We p rop ose a ne w system mo d el for asyn chron ous di stri buted
sy stems that we ca ll the m essage classi cation m odel. Moti -
vati on for thi s mo d el i s its ab il i ty 1) to s upp ort a re stricted
bu t u seful form o f \commun ic atio n by ti me" by cla ssi fy in g
mess ages as ei ther \sl ow" or \fast" b ut wi thou t in corp ora tin g
ne ith er real -ti me cl o cks n or \ti me-outs", and 2) to des crib e
tran sie nt an d p erman ent n etwork pa rtiti ons . The messag e
cl assi ca tion mo del al l ows the de ni tion of di erent cl ass es of
cl assi ca tion sch emes. To s how tha t the mo del i s i nd eed u se-
ful , we s how how one can sol ve the con sensu s and th e ele ction
pr obl em for a certa in cl ass of messa ge cl ass i catio n s chemes.