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Configuring the WAN Physical Link
Clock Source
A clock is used to synchronize data transmission on the line. Generally, one end of the
link provides the master clock, and the other end of the link recovers the clock from the
signal on the line. By default the clock source is derived from the line. If needed, an
internal clock is available. To configure the clock source, use the following command:
config ports <portlist> [t1 | e1 | t3] clocksource [internal | line]
Note: If the clock source is configured as "line", but the clock cannot be
recovered from the signal on the line, the hardware will use the internal clock
instead.
Facility Data Link
Facility data link (FDL) for T1 links uses twelve bits in the ESF frame to signal
information about line and connection status. Since FDL is only meaningful for ESF
framing, FDL settings are ignored when a port is configured for SF framing. See
"Inband Loopback Detection" for information on configuring framing.
The two T1 standards supported for FDL are ATT, described by the ATT 54016
specification, and ANSI, described by the T1.403 standard. The default value is off. To
configure FDL, use the following command:
config ports <portlist> t1 fdl [off | att | ansi]
Framing
Framing is used to synchronize data transmission on the line. Framing allows the
hardware to determine when each packet starts and ends. The two choices for T1
framing are Super Frame (SF), also known as D4, and Extended Super Frame (ESF). The
ESF scheme is a newer standard and is enabled by default. To choose the T1 framing
scheme, use the following command:
config ports <portlist> t1 framing [esf | sf]
If you choose to use SF framing, you should disable yellow alarm detection for the T1
line. SF framing may generate false yellow alarms. See "Yellow Alarms" on page 2-6 for
more details.
The framing choices for E1 are CRC4 or no-CRC4. To choose the E1 framing scheme,
use the following command:
2-4
WAN Module Installation and User Guide
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