During his keynote this morning at VMworld, VMware CTO Steve Herrod announced VXLAN, the company’s attempt to allow virtual machines to span geographical data centers as part of the same Local Area Network. Short for Virtual eXtensible LAN, Herrod wrote on his blog that it “enables multi-tenant networks at scale, and it is the first step towards logical, software-based networks that can be created on-demand, enabling enterprises to leverage capacity wherever it’s available.”
In other words, VXLAN could help companies build true global clouds that are the sum of their parts rather than distinct sets of parts. Currently, virtual resources such as storage and compute are limited to the constraints of a single physical network within a single physical data center. Even when tools such as VMware’s vMotion or DRS move workloads or VMs from machine to machine, they can’t escape the data center’s four walls. Herrod describes the problem using a telephony analogy:
One of the fundamental challenges with today’s networking is that we use an IP address for two unrelated purposes, as an identity AND as a location. Tying these together restricts a (virtual) machine from moving around as easily as we would like. We had the same challenge with telephony before wireless came of age. . . our phone number rang for us at a specific destination rather than following us wherever we went!
VXLAN separates a VM’s network ID from its physical location using a Layer 2 abstraction. The result, writes Herrod, is that “VMs are completely unaware of the physical networks constraints and only see the virtual layer 2-adjacency [and] the fundamental properties of virtualization such as mobility and portability are extended across traditional network boundaries.”
Cisco already supports a similar capability with its Overlay Transport Virtualization technology, but the main difference appears to be that OTV is limited to Layer 2 networks (i.e., LANs) and Cisco Nexus gear. VXLAN can cross even Layer 3 boundaries to let users incorporate even cloud-based resources. Cisco’s Omar Sultan wrote on his blog that “VXLAN is the basis of a scalable cloud network where lots of logical networks (over 16M . . .) can be created instantly to meet the needs of the even the most complex and dynamic cloud.”
Also, VMware is pushing to make VXLAN an standard, and had broad network industry support, including from Cisco, Arista, Broadcom, Brocade, Emulex and Intel.
More information about the technology is available on Herrod’s blog, as well as on the group’s IETF submittal.
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