Technical data

Architecture and System Requirements
EN4442EN00EN_0002
© 2007 Siemens AG
Siemens
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2.5.6 DMC Considerations
Whenever a DMC connection is established, a “Master Connection” is setup as well.
The master connection is following the same path as the signaling through all the gateways
between to IP clients.
The master connection ensures that the necessary resources are always available whenever
a feature is invoked that results in a multi party call (e.g. conference). There is also no delay
for invoking these types of features because the connection is already setup.
However, there are drawbacks to the master connection concept as well:
● Additional bandwidth is required for sustaining the master connection
● Depending on the configuration significant delays and multiple hops can occur between IP
clients when voice payload is using the master connection. Especially when IP end points
are located on different IP Access Points on IP connected systems, delays may increase
beyond acceptable levels.
In Figure 2-2 DMC and Master Connection the DMC and Master Connection is shown between
two IP networked HiPath 4000 systems for a call between two IP clients (one on each system).
Figure 2-2 DMC and Master Connection
Enabling VAD will reduce the required bandwidth on the master connection to negligible levels.
Note that delays for each TDM to IP conversion accumulate. In the example above the master
connection goes through 3 hops which will result in approximately 200ms end to end delay
assuming G.711 encoding with 30ms sampling time and a high quality network (20ms delay).
The DMC connection goes only through one hop resulting in an end to end delay of about
80ms.