The Elements of Communication
* The first of these elements is the message source, or sender. Message sources are people, or electronic devices, that need to send a message to other individuals or devices. * The second element of communication is the destination, or receiver, of the message. The destination receives the message and interprets it. * A third element, called a channel, consists of the media that provides the pathway over which the message can travel from source to destination.
Components of the Network
* Devices and media are the physical elements or hardware of the network. Hardware is often the visible components of the network platform such as a laptop, a PC, a switch, or the cabling used to connect the devices. * Services and processes are the communication programs, called software, that run on the networked devices. Services include many of the common network applications people use every day, like e-mail hosting services and web hosting services. Processes provide the functionality that directs and moves the messages through the network.
End Devices and their Role on the Network
* The network devices that people are most familiar with are called end devices. * These devices form the interface between the human network and the underlying communication network. a. Computers (work stations, laptops, file servers, web servers) b. Network printers
c. VoIP phones
d. Security cameras
e. Mobile handheld devices (such as wireless barcode scanners, PDAs)
Intermediary Devices and their Role on the Network
* Networks rely on intermediary devices to provide connectivity and to work behind the scenes to ensure that data flows across the network. These devices connect the individual hosts to the network and can connect multiple individual networks to form an internetwork. f. Network Access Devices (Hubs, switches, and wireless access points) g. Internetworking Devices (routers)
h. Communication Servers and Modems
i. Security Devices (firewalls)
* Processes running on the intermediary network devices perform these functions: j. Regenerate and retransmit data signals
k. Maintain information about what pathways exist through the network and internetwork l. Notify other devices of errors and communication failures m. Direct data along alternate pathways when there is a link failure n. Classify and direct messages according to QoS priorities o. Permit or deny the flow of data, based on security settings
* Communication across a network is carried on a medium. The medium provides the channel over which the message travels from source to destination. p. Metallic wires within cables
q. Glass or plastic fibers (fiber optic cable)
r. Wireless transmission
* Criteria for Choosing a Network Media
s. The distance the media can successfully carry a signal. t. The environment in which the media is to be installed. u. The amount of data and the speed at which it must be transmitted. v. The cost of the media and installation
Local Area Networks
* Networks infrastructures can vary greatly in terms of:
* The size of the area covered
* The number of users connected
* The number and types of services available
* A LAN is usually administered by a single organization. * The administrative control that governs the security and access control policies are enforced on the network level.
Wide Area Networks
* Networks that connect LANs in geographically separated locations. * WANs use specifically designed network devices to make the interconnections between LANs.
* A global mesh of interconnected networks (internetworks) meets these human communication needs. * The most well-known and widely used publicly-accessible internetwork is the Internet.
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