▁original ▁communication ▁stack ▁ ▁M MS ▁was ▁standard ized ▁in ▁ 1 9 9 0 ▁under ▁two ▁separate ▁standards ▁as ▁ ▁ISO / IE C ▁ 9 5 0 6 - 1 ▁( 2 0 0 3 ): ▁Indust rial ▁Autom ation ▁systems ▁- ▁Man ufact uring ▁Message ▁Spec ification ▁- ▁Part ▁ 1 : ▁Service ▁Definition ▁ ▁ISO / IE C ▁ 9 5 0 6 - 2 ▁( 2 0 0 3 ): ▁Indust rial ▁Autom ation ▁systems ▁- ▁Man ufact uring ▁Message ▁Spec ification ▁- ▁Part ▁ 2 : ▁Pro tocol ▁Spec ification ▁This ▁version ▁of ▁M MS ▁used ▁seven ▁layers ▁of ▁O SI ▁network ▁protocol s ▁as ▁its ▁communication ▁stack : ▁ ▁M MS ▁stack ▁over ▁TCP / IP ▁ ▁Because ▁the ▁Open ▁Systems ▁Inter connection ▁protocol s ▁are ▁challeng ing ▁to ▁implement , ▁the ▁original ▁M MS ▁stack ▁never ▁became ▁popular . ▁In ▁ 1 9 9 9 , ▁Bo eing ▁created ▁a ▁new ▁version ▁of ▁M MS ▁using ▁Internet ▁protocol s ▁instead ▁of ▁the ▁bottom ▁four ▁layers ▁of ▁the ▁original ▁stack ▁plus ▁R FC ▁ 1 0 0 6 ▁(" ISO ▁Transport ▁over ▁TCP ") ▁in ▁the ▁transport ▁layer . ▁The ▁top ▁three ▁layers ▁use ▁the ▁same ▁O SI ▁protocol s ▁as ▁before . ▁ ▁In ▁terms ▁of ▁the ▁seven - layer ▁O SI ▁model , ▁the ▁new ▁M MS ▁stack ▁looks ▁like ▁this : ▁ ▁With ▁the ▁new ▁stack , ▁M MS ▁has ▁become ▁a ▁glob ally ▁accepted ▁standard . ▁ ▁External ▁links ▁ ▁M MS