138 SBG1000 Wireless Cable Modem Gateway User Guide
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Configuration: Basic Gateway TCP/IP Wireless Print Server USB
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L2F Layer 2 Forwarding is an OSI layer 2 protocol that establishes a secure tunnel across the Internet to
create a virtual PPP connection between the user and the enterprise network. L2F is the most
established and stable layer 2 tunneling protocol.
L2TP Layer 2 Tunnel Protocol is a PPP extension that enables ISPs to operate VPNs. L2TP merges the
best features of the PPTP and L2F. L2TP is the emerging IETF standard.
LAC An L2TP access concentrator is a device to which the client directly connects through which PPP
frames are tunneled to the LNS. The LAC need only implement the media over which L2TP operates
to transmit traffic to one or more LNSs. The LAC may tunnel any protocol carried within PPP. The LAC
initiates incoming calls and receives outgoing calls. A LAC is analogous to an L2F NAS.
LAN A local area network provides a full-time, high-bandwidth connection over a limited area, such as a
building or campus. Ethernet is the most widely used LAN standard.
layer In networks, layers are software protocol levels. Each layer performs functions for the layers above it.
OSI is a reference model having seven functional layers.
LCP Link Control Protocol establishes, configures, and tests data link connections used by PPP.
latency The time required for a signal to pass through a device. It is often expressed in a quantity of symbols.
LED light-emitting diode
LNS An L2TP network server is a termination point for L2TP tunnels where PPP frames are processed and
passed to higher layer protocols. An LNS can operate on any platform that terminates PPP. The LNS
handles the server side of the L2TP protocol. L2TP relies only on the single media over which L2TP
tunnels arrive. The LNS can have a single LAN or WAN interface but can terminate calls arriving at
any of the LACs full range of PPP interfaces (asynchronous, synchronous, ISDN, V.120, etc.). The
LNS initiates outgoing calls and receives incoming calls. An LNS is analogous to a home gateway in
L2F technology.
loopback A test that loops the transmit signal to the receive signal. Usually the loopback test is initiated on a
network device. The test is used to verify a path or to measure the quality of a signal on that path.