CTC Store CTS Union IP DSLAM for ADSL IPDSLAM-A8/A16 - Manual (Page 138)

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synchronization to the millisecond of computer clock times in a network of
computers. Based on UTC, NTP synchronizes client workstation clocks to the U.S.
Naval Observatory Master Clocks in Washington, DC and Colorado Springs CO.
Running as a continuous background client program on a computer, NTP sends
periodic time requests to servers, obtaining server time stamps and using them to
adjust the client's clock.
PPP (Point to Point Protocol)
A successor to Serial Line IP (SLIP), PPP provides router-to-router and
host-to-network connections over synchronous and asynchronous circuits.
PPPoE
PPP over Ethernet. The transport of PPP frames over Ethernet.
PSTN (Public Switched Telephone Network)
General term referring to the variety of telephone networks and services in place
worldwide. Sometimes called POTS.
PVC( Permanent Virtual Circuit, or connection)
Virtual circuit that is permanently established. PVCs save bandwidth associated
with circuit establishment and tear down in situations where certain virtual circuits
must exist all the time. In ATM terminology, called a permanent virtual connection.
Rack mount
A structure that houses shelves (usually a maximum of four). The unit or container
that houses the internal modular circuitry. The shelf consists of slots that hold
each module and a backplane that interconnects all modules.
SAR
Segmentation and reassembly. One of the two sub-layers of the AAL CPCS,
responsible for dividing (at the source) and reassembling (at the destination) the
PDUs passed from the CS. The SAR sub-layer takes the PDUs processed by the
CS and, after dividing them into 48-byte pieces of payload data, passes them to
the ATM layer for further processing. See also AAL and ATM.
SDU (Service Data Unit)
Unit of information from an upper-layer protocol that defines a service request to a
lower-layer protocol.
Signal Noise Ratio (SNR)
This is a DSL transmission parameter, measured in dB, which indicates the