A unique value for each ATTACHMENT on a given
SMT. Its value ranges between 1 and the sum of
the values of snmpFddiSMTNonMasterCt {
snmpFddiSMTEntry 6 } and snmpFddiSMTMasterCt {
snmpFddiSMTEntry 7 } on the given SMT. The value
for each ATTACHMENT must remain constant at least
from one re-initialization of the entity's network
management system to the next re-initialization.