Glossary
S
- SDSL
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Symmetric Digital Subscriber Line. An uncommon flavor of DSL, in which downstream and upstream speeds are equal. It is most widely accepted in Europe.
- server
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A computer that provides services to other computers on the same network.
In the context of sharing an Internet connection, the server computer typically has 2 NICs and runs sharing software. It “serves” Internet access to one or more client computers.
- service
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Networking software that provides instructions for an activity.
On Windows computers, the most popular service is File and Printer Sharing for Microsoft Networks. Its name is fairly self-explanatory.
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Software that allows multiple computers to connect to the Internet using the same public IP address.
Sharing software only needs to be installed on a server computer. Then, one or more client computers can be configured to use the server computer as a gateway. When these client(s) make Internet requests, the sharing software kicks in to “translate” requests back and forth between client computers and the Internet.
Most sharing software is based on a technology called NAT; as such, most sharing software has the same basic functionality. However, there are often wide variations in performance, features, and ease-of-configuration. Confusion about these choices has contributed to the popularity of cable/DSL routers, which offer the same technology with much less hassle.
- spoof
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To force a device to use the MAC address of another device. Cable/DSL routers often allow users to spoof the MAC address of their computer’s NIC, making it appear as if their DSL or cable modem is still directly connected to a computer.
- star topology
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A network configuration in which all devices are connected to a central hub or switch. Almost all home networks use star topology.
Also see topology.
- static IP
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An IP address that is not subject to change. Typically reserved for business Internet services, while consumer Internet services use dynamic IPs.
- straight-through
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A category 5 cable in which the internal wires have the same arrangements at each end. The opposite of crossover. Most Cat-5 cables are wired in this way.
- subnet
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A group of computers that have the same IP address prefix.
- subnet mask
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A set of numbers that tells a router which parts of an IP address must be read. In a subnet mask, a binary digit of 1 says “read”, and 0 says “don’t read.” Subnet masks save routers from having to process an entire IP address, which makes routing more efficient.
Example: a subnet mask of 255.255.255.0, when translated into binary digits, is:
11111111.11111111.11111111.00000000
This tells a router to look at the first three parts of the IP address and ignore the last part.
- switch
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A device that serves as the central connection point for computers on a LAN. While it serves the same basic function as a hub, it does so more intelligently by forwarding packets directly to their destinations.