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Frequently Asked Questions


What is DSL ?
DSL stands for Digital Subscriber Loop. It shares the same phone line as the telephone service, but it uses a different part of the phone line's bandwidth. It does not interfere with normal phone service because there is a significant amount of unused capacity in current phone wires. ...

What is the Bandwidth?
The amount of data that can be transmitted in a fixed amount of time. For digital devices, the bandwidth is usually expressed in bits per second (bps) or bytes per second. The bandwidth is particularly important for I/O (input/output) devices.

What is Ethernet ?
The type of hardware most widely used throughout LANs. It consists of a single cable with hosts attached to it through connectors, taps, or transceivers. Simple Ethernets are quite inexpensive to install, which, together with a net transfer rate of 10 Megabits per second accounts for much of its popularity. A LAN protocol developed by Xerox Corporation in cooperation with DEC and Intel in 1976, the Ethernet specification served as the basis for the IEEE 802.3 standard, which specifies the physical and lower software layers. Presidia's products have an Ethernet interface which conforms to IEEE standards.

What is the IP ?
Internet Protocol. IP specifies the format of packets and the addressing scheme. Most networks combine IP with a higher-level protocol called Transport Control protocol (TCP), which establishes a virtual connection between a destination and a source. See TCP/IP.

What is LAN ?
Local-area network. A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN). There are many different types of LANs, Ethernets being the most common for PCs.

What is a Network ?
In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain sub networks.
The most common topologies or general configurations of networks include the bus, star, and ring topologies. Networks can also be characterized in terms of spatial distance as local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs).
A given network can also be characterized by the type of data transmission technology in use on it (for example, a TCP/IP or SNA network); by whether it carries voice, data, or both kinds of signals; by who can use the network (public or private); by the usual nature of its connections (dial-up or switched, dedicated or no switched, or virtual connections); and by the types of physical links (for example, optical fiber, coaxial cable, and copper wire). Large telephone networks and networks using their infrastructure (such as the Internet) have sharing and exchange arrangements with other companies so that larger networks are created.

What is a Router?
A device that connects any number of computers to the ADSL. Routers use headers and a forwarding table to determine where packets go, and they use ICMP to communicate with each other and configure the best route between any two hosts.


What is a Switch ??
In telecommunications, a switch is a network device that selects a path or circuit for sending a unit of data to its next destination. A switch may also include the function of the router, a device or program that can determine the route and specifically what adjacent network point the data should be sent to. In general, a switch is a simpler and faster mechanism than a router, which requires knowledge about the network and how to determine the route.

What is the ADSL Splitter ?
A DSL splitter is a small box which attaches to the wire pair and splits it into two separate wire pairs, one for voice traffic and the other for DSL traffic.

What is Sharing Ratio ?
meaning that the network bandwidth available is shared between a number of subscribers. The ratio to which the available bandwidth is shared between users is called the "contention ratio". Services targeted at casual home users are frequently cheaper, but have a higher contention ratio. This means that the available network capacity is shared between a greater number of users. For example, most standard residential services offered today have a contention ratio of 50 to 1, this means the bandwidth may be shared with up to 50 other subscribers. Although the residential services are cheaper, businesses are advised to opt for the lower contended 'business services' which typically have a much lower contention ratio of 20:1 (meaning the bandwidth is shared with no more than 20 other subscribers), and thus will provide a more consistent level of performance.

What is Spam ?
Spam is flooding the Internet with many copies of the same message, in an attempt to force the message on people who would not otherwise choose to receive it. Most spam is commercial advertising, often for dubious products, get-rich-quick schemes, or quasi-legal services. Spam costs the sender very little to send -- most of the costs are paid for by the recipient or the carriers rather than by the sender.
There are two main types of spam, and they have different effects on Internet users. Cancelable Usenet spam is a single message sent to 20 or more Usenet newsgroups. (Through long experience, Usenet users have found that any message posted to so many newsgroups is often not relevant to most or all of them.) Usenet spam is aimed at "lurkers", people who read newsgroups but rarely or never post and give their address away. Usenet spam robs users of the utility of the newsgroups by overwhelming them with a barrage of advertising or other irrelevant posts. Furthermore, Usenet spam subverts the ability of system administrators and owners to manage the topics they accept on their systems.
Email spam targets individual users with direct mail messages. Email spam lists are often created by scanning Usenet postings, stealing Internet mailing lists, or searching the Web for addresses. Email spam's typically cost users money out-of-pocket to receive. Many people - anyone with measured phone service - read or receive their mail while the meter is running, so to speak. Spam costs them additional money. On top of that, it costs money for ISPs and online services to transmit spam, and these costs are transmitted directly to subscribers.

One particularly nasty variant of email spam is sending spam to mailing lists (public or private email discussion forums.) Because many mailing lists limit activity to their subscribers, spammers will use automated tools to subscribe to as many mailing lists as possible, so that they can grab the lists of addresses, or use the mailing list as a direct target for their attacks.



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