Comrex BRIC-Link II, Product Manual

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OPERATING BRIC LINK II IN A 24/7 ENVIRONMENT
A BRIC-Link II audio connec on can be con fi gured for “always on” opera on. This allows for constant STL
communica on and opera ons requiring long-term connec ons. A backup connec on can also be set for automa c
“fallback” if the primary connec on fails, ensuring transmissions stay ac ve. This sec on will detail how to maintain
a constant and persistent connec on between codecs even during network disrup ons.
HOW BRIC NORMAL CONNECTIONS WORK
In BRIC Normal mode (the default mode of opera on), BRIC-Link II transfers all its audio data via the UDP 9000
protocol. This is in contrast to most web-based connec ons like browsing and email, which use the bidirec onal
TCP protocol. UDP, unlike TCP, is not “connec on oriented” (i.e., no virtual connec on actually exists in this protocol
layer between the devices). In UDP, the transmi er simply launches packets into the network with the correct
address, hoping the network will make its best e
ff ort to deliver the packets in a mely fashion. If a packet is delayed
or lost, no error message is sent from the receiving unit and no packets are retransmi ed. It is up to the receiver to
cover up any lost data, if possible. This allows the Internet to deliver packets with the smallest amount of overhead
and delay. As there is no coherent connec on built between the codecs, there isn’t any connec on to break in the
event of network failure. The encoder simply propels packets into the network, regardless of whether they arrive. If
the network fails and is later restored, the packets stream will be restored to the decoder.
For most broadcas ng applica ons, it’s useful to simulate a connec on-oriented stream, so BRIC-Link II uses a
low-bandwidth sub channel to deliver informa on back to the encoder about overall connec on status. It does this
in its “applica on layer”, rather than the “transport layer” where UDP exists. By default, it monitors the health of a
connec on and if no data is detected as received by the decoder for 60 seconds (this is a user de
fi ned meout), it
“tears down” this connec on and reverts to an idle state. This indicates to the user that the network has failed and
the problem must be addressed.
One bene fi t of having the connec on protocol in the applica on layer is that its use is op onal, and it can be
modi fi ed for par cular applica ons. For 24/7 opera on, there is no advantage to the connec on ending if no data
is received for the meout interval. In fact, it is preferable to con nue the UDP audio stream using the “Always
Connect To” func on.
ALWAYS CONNECT TO
“Always Connect To” is a system-wide se ng for BRIC-Link II which locks the codec into a dedicated mode,
removing certain user controls in favor of maintaining constant connec on to a given remote. This is the primary
method for establishing 24/7 opera on.
When Always Connect To is enabled, BRIC-Link II will take the following ac ons:
1 A connec on is immediately established between BRIC-Link II and the chosen remote codec.
2 The meout value is ignored for the ac ve connec on; the audio data stream will never
be torn down regardless of “applica on layer” data status. Note: The meout value is s ll
calculated for the purpose of the
Backup Remote op on, as described later in this sec on.