[[FrontPage]] *Whole block [#k30061e1] It is the modularized layer structure which made the four following things one unit.~ At present, it has only a module relevant to "SIP." ~ In the future, other things are due to be added. -[[B2BUA Layer>architecture#gf94fd32]] -[[UA Layer>architecture#nde67d6f]] -[[Stack Layer>architecture#fb15ebe6]] -[[Transport Layer>architecture#ec301860]] ***design [#rc287cc3] -[[detail design>development/design]] *B2BUA Layer [#gf94fd32] This layer defines a sequence required as operation of UA.~ and it has responsibility about two or more transactions and dialogs. *UA Layer [#nde67d6f] This layer implements the function in the single functional unit.~ It exists as a module (API) for B2BUA Layer to use it. *UA Layer [#nde67d6f] *Stack Layer [#fb15ebe6] This layer has responsibility to processing of a transaction level. *Transport Layer [#ec301860] This layer treats processing of the Socket level which adopted [[MINA:http://mina.apache.org/]].