Computer Networking Fundamentals
The sharing of fax machines, printers, and modems amongst many computers and users reduce the operational cost. A database on a computer network is a very important application as it stores and runs many important data and jobs. Emails and chats can be used for instantaneous communication and sending of files on a computer network.
The computer networks are classified, depending upon the size, as Local Area Networks (LAN), Wide Area Networks (WAN), Metropolitan Area Networks (MAN) and Personal Area Networks (PAN). The topology (topology is the way the computer networks and network resources are connected) of the networking can be classified as Bus Network, Ring Network and Star Network.
The networking hardware basically consists of wiring, network cards and a hub. Computer network cards are required so that one computer can understand what the other computer is “talking”. Network cards have a unique MAC address to identify computers on a computer network. Hubs connect all the computers in the network. Hubs can also be used to connect to other hubs to increase the size of the computer network. Two computers can be connected using Ethernet cards or phone lines or power lines for communication, with hardware kits available at roughly a cost of $100.
Network Router
A router is a device that determines the proper path for data to travel between different networks, and forwards data packets to the next device along this path. They connect networks together; a LAN to a WAN for example, to access the Internet. Some units, are available in both wired and wireless models.
Wired Router Model
Wireless Router Model
Function
A more precise definition of a router is a computer networking device that interconnects separate logical subnets. Routers are now available in many types, though all are fundamentally doing the same job. A router is a computer whose software and hardware are usually tailored to the tasks of routing and forwarding, generally containing a specialized operating system (e.g. Cisco’s IOS or Juniper Networks JunOS or Extreme Networks XOS), RAM, NVRAM, flash memory, and one or more processors. High-end routers contain many processors and specialized Application-specific integrated circuits (ASIC) and do a great deal of parallel processing. However, with the proper software (such as XORP or Quagga), even commodity PCs can act as routers.
Routers connect with two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router.
The term switch or layer 3 switch or network switch often is used interchangeably with router, but switch is really a marketing term without a rigorous technical definition (though a switch is commonly understood as a network hub with switched ports, which might or might not also perform additional routing functions).
Chassis systems like the Nortel MERS-8600 or ERS-8600 routing switch, allow for a wide variety of LAN, MAN, METRO, and WAN port technologies or other connections that are customizable.
Routers operate in two different planes:
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Network Switch
A network switch is a computer networking device that connects network segments.
Low-end network switches appear nearly identical to network hubs, but a switch contains more “intelligence” (and a slightly higher price tag) than a network hub. Network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately. By delivering each message only to the connected device it was intended for, a network switch conserves network bandwidth and offers generally better performance than a hub.
In the past, it was faster to use layer 2 techniques to switch, when only MAC addresses could be looked up in content addressable memory (CAM). With the advent of ternary CAM (TCAM), it was equally fast to look up an IP address or a MAC address. TCAM is expensive, but very appropriate for enterprise switches that use default routes plus a moderate number of other routes. For routers that need a full Internet routing table, TCAM may not be cost-effective.
Function
As with hubs, Ethernet implementations of network switches are the most common. Mainstream Ethernet network switches support either 10/100 Mbit/s or 10/100/1000 Mbit/s ports Ethernet standards. Large switches may have 10 Gbit/s ports.
The network switch, packet switch (or just switch) plays
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Wide Area Network (WAN)
Wide Area Network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries). Or, less formally, a network that uses routers and public communications links . Contrast with personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city) respectively. The largest and most well-known example of a WAN is the Internet.
WANs are used to connect LANs and other types of networks together, so
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Metropolitan Area Network (MAN)
Metropolitan area networks, or MANs, are large computer networks usually spanning a city. They typically use wireless infrastructure or Optical fiber connections to link their sites.
The IEEE 802-2001 standard describes a MAN as being:
| “ | A MAN is optimized for a larger geographical area than is a LAN, ranging from several blocks of buildings to entire cities. As with local networks, MANs can also depend on communications channels of moderate-to-high data rates. A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations. MANs might also be owned and operated as public utilities. They will often provide means for internetworking of local networks. | ” |
Some technologies used for this purpose are ATM, FDDI, and SMDS. These older technologies are in the process of being displaced by Ethernet-based MANs (e.g. Metro Ethernet) in most areas. MAN links between LANs have been built without cables using either microwave, radio, or infra-red laser links.
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Campus Area Network (CAN)
A campus area network (CAN) is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting.
In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network (WAN)en.wikipedia.org
Local Area Network (LAN)
A local area network (LAN) is a computer network covering a small geographic area, like a home, office, or group of buildings. The defining characteristics of LANs, in contrast to Wide Area Networks (WANs), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.
Ethernet over unshielded twisted pair cabling, and Wi-Fi are the two most common technologies currently, but ARCNET, Token Ring and many others have been used in the past.
History
In the days before personal computers, a site might have just one central computer, with users accessing this via computer terminals over simple low-speed cabling. Networks such as IBM’s SNA (Systems Network Architecture) were aimed at linking terminals or other mainframes at remote sites over leased lines—hence these were wide area networks.
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Personal Area Network
A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink).
Personal area networks may be wired with computer buses such as USB and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA, Bluetooth and UWB.
Wireless
A Bluetooth PAN is also called a piconet, and is composed of up to 8 active devices in a master-slave relationship (a very large number of devices can be connected in “parked” mode). The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master. A piconet typically has a range of 10 meters, although ranges of up to 100 meters can be reached under ideal circumstances.
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Network Card
A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It is both an OSI layer 1 (physical layer) and layer 2 (data link layer) device, as it provides physical access to a networking medium and provides a low-level addressing system through the use of MAC addresses. It allows users to connect to each other either by using cables or wirelessly.
Although other network technologies exist, Ethernet has achieved near-ubiquity since the mid-1990s. Every Ethernet network card has a unique 48-bit serial number called a MAC address, which is stored in ROM carried on the card. Every computer on an Ethernet network must have a card with a unique MAC address. No two cards ever manufactured share the same address. This is accomplished by the Institute of Electrical and Electronics Engineers (IEEE), which is responsible for assigning unique MAC addresses to the vendors of network interface controllers.
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