements with the release of 1.11 ( flow wildcarding!) and in the 2.x series there are even more improvements coming. This means everyone running those old versions of OVS (I’m looking at you, <=1....
In the physical world when you power on a server it’s already cabled (hopefully). With VMs things are a bit different. Here’s the sequence of events when a VM is started in Nova and what happens on XenServer to wire it up with Open vSwitch. nova-compute starts the VM via XenAPI XenAPI VM.start creates a domain and creates the VM’s vifs on the hypervisor The Linux user device manager manages receives this event, and scripts within /etc/udev/rules....
DISCLAIMER: I’m still getting my feet wet with Open vSwitch. This post is just a cleaned up version of my scratchpad. Open vSwitch has a few ways of providing rate limiting - this deep dive will go into the internals of reverse engineering an existing virtual interface’s egress rate limits applied with tc-htb. Hierarchy Token Bucket (htb) is a standard linux packet scheduling implementation. More reading on HTB can be done on the author’s site - I found the implementation and theory pretty interesting....