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Telephony · Understand
VoIP is a way of transporting voice, SIP a protocol, an IP PBX a phone system, UCaaS a service. These terms cannot be compared with one another. The real decision involves three points: who operates the phone system, whether it is shared with other customers, and how it stays reachable when a site or a link goes down.
VoIP (Voice over IP): the voice is split into packets and carried over an IP network, the Internet or a private network, instead of a traditional phone line. It is a means of transport, not a product.
SIP (Session Initiation Protocol): the protocol standardized by the IETF in RFC 3261 for establishing, modifying and terminating sessions, including calls. It is a signaling protocol: it organizes the call. The voice itself generally travels over another protocol, RTP, or its secure version SRTP.
IP PBX: the company’s phone system, in its IP version. It manages extensions, direct numbers, groups, the auto attendant, call queues and forwarding. It can run on your premises or at a third party.
UCaaS (Unified Communications as a Service): a suite hosted and operated by a third party, often combining voice, presence, instant messaging and video conferencing.
Two more terms complete the buying vocabulary. A SIP trunk is the connection of your phone system to the public telephone network, provided by a carrier. A cloud PBX, or hosted IP Centrex, is a hosted phone system shared among several customers, each seeing only its own part.
Remember one rule: an IP PBX can be on your premises or at a third party; UCaaS is always a service operated by a third party. Many UCaaS offerings are in fact built on an IP PBX, plus a set of applications around it.
Both are hosted. They do not answer three questions in the same way.
| Question | Shared cloud PBX | Hosted dedicated IP PBX | On-premises IP PBX |
|---|---|---|---|
| Who administers it | The provider; you configure your part | The provider or you, depending on the contract | You or your installer |
| Neighbors on the machine | Other customers | None | None |
| Power outage at the office | The phone system remains reachable | The phone system remains reachable | The phone system stops, unless there is a UPS |
| Updates | Provider, at the platform’s pace | Provider, can be scheduled for you | You or your installer |
| Exit | Export as provided for by the platform | Isolated configuration and data, easier to extract | Everything is on your premises |
A dedicated system isolates the organization: a configuration error or an overload at another customer does not affect it, and data is not mixed. It does not change the question of who the operator is. A dedicated server is still operated by someone, who can restore it and can therefore access it.
Hosting the phone system on your premises gives you control over the hardware, the network and the timing of updates. That comes at a price, which must be read in full.
Self-hosting is not automatically more sovereign. If a provider administers the server remotely, it has access just as a hosting provider would. The guide What is a sovereign cloud? sums it up: what matters is the operator, the law that applies to it and the exit, more than the building.
On-premises installation is justified when a network must remain isolated, when data must not leave a location, or when an in-house team knows how to operate it.
It is poorly suited to a small organization with no one to keep up with updates, or to teams that are often out of the office.
The question is not about the term VoIP. It is about two things: the company that operates the phone system, and the path the communications take.
For the operator, the criteria are those of any data entrusted to a third party: its nationality, the law that applies to it, its subcontractors, the traceability of its access. They are developed in Protecting a company from the CLOUD Act and European cloud or American cloud.
For the path, one limitation must be accepted: a call to an external party crosses carrier networks that neither you nor your provider control. You can choose the phone system’s operator and encrypt the path up to it. The rest of the route depends on the carriers.
Two setups are possible.
Three criteria help you choose.
How to actually connect multiple sites to Klytic Tel is described in Connecting multiple sites to Klytic Tel.
No. VoIP refers to transporting voice over IP. SIP is the protocol that sets up and ends calls in most IP phone systems.
Neither more nor less by nature. It all depends on the operator, the isolation of your data and the anti-fraud controls. See Securing IP telephony.
Not necessarily. An IP phone system can connect to the existing carrier if the connection is compatible.
Yes, through number porting, which transfers a number from one carrier to another. See Connecting multiple sites to Klytic Tel.
Klytic Tel is a dedicated IP PBX, operated by Klytic, with applications around it. Each organization has its own phone server. It is hosted by default in a European cloud, in Mauritius or in a geographic zone compliant with the applicable jurisdiction, at your request, or installed on your servers. In all cases, Klytic operates it. In the cloud, Klytic Tel relies on a leading cloud hosting provider, with an enterprise-grade availability commitment of 99.99% (excluding planned maintenance announced in advance) and failover between several hosting sites in the event of an outage: resilience to outages is very high. Klytic can also deploy the solution with another cloud provider of your choice. Klytic is operated by Dedicace Software, a French company.
Four line types can be combined on this server, each including the previous one:
A physical phone is not required; desk phones are available for rent and replaced if broken. Your numbers can be ported. You can keep your carrier, subject to compatibility, or take Klytic’s landline and mobile calling plans. For multiple sites, Klytic Tel works with a single server for all sites, or with several servers, each associated with certain sites and connected to one another, which makes internal calls between sites free and secure.
Klytic Tel is not a SecNumCloud-qualified offering. Nor is it a feature-for-feature equivalent of an American communications suite: compare based on your actual usage.
Consulted in October 2026.
Tell us how many lines and sites you have: we will propose the right configuration.
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