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Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
In general, communications take place between peer layer protocols by the exchange of protocol data units (PDUs), which contain all of the information required for the receiving protocol entity to provide the required service. For the PIRM, we say that applications exchange messages, layer 4 entities exchange segments, layer 3 entities exchange datagrams, layer 2 entities exchange frames, and layer 1 protocols exchange 1-PDUs. It should be mentioned that datagrams are packets that traverse networks using connectionless layer 3 protocols. Equivalently, we can say that the packet-switched Internet is a datagram network because IP is the only layer 3 protocol, and it provides connectionless service.
Overview of NRSC-5
Published in David P. Maxson, The IBOC Handbook, 2007
Following the chapter on audio coding and transport, the path of the “PDU” is followed into the Audio Transport and on to Layers 2 and 1. The term PDU stands for Protocol Data Unit. Each block in the protocol stack takes information in, performs work on it, and puts the newly structured information out the other side. The inputs and outputs of each layer are called PDUs. As will become apparent in the following chapters, the “work” performed by a layer may consist of synthesizing a new PDU from content data, combining or processing incoming PDUs, or a little of both.
Wiring, Installation, and Commissioning
Published in Sunit Kumar Sen, Fieldbus and Networking in Process Automation, 2014
Network communication takes place in a layered fashion. The open systems interconnection (OSI) model has seven layers with each layer performing a specific networking function. Protocols govern these functions and manage end-to-end communication between devices. As user data is passed from the upper layers down below, each layer adds a header (and sometimes a trailer also) to data. These headers contain protocol information and are termed as protocol data units (PDUs). The process of adding headers to the layers is known as encapsulation.
SCADA Research Lab Kit for Educational Institutes
Published in IETE Journal of Education, 2019
Lagineni Mahendra, Rajesh Kalluri, R.K. Senthil Kumar, B.S. Bindhumadhava, G.L. Ganga Prasad
Network access for IEC 60870-5-101 [4] using standard transport profiles is defined in IEC 60870-5-104 protocol. The length of the Application Protocol Data Unit (APDU) defines the length of the body of the APDU, which includes the four control field octets of the Application Protocol Control Information (APCI) and the Application Service Data Unit (ASDU) and is shown in Figure 4. Most of the type identifications of ASDU are defined IEC 60870-5-101standard and few new type identifications are defined in the IEC 60870-5-104 standard.