Manuals

ADSL Glossary: Cisco 605D Personal PCI ADSL Adapter Card

A | B | D | I | L | M | P | R | T | U

A

address mask. A bit mask used to select bits from an Internet address for subnet addressing. The mask is 32 bits long and selects the network portion of the Internet address and one or more bits of the local portion. Sometimes called subnet mask.

ADSL. Asymmetric Digital Subscriber Line. A digital subscriber line (DSL) technology in which the transmission of data from server to client is much faster than the transmission from the client to the server.

ADSLAM. Advanced Digital Subscriber Line Access Multiplexer.

B

bandwidth. The range of frequencies a transmission line or channel can carry�the greater the bandwidth, the greater the information-carrying capacity of a channel. For a digital channel, bandwidth is defined in bits. For an analog channel, bandwidth is dependent on the type and method of modulation used to encode the data.

D

downstream rate. The line rate for return messages or data transfers from the network machine to the customer’s premise machine.

DSLAM. Digital Subscriber Line Access Multiplexer.

I

Internet. A collection of networks interconnected by a set of routers that allows networks to function as a single, large virtual network. When written in uppercase, Internet refers specifically to the Defense Advanced Research Projects Agency (DARPA) Internet and the TCP/IP protocols it uses.

Internet address. An IP address assigned in blocks of numbers to user organizations accessing the Internet. These addresses are established by the United States Department of Defense’s Network Information Center. Duplicate addresses can cause major problems on the network, but the NIC trusts organizations to use individual addresses responsibly. Each address is a 32-bit address in the form of x.x.x.x where x is an 8-bit number from 0 to 255. There are three classes (A, B, and C), depending on how many computers on the site are likely to be connected.

Internet Protocol (IP). The Network Layer Protocol for the Internet Protocol suite.

IP address. The 32-bit address assigned to hosts that want to participate in a TCP/IP Internet.

ISP. Internet Service Provider. A company that enables home and corporate users to connect to the Internet.

L

loopback. A diagnostic test that returns the transmitted signal back to the sending device after it has passed through a network or across a particular link. The returned signal can then be compared to the transmitted one. The discrepancy between the two help to trace the fault. When trying to locate a faulty piece of equipment, loopbacks are repeated, eliminating satisfactory machines until the problem is found.

M

MAC. Media Access Control Layer. A sub-layer of the Data Link Layer (Level Two) of the ISO OSI Model responsible for media control.

P

PCI. Peripheral Component Interconnect. An industry local bus standard. Supports up to 16 physical slots but is electrically limited to typically three or four plug-in PCI cards in a PC. Has a typical sustained burst transfer rate of 80 Mbs, which is enough to support 24-bit color at 30 frames per second (full-color, full-motion video).

permanent virtual connection (PVC). A fixed virtual circuit between two users: the public data network equivalent of a leased line. No call setup or clearing procedures are needed.

POTS. Plain Old Telephone Service.

PPP. Point-To-Point-Protocol.

R

RADSL. Rate Adaptive Digital Subscriber Line (RADSL). A technique for keeping the quality of transmissions within specified parameters.

T

TCP. Transmission Control Protocol. The major transport protocol in the Internet suite of protocols that provides reliable, connection-oriented, full-duplex streams.

training mode. Characteristic of a router that allows it to use RADSL technology to adjust its line speed according to noise conditions on the transmission line.

twisted pair. Two insulated copper wires twisted together with the twists or lays varied in length to reduce potential signal interference between the pairs.

U

upstream rate. The line rate for message or data transfer from the source machine to a destination machine on the network.

virtual connection (VC). A link that seems and behaves like a dedicated point-to-point line or a system that delivers packets in sequence, as happens on an actual point-to-point network. In reality, the data is delivered across a network through the most appropriate route. The sending and receiving devices do not have to be aware of the options and the route is chosen only when a message is sent. There is no prearrangement, so each virtual connection exists only for the duration of that one transmission.