SRIOV bypasses vrouter for passthrough networking
SR-IOV or sriov interfaces have both physical functions (PFs) and multiple virtual functions (VFs).
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https://www.juniper.net/documentation/en_US/contrail4.0/topics/concept/sriov-with-vrouter-vnc.html
virtio
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: https://wiki.libvirt.org/page/Virtio
So-called "full virtualization" is a nice feature because it allows you to run any operating system virtualized.
However, it's slow because the hypervisor has to emulate actual physical devices such as RTL8139 network cards .