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modem .
MOdulator/DEModulator. Equipment that converts digital signals to analog signals and vice versa. Modems are used to send data signals (digital) over the telephone network, which is usually analog. The modem
modulates the 1s and 0s into tones that can be carried by the phone network. At the other end, the demodulator part of the modem converts the tones back into digital 1s and 0s.
network interface card (NIC).
The circuit board or other form of computer hardware that serves as the interface between a computer (or other form of data terminal equipment) and the communications network; in ADSL, a common NIC is an Ethernet
NIC, which serves as the interface to the ADSL modem from the computer. See also adapter .
network interface device (NID). A device
that terminates a copper pair from the serving central office to the user's destination. The NID is typically found installed on the exterior premises of the destination location.
NOC . Network Operating Center.
Covad's™ NOC monitors network elements 24 hours a day, seven days a week. The NOC provides the customer's corporate IT staff with access to automated information regarding issues or network outages that affect
the customer's teleworkers.
packet switched network . A network that does not establish a dedicated path through the network for the duration of a session but, instead, transmits data in units called packets in
a connectionless manner. Data streams are broken into packets at the front end of a transmission, sent over the best available network connection, and then reassembled in their original order at the destination
endpoint.
- packet . A sub-unit of a data stream; a grouping of information
that includes a header (containing information such as address destination) and, in most cases, user data.
- packet switching . A switching system that uses a physical
communications connection only long enough to transmit a data message; data messages are disassembled into packets and reassembled at the receiving end of the communications link; packets may travel over many
diverse communications links to get to the common endpoint. Packet switching is most often contrasted with circuit switching in data communications, where all data messages transmitted during a session are
transmitted over the same path for the duration of the session. See also circuit switching .
PCLEC . Packet Competitive Local Exchange
Carrier. Covad's coined this term to align itself with the rapid innovation and service deployment found in the PC industry, and strives to provide new services at speeds and customer satisfaction levels not found
in the current telecommunications industry.
permanent virtual circuit (PVC). A term
found in frame relay and ATM networking in which a virtual connection between two fixed end-points is established through the network. See also switched virtual circuit .
plain old telephone service (POTS). This
term commonly refers to standard telephony, as in placing and receiving telephone calls.
PPP . Point-to-Point Protocol. This
protocol allows a computer to connect to the Internet with a standard dial-up telephone line and a high-speed modem and enjoy most of the benefits of a direct connection, including the ability to use graphical front
ends such as a Mosaic and Netscape. PPP is considered to be better than SLIP, because it features error detection, data compression, and other elements of modem communications protocols which SLIP, the older
Internet protocol, lacks. See also SLIP .
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