What is SIP Trunking?

Over the past few years, many companies have begun to switch to VoIP services over traditional land lines to increase cost efficiency. In doing so, many have sought different means in obtaining quality service. One method (or type) of VoIP that allots for lower costs without cutting quality is SIP Trunking. SIP Trunking is a service that uses voice over IP (VoIP) to facilitate the connection of private branch exchange (PBX) to the Internet. In this service, the Internet replaces the traditional telephone trunk and allows users to communicate with fixed and mobile telephone subscribers all over the world.

SIP Trunking combines SIP, or Session Initiation Protocol, with Trunking, which is a term that refers to telephone systems to describe a large number of users sharing a much smaller number of communication paths. In order to better understand the SIP Trunking service as a whole, it is important to understand what its concepts are:

A “Trunk” is a single line or link, which is able to carry many signals at once, connecting major switching centers or nodes in a communications system. Additionally, Trunking, which is the using of trunks, provides network access to many clients by sharing a set of lines and/or frequencies instead of providing them individually.

SIP is an acronym standing for “Session Initiaition Protocol.” SIP has a large number of applications that include controlling communication sessions (i.e. voice and video over IP) and integrating phone and internet services such as phone calls, audio and video conference calls, file transfers, instant messaging, and online gaming. Additionally, new applications for SIP are being added and developed constantly.

Together, these components are able to blend connections for both data and voice into a single line. In connecting an SIP Trunk to an internal PSTN (public switched telephone network) companies are able to communicate over IP outside the enterprise itself. Subsequently, SIP Trunking can eliminate traditional fixed PSTN lines with an IP phone system connected (externally) through an SIP Trunking Service. Though this route offers a number of benefits, SIP Trunking requires three primary components in order to utilize the various advantages.

  • IP PBX: An IP PBX communicates with all end points over an IP network. In addition to this, it also switches calls between VoIP users (on local lines) and also allows users to share numerous phone lines. Along with this switching, IP PBX typically switches calls between a VoIP user and traditional phone user.
  • ITSP: The Internet Telephone Service Provider ensures the connection to PSTN from an IP network for both mobile and stationary devices. It also carries IP communications across a private IP network or public Internet.
  • Border Element: This facilitates connection between a business’s IP network, the PSTN, and an external IP carrier network. This element can be anything from a SIP-capable firewall to a switch that transfers calls both in and out of the PSTN. –Note:Border elements are usually managed by the service provider.

Once these components have all been accounted for, the SIP Trunking device can allow the data network to carry voice traffic.

Some companies may be wary in switching to SIP Trunking as there are a number of factors to account for initially: startup costs may be expensive, entire phone networks must be comprised of VOIP phones, the need for security from hackers and viruses/worms is higher, the cost of increased bandwidth, and the suitability for business based on size. Despite these relative disadvantages, SIP Trunking offers a number of benefits including: greater cost efficiency (with calls to both SIP networks and PSTN phones), future-proof technology and ease of scalability, the ability to take your number with you if you travel or move offices, call routing to other offices in the event of a network outage, suitability for medium and large business with more than 25 phones, suitability for businesses with international offices, and enhanced 911/Emergency calls.

SIP Trunking offers a widely inclusive, quality, and cost efficient alternative to phone service. Though it may not be suited for every business, its long list of features and advantages make this service increasingly appealing. Additionally, advances are constantly being made in the technology; therefore, companies using the service can rest assured knowing that they have the most up-to-date and advanced solution available to them. 

Related Articles:
- Compare SIP Trunking Providers
- How Will SIP Trunking Help My Business
- What is a SIP Uri?