Networking

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...

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?

   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 . Comm...

  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...

 NETWORK TYPES

  Bus Topology What is Bus Topology ?   is multipoint.  One long cable acts as a backbone to link all the devices in a network . Nodes are connected to the bus cable by drop lines and taps. A drop line is a connection running between the device and the main cable. A tap is a connector that either splices into the main cable or punctures the sheathing of a cable to create a contact with the metallic core.  As a signal travels along the backbone, some of its energy is transformed into heat.  Therefore, it becomes weaker and weaker as it travels farther and farther.  For this reason there is a limit on the number of taps a bus can support and on the distance between those taps. What are Bus topology advantages and disadvantages? What are the advantages of a Bus network ( topology) ? Advantages of Bus topology : Advantages of a bus topology include ease of installation.  Backbone cable can be laid along the most efficient path, then connected to the n...

  What is the difference between star topology and mesh topology ?   In the star topology : star topology In a star topology, each device has a dedicated point-to-point link only to a central controller  usually called a hub. The devices are not directly linked to one another. Unlike a mesh topology. a star topology does not allow direct traffic between devices. The controller acts as an exchange:  If one device wants to send data to another, it sends the data to the controller, which then relays the data to the other connected device . A star topology is less expensive than a mesh topology.  In a star, each device needs only one link and one I/O port to connect it to any number of others. In a mesh topology : Mesh Topology  every device has a dedicated point-to-point link to every other device. The term dedicated means that the link carries traffic only between the two devices it connects.   😉thank you all my friends 

  Ring Topology What is Ring Topology ?  Ring Topology : In a ring topology, : each device has a dedicated point-to-point connection with only the two devices on either side of it.  How does a ring topology work? A signal is passed along the ring in one direction, from device to device, until it reaches its destination. Each device in the ring incorporates a repeater. When a device receives a signal intended for another device.  its repeater regenerates the bits and passes them along . What is Mesh Topology ?   What are the advantages and disadvantages of a mesh network ( topology) ? What are Ring topology advantages and disadvantages? What are the advantages of a Ring network ( topology) ? Why do we use ring topology? Advantages of Ring topology : A ring is relatively easy to install and reconfigure. Each device is linked to only its immediate neighbors (either physically or logically). To add or delete a device requires changing only two connections. fault iso...

  Mesh Topology What is Mesh Topology ?  In a mesh topology :  every device has a dedicated point-to-point link to every other device.  The term dedicated means that the link carries traffic only between the two devices it connects. What is the example of mesh topology? What is a full mesh topology? Full mesh topology occurs when every node has a circuit connecting it to every other node in a network. A fully connected mesh topology. What are the advantages of a mesh network ( topology) ? Advantages of mesh topology : A mesh offers several advantages over other network topologies. First, the use of dedicated links guarantees that each connection can carry its own data load, thus eliminating the traffic problems that can occur when links must be shared by multiple devices. Second, a mesh topology is robust. If one link becomes unusable, it does not incapacitate the entire system. Third, there is the advantage of privacy or security. When every message travels along a ...

  Physical Topology types of physical topology :   The term physical topology : What meant by topology : refers to the way in which a network is laid out physically. Two or more devices connect to a link.  two or more links form a topology. The topology of a network is the geometric representation of the relationship of all the links and linking devices (usually called nodes) to one another. What are Types of network topology : There are four basic topologies possible:  1_mesh  2_star 3_bus 4_and ring. 1_mesh : What is Mesh Topology ?  In a mesh topology :  every device has a dedicated point-to-point link to every other device.  The term dedicated means that the link carries traffic only between the two devices it connects. What is the example of mesh topology? What is a full mesh topology? Full mesh topology occurs when every node has a circuit connecting it to every other node in a network. A fully connected mesh topology. What are the adva...

  Star Topology : What is star topology?  In a star topology:  each device has a dedicated point-to-point link only to a central controller, usually called a hub. The devices are not directly linked to one another. Unlike a mesh topology. a star topology does not allow direct traffic between devices. How does star topology work? The controller acts as an exchange:  If one device wants to send data to another, it sends the data to the controller, which then relays the data to the other connected device . What is the difference between star topology and mesh topology ?   In the star topology : In a star topology, each device has a dedicated point-to-point link only to a central controller  usually called a hub. The devices are not directly linked to one another. Unlike a mesh topology. a star topology does not allow direct traffic between devices. The controller acts as an exchange:  If one device wants to send data to another, it sends the data to the c...

  physical structure of computer network  :    physical structures in data communications :   What is the physical structure of computer network ?   What are  network attributes ?  What are the types of connection in the network ?  1___Type of Connection :  A network is two or more devices connected through links.  What is A link ?  is a communications pathway that transfers data from one device to another. -  For communication to occur : two devices must be connected in some way to the same link at the same time. There are two possible types of connections: 1_ point-to-point  Connection  2_ and multipoint  Connection   what is difference between point to point and multipoint connection ? What is a Point to Point Connection? A point-to-point connection provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between those two devices.  Mo...

  What are components of data communication ? A data communications system has five components :  1__Message : What is Message ? The message is the information (data) to be communicated.  Popular forms of information include text, numbers, pictures, audio, and video.  2__Sender: What is sender ?  The sender is the device that sends the data message.  It can be a computer, workstation, telephone handset, video camera, and so on . 3__Receiver: What is Receiver ? The receiver is the device that receives the message.  It can be a computer, workstation, telephone handset, television, and so on. 4__Transmission medium: What is Transmission medium ? The transmission medium is the physical path by which a message travels from sender to receiver.  Some examples of transmission media include : What are transmission media :  twisted-pair wire  coaxial cable  fiber-optic cable and radio waves. 5__Protocol : What is protocol ? A protocol is a se...