Description of SIP Trunking from PSTN to SIP Trunk


The end is coming to the trusted old PSTN. Whether analog, ISDN BRI, E1 or t1 lines, the telephone system is migrating from the PSTN to the newer and more flexible SIP trunks.

Leading telecommunications providers are accelerating the move to reject older PSTN features and urging customers to move their phone schemes to IP. Therefore, there is no doubt that SIP trunk and telephone systems will be upgraded in the near future.

As a result, the percentage of Session Initiation Protocol (SIP) trunking increased by 62% in 2015 from the previous year. The region of increase was mainly North America. The move to SIP trunks is very beneficial for a single enterprise. This guide describes SIP trunks, their benefits, and how to migrate.

Benefits of SIP trunking

Saying goodbye to the PSTN gives businesses many benefits. Advantages of SIP trunks:

  • Cheaper Lines and DID Monthly Rental Fees  – SIP trunks can significantly reduce the high monthly fees associated with many lines installed in your office. DID costs are also significantly reduced.
  • Cheaper Phone Charges  – There are many and competing providers of SIP trunks, so you can save a lot of money on your phone charges. There are also SIP trunks with no call restrictions.
  • Better Customer Service  – Improve the quality of customer service by adding more region and international numbers. Simply add a number to your SIP trunk and terminate it to your IP PBX, giving your dial-in customers more choice while significantly reducing costs. Remove communication obstacles and increase sales.
  • You don’t have to change your number when you move your office . The SIP trunk is unpositioned, saving you the trouble of changing peripherals or giving your customers a new number when you move your office. You no longer have to pay your carrier for call forwarding.
  • Eliminate VoIP Gateways  – SIP trunks eliminate the need to purchase and manage VoIP gateways. All calls are made over IP. The fact that there is no need for extra conversion means that the quality of the call is also improved.
  • Leveraging the  latest IP PBX – The latest IP PBX / integrated communication solutions bring productivity, mobility, and sales growth to your customers. Connecting an IP PBX to a SIP trunk is much easier than via a PSTN.
  • Flexibility  – It’s easy to add channels to your SIP trunk to handle the growing number of calls. You can add channels with a simple phone call. In many cases this can be done immediately. Compare the effort of installing additional lines to increase the number of lines and upgrading your old PBX.
  • Exact number of channels  – SIP trunks make it easy to choose the right number of channels according to your needs. In contrast, for ISDN / T1, you often have to choose between adding 15 or 30 lines. The large number of lines ultimately leads to higher costs.

Choose the right SIP trunk provider

The next step is to choose a SIP trunk provider that will supply the required SIP trunks. There are several factors in deciding this:

  • Security  – Since SIP trunks connect to the Internet, it is very important that a secure network and fraud prevention system is in place for SIP trunks. The fraud prevention system must monitor the system and block fraudulent calls.
  • Proprietary Network  – Determines if the SIP trunk provider is running its own network or a rebranded service. There are many companies that resell SIP trunks from other providers. Choose a provider that has control over your services and network.
  • Cost Performance  – Costs vary greatly depending on the type of service. Some vendors charge a large amount for the use of SIP trunks. Not only to check the cost performance, but also to check the business quality of SIP trunk service. For example, some telecommunications providers offer relatively low quality to internet phone shops at low prices. Keep in mind the cost and assume that you will be charged for business class services.
  • Number Porting  – Can the selected provider port your phone number? Make sure the provider of your choice can port all existing numbers. Not all providers can be ported to all regions.

Internet connection upgrade

After choosing a SIP trunk provider, the next step is to consider an internet connection dedicated to that SIP trunk. Most firewall features can support multiple WAN connections. Also, given that the cost of connecting to the Internet is low in most places, individual VoIP connections are probably the most reliable way to guarantee the quality of VoIP calls.

However, some SIP trunk providers already offer services over a dedicated internet connection. This allows you to separate voice and data traffic. The selection criteria will vary greatly depending on your cost and your network infrastructure. Make sure your firewall features are up-to-date and capable of properly handling VoIP traffic.