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. |
A 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. |
A 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 |
A 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 |
A 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. |
Thursday, February 5, 2009
Classification by Services Provided
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