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It is immediately followed by the Ethernet frame, which starts with the destination MAC address. [1] In computer networking, an Ethernet frame is a data link layer protocol data unit and uses the underlying Ethernet physical layer transport mechanisms. In other words, a data unit on an Ethernet link transports an Ethernet frame as its payload. [2]
The data link layer is concerned with local delivery of frames between nodes on the same level of the network. Data-link frames, as these protocol data units are called, do not cross the boundaries of a local area network. Inter-network routing and global addressing are higher-layer functions, allowing data-link protocols to focus on local ...
In the OSI model of computer networking, a frame is the protocol data unit at the data link layer. Frames are the result of the final layer of encapsulation before the data is transmitted over the physical layer. [1] A frame is "the unit of transmission in a link layer protocol, and consists of a link layer header followed by a packet."
EtherType is a two-octet field in an Ethernet frame. It is used to indicate which protocol is encapsulated in the payload of the frame and is used at the receiving end by the data link layer to determine how the payload is processed. The same field is also used to indicate the size of some Ethernet frames.
By far the most popular FCS algorithm is a cyclic redundancy check (CRC), used in Ethernet and other IEEE 802 protocols with 32 bits, in X.25 with 16 or 32 bits, in HDLC with 16 or 32 bits, in Frame Relay with 16 bits, [3] in Point-to-Point Protocol (PPP) with 16 or 32 bits, and in other data link layer protocols.
The Layer 3: network layer PDU is the packet. The Layer 2: data link layer PDU is the frame. The Layer 1: physical layer PDU is the bit or, more generally, symbol. Given a context pertaining to a specific OSI layer, PDU is sometimes used as a synonym for its representation at that layer.
The link layer corresponds to the OSI data link layer and may include similar functions as the physical layer, as well as some protocols of the OSI's network layer. These comparisons are based on the original seven-layer protocol model as defined in ISO 7498, rather than refinements in the internal organization of the network layer.
In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. [1]: 25 The MTU relates to, but is not identical to the maximum frame size that can be transported on the data link layer, e.g., Ethernet frame.