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Principles of Operation
4-253610-A2-GB41-60 March 1999
MCMP Operation
For proper MCMP operation, the network must be
initialized, with the tributary DSUs added to the control
DSU’s poll list. Each newly installed circuit should be
verified as a working single port multipoint circuit, per
Technical Publication 62310 – 1987, prior to the MCMP
capability being activated to ensure that the DSUs operate
properly.
Initialization
The first time the MCMP capability is activated on the
network or after the network has been reconfigured, the
Acquire Poll List command must be issued from the
control DSU’s DCP or from NMS to start the initialization
process. During the initialization process, the control DSU
with MCMP performs the following tasks:
• Determines which tributaries are present on the
network.
• Determines the roundtrip delay to each tributary.
• Loads the Channel Speed and Asynchronous
configuration options into each tributary.
CAUTION
The initialization process is
typically performed in less
than 8 seconds, and is
disruptive to customer data.
In response to the Acquire Poll List command, the
control DSU with MCMP broadcasts a query message on
the network asking what tributaries are to be on the poll
list. All active tributary DSUs on the network respond by
sending an affirmation message to the control DSU, and
the control DSU adds those tributaries to the poll list.
The following configuration options are loaded into
each tributary from the control DSU during initialization:
• Channel Speed
• Async/Sync
• Async Rate
• Async Bits/Character
• Stop Bits
During MCMP operation, the Channel Speed and
Asynchronous configuration values at the control DSU are
downloaded to the tributaries on the control DSU’s poll
list every 10 seconds. The downloading is accomplished
via the management channel so there is no disruption to
user-transmitted data.
Network Modification
When an additional tributary DSU is added to a
multipoint circuit, the new DSU is not automatically
included in the control DSU’s poll list and the tributary
DSU will not allow the DTE to respond to FEP polling.
The tributary DSU must be added to the poll list.
A Change Poll List command must be issued from the
control DSU’s DCP or from NMS to the control DSU to
update the poll list.
The Change Poll List command can also be used to
delete a DSU from the poll list. When a tributary DSU is
deleted from the list, associated DTE(s) no longer respond
to FEP polling.
Switched-Carrier Emulation
In MCMP transmission, switched-carrier emulation for
each channel is standard in the inbound direction (toward
the control DSU). Transmission of signaling codes is not
required; the control DSU toggles the Line Signal Detect
(LSD) lead, based upon whether or not data is received for
that channel.
MCMP Applications
There are five applications using MCMP capability
included in this section. They include using MCMP
capability for multichannel multipoint operation, digital
sharing, extended diagnostics, FEP port sharing, and
backup.
There is no need to set these configuration options at
the tributary DSUs. Any values assigned to the
configuration options prior to initialization are overwritten
during initialization. (For configuration options, see MUX
Configuration Options and Port Speed Configuration
Options sections of Chapter 5.)