VXLAN: Moving Towards Network Virtualization

Thanks, Steve Herrod.

If you missed it, VMware, Cisco, Broadcom and others announced support for VXLAN a new tunneling format. For the curious, here is the RFC draft.

So quickly, what is VXLAN?  It’s an L2 in L3 tunneling mechanism that supports L2 learning and tenancy information.

And what does it do for the world?  A lot really.  There currently is fair bit of effort in the virtualization space to address issues of L2 adjacency across subnets, VM mobility across L3 boundaries, overlapping IP spaces, service interposition, and a host of other sticky networking shortcomings.  Like VXLAN, these solutions are often built on L2 in L3 tunneling, however the approaches are often form-fitted and rarely are they compatible with another implementation.

Announcing support for a common approach is a very welcome move from the industry. It will, of course, facilitate interoperability between implementations, and it will pave the way for broad support in hardware (very happy to see Broadcom and Intel in the announcements).

Ivan (as usual, ahead of the game) has already commented on some of the broader implications. His post is worth a read.

I don’t have too much to add outside of a few immediate comments.

First, we need an open implementation of this available.  The Open vSwitch project has already started to dig in and will try and have something out soon — perhaps for the next OpenStack summit. More about this as the effort moves along.

Second, this is a *great* opportunity for the NIC vendors to support acceleration of VXLAN in hardware.  It would be particularly nice if LRO support worked in conjunction with the tunneling so that interrupt overhead from the VMs is minimized, and the hardware handles segmentation and coalescing

Finally, it’s great to see this sort of validation for the L3 fabric, which is an excellent way to build a datacenter network.  IGP + ECMP + a well understood topology (e.g. CLOS or Flattened butterfly) is the foundation of many large fabrics today, and I predict many more going forward.

Exciting times.



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