Comtech EF Data CDM-840 - Manual (Page 225)

CDM-840 Remote Router Revision 2
Appendix F MN-CDM840
F–5
F.2.2 CDM-840 Remote Router Terminals
Chapter 6. ETHERNET-BASED REMOTE PRODUCT MANAGEMENT
For the CDM-840: Select the ECM mode as Online, Wait or Offline. Each ECM state establishes a
different role for the CDM-840 in the overall Advanced VSAT Network operations:
• Online – This is the most common ECM state, whereby the CDM-840 powers up,
requests network registration, and switches to dSCPC at the minimum site policy data
rate setting.
• Wait – Keeping a CDM-840 in the ECM channel can result in oversubscription, where
some percentage of CDM-840s waits their turn for SCPC pooled resources. To avoid
oversubscription, this ECM state provides the network operator with the ability to
selectively control the CDM-840s through manual, scheduled, or externally switched
request commands.
With the CDM-840s set to Wait, they continue to send their health status update
messages to the VMS and to the CTOG-250 Comtech Traffic Optimization Gateway (with
integrated CDM-800 Gateway Router). The VMS messages update connected link status;
when dynamic routing mode is enabled, the ACM, CDRP, and data traffic statistics
messages sent to the CTOG-250 maintain the forward path ACM and routing tables.
• Offline – In this ECM state, the CDM-840 does not transmit and remains idle until a new
ECM state is selected either locally or from the VMS. Examples for use of this particular
ECM state are COTM (communications on the move) or military maneuvers providing
radio silence conditions.
Figure F-3 illustrates the internal logic diagram of the remote processing registration message.
• The CDM-840s are configured to receive the outbound carrier and are given a TAP
(Group) identifier number (default 1) that sets the internal filtering if multiple TAPs are
used.
• Upon receipt of the TAP message, the CDM-840 sets modem transmission parameters (if
required), initializes timing, and picks at random an SAS to start entry by sending a
probe (slot transmission).
• The CDM-840, based on its current ECM state, either requests an assigned slot or waits
to be switched:
o An assigned slot request indicates to the HCC if the CDM-840 has more data (e.g.
registration protocol) to send.
o A switch request indicates that the CDM-840 is requesting dSCPC bandwidth. These
two flags are independent.