Page 26
Series 2000/3000 IDU User’s Manual
Revision P4
SIT Opera-
tional State
The current state of the SIT:
• Idle. The IDU has completed all subsystem self-tests and has not acquired
the forward link.
• Initialized. The IDU has acquired the forward link and can support multi-
cast services. The IDU can initiate acquisition of the return link only if the
return link status is “Initialized”.
• OamActive. The IDU maintains acquisition of the forward link, has
acquired the return link, has validated with the hub, and is assigned an
OAM VCC. This implies that the IDU can respond to OAM data.
• Active. The IDU maintains acquisition of the forward link, has acquired
the return link, has validated with the hub, has an OAM VCC and a traffic
VCC. The traffic VCC is used when the IDU Bypass VCC is “0”. If
RADIUS is enabled, then user authentication must first be established to
go into “Active” state. If IPSec is enabled, an IPSEC tunnel must be estab-
lished before user traffic can be sent and received.
• Hold. The IDU will go to Hold state if (1) a disable IDU Tx command is
received from the hub, or (2) the Return Link Disable button is clicked on
the IDU Control page (see
section 2.2
). The enable Tx command must be
sent for the IDU to leave the Hold state (see
section 2.2
). Note that during
Hold state, the IDU Ready LED blinks.
• Fault. The IDU hardware could not initialize properly.
FL Status
Initially, the forward link status is “Not acquired”. When the IDU receives the
correct signalling tables and stabilizes to the PCR, the forward link status
becomes “Acquired”.
RL Status
The return link status may be displayed as follows: “Not initialized”, “Initial-
ized”, “CSC”, “ACQ”, “SYNC”, “Ready mode” and “Test Mode”.
• Initially, the return link status is “Not initialized”. The forward link status
shall be “Acquired” before the return link status can change. When the for-
ward link status is “Acquired” and frequency compensation is achieved,
the return link status becomes “Initialized”. This implies that all conditions
are present for a successful return link acquisition attempt.
• When the acquisition process is activated, the return link status becomes
“CSC” and remains in this state until the SIT is promoted to the ACQ
mode or until the maximum number of CSC tries is sent. In the latter case,
the hub most likely did not receive the CSC bursts correctly and the return
link acquisition thus failed.
• If the IDU is promoted to acquisition mode, the return link status becomes
“ACQ”. The return link status remains “ACQ” until coarse synchronisa-
tion is achieved (“SYNC”) or until the maximum number of ACQ bursts is
sent. In the latter case, a faulty transmission may have occurred and the
IDU thus fails the return link acquisition.
• The IDU is promoted to “Ready mode” when fine synchronisation is
achieved. This status indicates that the IDU is able to carry traffic on the
return link.
• “Test Mode” is displayed when the installer sends a test signal. Refer to the
IDU’s Installation Manual for more details.
Table 7:
