ViaSat ArcLight, User Manual, Page: 41 / 368

ArcLight Hub User’s Guide
General System Description
Rev. 001 1081006 1-5
provides network control functions, and serves as the operator interface
to the network.
The ArcLight VMTs receive the Hub forward link broadcast signal,
transmit the CRMA return link, and support the exchange of
broadband IP data to and from the VMT local LAN using a 100baseT
Ethernet interface. User devices connected to the VMT local Ethernet
segment send IP traffic destined for the corporate LAN or Internet to the
VMT who instantly burst them over the satellite, on the CRMA channel,
to the Hub demodulator at 32 Kbps to 512 Kbps. Each VMT transmits a
single carrier with a predetermined bit rate. The Hub demodulator
(MCD) detects, demodulates and re-assembles the IP packets and
forwards them to the Hub routing subsystem. The routing subsystem
directs the received packets to their intended destination.
The Hub Real-time NMS (RtNMS) provides the VMT population with
their parameters, required uplink power adjustments, and network
congestion control.
Proprietary ViaSat, Inc. Management Download Protocol (MDLP), an
application layer protocol riding on top of IP and UDP, is used for VMT
software and some configuration purposes. Broadcast mechanisms
efficiently distribute software to multiple VMTs at the same time. MDLP
is also used to send some configuration parameters to the VMTs. The
parameters required for network login are sent using proprietary
messaging, instead of MDLP.
1.2 Hub System
The ArcLight hub system performs several functions to manage the
system through a combination of hardware and software resources. The
functions performed by the ArcLight Hub include the following:
o
Traffic management (1.5.3)
o
Provisioning (1.5.5)
o
Power control (1.2.5)
o
Return channel access control (1.2.4)
o
Frequency control (1.5.2.2)
o
Congestion control (1.2.6)
o
Status monitoring and control (1.5.6)
1.2.1 Hub Components
Figure 1-4 illustrates the interconnection of the major blocks of
hardware that make up the ArcLight hub (illustrations of additional
configurations are provided in Appendix B.
The hub has many components, some of which are mounted in the
rack, and some are blade servers installed in the ArcLight Blade System
(ABS). The main components consist of:
NMS
The NMS machine provides the basic operator interface to the ArcLight
network using NRTC. NRTC uses the NRTS as a channel to
communicate with the ORDBMS. The NMS machine also runs and
MDLS process used to download software and selected configuration to
the VMT population.