what is sip protocol

What Is SIP Protocol? +9 Frequently Asked Questions About SIP Trunking

Session Initiation Protocol (SIP) is a very common protocol. While most people may know what is SIP protocol from Voice Over Internet Protocol (VoIP), many businesses are now implementing it as a business standard telecom system called SIP Trunking. This is mainly due to the cost advantages and the ability to update and boost revenue at the same time. Many see it as a win-win!

SIP Trunk phone systems are versatile, easily upgradable as well as expandable, and have a failsafe system that covers you even in the event of an outage by rolling over to mobile devices. Now, this is just for starters, keep reading to learn more.

What Are SIP Trunks?

Do you remember ISDN? Well SIP Trunks are a modern version that many organizations are now using to make phone calls and more. SIP Trunks can be connected to your PBX (depending on how old it is), just like the ISDN had been, and then to the Public Switch Telephone Network (PTSN). It does this for a lot cheaper than ISDN used to and is more efficient, too.

What Is SIP?

SIP is an abbreviation for Session Initiation Protocol. While many people are just learning about SIP, it was designed in 1996 by Mark Handley and his team. Later it received approval from the Internet Engineering Task Force (IETF). It is an IP standard established by the Internet Engineering Task Force. There are many protocols that can be used for VoIP, but SIP is the most common and widely used.

Did you know that SIP is a text-based protocol and works very similarly to HTTP? While HTTP controls webpages, SIP does the same for calls and messaging. It establishes how a session starts, is set up and ended. When you make a VoIP call it is SIP that is establishing the connection, end to end.

What is SIP Trunking?

SIP Trunking is a service offered by companies that are resellers or providers for communication services. SIP Trunking is deployed all over the world and more recently many traditional providers, like Verizon, have phased out ISDN altogether.

SIP Trunks are the software used for VoIP calls. The SIP Trunks bring the two domains together enabling this communication.

When SIP trunking is set up over existing ethernet or Multiprotocol Label Switching (MPLS) network infrastructure, the cost drops as well as the management complexity associated with legacy digital platforms.

What is SIP used for?

SIP is primarily used for initiating, maintaining, modifying and terminating real-time sessions (connections) that involve video, voice, messaging and other communications applications and services between two or more endpoints on networks over I.P. (internet protocol).

How Can Switching to SIP Trunks Benefit Your Business?

When you switch to SIP trunking, phone calls travel over the Internet like other forms of media. In the same way that you don’t pay for each individual email, you send to a colleague, calls made between employees in your company are free.

It doesn’t matter if they’re located in different offices or one of them is working from home. Even long-distance calls cost a lot less since the call travels over the PSTN for a short distance.

How Does It Work?

Business phone systems have traditionally been comprised of two components. A PBX that handles the call management and features like Auto Attendants, Voice Mail and PRI lines that route calls to the PSTN from where the get connected to their final destination phone number. If SIP trunks are present there will be an IP enabled PBX connected to a network instead of PRI lines and voice calls are then sent over the internet to reach the PSTN.

There are also options for business with older PBX systems. Analog adapters or SIP to T1 gateways. Worth checking into for any business considering a move to SIP.

What Are The Key Characteristics of SIP Trunking


The SIP protocol has five characteristics it uses when establishing and determine multimedia sessions:

1. User Location

Users and endpoints are detected with a single identifier called a uniform resource identifier (URI):

2. User Capabilities

The media and media parameters to being used.

3. User Availability

Check whether the called party can take the call.

4. Call Setup

Establish call parameters.

5. Call Handling

Transfer and termination of calls.

What Are The Benefits of SIP Trunks

More organizations are implementing SIP as it offers scalability and flexibility, at an affordable price.

If you are considering the switch to SIP already, I’m sure you are family with the cost advantages. If your company makes a lot of long-distance or international calls, the savings can be astronomical.

While these aspects are attractive there are a lot of benefits aside from financial. Here’s a look at 10 of the most common ones:

1. Cost Savings

With a traditional phone company, you may need a translator to decipher the myriad of charges that appear on your monthly bill. Often it’s like reading a foreign language. On SIP, firms usually enjoy a stable, predictable monthly bill. In fact, most companies report having saved 50% or more after the switch.

2. Immediate ROI (Return on Investment)

Since it has a low to no investment to startup, companies get a return almost immediately.

3. Global Potential and Mobility

With the system being network and internet-based, supporting remote workers and global offices becomes simplified.

4. Unified Communications

Selecting a provider that offers a powerhouse of communication tools like video conferencing and fiber-optic internet, your company can take advantage of IP Based services including Unified Communications As A Service (UCaaS).

5. Mobility

With SIP your employees can be always connect using their devices with flexible, user-friendly VoIP apps that can be securely installed. This feature of SIP and VoIP also provides organizations a failsafe way to maintain communications should their internet line go down.

6. Network Consolidations

SIP trunking allows organizations to group their voice and data into a single network where voice calls get treated as data transmissions.

7. No Expensive Hardware to Buy

This also relates back to number 7. With SIP trunking you don’t need any more hardware purchases. Your SIP provider simply scales your monthly service when you need to add phone lines or add-on services. It’s as simple as purchasing an additional handset.

8. Reliability

While a regular phone system can face interrupts for many reasons, SIP is reliable. With a SIP provider that offers mobile-failover for redundancy, your mobile devices take over in the event it’s needed.

10. Simple Management

SIP trunking and VoIP phones have easy-to-use management portals for on-site administration. Everything from adjusting call routing, changing extensions, or adding phone lines completely on-demand.

What You Should look for in a SIP Trunking Provider

So, you’re ready to make your move but aren’t sure which provider is the right one for you. There so many out there, but how to shortlist them?

There are a few key things you should look for when searching for a provider to ensure you make the best choice for your company.

1. Do They Offer a User-Friendly Control Panel?

A SIP trunking platform’s control panel should be powerful, and yet still easy to use. The control panel is where you can manage calls, contacts, services, billing, and get call data records.

2. Outbound Dialer

SIP trunking providers very often can’t handle automated outbound dialing and telemarketing traffic. Still, these features can be important for growing your business. Make sure to check for this feature.

3. Simple Pricing

If any provider you contact is providing complex pricing quotes along with other fees, walk away.

4. Flexible Internet Service

If a provider tries to bundle their internet service into the package, look for one the lets you decide your own internet service provider.

5. Fraud Protection

Another important thing to look for when searching for a SIP service provider is fraud protection, especially international fraud protection. Check that they have real-time protection that will catch call frauds and stop them immediately.

6. Voice Quality

Look for a SIP provider who can ensure that your users can send and receive phone calls efficiently and clearly. One that works with Tier-1 voice carriers and doesn’t use Least Cost Routing (LCR), which compromises quality for cost.

7. Interoperability

If your company has already invested in a phone network, you look for a provider that can offer interoperability with your existing infrastructure. A good SIP trunk provider should be able to do this.

8. Good Customer Support

Business communications are a 24/7 business, which is why 24/7/365 support shouldn’t be optional. Look for a provider who agrees.

Choosing SIP For Your Company

The SIP protocol was designed to be very simple and it is. It is being adopted by many businesses in various industries. There is a lot of information to firms trying to make the move and it can be complex.

With traditional telephone companies phasing out ISDN, SIP is the better option for most companies. Easy to set up, expand and manage without extensive equipment or overhead costs.

This has made migration to a SIP Protocol system a simple choice for most businesses. Learning what is SIP Protocol isn’t difficult anymore. Providers like SIP.US are ready to step you through all the details, so you can get your SIP setup now.

Free SIP Trunk in 60 Seconds

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