Glossary

MSN (Multiple Subscriber Number) - Allows a caller to specify an individual terminal adapter when more than one unit is connected to your network terminator. An MSN consists of a base address and a subaddress. If you assisgn a base address only, the unit accepts any incoming call with the same base address, regardless of whether a subaddress is included. If you assign a base address and a subaddress, the unit only accepts calls that match both the base address and the subaddress.

multilink— In point-to-point protocol, literally many links. A procedure used to route data packets over many links for increased bandwidth (e.g., two B-channels on a single BRI for 128 Kbps).

mux (multiplexer)— A device that merges several signals into one composite signal for transmission over a single medium or channel. A demultiplexer, built into most muxes, reverses the process at the receiving end.

nailed connection— A permanent or dedicated circuit of a previously switched circuit or circuits.

nailed-up circuit— A semi-permanent circuit established through a circuit-switching facility for point-to-point connectivity.

NAK (negative acknowledgment)— A communications code used to indicate that a message was not properly received, or that a terminal does not wish to transmit. Contrast with ACK.

network— A group of computers connected by cables or other means and using software that enables them to share equipment, such as printers and disk drives to exchange information.

NI-1(National ISDN-1)— A physical standard to make all compliant ISDN lines appear the same. With ISDN-1 installed, additional costs are not incurred when changing from prestandard ISDN to standard ISDN. Most RBOCs now are moving to ISDN-1.

NI-2(National ISDN-2)— A physical standard subsequent to NI1. When tested and deployed, NI-2 will provide additional features and enhanced plug and play capabilities.

node— Any point within a network that has been assigned an address.

NT (network termination)— Devices that form the boundary between customer premise equipment and telephone company equipment. Two types of NTs are used: NT1 and NT2.

NT1 (Network TerminationType 1)— An interface device used in the BRI portion of ISDN to connect four-wire (S/T) ISDN devices to the two- wire (2BIQ U) IDN. It provides basic rate access in a 2B+D format with two 64 bps channels for voice, data, and video communications. It also provides one 16 Kbps channel for packet-mode signalling, low-speed data and telecommunications services at the OSI Layer 1 level. Similar in function to a DSU/CSU device.

NT2 (Network TerminationType 2)— A device at the customer premise (user) side responsible for the ISDN network connection and for functions such as multiplexing and switching (may be an intelligent device).

NTE (network terminating equipment)— A set of ISDN functions residing at the boundary of the IDN and the subscriber.

NUI (network user identification)— A unique alphanumeric number provided to dial-up users to identify them to packet-switched networks world-wide. The number is used for network access and billing.

OHCI (OpenHCI): Open Host Controller Interface Specification for USB. All transfers on the USB are initiated by the host system’s host controller. The host controller is responsible for controlling traffic on the USB and can be appropriately programmed to transfer data to and from USB devices. This is typically a PCI device that can be programmed to run a given schedule of transfers on the USB and bus master the results into memory for processing by the host software. There are currently two standards for host controllers: OpenHCI (OHCI or Open Host Controller Interface) and UHCI (Universal Host Controller Interface). Both these standards define register level interfaces of the host controller to PCI bus. Bandwidth allocation over the USB is software managed and is done by the programming of the host controller.

off-hook— The condition of a device that has accessed a phone line (with or without using the line). In modem use, this is equivalent to a telephone handset being picked up. Dialing and transmission are allowed, but incoming calls are not answered.

on-demand dialing— A cost-saving feature of ISDN that sets up, transfers, and then closes a call only when the ISDN device detects a data packet addressed to the remote network, but will not perform setup/transfers of just administrative (non-user data) packets.

out-of-band signaling— A system that uses a separate communications channel or frequency outside the voice band for signaling. Modern systems use a separate channel, either TDM or virtual. SS7 uses messages for signaling that are carried on signaling links distinct from voice channels. ISDN uses messages for signaling that are carried on the

D-channel distinct from the voice carried on the B-channels. Frame Relay and ATM use messages that are carried on a separate virtual connection reserved for signaling.

on-hook— The condition of a device which has not accessed a phone line. In modem use, this is equivalent to a telephone handset that has not been picked up. In other words, it can receive an incoming call.

packet data— Packet-mode calls.