# Glossary

Calico

  A virtual networking solution that uses IP routing (layer 3) to provide connectivity in the form of a flat IP network instead of bridging and tunneling.

  Refer to the Calico documentation for more information.

Fast Path

  When used, 6Wind’s proprietary fast path technology behaves as a transparent acceleration layer for traditional switches (Open vSwitch, Linux Bridge) and for alternative networking mechanisms (Calico, Midonet).

Linux Bridge

  The native networking “backend” found in Linux.

  Refer to the Linux Foundation wiki for more information.

Open vSwitch

  A software implementation of a virtual multilayer network switch

  Refer to the OVS documentation for more information.

VEB
Virtual Ethernet Bridge

  A virtual Ethernet switch that implmented in a virtualized server environment. It is anything that mimics a traditional external layer 2 (L2) switch or bridge for connecting VMs. Generally implemented as a vSwitch, though hardware-based VEBs using SR-IOV are possible.

  Refer to this Virtual networking technologies brief for more information.

vSwitch
Virtual Switch

  A software-based virtual switch that connects virtual NICs to other virtual NICs and the broader physical network.

  Refer to this presentation for more information.

VEPA
Virtual Ethernet Port Aggregator

  An approach to virtual networking where VM traffic is handled on the physical network rather than by a virtual switch. Unlike VNTag, frames are not tagged and the switch will use a single port to handle all VIFs for a host.

  The basis of the 802.1Qbg spec.

  Refer to this presentation for more information.

VN-Tag
VNTag

  An approach to virtual networking where an interface virtualizer (IV) is used in place of a VEB to connect multiple VIFs to a single, external, IV-capable hardware bridge. Each VIF is tagged with a unique ID (vif_id) which is used to route traffic through IVs, and VIFs are then treated like any other interface.

  The basis of the 802.1Qbh and 802.1Qbr specs.

  Refer to this Cisco presentation for more information.

vhost

  An alternative to virtio that allows userspace guest processes to share virtqueues directly with the kernel (or, more specifically, a kernel module) preventing the QEMU process from becoming a bottleneck.

vhost-user

  A variation of vhost that operates entirely in userspace. This allows userspace guest processes to share virtqueues with other processes operating in userspace, such as virtual switches, avoiding the kernel entirely and maximize performance.

  When used, a guest exposes a UNIX socket for its control plane, allowing the external userspace service to provide the backend data plane via a mapped memory region. This process must implement the corresponding virtio vhost protocol, such as virtio-net for networking, on this socket.

  Refer to the QEMU documentation for more information.

virtio

  A class of virtual device emulated by QEMU. Virtio devices have virtqueues which can be used to share data from host to guest.

  Refer to the libvirt Wiki for more information.

virtio-net

  A network driver implementation based on virtio. Guests share virtqueues with the QEMU process, which in turn receives this traffic and forwards it to the host.

  Refer to the KVM documentation for more information.

VIF

  A virtual network interface.

IEEE 802.1Q
802.1Q

  A networking standard that supports virtual LANs (VLANs) on an Ethernet network.

  Refer to the IEEE spec for more information.

IEEE 802.1Qbg
802.1Qbg

  An amendment to the 802.1Q spec known as “Edge Virtual Bridging”, 802.1Qbg is an approach to networking where VM traffic is handled on the physical network rather than by a virtual switch. Originally based on VEPA.

  Refer to the IEEE spec for more information.

IEEE 802.1Qbh
802.1Qbh

  A withdrawn amendment to the 802.1Q spec known as “Bridge Port Extensions”, replaced by 802.1Qbr spec.

  Refer to the IEEE spec for more information.

IEEE 802.1Qbr
802.1Qbr

  An amendment to the 802.1Q spec known as “Bridge Port Extensions”,

  Refer to the IEEE spec for more information.

tc

  A framework for interacting with traffic control settings (QoS, essentially) in the Linux kernel.

  Refer to the tc(8) man page for more information.

SR-IOV
Single Root I/O Virtualization

  An extension to the PCI Express (PCIe) specification that allows a device, typically a network adapter, to split access to its resources among various PCIe hardware functions, physical or virtual.

  Refer to this article by Scott Lowe or the original PCI-SIG spec (paywall) for more information.

PF
Physical Function

  In SR-IOV, a PCIe function that has full configuration resources. An SR-IOV device can have up to 8 PFs, though this varies between devices. A PF would typically correspond to a single interface on a NIC.

  Refer to this article by Scott Lowe for more information.

VF
Virtual Function

  In SR-IOV, a PCIe function that lacks configuration resources. An SR-IOV device can have up to 256 VFs, though this varies between devices. A VF must be of the same type as the parent device’s PF.

  Refer to this article by Scott Lowe for more information.

this page last updated: 2026-07-16 15:19:59

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