The Stack's core transaction processing architecture uses a SIP message-based interface between the Transaction (and lower) layers and the Transaction User layers. DUM is one example of a Transaction User.
This diagram shows the reSIProcate Transaction and Transport Architecture. Common colours indicate related, thread connected components. File:Http://scm.sipfoundry.org/viewsvn/*checkout*/resiprocate/main/sip/resiprocate/doc/ResipArchitecture.jpg
This file is generated by OmniGraffle Pro 3.0 and is also available in the reSIProcate SCM repository as a <a href="http://scm.sipfoundry.org/viewsvn/*checkout*/resiprocate/main/sip/resiprocate/doc/ResipArchitecture.pdf">PDF</a> file and the original <a href="http://scm.sipfoundry.org/viewsvn/*checkout*/resiprocate/main/sip/resiprocate/doc/ResipArchitecture.graffle">graffle source</a>.