Avaya Aura® Contact Center (AACC) integrates with Avaya Aura® Communication Manager via Application Enablement Services (AES). The core protocol for this Computer Telephony Integration (CTI) link is the Telephony Services Application Programming Interface (TSAPI). The AACC server establishes a persistent TSAPI connection to the AES server. This connection allows AACC to monitor agent extensions, receive call events, and execute third-party call control functions (e.g., answer, hold, transfer), which are fundamental for contact center operations and are reflected on the agent's desktop application.

A. WCF: Windows Communication Foundation (WCF) is a Microsoft framework for building applications; it is not the specific CTI protocol used for AACC-to-AES communication.

C. TR/87: While AES supports TR/87 for web services-based CTI, AACC's primary and foundational CTI integration for server-based call control relies on the stateful TSAPI protocol.

D. DMCC: Device, Media, and Call Control (DMCC) is used for first-party call control, typically for softphone applications to control a specific device and its media stream, not for the server-level third-party call control that AACC requires.

1. Avaya Aura® Contact Center - Solution Description (NN42001-110, Issue 11.01, June 2017): In the "Avaya Aura® Contact Center CTI service" section, it states, "The CTI service uses a Telephony Services Application Programming Interface (TSAPI) link to Avaya Aura® Application Enablement Services to provide telephony integration with Communication Manager." (See Chapter 2: Architecture, Page 2-10).

2. Avaya Aura® Application Enablement Services Overview and Specification (02-300363, Issue 11.0, November 2016): This document describes the services offered by AES. In the section on TSAPI Service, it details its function for third-party call control, which is the model used by applications like AACC. It explicitly lists "Contact Center" as a primary application type for the TSAPI service. (See Chapter 2: AE Services, Section: TSAPI Service).

3. Implementing Avaya Aura® Contact Center (7.0), Course Number 72301C, Student Guide: The course material on AACC architecture consistently depicts the Communication Control Toolkit (CCT) server component of AACC connecting to AES via a TSAPI link for CTI messaging. (Module: AACC Architecture).