Alcatel Omni Switch/Router, Руководство пользователя

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Obtaining Status and Statistical Information
Page 29-40
Clocking
This field indicates the type of clocking used to clock transmit and receive data in and out of
the serial port. When the clock is out-of-phase, you receive errors. If this value is set to Exter-
nal, then clocking is controlled by the external
DCE
(a
DSU
or other
DCE
device on the other
end of the cable from the
WSX
port). External clocking is the default option when the
WSX
is
a physical
DTE
device (i.e., controlled by an external
DCE
device).
Note
See Chapter 49, “Managing
WAN
Modules,” for docu-
mentation on setting the clocking mode for serial ports,
see Chapter 54, “Managing
T1
and
E1
Ports,” for docu-
mentation on setting the clocking mode for
T1
and
E1
ports, and see Chapter 55, “Managing
DS3
/
E3
Modules,”
for documentation on setting the clocking mode for
DS3
and
E3
ports.
If this value is set to Internal, then clocking is controlled by the internal
DCE
(the
WSX
). Inter-
nal clocking should only be selected if the
WSX
is a physical
DCE
device and you are using an
RS-232 cable. Internal clocking is the default when the WSX is a physical DCE device and an
RS-232 DCE
cable is connected to this port. For T1 and E1 ports, internal clocking is equiva-
lent to local timing.
Note
The Clocking value only makes a difference if the
WSX
port is a physical
DCE
port (i.e.,
DCE
cable plugged into
the
WSX
port). If the
WSX
port is a physical
DTE
port,
then Clocking will default to External.
Split clocking, which is also known as “loop timing,” uses additional control signals (
TXCE
and
RXCE
) to keep the
WSX
and
DSU
clocking in sync. Split clocking takes the incoming clock
signals (TX clock and RX clock) and loops them back out to the
DSU
. The
WSX
and
DSU
uses
these additional signals to communicate the current status of their clocks. Split clocking
should only be used if the
WSX
is a physical
DCE
device and you are using a non-
RS-232
cable, such as
V.35
.
♦
Important Note
♦
Split clocking is required if the access rate of the Frame
Relay line is greater than 256 Kbps. If Split clocking is
not used at these data rates, then data out-of-phase
errors, aborts, or CRC errors may occur.
Split clocking is the default when the
WSX
is a physical
DCE
device and a non-
RS-232 DCE
cable is connected to the port. For T1 and e1 ports, external or split clocking is the same as
loop timing.