3Com 3C63400-3AC-C - PathBuilder S700 Switch Reference Manual page 146

132 C 5: C
HAPTER ONFIGURING
P B S700 M , P
ATH UILDER ODULES
use of overhead bits for administration and maintenance allows the service
provider more visibility in isolating any issues with the physical line connections
through the WAN. You must match this setting at the two ends of the DS3
trunk.
ATM Cell Mapping—How the carrier will provision the DS3 UNI service from
the carrier ATM switch: Clear (HEC) or PLCP (Physical Layer Convergence
Protocol). Clear is the option preferred by both domestic and international
service providers and within private ATM networks, as it gives more payload
bandwidth than PLCP. You must match this setting at the two ends of the DS3
trunk.
ATM Payload Scramble—Enables (Yes) or disables (No) payload scrambling
for the DS3 port. Payload scrambling scrambles the 48-byte payload in
outgoing cells in a defined manner and unscrambles the payload in incoming
cells. It is a technique used to avoid certain transmission equipment behaviors
(for example, erroneous alarm conditions) that are caused by sensitivity to
certain bit patterns in the ATM payload. You must match this setting at the
two ends of the DS3 trunk.
Peak Rate—The peak DS3 payload, in Mbps: 5.1 to 40.7 if Cell Mapping is set
to Clear; 5 to 40 if Cell Mapping is set to PLCP. This parameter is a feature
specifically designed for the PathBuilder S700. It allows you and your service
provider to traffic shape all connections to an optimum rate, assigned as part
of the ATM service contract.
FEAC Loopback—Enables or disables the system from responding to FEAC
(Far-End Alarm Condition) loopback commands (loopback activate and
deactivate FEAC codes) from the central office. FEAC is a DS3 overhead
function that the service provider may use for establishing loopback for
problem resolution of the network. The service provider uses FEAC codes to
obtain downstream or upstream conditions of a DS3 network. When the FEAC
Loopback option is enabled, the system responds to a loopback activate
command by enabling the DS3 line loopback. The system removes the
loopback automatically after 15 minutes or when it receives the deactivate
command.
DS3 Timing Source—The timing source for the DS3 transmit clock: system or
loop. If you set the DS3 Timing Source to system at one end of the DS3 trunk,
you must set it to loop at the other end.
System—Configures the port interface to use the system reference clock
within the shelf as a reference for transmitting.
Loop—Configures the port interface to use the input port Rx clock as the
timing source; timing is received from the service "loop." Select this option
if the DS3 UNI module is used for the network/carrier service termination, in
which case the carrier (the service "loop") typically provides the timing
source.
PLCP Timing Source—The PLCP timing source for the DS3 port:
System Clock—PLCP is timed from the internal 8kHz backplane clock.
DS3 Timing—PLCP is timed from the 8kHz reference clock derived from
the received PLCP.
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ORTS AND PPLICATIONS