SIP Calling Explained: Everything You Need to Know

7 min readMar 9, 2021

Good communication is key for business success, and this is not exclusively dependent on your employee’s skills, but also on your business phone system setup and other communication channels. Are you still losing your money on inefficient traditional phone systems? Maybe it’s time for a switch.

Many companies are switching to Voice Over Internet Protocol (VoIP) phone systems. It’s an internet-based solution that reduces your costs and improves your business’ efficiency. To use VoIP’s features to its full potential (for example sending chat and media), a Session Initiation Protocol (SIP) is used as one of the most adopted signaling control protocols.

What is SIP calling? And how do SIP calls work? Keep reading and you’ll find out everything you need to know about the SIP protocol.

SIP Calling Made Simple

SIP calling allows companies to make local, national and international calls just by having an internet connection.

Imagine you walk by a friend that’s looking down at their smartphone when walking, you call their name in order to get their attention and the conversation starts by effusively saying hi at each other. You talk about how long it’s been since the last time you met and quickly catch up with what you’ve been doing lately. You both have to continue walking your path, so one of you makes a signal that the conversation should now end, you say goodbye and continue down your path.

This is a very easy way to understand SIP calling; SIP is a signalling protocol that sets up an IP communication session, AKA a phone call through the internet. It contains all the rules and instructions in order to start a session by signaling the other party about your intention to start a communication flow. In our previous example this is the part where you call your friend by their name to catch their attention.

Then, it determines the channels and rules through which the communication will be carried out from one party to the other, this is the part where you catch up with your friend. And ultimately, it gives the signal of when the conversation (aka the session) must stop, meaning the IP phone call has ended.

With SIP, you can run your voice calls, make video conferences, share files, and chat with your team members and customers without using cellular data. To take full advantage of these features, let’s break down how SIP calling works:

How do SIP Calls Work?

As mentioned before, SIP is a type of protocol that is used for establishing multimedia communications.

To get a deeper understanding of how SIP calling works, let’s review the parts of a traditional phone system:

PBX (Private Branch Exchange): The on-premise system that manages your calls
PRI (Primary Rate Interface) lines: PRI is a voice-only connection dedicated to connect calls to the PSTN.
PSTN (Public Switched Telephone Network): Its function is to route calls to their destination

With SIP calling, you can skip the PRI lines. The SIP trunk virtual installation together with your Internet connection will connect your PBX directly to the PSTN. Hence, a faster and more cost-effective way to make and receive calls.

Moreover, SIP calling enables companies to use call management features such as call forwarding, instant messaging, voicemail, and auto attendants. It allows for multiple communication sessions, making it an ideal solution for startups, small businesses, and large companies.

Benefits of SIP Connectivity for Business

You’ve already learned that SIP phone systems are cost-effective and help improve your business communication. Here are additional benefits of SIP calls.

It Reduces Costs

SIP trunks provisioned virtually and can be increased and decreased as needed. This means that you won’t need to pay for physical on-premises phone lines. You won’t have to make constant hardware purchases to scale your systems, and you’re getting rid of maintenance costs, which results in massive savings.

To give you an idea, small businesses that switch to a SIP Calling network can save up to 40% on their local calls and up to 60% on their international calls

Moreover, SIP calling reduces your costs by:

Eliminating complex installation steps
Eliminating the need for multiple networks
Eliminating multiple subscription fees
Eliminating phone bills and their extra charges
Reducing your maintenance costs

If you’re a startup or running a small business, you should definitely consider switching from a traditional phone system to a SIP cloud solution.

Provides Insightful Data

There are SIP features that allow you to track and route your calls automatically. A SIP phone system can identify user location, user availability, and media capabilities. You may also record your calls and easily search, categorize and access those recordings.

All Your Communications in One Place

Whether your team is working remotely or at the office, managing your communications is easier with SIP calling. Aside from audio calls, SIP provides instant messaging, video conferencing, call routing, and chat support.

Your team members can answer calls literally anytime, anywhere. Plus, you don’t need to switch between communication channels because everything is centralized and synchronized in a single system.

Flexibility and mobility are important for every business in today’s world. They enhance your team’s productivity and improve the quality and quantity of customer interactions. With SIP calling, all communications are unified, and everyone is reachable not just on telephones but especially on mobile devices.

Scale Up Your Business

SIP calling allows easy scalability. Thanks to SIP you can deal with as many channels as your business requires, and add or reduce them in the future as well.

It’s also easy to access call recordings and voice analytics, all you need is a solid Internet connection. Technically, all carrier services are possible on the SIP protocol.

Is SIP Calling Free?

We’ve been talking about reducing costs and increasing savings. But another question still remains: “is SIP calling free?”

SIP calling is cheaper than traditional landlines but it’s not free. You need to pay for a VoIP service or SIP phone system that will be your main provider. You also need to pay for connection since SIP is powered through the Internet. Once you have this figured out, you can now enjoy your SIP advantages. These include:

Making and receiving calls on any devices (landline, smartphones, laptops, and tablets)
Making long-distance calls and international calls at reduced cost
Collaborating with video chat and messaging

Are you thrilled about the perks that SIP phone systems offer? Read the next section to learn how to switch from traditional landlines to SIP calling.

How to Switch to SIP Calling?

Unlike traditional phone systems, SIP phones can perform independently without a desktop or computer. Hence, switching from traditional systems to SIP makes your call handling faster and easier. However, the process is different for Android devices and iPhones. Some factors should also be considered when switching to SIP calls.

Enabling SIP calls on Android:

To configure your SIP calling, open your Phone app and click the More menu.
Go to Settings > Calls > Calling Accounts > SIP accounts.
You can now enter your username, password, and SIP server.
If you don’t know your credentials, contact your VoIP or SIP provider.
You can also use your service provider App without the need to configure the android SIP client.

Enabling SIP calls on iPhone:

Download a SIP calling app from your App Store.
Open the app and enter your username, password, and SIP provider.
If you don’t know your credentials, contact your VoIP or SIP provider.

Factors to Consider:

Make sure your equipment or device will work with your carrier.
Update your carrier switches and caller ID.
Leverage into a Cloud-based PBX.
Some phone systems might require SBC.

Expanding SIP Calling with a Session Border Controller (SBC)

A Session Border Controller is a device that acts as a firewall for your VoIP and SIP networks. It’s purpose is controlling signaling as well as media streams on each call session. SBC is deployed to protect SIP-based Voice Over Internet Protocol (VoIP) networks from malicious activities including data theft.

Based on predetermined criteria, SBC can reject or allow calls to happen. For example, if you don’t want to receive any international calls because your operations are all domestic, with a SBC you can automatically block any international number and only let local calls to be received.

This device also helps you unify even further your business communications. For example, if you are using Microsoft Teams as your communication software, you can integrate it with your phone systems through direct routing SBC. You will then be able to make and receive phone calls through the MS Teams app, improving your internal communications and team productivity.

Get a SIP Calling System for Your Business

From calling international customers to building relationships with your team members, SIP systems can bring great benefits to your business. If you’re using the Internet regularly, then setting up a SIP system is a no-brainer.

Now, you might be wondering if you need a different phone number for this service. You can always keep your same phone number and port them to your new SIP provider or you can acquire a new phone number from your new provider that works the same way your traditional phone numbers work.

If you want to save costs while improving your business’ efficiency, you should take the plunge and try ULTATEL’s SIP trunking services. Staying old-school is costly, so enjoy the perks of new technology while they last. Get a SIP calling system for your business now!