A method for transferring state information in a network transmission, the method executing in a sending device coupled to a network, the method comprising: (i) sending state information about a process in a sending device from the sending device to a receiving device over the network, wherein sending the state information comprises: creating a first Session Initiation Protocol, SIP, message adapted for transfer to the receiving device, wherein the first SIP message includes a via in a header of the SIP message; storing state information about the process in the sending device in the via; and sending the first SIP message to the receiving device; wherein the state information is used to implement one or more state machines in at least the receiving device; and (ii) adding state information about a process in the sending device to a second SIP message received from a first external device and sending the message to an external device that may be either the first external device or a second external device, wherein adding state information comprises: receiving the second SIP message from the first external device, wherein the received second SIP message includes a via having state information about a process in an external device that may be either the first external device or another external device; adding state information to the via in the received second SIP message, wherein the added state information includes state information about a process in the receiving device; and sending the second SIP message to either the first external device or to the second external device; wherein the state information is used to implement one or more state machines in at least the first external device or the second external device. (i) sending state information about a process in a sending device from the sending device to a receiving device over the network, wherein sending the state information comprises: creating a first Session Initiation Protocol, SIP, message adapted for transfer to the receiving device, wherein the first SIP message includes a via in a header of the SIP message; storing state information about the process in the sending device in the via; and sending the first SIP message to the receiving device; wherein the state information is used to implement one or more state machines in at least the receiving device; and creating a first Session Initiation Protocol, SIP, message adapted for transfer to the receiving device, wherein the first SIP message includes a via in a header of the SIP message; storing state information about the process in the sending device in the via; and sending the first SIP message to the receiving device; (ii) adding state information about a process in the sending device to a second SIP message received from a first external device and sending the message to an external device that may be either the first external device or a second external device, wherein adding state information comprises: receiving the second SIP message from the first external device, wherein the received second SIP message includes a via having state information about a process in an external device that may be either the first external device or another external device; adding state information to the via in the received second SIP message, wherein the added state information includes state information about a process in the receiving device; and sending the second SIP message to either the first external device or to the second external device; wherein the state information is used to implement one or more state machines in at least the first external device or the second external device. receiving the second SIP message from the first external device, wherein the received second SIP message includes a via having state information about a process in an external device that may be either the first external device or another external device; adding state information to the via in the received second SIP message, wherein the added state information includes state information about a process in the receiving device; and sending the second SIP message to either the first external device or to the second external device;