Ethernet Frame

Data Packet — An all encompassing term that represents any single set of binary data being sent across a network link.Data packets at the ethernet level are knows as Ethernet frames.

Ethernet Frame is a highly structured collection of information presented in a specific order.All sections of ethernet frame are mandatory.

Preamble — A preamble is 8 bytes of 64 bits long and can be split into two sections.The first 7 bytes act partially as a buffer between Frames and can also be used by network interfaces to synchronize internal clocks.Last byte in preamble is known as SFD of start frame delimeter.SFD signals to a receiving device that the preamble is over and that the actual frame contents will now follow.

Ether-type-field — 16 bits long and used to describe the protocol of the contents of the frame.

Destination MAC Address — It is the hardware address of the intended recipient.

Source MAC Address — It is the address where the frame originated from.

VLAN header — VLAN (Virtual LAN ) is a technique that lets you have multiple logical LAN’s operating on the same physical equipment.VLAN header indicates that the frame itself is what’s called a VLAN frame.If a VLAN header is present ,the ether type field follows it.

Payload — It is the actual data being transported ,whis is everything that isn’t a header.It’s range is from 0–1500 bytes.

Frame check sequence — A 4 byte (or 32 bit) number that represents a checksum value for the entire frame.The checksum value is calculated by performing cyclical redundancy check against the frame.