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                                                                                                                                       ISO-OSI 7-Layer Network Architecture

This lecture introduces the ISO-OSI layered architecture of Networks. According to the ISO standards, networks have been divided into 7 layers depending on the complexity of the fucntionality each of these layers provide. The detailed description of each of these layers is given in the notes below. We will first list the layers as defined by the standard in the increasing order of function complexity:

1-Physical Layer 2-Data Link Layer 3-Network Layer 4-Transport Layer 5-Session Layer 6-Presentation Layer 7-Application Layer

Physical Layer

This layer is the lowest layer in the OSI model. It helps in the transmission of data between two machines that are communicating through a physical medium, which can be optical fibres,copper wire or wireless etc. The following are the main functions of the physical layer: Hardware Specification: The details of the physical cables, network interface cards, wireless radios, etc are a part of this layer.