vLANs Could Address Scalability Challenges

vLANs and SDN could be the answer to scalability challenges posed by virtualization and the cloud. But which standards will win out?

By Arthur Cole | Posted Aug 31, 2012
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IT remains one of the few bright spots in an otherwise dismal economy, a feat that is the direct result of the continued high level of innovation in the sector.

The name of the game these days is to leverage last decade's investment in virtual technology to more advanced cloud architectures. Naturally, this process isn't as easy as it sounds, and nowhere is the pain more acute than in the network. Things were bad enough when we had to deal with a few hundred virtual machines. In the cloud, scalability can easily push that to a thousand or more, with the IT department having less and less control over where data is going.

The antidote, of course, is to introduce virtualization onto the network, a process that spans the gamut from virtual LANs (vLAN) and virtual private networks (VPN) to the latest software defined networking (SDN) platforms hitting the channel. But no matter what you call it, the goal is to introduce any number of overlay networks on top of existing infrastructure.

Telecommunications companies have been dealing with overlay networks for decades. The Internet itself is an overlay network in that it represents a logical abstraction running atop the Public Switched Telecommunications Network (PTSN). The cloud can be considered the enterprise overlay network, considering it usually provides a virtual extension of internal compute, storage and network infrastructure.

As usual, whenever networking is involved, there are standards. The two vying for credibility right now are VMware's Virtual eXtensible Local Area Network (VXLAN) and Microsoft’s Network Virtualization using Generic Routing Encapsulation (NVGRE). Both formats seek to compensate for the limitations preventing vLAN technology from providing effective service to the cloud, namely, its relative inflexibility in provisioning or extending network resources, low fault tolerance and an inability to handle large numbers of IP addresses. The main differences between the two lie in the way they tunnel, say, Layer 2 data within Layer 3 packets, although it doesn't seem the networking industry has established a clear consensus as to which approach is better.

Vendor lines, however, are already being drawn, with VMware and Cisco championing VXLAN while Microsoft has drawn support from Intel, Dell, Broadcom and others. Cisco, in fact, is building a good chunk of its SDN strategy around VXLAN, employing it in the Cisco Open Network Environment (Cisco ONE) as the primary bridge between existing VLANs and newly deployed virtual overlay networks on leading switch platforms like the Nexus 1000V.

The ultimate goal in all this is to establish a truly virtual network environment, one in which logical network resources are completely decoupled from underlying hardware. That should provide the flexibility to configure and reconfigure virtual network infrastructure in ways that can fully support the kind of dynamic cloud architectures the industry has been striving for.

If you're not familiar with overlay network technology yet, now would be a good time to bone up on the subject. You'll probably hear a lot more about it as the cloud era unfolds.

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