Quantum and Evolution Series Installation and Operating Handbook
8-40
Thirdly, there is a mesh network mode where a number of remote sites each have one Tx
carrier that is used to communicate with the other sites. Each site also has one Rx-modem
for every site, to allow it to receive from each of the other sites. (Partial mesh networks are
also supported where one or more of the sites communicate with only a subset of the other
sites.)
These are described in the following sections.
Note that for multicast, it does not matter whether you use point-to-point bridging or point-
to-multipoint bridging or routing – in all cases the modem just passes the multicast traffic.
8.12.7.1 Ethernet Point-to-Point Bridging
•
An Ethernet bridge in the modem passes IP packets transparently, as if the modem is
not actually there.
•
The bridge learns which interface (terrestrial or satellite) devices are attached to and
consequently only forwards packets over satellite when required.
•
IP packet contents are unchanged going over the bridge (the source Ethernet MAC
address will be changed to the modem’s MAC address, which is normal).
•
Because the modem does not change the contents, any protocol that can be used over
Ethernet can be used (VPN, MPLS, VLAN, HTTP, SMTP, etc.).
•
Point-to-point bidirectional bridged links over satellite work in exactly the same way as a
terrestrial bridge.
•
A protocol called Spanning Tree is used to ensure that network loops do not occur and
that a single path is used between any two points.
•
If you do not need to access the modem for M&C purposes then it is not actually
necessary to set any IP address to use bridge mode – the modem will pass traffic out of
the box.