CSTA (Computer-Supported Telecommunications Applications) specifies an Applications Interface and Protocols for monitoring and controlling calls and devices in a communications network.

The CSTAp3XML Asn1API is compliant with :

• ECMA-323 (June 2004) which defines the CSTA phase III protocol based on an XML Schema for handling XML encodings. An equivalent ASN.1 syntax with the Extended XER encoding rules can be used instead and is the base for this API. CSTA phase III is an extension of CSTA phase I and phase II.
• ECMA-354 (June 2004) which is used to establish and maintain a relationship between an application and a server for the purpose of exchanging application messages. For the purpose of this Standard this relationship is called an application session.ECMA 323 may require an association establishment.

The definition of the CSTA phase III services can be found at ECMA-269.

The CSTA phase I was created in 1992 by ECMA and the protocol has continued to be refined over years with the CSTA phase II and phase III. The latest evolution is the CSTA phase III protocol in XML. The protocol is now being actively promoted in SIP environments. The ECMA technical report ECMA-TR87 explains the use of SIP+CSTA.

uniGone provides an Asn1API for each phase of the CSTA standard from the CSTAp1 Asn1API to the CSTAp3XML AsnAPI...