A method for communicating compacted information between two entities including a String Sender and a String Receiver, which each include a user agent, UA, a network node, or other network entities, using an I1 interface, the I1 interface providing a session control channel, the method comprising: the String Sender preparing a session initiation protocol, SIP, encoded message to be transmitted using the I1 interface; the SIP encoded message including several strings and several verbose data elements that generate SIP encoded messages that are larger than a maximum payload of the I1 interface, reducing a size of the SIP encoded message by: the String Sender stepping through each of the strings to determine whether it is eligible for compression by replacing strings with indicia, identifying a first string to be transmitted in the SIP encoded message to at least one of a user agent, UA, and a network node, the first string including at least one of a uniform resource identifier, URI, a Public User Identity and a SIP UA capability; and wherein the String Sender and the String Receiver have shared a synchronization table associating the first string and an indicium, the String Sender looking up the first string value in the synchronization table to identify the indicium associated with the first string of the SIP encoded message; and when finding the first string value of the SIP encoded message in the synchronization table the String Sender inserting the indicium that corresponds to the first string into the SIP encoded message, and the String Sender transmitting the SIP encoded message to the String Receiver using the I1 interface. the String Sender preparing a session initiation protocol, SIP, encoded message to be transmitted using the I1 interface; the SIP encoded message including several strings and several verbose data elements that generate SIP encoded messages that are larger than a maximum payload of the I1 interface, reducing a size of the SIP encoded message by: the String Sender stepping through each of the strings to determine whether it is eligible for compression by replacing strings with indicia, identifying a first string to be transmitted in the SIP encoded message to at least one of a user agent, UA, and a network node, the first string including at least one of a uniform resource identifier, URI, a Public User Identity and a SIP UA capability; and wherein the String Sender and the String Receiver have shared a synchronization table associating the first string and an indicium, the String Sender looking up the first string value in the synchronization table to identify the indicium associated with the first string of the SIP encoded message; and when finding the first string value of the SIP encoded message in the synchronization table the String Sender inserting the indicium that corresponds to the first string into the SIP encoded message, and the String Sender transmitting the SIP encoded message to the String Receiver using the I1 interface. the String Sender stepping through each of the strings to determine whether it is eligible for compression by replacing strings with indicia, identifying a first string to be transmitted in the SIP encoded message to at least one of a user agent, UA, and a network node, the first string including at least one of a uniform resource identifier, URI, a Public User Identity and a SIP UA capability; and wherein the String Sender and the String Receiver have shared a synchronization table associating the first string and an indicium, the String Sender looking up the first string value in the synchronization table to identify the indicium associated with the first string of the SIP encoded message; and when finding the first string value of the SIP encoded message in the synchronization table the String Sender inserting the indicium that corresponds to the first string into the SIP encoded message, and the String Sender transmitting the SIP encoded message to the String Receiver using the I1 interface.