Virtual Switches Demand Rethinking Connectivity for Servers
Virtual Switches Demand Rethinking
Connectivity for Servers
With the creation of multiple virtual machines on each physical host server, network adapters
now connect servers to the network with equivalency to a traditional top-of-rack switch.
This shift can be further described as follows:
•Yesterday’s data center: Physical edge switches. In
conventional, non-virtualized data centers, servers were
connected to top-of-rack switches by multiple Gigabit Ethernet
(GbE) connections, and those switches connected to core
switches with large trunked uplinks.
•Virtualized data centers: Virtual edge switches within
servers. Today’s virtualized host servers process network
traffic in software, with the hypervisor’s virtual switch replacing
the top-of-rack switch for server connectivity, and the trunked
uplinks are handled by the host server’s Ethernet adapters.
•Supporting the new paradigm: Implications for networking.
Each physical host server in a virtualized environment is the
logical equivalent of a rack in the non-virtualized one, meaning
that each physical host server’s network connection must
actually be treated like a trunked uplink found on switches.
In the typical virtualized environment, data is segregated
within trunked connections using multiple virtual LANs (VLANs).
This approach provides logical separation between the data
streams that enables them to be prioritized and secured as
needed. VLANs have become a preferred topology in many
mainstream implementations.
The adoption of virtualization has led to a paradigm shift in the data center. At the core of these changes is the fact
that a single host server running multiple virtual machines (VMs) can now represent the equivalent of multiple physical
servers.TrafcamongtheVMsandwiththeoutsideworldisnowmanagedandcoordinatedbyavirtualswitch.
The virtual switch exists in software built into the hypervisor, meaning that it resides within the server itself, rather
than as a separate physical device. Therefore, the network connectivity that was situated between the servers and a
top-of-rack switch now occurs within the host server. By extension, the host server’s network adapters now handle the
connections that formerly existed between the top-of-rack switches and core switches.
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Hypervisor
Software Virtual Switch
Figure 1. In a virtualized environment, the hypervisor running on the
physical host server includes a software-based virtual switch.
TECHNOLOGY BRIEF
Intel® Ethernet Server Adapters
Virtualization