It is common for the operating system kernel to maintain a table of virtual network interfaces in memory.
It may also allow processes on the system to interact concerning network connections in a more granular fashion than simply assuming a single amorphous Internet (of unknown capacity or performance).
[citation needed] W. Richard Stevens, in volume 2 of his treatise entitled TCP/IP Illustrated, refers to the kernel's Virtual Interface Table in his discussion of multicast routing.
[citation needed] This extra layer of network abstraction is often unnecessary and may have a minor performance penalty.
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, its usage is rare.