Frame (networking)

A data frame is a Protocol Data Unit at the data link layer of the OSI model. The term frame is clearly distinguished in the OSI model of the term package, because it is used for the network layer.

A data frame consists of:

  • Delimiter to mark the beginning and end of the frame
  • Called class-specific, and hardware or MAC addresses: destination and source addresses
  • Control information for data flow control
  • Payload of the packet network layer
  • Checksums to ensure data integrity

The data frame in Ethernet ( IEEE 802.3)

By default, the Ethernet data frame is 1518 bytes in size, of which 18 bytes are reserved for the header and trailer. Then available for the data field of 1500 bytes available, of which 46 bytes must be used so that the minimum frame length of 64 bytes to ensure the collision detection is observed.

Since an IP packet can be 64 kB in size, it would not fit into a data frame. Therefore, an IP packet is split prior to transfer to the film 2 so that it fits within a frame of data. This decomposition is called fragmentation. About the Maximum Transmission Unit (MTU), the maximum packet size can be set, which can be transmitted over a network, without that the data packet needs to be fragmented.