Cisco 678 Installation And Operation Manual page 171

Numerics
The 2B1Q (two binary, one quaternary) line encoding was intended for use by the
2B1Q line encoding
ISDN DSL and SDSL. 2B1Q is a four-level line code that represents two binary
bits (2B) as one quaternary symbol (1Q). ("Quaternary" means consisting of four,
in this case, a four-level line code.) The 2B1Q line coding was seen as a major
enhancement over the original T1 line coding, because 2B1Q encoded two bits
instead of just one with every signaling state (baud).
A
A bit mask used to select bits from an Internet address for subnet addressing. The
address mask
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.
ATM Adaptation Layer. This layer maps higher layer user data into ATM cells,
AAL5
making the data suitable for transport through the ATM network.
Asymmetric digital subscriber line. A digital subscriber line (DSL) technology in
ADSL
which the transmission of data from server to client is much faster than the
transmission from the client to the server.
Asynchronous Transfer Mode. A cell-based data transfer technique in which
ATM
channel demand determines packet allocation. ATM offers fast packet
technology, real time, demand led switching for efficient use of network
resources.
A security feature that allows access to information to be granted on an individual
authentication
basis.
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Cisco 600 Series Installation and Operation Guide
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