5.6.2018 Blog

The Right SIP Trunking Provider Is Key to VoIP Migration

Follow these VoIP migration tips whether you replace your whole telephony infrastructure or interface a PBX system with a SIP trunking provider.

With voice over IP (VoIP) being a hot topic in the unified communications market, many businesses may be looking to migrate from a PSTN telecommunication provider to a SIP trunking provider. In some cases, a VoIP migration involves replacing the whole PBX system with a newer generation VoIP PBX, while some businesses might instead choose to keep costs down by interfacing their PBX with a SIP provider.

During this transition, IT departments are often overwhelmed with the problems that can arise. This article provides some key points that aim to make a VoIP migration as painless as possible.  PBXs that do not support SIP trunking will require a voice gateway to connect to their SIP provider. The voice gateway is placed between the PBX and SIP provider, connecting with the PBX on one end (usually using T1/E1 ISDN lines) and the SIP provider on the other end via IP:

It is important to ensure the voice gateway supports an equal amount of concurrent calls on both legs: SIP provider–voice gateway and voice gateway–PBX. The second leg, voice gateway to PBX, is where we usually find T1/E1 interfaces that provide a capacity of 24/32 concurrent calls respectively. If additional call capacity is required, multiple T1/E1 lines are installed, assuming the PBX can handle this capacity.

Selecting the right SIP service provider is one of the most important steps. The SIP provider must provide a stable service without interruptions, but must also own the physical delivery medium to the company’s premises, also known as the last mile, in order to guarantee quality of service (QoS).

Before transferring company numbers to the SIP provider, also known as local number portability, a test number should be requested from the SIP provider to make some calls and evaluate the SIP service, voice quality and line stability. When satisfied with the result, you can safely transfer all company numbers to the SIP provider, keeping in mind that transfer process usually requires a few hours. During the transfer, incoming phone calls are likely to be lost, so it is important that the transfer is initiated during out-of-office hours.

Another good practice during a VoIP migration is to note all the company numbers that need to be transferred to the SIP trunking provider. If any numbers are missed, they could be lost after the transfer is complete and the PSTN lines are cancelled.

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