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Classification by Services Provided

Classification by Services Provided

Computer networks may be classified according to the services which they provide, such as Storage area networks, Server farms, Process control networks, Value-added network, SOHO network, Wireless community network, XML appliance, Jungle Networks, khadar network, etc.
Storage area network
In computing, a storage area network (SAN) is a network (referred to as a fabric) designed to attach computer storage devices such as disk array controllers and tape libraries to servers. As of 2007, SANs are most commonly found in enterprise storage.
SAN allows a machine to connect to remote targets such as disks and tape drives on a network for block level I/O.
From the point of view of the class drivers and application software, the devices appear as locally attached devices.
There are two variations of SANs:
1. A network whose essential purpose is the transfer of data between computer systems and storage elements.
A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust.
The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services.
2. A storage system consisting of storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over an ethernet network.
Storage networks are distinguished from other forms of network storage by the low-level access method that they use.
Data traffic on the SAN Fabric is very similar to those used for internal disk drives, like ATA and SCSI.
In a storage network, a server issues a request for specific blocks, or data segments, from specific disk drives. This method is known as block storage.
The device acts in a similar fashion to an internal drive, accessing the specified block, and sending the response across the network.
Server farm
The Server Farm.
server farm is a collection of computer servers usually maintained by an enterprise to accomplish server needs far beyond the capability of one machine.
Often, server farms will have both a primary and a backup server allocated to a single task, so that in the event of the failure of the primary server, a backup server will take over the primary server’s function.
Server farms are typically co-located with the network switches and/or routers which enable communication between the different parts of the cluster and the users of the cluster.
Server farms are commonly used for cluster computing. Many modern supercomputers consist of giant server farms of high-speed processors connected by either Gigabit Ethernet or custom interconnects such as Myrinet.
Another common use of server farms is for web hosting
Process control network
Process Control Network (PCN) is a communications network that is used to transmit instructions and data between control and measurement units and Supervisory Control and Data Acquisition (SCADA) equipment.
These networks have, over the years, used many of the technologies and topologies utilized in other network applications.
However, Process Control Networks (PCNs) have several special requirements that must be met in order for the solution to be acceptable to the industry.
These requirements are, in no particular order: Robustness, Determinacy, Compatibility.
Robustness includes requirements such as connection redundancy, reduced sensitivity to Electromagnetic Interference (EMI), and good error checking and correction.
Determinacy involves assuring that each device is guaranteed access to the network, and in many cases mechanisms to allow priority information (such as alarms) through the system.
Compatibility allows SCADA and Distributed Control Systems (DCS) from various manufacturers to communicate with control and measurement equipment from others.
Value-added network
value-added network (VAN) is a specialized application service provider (ASP) that acts as an intermediary between trading partners sharing data or business processes.
VANs traditionally transmitted data formatted as Electronic Data Interchange (EDI) but increasingly they also transmit data formatted as XML.
VANs usually service a given vertical or industry and provide value-added services such as data transformation between formats (EDI?XML, EDI?EDI, etc.).
At one extreme a VAN hosts only horizontal business-to-business (B2B) application integration services, hosting general-purpose integration services for any process or industry.
At the other extreme a VAN also hosts process-specific or industry-specific pre-defined integration capabilities (e.g., data synchronization services as part of the Global Data Synchronization Network (GDSN)) and applications (e.g., supply chain order visibility).
Traditionally, most VANs primarily only supported general-purpose B2B integration capabilities focused on EDI but these service providers are quickly evolving to become more process- and industry-specific over time, particularly in industries such as retail and hi-tech manufacturing.
SOHO network
“SOHO network” is occasionally used to refer to a local area network as used in a Small office/home office business.
The term is mainly useful to define a market segment which has no internal IT staff, and possibly no dedicated server, structured cabling or server room, and where very high levels of performance and robustness are not warranted.
Compared to 19-inch rack based traditional business equipment, products designed for the SOHO market tend to be simpler, quieter, cheaper and “prettier”.
Wireless community network
Wireless community networks or wireless community projects are the largely hobbyist-led development of interlinked computer networks using wireless LAN technologies.
Taking advantage of the recent development of cheap, standardised 802.11b (Wi-Fi) devices to build growing clusters (group of the same or similar elements gathered) of linked, citywide networks, or in rural areas where conventional DSL services are unavailable.
Some are being used to link to the wider Internet, particularly where individuals can obtain unmetered internet connections such as ADSL and/or cable modem at fixed costs and share them with friends.
Where such access is unavailable or expensive, they can act as a low-cost partial alternative, as the only cost is the fixed cost of the equipment.