A string of octets containing one bit per VLAN in the
management domain on this trunk port. The first octet
corresponds to VLANs with VlanIndex values of 0 through 7;
the second octet to VLANs 8 through 15; etc. The most
significant bit of each octet corresponds to the lowest
value VlanIndex in that octet.
If the bit corresponding to a VLAN is set to '1', then the
local switch is currently sending joins for this VLAN on
this trunk port, i.e., it is asking to receive frames for
this VLAN; if the bit is set to '0', then the local switch
is not currently sending joins for this VLAN on this trunk
port.