|  | 8.1 | Basic Networking Knowledge
| 8.1.11 | Full and Half-Duplexing, WAN and LAN; Server, workstation, and host; Server-based networking and peer-to-peer networking; Cable, NIC, and router; broadband and baseband; Gateway (as both a default IP router and as a method to connect dissimilar systems or protocols)
Full and Half-Duplexing There are three different terms used to describe how transmitters and receivers interact during communications, simplex, half-duplex, and full-duplex. In simplex communications, the data travels only one way and no response is needed or possible. An example of simplex is a school Public Address (PA) system. In half-duplex communications, data travels from a transmitter to a receiver, then from the receiver to the transmitter, repeatedly, however, never simultaneously - simultaneous transmission and reception of data is not possible. Examples of half-duplex are walkie-talkies and 10BASE-T Ethernet. In full-duplex communications, both transmitter and receiver may send and receive simultaneously. Clearly this is the fastest way to communicate, but requires more sophisticated electronics. Examples of full duplex are the telephone and 100BASE-TX (Fast Ethernet). WAN and LAN A Wide Area Network (WAN) is geographically unlimited; while, a Local Area Network (LAN) is limited to a smaller region. WANs can span over a cities, countries, and multiple locations; LANs are limited to a single building or school campuses. LANs operate within a limited geographic area, such as a single building, connecting workstations, peripherals, and other devices on a single network. LANs provide a business with complete computer technology to share devices on a network. WANs are geographically unlimited and vary in size, between cities, states, or even globally. WANs provide an efficient way to move information from one network (a LAN) to another network. Server, Workstation, and Host Servers are typically powerful computers, which provide resources and services to other computers on a network. Workstations (clients) are devices, which are capable of local processing of data, and use resources and services provided by the server. Host is the special name given to ANY addressable computer system on a network running TCP/IP, examples of hosts include workstations, servers, minicomputers, mainframes, and even routers. Server-Based Networking and Peer-To-Peer Networking Two types of networks are Server-Based and Peer-to-Peer. A server-based network, also known as client/server, connects numerous hosts to a centralized computer. This computer serves as a server, providing security functions and access to the network and resources, allowing for a central security system. As the network grows and the number of nodes increase, this type of network can add specific servers to address to specific needs and resources. Examples include file and print servers, application server, domain controllers, and directory servers. Client-Server networks require typically a powerful server computer, running a network operating system, and administration by highly trained personnel. Advantages are the variety of services that can be provided and the central administration of those services; however, the disadvantages include cost and complexity. In a peer-to-peer network, there is no centralized server or security system. Each node on the network works as its own server, granting permission to the other nodes on the network to access its resources. This type of network is limited to approximately 10 nodes connected to each other. Advantages include simplicity, low cost, and ease of administration, while disadvantages include slow speed and a severely limited range of services that can be provided. Cable, NIC, and Router In order to create a properly functioning network, the main necessities required include cables, NICs, and routers. A cable is the physical media used to wire networks. The cables that can be used to wire a network include unshielded and shielded twisted pair (UTP and STP), coaxial, fiber optic, or wireless (if no cables are required). These physical media are used in combination with the network interface card (NIC), which allows the computer to communicate with the network. Another way to look at the NIC is that it allows the workstation Operating System (OS) to communicate with the local area network operating system (NOS). A router is a layer 3 device which performs best path selection and packet switching, and is used to connect one or more Local Area Networks (LAN) together to create a Wide Area Network (WAN). Broadband and Baseband Two types of signaling are Broadband and Baseband. Broadband is an analog signaling technique normally used in cable television. This type of signaling can carry video, voice, and data across a wire. It shares the medium's bandwidth over different channels, often using different carrier frequencies. One sharing technique is called frequency division multiplexing (FDM). Baseband is a digital signaling technique, which uses the entire medium's bandwidth for a single channel at a time and allows very high throughputs (the actual measured bandwidths are possible due to this single-channel-at-a-time technique). Signals are in the form of voltage pulses on copper, light pulses on optical fiber, or electromagnetic waves in the atmosphere. A form of multiplexor (MUX) device is usually required so that multiple devices can take their turns using the medium. Gateway A gateway, which works as a translator, provides communication between different operating systems and frequently services the Internet. A gateway must exist if two different types of operating systems, such as Windows and UNIX, are to communicate. In order to communicate with node on a different network over the Internet, the device must be connected to a LAN or a dial up connection. Gateway also refers to default gateway, an IP address is used to forward packets from one subnet to another subnet, if there is no other routing information available.
| Web Links
| CompTIA Home/Net + Certification
| Cisco Connection Online
| Cisco Documentation
| Search Cisco