Gateway - Gateways are points of entrance and exit from a communications network. Viewed as a physical entity, a gateway is that node that translates between two otherwise incompatible networks or network segments. Gateways perform code and protocol conversion to facilitate traffic between data highways of differing architecture.
Gigabit Ethernet Converters - Gigabit Ethernet converters typically link copper cabling (UTP) with fiber optics or multimode fiber with single-mode fiber cables, to enable transport of Gigabit Ethernet traffic over diverse media.
GFP (Generic Framing Procedure) - Defined by ITU-T G.7041, generic framing procedure allows efficient mapping of variable length, higher-layer client signals, such as Ethernet, over a transport network like SDH/SONET. Recently, GFP has been extended to lower speed PDH networks.
Grooming - In telecommunications, the process of separating and segregating channels by combing, such that the broadest channel possible can be assembled and sent across the longest practical link. The aim is to minimize de-multiplexing traffic and reshuffling it electrically.
G.SHDSL - G.SHDSL, or SHDSL, is a standardized method (ITU-T G.991.2) to transport symmetrical data rates on copper pair access lines. G.SHDSL offers bitrates from 192 kbps to 2.3 Mbps over a 2-wire single pair and up to 9.2 Mbps over four bonded pairs.
G.SHDSL Modem- A G.SHDSL modem is a customer located transceiver, connecting users to a G.SHDSL service via the local DSLAM.
H
HDLC (High-level Data Link Control) - A synchronous, bit-oriented link layer protocol for data transmission. Frame Relay is an example of an HDLC-based packet protocol.
HDSL (High Bit-Rate Digital Subscriber Line) - A high performance twisted pair transmission technology, best known as an enhanced transport mechanism for T1 or E1 service. It is designed for the Local Loop between a customer’s premises and an area exchange central office.
I
IEEE (Institute of Electrical and Electronic Engineers) - An international professional society issuing its own standards. The IEEE is a member of ANSI and ISO.
IETF (Internet Engineering Task Force) - Body which was initially responsible for developing the specifications required for the interoperable implementation of IP.
IMA (Inverse Multiplexing over ATM) - A method to pass ATM traffic over multiple E1/T1 links while keeping the ATM’s quality of service and optimization of bandwidth usage.
In-band Signaling - The transmission of signaling information over the same path as data and/or voice information. Another term for in-band signaling is robbed-bit signaling. Robbed-bit refers to the 8 kbps of each channel used for signaling. T1 access lines containing one or more switched channels, and switched-56 lines use in-band signaling.
Integrated Access Devices - Integrated access devices (IAD) deliver voice and data services from user equipment to metro or wide area networks, over a shared xDSL access line.
Interface - A shared boundary, defined by common physical interconnection characteristics, signal characteristics, and meanings of exchanged signals.
Interface Converters - Interface converters are devices that convert physical media, data rates and transmission protocols, allowing service interworking between different communication interfaces.
Inverse Multiplexing - A method in which the inverse multiplexer slices the data stream into equal portions and transmits each portion over an available circuit. The receiving end adjusts for network-induced delay and reassembles the data packets into their proper order. Therefore, an inverse multiplexer allows lower speed channels across a network to be combined into a single, higher speed data stream.
IP (Internet Protocol) - A networking protocol for providing a connectionless service to the higher transport protocol. It is responsible for discovering and maintaining topology information and for routing packets across homogeneous networks. Combined with TCP, it is commonly known as the TCP/IP platform.
IP Address - Also known as an Internet address. An IP address (Internet Protocol address) is a unique reference number used by devices attached to a network when sending information through a Local LAN, Wide area WAN or the Internet networks.
IP DSLAM - A central office (CO) device for delivering digital subscriber line services that link DSL connections to a single high-speed broadband (IP) line.
IP Telephony - The transmission of voice over an Internet Protocol (IP) network. Also called Voice over IP (VoIP), IP telephony allows users to make phone calls over the Internet, intranets, or private LANs and WANs that use the TCP/IP protocol.
ISDN (Integrated Services Digital Network) - A carrier-provided service that allows a variety of switched digital data and voice transmissions to be accommodated simultaneously. ISDN is available as BRI, PRI and B-ISDN.
ISDN BRI (Basic Rate Interface) Line - An ISDN line that uses two B-channels for user data, and one 16 kbps D-channel for signaling. Both B-channels can be switched or nailed up, or one channel can be switched and the other nailed up. A line of this type can connect to standard voice service, switched 56 kbps data service or switched 64 kbps data service.
ISDN PRI (Primary Rate Interface) Line - An ISDN interface providing 23 B-channels, each operating at 64 kbps, and a single D-channel also operating at 64 kbps to customer’s premises.
ITU (International Telecommunication Union) - A European-based, international advisory committee recommending worldwide standards for transmission.
J
Jitter - The deviation of a transmission signal in time or phase. It can introduce errors and loss of synchronization in high speed synchronous communications.
Jitter Buffer - Variation in the arrival times between packets, also called jitter, causes unnatural-sounding voice instead of a smooth voice stream. If a packet does not arrive in time to fit into the voice stream, the previous packet is replayed. This can seriously detract from voice quality. Since the jitter buffer adds to the overall delay of voice transmissions, the optimal jitter buffer should fit the network's differential delay. Adaptive jitter buffering continuously monitors the network delay and adjusts the queuing period accordingly.
Glossary
