Newer technologies like Virtual Extensible LAN (VXLAN) and Network Virtualization Generic Routing and Encapsulation (NVGRE) are also intended to virtualize networks and scale VLANs. Cisco, VMware and Arista are co-authors of VXLAN, while Microsoft, Dell and Intel back NVGRE.
VXLAN and NVGRE are encapsulation and tunneling schemes designed to overlay, proponents say, virtualization onto existing network infrastructures. VXLAN, server-based virtual switching and virtualized Layer 3-7 services, such as firewalls, load balancing, NAT and e-mail gateways, are the underpinnings of VMware's SDN strategy.
"Rather than wait for the SDN/OpenFlow world to start penetrating into enterprises - which, we'd be here a long time - we had an immediate need of virtualizing the network," said Allwyn Sequeira, CTO and vice-president of Cloud Networking and Security at VMware. "That's why we started with vSwitches, virtual distributed switches and VXLAN. That works and it solves a bunch of problems, and it has a lot of the elements of software-defined networking: you have a controller - we have our vCloud Director, vCloud Network and Security Services, we bring up VXLANs on the fly that map onto all kinds of existing (networks), and is future-proof. It could map onto OpenFlow.
"Here, we don't really need to program the boxes as much as we make sure we give different tenants space, their own virtual wire," Sequeira says. "That's one of the things about VXLAN: it has the notion of a tenant ID built in so that you can have different tenants with their own name spaces on the network."
VMware's vShield Edge handles the higher-level virtual services, Sequeira says.
But NEC and Nicira see VXLAN and NVGRE as not capably tackling the network virtualization problem.
"VXLAN and NVGRE are complementary" to OpenFlow, NEC's Clark says. "They provide address virtualization, but not network virtualization. Having the control within the network is still required especially for large deployments being contemplated for these, where VLAN exhaustion is an issue."
Clark says NEC will soon demonstrate interoperability between the company's ProgrammableFlow switches and Microsoft's Windows Server 2012 with NVGRE to show the complementary nature of the two technologies.
Nicira's Casado says NVGRE and VXLAN are just not up to the task at hand.
"They are tunneling protocols that are just a way of getting a packet across a network," he says. "We don't care what kind of tunneling protocol you use. We're very happy to support NVGRE and VXLAN if anybody asks us to, which no one has yet."
In the data path, VXLAN and NVGRE are too slow, he says. They don't support hardware acceleration on network interface cards.