The terms "virtual number" and "IP telephony" are often confused, although they are not the same thing. IP telephony is a way of transmitting voice (a technology), while a virtual number is the phone number itself (an identifier). Moreover, virtual numbers come in two natures: on a physical SIM from a real carrier, and purely software-based (VoIP). The difference between them is critical when it comes to receiving SMS and passing verifications. Let's go through it in order.
What IP telephony is
IP telephony (VoIP, Voice over IP) is a technology for transmitting voice as data packets over the internet instead of the traditional telephone network. When you speak through a SIP client, your voice is digitized, split into RTP packets, and delivered to the other party over IP. IP telephony answers the question "how to transmit voice," but by itself it does not define which number you have or where it came from.
Key elements of IP telephony
- SIP: the protocol for establishing and managing a communication session.
- RTP: the protocol for transmitting the voice stream itself.
- SIP trunk: the channel between the provider and your equipment.
- Codecs: G.711, G.729 and others — they determine quality and compression.
What a virtual number is
A virtual number is a phone number not rigidly tied to a specific physical handset on your desk. You can receive calls and SMS on it over the internet. But a virtual number can have different "internals," and exactly that determines its capabilities.
Virtual number on a physical SIM
This is a real mobile carrier SIM card installed in a GoIP gateway or a Simpool array. To the network it is an ordinary subscriber: a real IMSI, a real mobile range. Such a number receives both SMS and calls and passes verifications where purely software numbers are blocked.
Purely software VoIP number
This is a DID or a number that exists only in software telephony, without a SIM. It works great for voice, but many platforms recognize its range as "virtual" and refuse SMS verification.
The main difference in one table
| Parameter | IP telephony (VoIP) | Number on a physical SIM |
|---|---|---|
| What it is | Voice transmission technology | Number of a real carrier |
| Call reception | Yes | Yes |
| SMS reception | Often limited | Yes, natively |
| Verification deliverability | Low on "virtual" ranges | High |
| Equipment | Software only | GoIP / Simpool with a real SIM |
Why this matters in practice
If your task is voice only (a call center, call forwarding, a DID of the required country), classic IP telephony is enough. But if you need to receive SMS codes and pass registrations on services sensitive to the number's source, the difference becomes decisive.
SMS reception
Purely software VoIP numbers often do not receive service SMS at all: the sending carrier either does not route short codes to the VoIP range, or the platform blocks such numbers in advance. A physical SIM from a real carrier in a GoIP receives SMS like an ordinary phone.
Passing anti-fraud systems
Anti-fraud systems maintain databases of "virtual" ranges. A number on a physical SIM does not end up in that database, because it is technically indistinguishable from a subscriber with an ordinary SIM in their pocket.
How they work together
In practice the two technologies do not contradict each other but complement one another. A physical SIM in a GoIP gateway provides a "legitimate" number from a real carrier, while IP telephony (SIP) provides a convenient channel to deliver calls and SMS to your computer or PBX. So you get the best of both: the deliverability of a real SIM plus the flexibility of VoIP. For 17 countries this means real mobile numbers with SMS and call reception over the internet.
- Number layer: a physical SIM from a real carrier.
- Transport layer: IP telephony to deliver the signal.
- Equipment layer: GoIP and Simpool as a bridge between GSM and IP.
Frequently asked questions
Are IP telephony and a virtual number synonyms?
No. IP telephony is a way of transmitting voice over the internet, while a virtual number is the identifier itself. The same number can be delivered via IP telephony, but the number's nature (SIM or pure VoIP) matters more for receiving SMS.
Why does my VoIP number not receive SMS?
Purely software VoIP ranges often do not route service SMS and are blocked by platforms. The solution is a number on a physical SIM from a real carrier, which receives SMS natively.
Can I receive calls on a number with a physical SIM?
Yes. A number on a physical SIM in a GoIP gateway receives both SMS and calls at one point, and is delivered to you via IP telephony.
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