HP ProCurve 7000dl Series Basic Management And Configuration Manual page 849

testing is required for vendors who wish to sell equipment to the Regional Bell
Operating Companies (RBOCs) and the Competitive Local Exchange Carriers
(CLECs). Level 3 testing is the most stringent level of testing.
Network A generic term describing computers that are interconnected and can com-
municate with each other. Used more specifically, a network divides hosts into
groups that can communicate without a router. A packet sent from one host
to another host in the same network can be switched to its destination
according to information in the Layer 2 header. A packet sent to a host in a
different network must be routed by a device (such as a router) that can read
the packet's Layer 3 header. In telecommunications, a network usually refers
to infrastructure that provides voice and data transmission to users.
Network Layer Layer 3 of the OSI model. This layer provides switching and routing protocols
that control how packets are moved from node to node to their destinations.
Routing and forwarding are functions of this layer, as well as addressing,
internetworking, error handling, congestion control, and packet sequencing.
NEXT Near End Crosstalk. An error condition that can occur when connectors are
attached to twisted pair cabling. NEXT is usually caused by crossed or crushed
wire pairs and occurs when the conductors inside the wires become exposed.
Two conductors only need to be close enough that the radiating signal from
one of the wires is able to interfere with the signal traveling on the other wire
for the connection to have a crosstalk problem.
NIC Network Interface Card. Hardware that grants a computer the ability to access
the network. A NIC is identified by a MAC address.
NIU Network Interface Unit. Also known as the smart jack in the United States.
The NIU automatically maintains the WAN connection and allows public
carrier employees to perform simple management tasks remotely. The NIU is
past the subscriber's line of demarc and is part of the public carrier's
equipment.
NNI Network-to-Network Interface. A standard that defines the interface between
two ATM or Frame Relay switches. Sometimes, however, the interface
between a switch in a private network and a switch in a public interface is
defined as a user-to-network interface (UNI). See also UNI.
NOC Network Operations Center. A place from which a telecommunications net-
work is supervised, monitored, and maintained. Enterprises with large net-
works and large network service providers typically have an NOC.
NRM Normal Response Mode. In an HDLC connection between two devices, a
secondary device may only transmit when the primary device expressly
instructs it to do so. See also HDLC, ABM, ARM.
Appendix B: Glossary
B-35