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OSI model. Protocol data units of the OSI model are: [1] The Layer 4: transport layer PDU is the segment or the datagram. 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 ...
Modbus defines a protocol data unit (PDU) independently to its lower layer protocols in its protocol stack. Mapping MODBUS protocol on specific buses or networks requires some additional fields, defined as the application data unit (ADU). The ADU is formed by a client inside a Modbus network when the client initiates a transaction. Contents are ...
Each PDU contains a payload, called the service data unit (SDU), along with protocol-related headers or footers. Data processing by two communicating OSI-compatible devices proceeds as follows: The data to be transmitted is composed at the topmost layer of the transmitting device (layer N) into a protocol data unit (PDU). The PDU is passed to ...
Encapsulation is the computer-networking process of concatenating layer-specific headers or trailers with a service data unit (i.e. a payload) for transmitting information over computer networks. [2][3][4] Deencapsulation (or de-encapsulation) is the reverse computer-networking process for receiving information; it removes from the protocol ...
Smart card application protocol data unit. In the context of smart cards, an application protocol data unit (APDU) is the communication unit between a smart card reader and a smart card. The structure of the APDU is defined by ISO/IEC 7816 -4 Organization, security and commands for interchange. [1]
The term TCP packet appears in both informal and formal usage, whereas in more precise terminology segment refers to the TCP protocol data unit (PDU), datagram [15] to the IP PDU, and frame to the data link layer PDU: Processes transmit data by calling on the TCP and passing buffers of data as arguments. The TCP packages the data from these ...
Maximum transmission unit. 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.
Protocol data unit (PDU) Function [3] Host layers 7 Application: Data: High-level protocols such as for resource sharing or remote file access, e.g. HTTP. 6 Presentation: Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption: 5 Session