Network Characteristics

The following characteristics should be considered in network design and ongoing maintenance:
Cost

Includes the cost of the network components, their installation, and their ongoing maintenance.
Security
Includes the protection of the network components and the data they contain and/or the data transmitted between them.
Speed
Includes how fast data is transmitted between network end points (the data rate).
Topology
Describes the physical cabling layout and the logical way data moves between components.
Scalability
Defines how well the network can adapt to new growth, including new users, applications, and network components.
Reliability
Defines the reliability of the network components and the connectivity between them. Mean time between failures (MTBF) is a measurement commonly used to indicate the likelihood of a component failing.
Availability
Measures the likelihood of the network being available to the users, where downtime occurs when the network is not available because of an outage or scheduled maintenance. Availability is typically measured in a percentage based on the number of minutes that exist in a year. Therefore, uptime would be the number of minutes the network is available divided by the number of minutes in a year.
Network classification
The following list presents categories used for classifying networks.
Connection method
Computer networks can also be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as Optical fiber, Ethernet Card, Wireless LAN, HomePNA, or Power line communication.
Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges and/or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium.
Scale
Based on their scale, networks can be classified as Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN), Personal Area Network (PAN), Virtual Private Network (VPN), Campus Area Network (CAN), Storage Area Network (SAN), etc.
Functional relationship (network architecture)
Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture.
Network topology
Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network, star-bus network, tree or hierarchical topology network. Network topology signifies the way in which devices in the network see their logical relations to one another. The use of the term “logical” here is significant. That is, network topology is independent of the “physical” layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks.
Network Components
Applications, which enable users to perform various tasks, make up a key component
of networking. Many applications are network-aware, allowing you to access and use resources that are not located on your local computer. While the number of networking applications ranges in the thousands, some of the more common networking applications include e-mail applications for sending mail electronically, File Transfer Protocol (FTP) applications for transferring files, and web applications for providing a graphical representation of information.
Protocols are used to implement applications. Some protocols are open standard, meaning that many vendors can create applications that can interoperate with each other, while others are proprietary, meaning that they work only with a particular application. Common protocols used on the Internet are Simple Mail Transfer Protocol (SMTP), Internet Message Access Protocol version 4 (IMAP4), and Post Office Protocol 3 (POP3), which implements e-mail applications such as Sendmail and Microsoft Exchange; File Transfer Protocol (FTP), which implements file
transfer programs such as FTP Explorer, Cute FTP, and WSFTP; and Hypertext Transfer Protocol (HTTP), which implements web browsing applications such asInternet Explorer and Firefox and web server applications such as Microsoft Internet Information Services (IIS) and Apache.
Some applications, such as e-mail, require little bandwidth, while others, such as backup software, video software, and file transfer software, require a lot. Some applications operate in real-time, such as voice over IP (VoIP) and video; some operate interactively, such as instant messaging or database queries; and some operate in a batch mode, requiring little user interaction. Today’s networks need to accommodate all these different types of resources and applications, including their specific requirements such as bandwidth for large transfers or minimal delay and latency for VoIP and video. Quality of service (QoS) features are commonly used to meet these requirements.

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