This object indicates which entity to use this domain name.
gateway(1) - The domain name of media gateway.
With the same cmgwIndex, there is one and
only one entry allowed with the value
'gateway(1)' of this object.
dnsServer(2) - The domain name of DNS name server that is used
by Media gateway to find Internet Network
Address from a DNS name.
mgc(3) - The domain name of a MGC (Media Gateway
Controller) associated with the media
gateway.