This attribute indicates the results of negotiating ingress minimum
and maximum rates for voice, modemFax and fax traffic with the
remote end across the subnet. The parameters used for negotiating
with the remote end are provisioned in maxVoiceG711G726Rate,
minVoiceG711G726Rate, maxModemFaxG711G726Rate and
minModemFaxG711G726Rate.
negotiatedIgRates can be different on either side of a VoiceService.