Network Interface
What Is a Network Interface?[1]
A network interface is the point of interconnection between a computer and a private or public network. A network interface is generally a network interface card (NIC) but does not have to have a physical form. Instead, the network interface can be implemented in software. For example, the loopback interface (127.0.0.1 for IPv4 and ::1 for IPv6) is not a physical device but a piece of software simulating a network interface. The loopback interface is commonly used in test environments.
The network interface may refer to:
- Network interface controller, a computer hardware component that connects a computer to a computer network
- Network interface device, a device that serves as the demarcation point between a telephone carrier's local loop and the customer's wiring
- Virtual network interface, an abstract virtualized representation of a computer network interface
- Loopback interface, a virtual network interface that connects a host to itself
TCP/IP Network Interfaces[2]
The TCP/IP Network Interface layer formats IP datagrams at the Network layer into packets that specific network technologies can understand and transmit.
A network interface is a network-specific software that communicates with the network-specific device driver and the IP layer in order to provide the IP layer with a consistent interface to all network adapters that might be present.
The IP layer selects the appropriate network interface based on the destination address of the packet to be transmitted. Each network interface has a network address. The Network Interface layer is responsible for adding or removing any link layer protocol header required to deliver a message to its destination. The network adapter device driver controls the network adapter card.
Although not required, a network interface is usually associated with a network adapter. For instance, the loopback interface has no network adapter associated with it. A machine must have one network adapter card for each network (not network type) to which it connects. However, a machine requires only one copy of the network interface software for each network adapter it uses. For instance, if a host attaches to two token-ring networks, it must have two network adapter cards. However, only one copy of the token-ring network interface software and one copy of the token-ring device driver is required.
TCP/IP supports types of network interfaces:
- Standard Ethernet Version 2 (en)
- IEEE 802.3 (et)
- Token-ring (tr)
- Serial Line Internet Protocol (SLIP)
- Loopback (lo)
- FDDI
- Serial Optical (so)
- Point-to-Point Protocol (PPP)
- Virtual IP Address (vi)