SIP Trunks provide the quality and reliability of traditional phone lines. Only, at a fraction of the cost. With SIP Trunking, your existing phone system is able to deliver calls via your internet connection. You don’t need pay for expensive PSTN or ISDN lines.SIP Trunks are interoperable with all major analogue and IP phone systems. SIP Trunking can also provide the voice calling component in Unified Communications software – such as Skype for Business (Microsoft Lync).