What Is SIP Trunking?

SIP stands for Session Initiation Protocol. Simply put, SIP is a communication standard that all telephony providers and equipment manufacturers use so that data can be passed between networks. SIP trunking is ideal for organisations that want to make the fullest use of their existing network or networks.

How Does a SIP Trunk Work?
A SIP trunk makes a direct connection between the local network – perhaps in an office – to the outside world via the chosen ITSP. It therefore enables network supervisors to extend voice telephone calls that use internet protocols beyond that local network. Voice over IP telephone calls, better known as VoIP, have been around for many years and there are plenty of private branch exchanges and telephone systems that use the technology. However, in a traditional model a caller in one office still has to dial out over the public telephone network to make a call to another office in the business – even if, when they call to an extension in the same office, they use IP technology. As you might expect this has a cost implication for many organisations in terms of their telephone charges. With a SIP trunk in place it is possible to place a VoIP call from one telephone handset to another and to do so by going outside of the business’ firewall without any need for a gateway device. The SIP trunk also allows for data communication to be made between sites so that servers can be stored centrally, for example.
The Advantages of a SIP Trunk
The simpler configuration that a SIP trunk provides most network supervisors and IT engineers with makes for a system that is easier to manage. It also offers a network which provides greater flexibility. A SIP trunk is usually less expensive to design as well as to operate. Maintenance and upgrade costs are also usually preferable, depending on the number of sites that the organisation has and the degree of communication required between them. Because ITSPs are able to deliver VoIP services with substantial savings, particularly when it comes to long distance voice calls, the advantages really start to be noticed when you have a multi-site business that has remote offices up and down the length and breadth of the country.
By using Session Initiation Protocol trunking, network engineers can rationalise their systems. For many in IT, it remains a logical goal to have a single IP-based network that works for both computer communication and voice. Rather than running a private telephone network and a separate data one, the two can be brought together – even over several different sites. This can mean a cost saving for certain types of IT departments because data and voice is brought together meaning that two sets of skills are no longer required to maintain the system.
In the past, VPNs have allowed multi-site communications for both voice and data. Nevertheless, this has meant sometimes heavy investment in digital phone lines, or ISDN trunks, which are rented from the telephone network provider. These often have to be bought in bulk meaning that sometimes there is too much capacity and sometimes too little. A SIP trunk offers much more flexibility with the amount of bandwidth that is required over a multi-site network.
How To Deploy SIP Trunks
A SIP trunk can be easily connected to an organisation’s telephone network so long as it is already enabled to work with IP. The ITSP will either connect it to the IP-PBX or via a mediation server. Simply put, a mediation server does all of the encrypting and decrypting that is required to ensure that data passing over the networks remains private. This sort of data translation is essential for any sort of VPN. No matter which manufacturer of telephone system you have, an IP-PBX should also perform this sort of functionality for you, too.
IT engineers should set up a virtual local area network using static routing between a mediation server and a router. For networks that use a VPN server, then a generic routing encapsulation device – or GRE – should be used in order to encrypt all of the data.