This attribute specifies whether echo cancellation is performed on
this VoiceRoute. v1 specifies whether echo cancellation is
performed by version 1 internal echo cancellers. v2 specifes
whether echo cancellation is performed by version 2 echo
cancellers. If echoCancellation is on, the internal echo canceller is
enabled and echo cancellation is performed. If echoCancellation is
off, the internal echo canceller is placed in transparent bypass mode
and echo cancellation is never performed.