Proxima ASA 7911 - Manual (Page 17)

11
Point-to-Multipoint
The RangeLAN2 Serial Adapter may also operate in a Point-to-
Multipoint topology. This configuration provides added flexibil-
ity, allowing one centralized unit, operating in Packetized mode,
to communicate with multiple units placed in remote locations.
When operating in Packetized mode, a central Serial Adapter
may be programmed to send either directed messages or broad-
casts to other Serial Adapters, by specifying the appropriate IP
address and send mode. The Packetized Mode Command Set
allows users to customize Serial Adapter communications to
meet their application needs. For more information on
Packetized mode, please see Ch. 4 and Appendix A, the
Packetized Mode Specification.
A Point-to-Multipoint topology may utilize the Broadcast mode,
so that multiple Serial Adapters can receive the same informa-
tion simultaneously. Note that a broadcasting Serial Adapter
does not wait for an acknowledgment of the packet’s receipt
from any receiving unit. Broadcast mode is an unacknowledged
service because it can be extremely inefficient to have every unit
acknowledge a message once a packet is received. Since these
broadcast packets are unacknowledged, a unit cannot retry
transmissions when in this sending mode. You may use the
Packetized Mode Command Set or another high-level applica-
tion in conjunction with the Broadcast mode to guarantee the
delivery of error-free transmissions to multiple units.
In Figure 4 below, Serial Adapters 1 through 5 are on Domain
0. Serial Adapter 1 is set to Broadcast mode. Serial Adapter 6 is
on Domain 1. Whenever a message is sent from unit 1, it is
received by units 2 through 5 and is processed by those units
which receive the transmission error-free. Since unit 6 is on a
different Domain, it will not process unit 1’s broadcast message.