The value of tmnxSubProfEgrEncapOffset specifies how
the fixed packet offset will be derived.
This fixed packet offset will be used in the adjustment of the
subscriber aggregate rate, to account for the fixed offset and per
packet variable expansion of the last mile for the specific session
used by the subscriber host.
The value 'none (0)' will disable the adjustments.
The value 'auto (1)' will derive the fixed packet offset from the
encapsulation type value signaled in the Access-loop-encapsulation
sub-TLV in the Vendor-Specific PPPoE Tags or DHCP Relay Options
[rfc4679].