Garbage Collection Timer

Timer used in a distance-vector network that represents the time remaining before a route is removed from the routing table.


GGSN call detail record. Collection of charges in ASN.1 format that is eventually billed to a mobile station user.

Generalized Multiprotocol Label Switching


generated route

Summary route that uses an IP address next hop to forward packets in an IP network. A generated route is functionally similar to an aggregated route.

generic routing encapsulation

See GRE.


Gateway GPRS support node. A router that serves as a gateway between mobile networks and packet data networks.

Gigabit Ethernet

A term describing various technologies for implementing Ethernet networking at a nominal speed of one gigabit per second. Gigabit Ethernet is supported over both optical fiber and twisted-pair cable. Physical layer standards include 1000Base-T, 1 Gbps over CAT-5e copper cabling, and 1000Base-SX for short to medium distances over fiber. See also Fast Ethernet.

Global System for Mobile Communications

See GSM.


Generalized Multiprotocol Label Switching. A protocol that extends the functionality of MPLS to include a wider range of label-switched path (LSP) options for a variety of network devices.


Gateway Mobile Switching Center.


See UTC.


General Packet Radio System. A packet-switched service that allows full mobility and wide-area coverage as information is sent and received across a mobile network.

graceful restart

Process that allows a router whose control plane is undergoing a restart to continue to forward traffic while recovering its state from neighboring routers. Without graceful restart, a control plane restart disrupts any services provided by the router.

graceful switchover

JUNOS software feature that allows a change from the primary device, such as a Routing Engine, to the backup device without interrupting packet forwarding.

gratuitous ARP

Broadcast request for a router's own IP address to check if that address is being used by another node. Primarily used to detect IP address duplication.


Generic routing encapsulation. A tunneling protocol that encapsulates a variety of IP packets to enable data transmission through an IP tunnel. GRE is used to create a virtual point-to-point link to routers at remote points in a network. See also tunneling protocol.


Collection of related BGP peers.

group address

IP address used as the destination address in a multicast IP packet. The group address functionally represents the senders and interested receivers for a particular mulitcast data stream.


Symmetric high-speed digital subscriber line (SHDSL). Standard published in 2001 by the ITU-T with recommendation ITU G.991.2 G.SHDSL. G.SHDSL incorporates features of other DSL technologies such as asymmetrical DSL (ADSL). See also SHDSL and ADSL.


Global System for Mobile Communications. A second-generation (2G) mobile wireless networking standard defined by ETSI that uses TDMA technology and operates in the 900-MHz radio band. See also TDMA.


GPRS tunneling protocol. A protocol that transports IP packets between an SGSN and a GGSN. See also tunneling protocol.


GGSN tunneling protocol, control. A protocol that allows an SGSN to establish packet data network access for a mobile station. See also tunneling protocol.


GGSN tunneling protocol, user plane. A protocol that carries mobile station user data packets. See also tunneling protocol.