What is SIP?

What is SIP?

This article covers SIP, IP PBX and SIP Trunking. If you’re looking to learn more about Voice over Internet Protocol (VoIP), you might like our article The Ultimate Guide to VoIP.

So, back to the question, what is SIP?

Well, take a deep breath because this topic could put anyone to sleep, even us SIP experts. But if you’re up for the challenge, we’ve done our best to cover the main points and give you some insight into SIP, SIP trunking, and IP PBX.


Session Initiation Protocol (SIP)

Put simply, SIP (Session Initiation Protocol) is a virtual version of the old analogue phone line. 

In order for VoIP calls to function correctly and handle multiple participants, VoIP services require SIP. 

SIP uses requests and corresponding responses to communicate and establish a call session, with SIP trunks essentially functioning as a ‘phone-line’ for VoIP services.

It allows multiple users within an IP network to create, modify, and terminate sessions for two-way or conference calls.


How does SIP work?

SIP routes phone calls over the internet so that each VoIP user can send and receive calls. 

SIP runs these phone calls by first setting up the call, which contains all the information necessary for users to begin talking to each other. 

Once the call has begun, a new set of protocols are used to wrap the voice data into ‘packets’ which are sent to other users and unwrapped once they reach them.


What is a SIP Trunk?

SIP trunks are essentially groups of phone lines and so provide additional capacity to your system and make it easier for businesses to scale up when the time comes.

The name ‘trunk’ comes from the telecom world and it means, more or less, a group of phone lines. Each SIP trunk supports SIP channels. A SIP channel is equivalent to one incoming or outgoing call. 

A SIP trunk can hold an unlimited number of channels, so your business only needs one SIP trunk no matter how many concurrent calls you expect.

One way to think about this is to think of the SIP Trunk as the trunk of a tree, with the SIP lines being the branches.

SIP trunking also allows an Internet Protocol Private Branch Exchange (IP PBX) such as 3CX to be easily integrated for business use as SIP trunks lower price as they are entirely digital and not physical hardware that has to be installed.


Differences between SIP trunking and VoIP

SIP trunking is the process by which phone calls can be made and voice data exchanged on the internet. On the other hand, VoIP is a service that works by using SIP trunks to transfer voice data to other users so that phone calls can be made.


What is an IP PBX?

An IP PBX is an online business phone system that uses the internet to send voice data, the PBX is the central switchboard for the business phones. 

The IP PBX is an important part of most VoIP systems, containing an IP PBX server (essentially a proxy server), VoIP phones, and sometimes a VoIP gateway for modifying analog phone calls into IP traffic. 


SIP Trunking: the way of the future?

IP Telephony is replacing the Public Switched Telephone Network at a rapid rate, which means more and more businesses are leveraging the flexibility and affordability of SIP trunks. 

Some small businesses are still relying on physical copper phone lines, rejecting modern IP phone systems and SIP trunks due to confusion or unavailability.

In Australia, there will eventually come a cut-off date for all traditional copper lines as they are replaced by the NBN rollout

This barrier could be costing them in both productivity and profitability, and at some point, most growing businesses that require rapid real-time or simultaneous communication will need to at least consider, if not upgrade to, an IP Telephony system.


Need to know more about SIP?

Congratulations on making it this far! You have either fallen asleep on your keyboard or are very interested in SIP. Either way, you shouldn’t need to learn more about SIP for your business. We’re sure there’s plenty of more interesting things you could be doing with your time. 

Instead, what you might need is an expert team who can provide you with 3CX supported SIP services for your business. C2 Communications’ SIP trunks were the first company to bring 3CX SIP services to Australia over 10 years ago.


Contact us today for a quote.

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