Because DTNA is a software implementation of the DTEA
adapter (with some codec limitations), there is an additional load
placed on the system unit due to Voice over IP processing. This manifests
itself in a higher than normal ‘System’ CPU time as indicated by performance
monitoring tools such as vmstat. The additional
load depends on a number of factors:
- The number of channels active.
- Whether or not the application is using compressed or uncompressed
voice. Where LPAR is in use, each DTNA system instance must be assigned
a minimum of two processors or processor cores for
each LPAR. (A development system with less than 30 channels may be
supported by a single processor). An IBM Power 6
or Power 7 with multiple processors or multiple core processors can
support 480 channels of a simple VoiceXML or state table application.
Note: This
is compressed voice within the Blueworx Voice Response application
(the 5:1 GSM compression algorithm) rather than compression on the
IP network. Most Blueworx Voice Response applications
use uncompressed voice, the notable exception being Unified Messaging
for Blueworx Voice Response which
can be configured to use either compressed or uncompressed voice.
- How the SIP call setup process has negotiated to
handle (mainly detection but possible generation) DTMF keys. The three
options are:
- DTMF ‘Inband’ tones
- RTP ‘Payload’ (known as RFC2833)
- SIP INFO DTMF
The use of ‘Inband’ DTMF detection significantly increases the
CPU load, therefore every attempt must be made to use the
one of the other two methods.