sip protocol

Did you know that SIP trunking accounts for less than 50% of installed business trunks?

Communication is key to any business, so if you haven’t already then you might want to consider installing SIP trunks into your business.

But what is SIP protocol and how does it work? Discover all you need to know about SIP with our useful guide.

What is SIP Calling?

Session Initiation Protocol (SIP) involves a signaling protocol used to set up, connect, and disconnect communication sessions. Often SIP calling uses voice or video calls over the internet.

Having excellent customer service and communication skills within your business is crucial. A recent study found that 92% of consumers would stop purchasing from a company after three or fewer bad customer service experiences. 

SIP calling can ensure that your business is always available for your customers to contact you. SIP uses the Internet to deliver communication sessions, so you have a more reliable form of communication. 

Why is SIP calling more reliable? Well because, it isn’t affected by other factors, which means there’s less to go wrong. Whereas traditional phone lines can be affected by bad weather, which usually takes a long time to get fixed, SIP trunks use the internet and can have back-ups set up to ensure that even if your internet connection goes, you aren’t offline for too long. 

SIP calling can also work out a lot cheaper than traditional phone lines. Small businesses that switch to VoIP reduce the cost of their local calls by up to 40% and save up to 90% on international calls. The only thing you’re paying for, once the initial setup is complete, is the Wi-Fi that you use to place these calls and your unlimited SIP trunk subscription. 

How SIP Protocol Works

SIP is an application layer protocol and is the foundation of interactive communication sessions over the Internet.

A protocol is defined as a set of rules that defines how two (or more) devices (such as laptops, phones, routers, and network switches) communicate with one another. 

There are several protocols that take place on the Internet. For example, when you’re making voice calls over the internet, there are many protocols all working together to make this possible. These multiple protocols build on top of each other in layers and this is a protocol stack.

Protocol stacks come in many shapes and sizes. The easiest one to understand is the Open Systems Interconnection model. This one consists of:

  1. Application (SIP)
  2. Presentation
  3. Session
  4. Transport
  5. Network
  6. Data link
  7. Physical 

The transport and the application layer of the protocol stack are the most important parts.

The transport layer controls the speed, reliability, and order in which the data is exchanged. The data during a voice call is broken into packets and transported over the Internet. 

The application layer specifies the protocols that the software applications need to use to communicate over a SIP network connection.

What Does SIP Do?

A common mistake that people make is that SIP trunking provides all services of their communication sessions. However, it doesn’t. SIP sets up a call, conference or any other form of communication sessions, and terminates it once it is finished. 

There are five parts involved in the setting up and terminating of calls that SIP does. These include:

  • User location, this tells the protocol where the end system is that’ll be used for the call.
  • User availability, this tells the protocol whether the called party is available to take the call.
  • User capabilities, this is the determination of the media that’ll be used for the call.
  • Session setup, this involves the ringing from one user to the other.
  • Session management, this involves the running of the communication session, for example, the transfer and termination of the call.

SIP in Action: How Does SIP Work During a Voice Call?

Voice information needs to be encoded with codecs before it is sent over the internet. This is so that the audio signals can be translated into data. There are two main types of codecs that are used G.711 codec and G.729.

Encoded packets of audio data are transported using a real-time transport protocol (RTP). RTP has its own protocol application layer which helps with the transporting of audio and video data in real-time. 

RTP control protocol works with RTP to ensure that the information about the RTP packet delivery is being used and the quality of the voice service is good. 

The RTP and the SIP packets are then transported by protocols at the transport layer. This can either be done using a Transmission Control Protocol or User Datagram Protocol. User Datagram Protocol is better for transporting Voice over Internet Protocol (VoIP) calls. 

And finally, another application layer protocol works with SIP, because SIP is a media-independent application. This is known as the Session Description Protocol and this signals what type of media the SIP client sending the call and the client receiving the call can support.

Learn About SIP Protocol and Introduce it in Your Business Today

Now you’ve learned more about SIP protocol and how it works. Why not see if introducing SIP can help your business? Installing SIP trunks into your business is easy to do and you can try it for free. So, whoever you are and whatever you do, you have a fantastic form of communication for your employees and customers. 

Want to learn more about SIP and how it can improve your business? Then why not get in touch with us and see how we can help you. 

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