The value of tmnxPppPlcyMlpppEpClass specifies the
type of endpoint.
If the value of 'tmnxPppPlcyMlpppEpClass' is equal to 'ipv4Address',
the address for the MLPPP Endpoint Discriminator Option is taken from
tmnxPppPlcyMlpppEpIpv4Address.
If the value of 'tmnxPppPlcyMlpppEpClass' is equal to 'macAddress',
the address for the MLPPP Endpoint Discriminator Option is taken from
tmnxPppPlcyMlpppEpMacAddress.
If the value of 'tmnxPppPlcyMlpppEpClass' is equal to 'null',
the MLPPP Endpoint Discriminator Option must not be transmitted.
A value other than 'null' is only allowed if this system performs
the role of LAC with respect to the PPP clients using this policy.