Next week's VMworld news will apparently include hardware partners for VMware's NSX, a development that could strengthen the product's case as a software-defined networking (SDN) controller option against OpenFlow and the Cisco Open Network Enviroment (ONE) architecture.

VMware has been working on making NSX — its upcoming product for network virtualization — communicate with top-of-rack switches and other hardware, as described last week by VMware Principal Engineer Bruce Davie on Network Heresy, the blog he runs with VMware's Martin Casado. In the comments, Davie added that some hardware partners are likely to be announced at VMworld.

That's because customers are asking hardware vendors for ways to converge the physical and virtual networks, Davie noted.

NSX is VMware's upcoming network virtualizations software, blending Nicira's Network Virtualization Platform (NVP) with VMware's vCloud Networking and Security software. Announced in March, NSX is due to ship before the end of the year.

NSX connects virtual switches via encapsulation tunnels -- an overlay model that can use standard protocols, such as VXLAN, whereas Nicira's NVP had relied on the Stateless Transport Tunneling (STT) protocol.

For the physical network, the initial NSX announcement included the concept of gateways for connecting to “non-virtual hosts,” as VMware coyly describes physical network and storage equipment. These gateways — additional NSX software that can link a physical port or a VLAN to an NSX virtual network — could even reside on the physical hardware, outside the data center.

Top-of-rack switch vendors have gotten interested in the concept. Their equipment is starting to support VXLAN to interwork with virtual networks, and that's led to an interest in letting NSX see the connections available into the physical network. Conversely, it would be useful for physical gear to know what the virtual network looks like.

VMware can make that work by taking advantage of the NSX's database capabilities, Davie explains. VMware designed a schema for recording network information — the MAC addresses of virtual machines, or the locations of VXLAN tunnels, for instance — which can be read using the Open vSwitch Database (OVSDB) Management Protocol. NSX had already been using OVSDB the for configuring and monitoring Open vSwitches; its availability in open-source form and its IETF backing made it a logical candidate for hardware-based devices to use as well.

VMware did all this because some points in the network can't go completely virtual -- either because the functions can't be virtualized or because the operation isn't ready for virtualization. But it could also help NSX cope with high-volume networks.

“Software gateways are a great solution for moderate amounts of physical-to-virtual traffic, but there are inevitably some scenarios where the volume of traffic is too high for a single x86-based appliance, or even a handful of them,” Davie writes.

Scale is an important issue for VMware to address. Along with the ability to wrap older, installed switches into an SDN plan, it's a key point that incumbent hardware vendors are likely to keep hammering when it comes to their SDN plans.