 and Regulatory Challenges for Services Over Ultra-Broadband For example, VoIP is provided via broadband IP access (although voice as a service does not require high bit rates), but several different business models for VoIP can be distinguished: Telco VoIP (as PSTN/ISDN replacement). This VoIP service is provided with QoS support end-to-end by using standardized network and service functions, typically NGN-based. Bundling VoIP service with other IP-based services. Telco VoIP is typically bundled with broadband Internet access services and/or IPTV as a resale product of the ser- vice provider, including fixed and mobile ones. Due to the global spread of mobile networks and their affordability in all countries (including developing ones), the bun- dled VoIP with QoS support via mobile network has significantly surpassed fixed telephony. Separate provision of VoIP service. VoIP is partly bundled with broadband access to the Internet, where the VoIP service can be offered to customers connected via other broadband access networks to Internet (i.e. VoIP provider and broadband access providers can be different business entities). Best-effort VoIP service (i.e. OTT VoIP). In this case telecom operators do not guar- antee delivery of VoIP packets because there is no relation between OTT VoIP ser- vice providers (e.g. Skype, Viber, WhatsApp) and telecom operators as broadband access providers. Although OTT VoIP is multiplexed with other Internet traffic on a best-effort basis, the telecom operators can apply traffic management techniques in their network to increase the QoE for OTT VoIP services. Some OTT VoIP services were offered free of charge (telecom operators do not charge the Internet traffic in such cases), aiming to attract new subscribers to Internet access service, but in cer- tain cases such differentiated charging was seen as jeopardizing the Internet network neutrality principle [24]. Mobile VoIP service (e.g. voice over long term evolution - VoLTE in 4G networks, voice over New Radio in 5G networks). These