Specifies the type of voice related encapsulation.
voice - voice encapsulation (voiceEncap ifType) on the
telephony network.
voip - VoIP encapsulation (voiceOverIp ifType) on the IP
network.
mmail - Media Mail over IP encapsulation (mediaMailOverIp
ifType) on the IP network.
voatm - VoATM encapsulation (voiceOverATM ifType) on the
ATM network.
vofr - VoFR encapsulation (voiceOverFR ifType) on the
Frame Relay network.