East Coast Datacom Nx8- Dual Composite MUX High-Speed 16-Port TDM..., Operation Manual

Page: 74 / 77

166119
8/31/2006 70
5.4 Configuring an Nx8-DualMUX Link for Simplex Operation
The Nx8-DualMUX may be used to support Simplex network traffic. Since the multiplexer is
designed to normally provide full duplex operation, simplex configurations are by nature,
special cases, and certain features of the multiplexer will be unavailable or inoperative. Also,
because the multiplexers at each end of the link are not equivalent in function, the differences
must be accounted for when setting up and configuring the systems.
The simplex link is comprised of a sending system and a receiving system. Because there is
no path for “upstream” data to the sending system, the inband management channel of the
multiplexer only works in one direction. This implies that for two systems to be configured
over a simplex link, the configuring terminal must be placed on the sending system.
Figure 28 illustrates a typical simplex network configuration.
Figure 28 – Multiplexers in Simplex Network Configuration
In the above network, the sending multiplexer requires, at a minimum a transmit data path, a
transmit clock, and a loop of the transmit data to the receive data input on the composite port.
This latter condition is imposed by the need to keep the sending mux in a synchronized state;
this is achieved in the looped condition by receiving it‟s own transmitted framing pattern.
While this may be implemented by means of a specially-wired cable, it is more readily
accomplished by using the transmit loopback feature of the sending multiplexer and a
standard cable.
The receiving multiplexer requires only the receive data path and a receive clock. From this,
the receiving mux is able to synchronize to the downstream framing pattern, receive inband
management channel configuration commands, and demultiplex the channel data.
5.4.1 Behavior of System Management in Transmit Loopback
Due to the transmit loopback at the sending end of the link, messages sent via the
management channel to the remote system are also received by the sending system. This
can cause unintended states to be entered unless some forethought is given to the effect of
the sending multiplexer receiving it‟s own commands. For example, invoking a channel
loopback on the receiving (remote) system will cause the same channel loopback to be
implemented on the sending (local) system.
In general, any menu option sent to the
remote system to change a configuration parameter will be mirrored on the local
system.
As long as the parameter in question is the same desired value or setting on both
the remote and local systems, no problem should be encountered. When the are different,
however, the user may have to take extra steps to insure the desired configuration is
achieved.