B-1
B
Appendix B: Glossary
Numeric
2B+D 2 Bearer + 1 Data. A method for describing channel designations in ISDN lines.
Bearer channels transmit data and voice. Data channels are reserved for
signaling information and call control. See also ISDN.
2B1Q 2 Bits 1 Quaternary. A compressed encoding scheme used by BRI ISDN that
provides for two bits to be encoded into one quaternary signal. 2B1Q can
transmit up to 5.49 km with few signal losses. As a result, 2B1Q requires fewer
repeaters on the local loop than E1- and T1-carrier lines require. 2B1Q
operates in full-duplex mode.
3DES Triple DES. A well-known public encryption standard that encrypts informa-
tion multiple times (encrypts, decrypts, and encrypts again). Each phase uses
a 56-bit key, making the total key length 168 bits. This 168-bit key provides
2168 or approximately 3.741e+50 possible combinations. IPSec, the industry
standard for VPNs, supports 3DES. See also IPSec and VPN.
10Base-T A standard line-hardware type that uses a twisted-pair cable with maximum
lengths of 100 meters. Cables in the 10Base-T system connect with RJ-45
connectors and operate up to 10 Mbps using baseband transmission methods.
100Base-T A standard line-hardware type that operates at 100 Mbps and uses baseband
transmission methods based on the older Ethernet standard.
A
AAA Authentication, Authorization, and Accounting. AAA is used to control net-
work access and enforce security policies. Authentication refers to the
process of confirming each user’s identity and is accomplished through the
use of passwords, keys, and often a Remote Authentication Dial-in User
Service (RADIUS) or TACACS+ server. Authorization ensures that the
authenticated user can access only the network resources to which that user
has rights. Accounting refers to the process of collecting information about
how resources are used. The collected information can then be used for trend
analysis, billing, or auditing. For more information about AAA, see Request
for Comments (RFC) 2989 (at http://www.ietf.org/rfc/rfc2989.txt).
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