A value which indicates the version(s) of SIP
that this interface supports. The value is a sum.
This sum initially takes the value zero. For each
version, V, that this interface supports, 2 raised
to (V - 1) is added to the sum. For example, a
port supporting versions 1 and 2 would have a
value of (2^(1-1)+2^(2-1))=3. The
sipL3VersionSupport is effectively a bit mask with
Version 1 equal to the least significant bit
(LSB).