Layer2Frames

Layer2Frames is a term used to describe the unit of data exchanged at the data link layer of the OSI model. It denotes the encapsulated payload that a network interface card delivers to or receives from a link, such as an Ethernet link. A Layer2Frame typically contains a header with destination and source hardware addresses, a EtherType or length field that indicates the protocol carried in the payload, and a trailer that may include a frame check sequence for error detection. In many networks, optional metadata such as VLAN tags (802.1Q) can be appended to the header, allowing segmentation and traffic management.

A Layer2Frame carries payload from layer 3, such as an IP packet, and may be subject to framing rules such as minimum and maximum frame sizes and maximum transmission unit (MTU). Common variants include Ethernet II framing, which uses an EtherType field, and IEEE 802.3 framing, which uses a length field and may employ LLC/SNAP headers. Wireless adaptations, such as 802.11 frames, follow similar concepts but with different header formats.

In practice, Layer2Frames are processed by switches and bridges to make forwarding decisions based on MAC addresses and VLAN tags. They are also used in network analysis and simulation tools to model traffic, capture flows, or study link-layer behavior. In software representations, a Layer2Frame object typically provides serialization to a byte sequence, functions for validation, and accessors for header fields, payload, and FCS. See also OSI model, Ethernet, VLAN, and switches.