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What are Functions of the OSI Layers ?

Functions of the OSI Layers There are the seven OSI layers. Each layer has different functions. A list of seven layers is given below: 1_Physical Layer : The main functionality of the physical layer is to transmit the individual bits from one node to another node. It is the lowest layer of the OSI model. It establishes, maintains and deactivates the physical connection. It specifies the mechanical, electrical and procedural network interface specifications. Functions of a Physical layer: Line Configuration: It defines the way how two or more devices can be connected physically. Data Transmission: It defines the transmission mode whether it is simplex, half-duplex or full-duplex mode between the two devices on the network. Topology: It defines the way how network devices are arranged. Signals: It determines the type of the signal used for transmitting the information. 2_Data-Link Layer : This layer is responsible for the error-free transfer of data frames. It defines the format of t
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Switching at Physical Layer ? Switches ?

What are Switches ? Sitches are devices capable of creating temporary connections between two or more devices linked to the switch. Switching at Physical Layer : At the physical layer, we can have only circuit switching. There are no packets exchanged at the physical layer. The switches at the physical layer allow signals to travel in one path or another. Switching at Data-Link Layer At the data-link layer, we can have packet switching. However, the term packet in this case means frames or cells.  Packet switching at the data-link layer is normally done using a virtual-circuit approach.  Switching at Network Layer At the network layer, we can have packet switching. In this case, either a virtual-circuit approach or a datagram approach can be used. Currently the Internet uses a datagram approach, as we see in Chapter 18, but the tendency is to move to a virtual-circuit approach.  What is network? Connected Devices? what is network criteria in data communication?
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TCP/IP PROTOCOL SUITE |What is the TCP/IP Model? Layers and Protocols Explained ?

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   TCP/IP PROTOCOL SUITE :   TCP/IP =Transmission Control Protocol/Internet Protocol. What is TCP/IP ? is a protocol suite (a set of protocols organized in different layers) used in the Internet today. It is a hierarchical protocol made up of interactive modules .  each of which provides a specific functionality. What is The term hierarchical : means that each upper level protocol is supported by the services provided by one or more lower level protocols. The original TCP/IP protocol suite was defined as four software layers built upon the hardware. Today, however, TCP/IP is thought of as a five-layer model.  What is Layered Architecture ? Layered Architecture : To show how the layers in the TCP/IP protocol suite are involved in communication between two hosts, we assume that we want to use the suite in a small internet made up of three LANs (links) . each with a link-layer switch.  We also assume that the links are connected by one router . Communication through an internet
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Network Models | What is protocol layering ? Principles of Protocol Layering

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definition | backbones , peering points , provider networks , customer networks , Internet Service Providers (ISPs)

  What is a backbones ? backbones are large networks owned by some communication companies such as Sprint, Verizon (MCI), AT&T, and NTT.  What is peering points ? The backbone networks are connected through some complex switching systems, called peering points. At the second level, there are smaller networks, called  provider networks  . What is provider networks ? that use the services of the backbones for a fee.  The provider networks are connected to backbones and sometimes to other provider networks. What is customer networks ? The customer networks are networks at the edge of the Internet that actually use the services provided by the Internet. They pay fees to provider networks for receiving services.  Read also : What is Internet ? Internet network ? ISPs vs customer vs provider vs backbones Network Switching Definition & Types ? circuit-switched networks VS packet-switched networks ? What is Intern et Service Providers (ISPs) ? Backbones and provider networks are also c
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What is Direct Connection to the Internet ?

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What is Accessing the Internet ? Dial-up service vs DSL Service vs. Cable ?

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