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QMultiFlex-400™ Installation and Operating Handbook
7.2 TCP/IP Traffic Management
Layer 2 bridging (including the use of VLANs) and Layer 3 routing are supported. Both
hardware and software bridges are available. The hardware bridge (switch) is capable of
processing many more packets (up to 200,000 per second) while the software bridge
supports a larger range of IP optimisation features such as TCP acceleration.
7.2.1
Point-to-Multipoint Bridging
Figure 7-4 shows the most basic configuration used for a point-to-multipoint bridging
solution. Ethernet switches can be deployed, as required, between the satellite devices
(QMultiFlex-400™, QFlex-400™) and the user network (the user network being any
combination of switches, routers and end-user devices). In this scenario, a single subnet is
used for the satellite modem network. However, beyond the modems, routers can be used
to connect to other subnets as required.
MAC address learning in the satellite modems and the hub multi-demodulator unit ensure
that packets automatically find their way correctly over satellite and across the network to
the destination devices.
There are several methods for filtering wanted packets from unwanted packets at the
remotes. One method (explained later) is to parcel each traffic stream for different remotes
(as part of a shared outbound) using Variable Coding and Modulation (VCM). In this
situation each remote picks off the stream (MODCOD) that is relevant to it. Another method
is to use VLAN tagging where packets are automatically tagged with the correct VLAN tag
for a particular remote. This can be done regardless of whether end-user traffic also uses
VLANs (in other words customer and service provider VLANs can be stacked and thereby
kept separate). Each remote will then filter out all other packets except the required
VLAN(s).
7-5
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