What is a telecommunications network protocol? What is telecommunications networ

Question

• What is a telecommunications network protocol? What is telecommunications network architecture? Select a network protocol and provide details on the steps that preceded the formal adoption of the protocol by the industry. Make sure you provide dates and organizations which were involved in the process.
• How are analog signals converted to digital signals for transmission over a telecommunications network? What are the advantages and disadvantages of digital over analog? What is the role of digital modulation in transmitting digital signals from source to destination? Make sure you use diagrams to support your discussion.
• In the OSI model, three layers divide the application layer from the network layer: presentation, session, and transport. The application layer is closest to the end user and the network layer is closest to the physical network. Based on the functions of the three layers between application and network, how do you anticipate the implementation of these layers changes from application to network, as information is moved from one layer to another? What is the importance of understanding the functions of these layers? How are layers represented in the TCP/IP model?

Explanation / Answer

The Open Systems Interconnection (OSI) model (ISO/IEC 7498-1) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO).

The model groups similar communication functions into one of seven logical layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of that path. Two instances at one layer are connected by a horizontal connection on that layer.

At each level, two entities (N-entity peers) interact by means of the N protocol by transmitting protocol data units (PDU).

A service data unit (SDU) is a specific unit of data that has been passed down from an OSI layer to a lower layer, and which the lower layer has not yet encapsulated into a protocol data unit (PDU). An SDU is a set of data that is sent by a user of the services of a given layer, and is transmitted semantically unchanged to a peer service user.

The SDU at a layer N was the PDU of layer N+1. In effect the SDU is the 'payload' of a given PDU. That is, the process of changing an SDU to a PDU, consists of an encapsulation process, performed by the lower layer. All the data contained in the SDU becomes encapsulated within the PDU. The layer N-1 adds headers or footers, or both, to the SDU, transforming it into a PDU of layer N-1. The added headers or footers are part of the process used to make it possible to get data from a source to a destination.

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