Introduction To SIP

“To ask the value of speech is like asking the value of life.”– Alexander Graham Bell

People today have more options for communication than ever before in history. Voice, text, and video can all be delivered across the world in real-time, all while transcending both traditional voice and data networks.

Since Alexander Graham Bell and the opening of the long-distance line from New York to Chicago in 1892; the traditional switch-based telephone system has been the main medium for transmitting communication. However with the relatively recent advent of the Internet and IP based systems, the need was felt to design a new phone and communications method and ‘backbone’ to take advantage the improved networking and advanced technologies.

Enter VoIP. VoIP, at the absolute most basic level, is the ability to make traditional phone calls and to communicate using the traditional devices (telephones, video etc.) except using digital communication lines.

Key Definitions:

PSTN –Public Switched Telephone Network, like the ones Alexander Graham Bell helped to build

VOIP – Voice over Internet Protocol, is a method for taking analog audio signals, like the kind you hear when you talk on the phone, and turning them into digital data that can be transmitted over the Internet.

SIP – Session Initiated Protocol, a protocol within VOIP

SIP Trunk – A connection between your network (or PBX) and an ITSP.

ITSP – Internet telephony service provider (ITSP) offers digital telecommunications services based on Voice over Internet Protocol (VoIP) that are provisioned via the Internet.

IVR/PBX – PBX stands for Private Branch Exchange, which is a private telephone network used within a company. Interactive Voice Response or IVR is a telephone technology allows customers to interact with the company’s host system through configurable voice menus, using DTMF tones in real time

What is SIP?

Session initiated protocol is a type of open signaling procedure used in controlling communications in real time (including voice and video over the internet.) It can be used for instant messaging, multimedia conferences Enhanced 9-1-1 calls and other real-time communication services as well. The direct connection between you and your internet telephony service provider (ITSP) is the SIP trunk. Using this, you can connect beyond your networks firewall.

Potential Cost Savings and Other Benefits

In an article by Brad Reed of Network world, Nemetes Research analyst Irwin Lazar estimates that companies with SIP trunks save 20% to 60% compared of TDM trunks. Forrester Consulting also reports that many achieve a 40% to 60% reduction in monthly services using SIP Trunks. SIP trunking can be fine-tuned to a business’s needs. The scalability is one of the most-appreciated features as your business can increase the number of voice sessions on an as-needed basis. When using a tradition PRI trunk, you would have to install new hardware and provide additional circuits. Another cost benefit is the reduction in long distance fees—when you are contacting your other offices or branches via your data network.

Connecting to the PSTN

To talk to anyone on a PSTN (Public Switched Telephone Network—the traditional phone) network, a SIP session will cross over to the PSTN for the last leg of the journey. There is a physical switched owned by large telephone companies that convert SIP sessions into PSTN calls and vice versa. All this happens behind the scenes and users never notice. An onsite PBX or IVR (the message and menu service that users receive when they call) can be used with an SIP too. These are often hosted from the cloud to make things even simpler.

Today, more companies than ever are using SIP to connect with others in and out of the firm. The major telcos, small communication companies, call centers and even small businesses with just a few lines use SIP because of the cost savings and ease of use. Once you see how simple the process is to switch, you may find that it is an excellent solution for your firm as well.

 “The day will come when the man at the telephone will be able to see the distant person to whom he is speaking” – Alexander Graham Bell (c. 1906)