ViaSat ArcLight, Руководство пользователя, Страница: 59 / 368

ArcLight Hub User’s Guide
General System Description
Rev. 001 1081006 1-23
1.5 Control Protocols
1.5.1 Control Messaging
Control messaging between the NMS and VMTs is transmitted as
simple IP packets, addressed to/from the Satellite Network IP address
of the VMT and NMS.
1.5.2 Control Protocols
1.5.2.1 VMB Login Protocol
1.5.2.1.1 Outlink (Forward Link) Acquisition
At the initiation of the log-in procedure, the Modulator configures the
receiver with the necessary initial parameters (Outlink center
frequency, PID numbers) and instructs it to acquire the Outlink.
The Modulator queries the forward channel receiver to determine it has
been acquired. The Modulator repeats this procedure until the Forward
Link is acquired, or the process is interrupted (cancelled) by an
ArcLight system operator.
1.5.2.1.2 Bulletin Board Message
Upon Outlink acquisition, the Modulator monitors the outbound
channel for the network Bulletin Board message.
The RtNMS transmits a Bulletin Board message, in the form of an IP
packet addressed to the network broadcast address, at a configurable
periodic interval. The Bulletin Board packet contains the following
information:
Network/Transponder ID
Return Channel Frequency
Return Channel Spreading Rate(s)
“Robust” Return Channel Data Rate
NMS IP Address
Packet Size(s) being operated in network
Network-wide Transmit Duty Cycle
On receipt of a Bulletin Board packet, the VMBR verifies that the
Network/Transponder ID contained in the packet agrees with the value
contained in its configuration database. If the numbers do not agree,
the login is aborted and the VMBR declares a fault.