Cisco Systems, Inc. is an American multinational corporation that designs, manufactures, and sells networking equipment. It has a full range of router products from small business to enterprise solutions, typically using its own Cisco IOS operating system. wikipedia.org

Cisco Unified Communications Manager (CUCM), formerly Cisco Unified CallManager and Cisco CallManager (CCM), is a software-based call-processing system developed by Cisco Systems. wikipedia.org

Linux-based operating system known as MikroTik RouterOS. Installed on the company's proprietary hardware (RouterBOARD), or on standard x86-based computers, it turns the computer into a network router and implements various additional features, such as firewalling, virtual private network (VPN) service and client, bandwidth shaping and quality of service, wireless access point functions and other commonly used features when interconnecting networks. wikipedia.org

"The CCNP is the credential that validates the ability to work with medium-sized networks (between 100 and 500 end devices) and with technology such as QoS, broadband, VPNs, and security-minded features."

Avaya Inc. is a privately held computer networking, information technology and telecommunications company that is a global provider of business communications systems. wikipedia.org

Asterisk is a software implementation of a telephone private branch exchange (PBX). It allows attached telephones to make calls to one another, and to connect to other telephone services including the public switched telephone network (PSTN) and Voice over Internet Protocol (VoIP) services. wikipedia.org

FreePBX is a GUI (graphical user interface) that controls and manages Asterisk, an open source telephony engine software.

The Kamailio SIP server is a Open Source software for building SIP services such as a SIP proxy, SIP Presence Server, and SIP location server.