Glossary · Industrial communication
Frame
Also known as: Data frame, Ethernet frame
German: Frame
In data communication, a frame is the unit of data at the data link layer: a sequence of bits or bytes with a defined structure of header, payload and checksum that is transmitted as a whole on a network link.
- Industrial communication
In one sentence
A frame is the data link layer unit of transmission, with header, payload and checksum, sent as a whole on a network link.
Example
A PROFINET RT frame carries the cyclic I/O data of one device directly in an Ethernet frame with its own EtherType, without an IP header.
How it applies
- Engineering: Frame structure limits how much payload fits in one transmission and how much overhead each exchange costs. Real-time Ethernet systems place process data directly in Ethernet frames to avoid IP overhead.
- Diagnostics: Network analyzers such as Wireshark decode frames layer by layer. Frame check sequence errors point to cabling or electromagnetic interference problems.
- Operation: Lost or corrupted frames are detected by checksums and by the protocol's watchdogs; how often this is tolerated before a connection fails is configurable in many systems.
- Documentation: The documentation team uses the term of the relevant specification consistently. Fieldbus documents often say Telegram where Ethernet documents say frame; a glossary note avoids readers thinking these are different mechanisms.
Frame vs. packet
A frame belongs to the data link layer (for example Ethernet). A packet belongs to the network layer (for example IP) and travels inside frames. When an IP packet crosses a router, it gets a new frame on every link.