Specifications

Engineering Guidelines
144
The MiVoice Border Gateway (Release 6.0 onwards) can provide packet rate adaptation
between the internal and external address interfaces. This can be used to provide a different
packet rate to a carrier compared to a local packet rate, thus allowing internal devices and
applications to run at a common rate that may be different from the carrier.
Service provider behavior
Some Service Providers require that a specific packet rate be used on both receive and transmit
streams, in these situations the 3300 ICP will attempt to comply with the Service Provider's
requirements.
In cases where the 3300 ICP cannot meet the Service Provider's requirements, some Service
Providers will allow the call to proceed with unacceptable packet rates, only to block the media
stream. Other Service Providers might fail the negotiation entirely, and the call will never be
connected.
For correct operation it is necessary that calls to or from a Service Providers contain, in the
original SDP (Session Description Protocol) negotiation, the packet rate (or "ptime" parameter)
that the Service Provider is willing to accept. The 3300 ICP will communicate this requirement
to the eventual endpoint.
Route Optimization
Route optimization improves signalling and response times in handling a call. For example, a
call from ICP A transferred from ICP B to ICP C continues directly between ICP A and ICP C,
bypassing the initial ICP B. This prevents ICP B from being kept in an unnecessary tandem
signalling connection. Hand-over between controllers occurs within 10 seconds of the call
transfer. The voice streaming automatically switches paths based on IP address information.
CAUTION: If some applications and/or phones that do not support variable
RTP packet rates are combined into a solution which requires variable RTP
packet rates it will result in undefined behaviors.
Specifically, the users may experience scenarios where there is no audio in
one direction or both directions. These types of audio problems can be difficult
to isolate and resolve.
Before deploying any phones or applications that employ variable RTP packet
rates, the administrator or installer should review all sets and applications that
comprise a particular solution to determine if they are all compatible with
variable RTP packet rates.
Special attention should be paid to Mitel applications that operate on a release
schedule that is independent from the 3300 ICP release schedule, such as
NuPoint Unified Messenger.
It should be noted that NuPoint is not initially compatible with variable RTP at
MCD 4.0.