Cisco Universal Broadband Router uBR10012 Hardware Installation Manual page 261

Internet Operating System. See
IOS
Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless internetwork
IP
service. IP provides features for addressing, type-of-service specification, fragmentation and
reassembly, and security. Defined in RFC 791.
Routing technique that allows IP traffic to be propagated from one source to a number of destinations
IP multicast
or from many sources to many destinations. Rather than sending one packet to each destination, one
packet is sent to a multicast group identified by a single IP destination group address.
Intermediate reach. SONET/SDH specification for transmit power and receive sensitivity that achieves
IR
a 9.3-mile (15-km) reach.
Internet Service Provider. A company that provides Internet access to other companies and individuals.
ISP
International Telecommunication Union Telecommunication Standardization Sector. International
ITU-T
body that develops worldwide standards for telecommunications technologies. The ITU-T carries out
the functions of the former CCITT.
L
Local-area network. High-speed, low-error data network covering a relatively small geographic area
LAN
(up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices
in a single building or some other geographically limited area. LAN standards specify cabling and
signaling at the physical and data link layers of the OSI model. Ethernet, FDDI, and Token Ring are
widely used LAN technologies. Compare with
Any I/O card that can be inserted in a modular chassis.
Line card
Local Management Interface. A set of enhancements to the basic Frame Relay specification. LMI
LMI
includes support for a keepalive mechanism, which verifies that data is flowing; a multicast
mechanism, which provides the network server with its local DLCI and the multicast DLCI; global
addressing, which gives DLCIs global rather than local significance in Frame Relay networks; and a
status mechanism, which provides an on-going status report on the DLCIs known to the switch. Known
as LMT in ANSI terminology.
See LAN.
Local-area network
A test in which signals are sent and then directed back toward their source from some point along the
Loopback test
communications path. Loopback tests are often used to test network interface usability.
Loss of signal. A SONET port status indicator that activates when an LOS defect occurs and does not
LOS
clear throughout the alarm integration period, which is typically 2.5 seconds. An LOS defect occurs
when the OC-3 port receives all zeros for 20 microseconds (+.3 ms). This occurrence begins the alarm
integration period. If this period elapses without the detection of two consecutive frames in which there
are no 20-ms periods of signal loss, the LOS indicator activates. The LOS indicator clears when an LOS
defect is not detected for an interval equal to the alarm deactivation period (typically 10 seconds).
OL-18259-09
Cisco IOS.
MAN and WAN.
Cisco uBR10012 Universal Broadband Router Hardware Installation Guide
Glossary
GL-7