Virtual Interface
Encyclopedia
A Virtual Interface or Virtual Network Interface (VIF) is an abstract virtualized representation of a computer network interface that may or may not correspond directly to a physical network interface.
There is some variation in usage of the term, with different groups using it to mean slightly different things. Usually context will clarify.
interfaces in memory. This may allow the system to store and operate on
such information independently of the physical interface
involved (or even whether it is a direct physical interface or for instance a
tunnel or a bridged interface). It may also allow processes on the system to
interact concerning network connections in a more granular fashion than simply
to assume a single amorphous "Internet" (of unknown capacity or performance).
The late W. Richard Stevens
, in volume 2 of his extensive treatise
entitled TCP/IP Illustrated
, refers to the kernel's Virtual Interface Table in his discussion of multicast routing. For example, a multicast router may
operate differently on interfaces that represent tunnels than on
physical interfaces (e.g. it may only need to collect membership information
for physical interfaces). Thus the virtual interface may need to divulge some
specifics to the user, such as whether or not it represents a physical
interface directly.
In addition to allowing user space applications to refer to abstract network
interface connections, in some systems a virtual interface framework may allow
processes to better coordinate the sharing of a given physical interface
(beyond the default operating system behavior) by hierarchically subdividing it
into abstract interfaces with specified bandwidth limits and queueing models.
This can imply restriction of the process, e.g. by inheriting a limited branch
of such a hierarchy from which it may not stray.
This extra layer of network abstraction is often unnecessary, and may have a
minor performance penalty. However, it is also possible to use such a
layer of abstraction to work around a performance bottleneck, indeed even to
bypass the kernel for optimization purposes.
abstracts network interfaces. Since most software need not concern
itself with the particulars of network interfaces, and since the desired
abstraction may already be available through the operating system, this
usage is rare.
Examples needed
There is some variation in usage of the term, with different groups using it to mean slightly different things. Usually context will clarify.
Operating system-level VIF
It is common for the OS kernel to maintain a table of virtual networkinterfaces in memory. This may allow the system to store and operate on
such information independently of the physical interface
involved (or even whether it is a direct physical interface or for instance a
tunnel or a bridged interface). It may also allow processes on the system to
interact concerning network connections in a more granular fashion than simply
to assume a single amorphous "Internet" (of unknown capacity or performance).
The late W. Richard Stevens
W. Richard Stevens
William Richard Stevens was one of the most famous and widely acclaimed authors of UNIX and TCP/IP books.-Biography:...
, in volume 2 of his extensive treatise
entitled TCP/IP Illustrated
TCP/IP Illustrated
TCP/IP Illustrated is the name of a series of 3 books written by W. Richard Stevens. Unlike traditional books which explain the RFC specifications, Stevens goes into great detail using actual network traces to describe the protocol, hence its 'Illustrated' title.The first book in the series,...
, refers to the kernel's Virtual Interface Table in his discussion of multicast routing. For example, a multicast router may
operate differently on interfaces that represent tunnels than on
physical interfaces (e.g. it may only need to collect membership information
for physical interfaces). Thus the virtual interface may need to divulge some
specifics to the user, such as whether or not it represents a physical
interface directly.
In addition to allowing user space applications to refer to abstract network
interface connections, in some systems a virtual interface framework may allow
processes to better coordinate the sharing of a given physical interface
(beyond the default operating system behavior) by hierarchically subdividing it
into abstract interfaces with specified bandwidth limits and queueing models.
This can imply restriction of the process, e.g. by inheriting a limited branch
of such a hierarchy from which it may not stray.
This extra layer of network abstraction is often unnecessary, and may have a
minor performance penalty. However, it is also possible to use such a
layer of abstraction to work around a performance bottleneck, indeed even to
bypass the kernel for optimization purposes.
Application-level VIF
The term VIF has also been applied when the application virtualizes orabstracts network interfaces. Since most software need not concern
itself with the particulars of network interfaces, and since the desired
abstraction may already be available through the operating system, this
usage is rare.
Examples needed