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Why and how are SIP Trunks and SIP Lines different?

William DawseyBy: William Dawsey


Telecom software has transformed the way phone calls are made in the world of business, education, and even at home. With the rise of ubiquitous high-speed internet, developers have found ways to transfer calls through network packets rather than outdated landlines.

After all, physical phone lines only support throughput of up to 56 kilobytes per second while inexpensive modern internet lines often support a capacity of over 50 megabits per second. Therefore, routing calls through the internet has the potential to improve audio quality while enabling greater customization and security with the help of modern software.

Unsurprisingly, a host of software developers have created programs and applications that solve almost any problem that a client might be facing. Modern telecom software solutions can enable a single system to control thousands of phones throughout an enterprise and allow for a very high level of scalability.

Telecom software development customizes communications through landlines, smartphones, and VoIP calls. Existing telecom solutions can be deployed immediately by most providers, but solutions exist that enable businesses to optionally enjoy full customization through an application layer.

What are SIP Trunks?

Today's phone systems have become much more reliable and efficient because of new technologies. With conventional telecom services, human operators had to manually connect phone lines to enable callers to reach each other. When callers had to speak to an operator, calling costs were much more expensive. In later periods, computerized systems were developed that could connect lines without requiring the assistance of an operator.

However, boxes with mazes of cables coming from every active line still had to be used to route calls. In many companies, so many lines were used that people in the telecom industry referred to the thick web of cables as a trunk. This trunk of wires was very expensive to maintain and customization was expensive. Worst of all, the necessity of manually moving wires meant that maintenance could lead to outages that lasted days.

Modern SIP trunks completely disrupted traditional call routing by moving the trunk of phone lines to a server where call routing could be virtualized by telecom software solutions. Today's SIP trunks now take full advantage of server technology to enable calls to be routed over more efficient internet connections while still acting as a bridge to send and receive calls through old landlines when necessary. Best of all, SIP trunks open up new possibilities since they can be modified to meet the precise needs of your business with custom telecom solutions.

SIP trunks also act as a bridge for companies that use an internal PBX system, a private telephone network that operates internally within an organization. By bridging the gap between older phone technologies and modern VoIP calling, SIP trunks now power most voice communications for enterprises and even small businesses.

What are SIP Trunks?

What are SIP Lines?

SIP lines are the individual phone lines that go into an organization's SIP trunk. As with conventional phone lines, all phone users within a company can be assigned their direct number. However, since phone lines in a SIP-based system are completely virtualized, there are zero infrastructure costs associated with each line. Businesses sometimes have to pay a very nominal fee per number to cover the cost of registering each phone number, but there are no installation or maintenance fees associated with installing any physical landlines.

SIP lines are different than ordinary telecom services because they are not bound to a particular phone number. Since each phone number is virtualized, it can be dynamically assigned to whatever SIP lines are available when a call is placed. Therefore, organizations can save money by increasing their line utilization.

Telecom solutions can even be used to route calls from cell phones and computers through SIP lines. In this way, businesses can get more control over calls that are placed by members of their organization to enhance security and achieve legal compliance.

It is important to keep in mind that SIP lines are not needed when internal calls are made between members of an organization. In most large organizations, the majority of call volume is internal. Therefore, the savings associated with moving over to SIP-based systems can be even greater than many organizations might believe at first glance.

What are SIP Lines?

Differences Between SIP Trunks and SIP Lines?

The difference between SIP trunks and SIP lines is not huge, but the distinction should still be understood by businesses that implement SIP-based systems. The bottom line is that SIP trunks act as call routers and efficient bridges between a company's phone system and the outside world. SIP lines, in contrast, are the individual lines that go through the SIP trunk.

It is important to understand the distinction between SIP trunks and SIP lines when you are planning how many lines your organization will need. In most cases, you will want to analyze historical data to see how many lines are being utilized at any given time and how much capacity is used during peak periods. In many organizations, less than 20 percent of lines are being used at any given time during peak periods.

You should be conservative when deciding how many SIP lines your organization should have to avoid running out of capacity. However, if your organization is worried about running out of capacity during an event that might cause a record spike in call volume, you should keep in mind that there are custom telecom solutions that can provide overflows to protect your business.

SIP Trunks vs. SIP Lines

SIP lines and SIP trunks are both needed to make your company's SIP-based calling system work properly. When implementing a SIP-based solution, it is crucial to do your research to ensure that you use a system that matches your needs. If you have unique needs, you can use telecom software development to fully customize your solution to support a broad range of additional functionality to get more control over how your calls are placed while obtaining more data that can be used by your organization. Overall, SIP-based calling solutions can help to modernize the communications of your business while adding to your bottom line by dramatically reducing costs.

Knowing the difference between SIP Trunks and SIP Lines matters when it comes to creating and pricing your phone service. Learn all about SIP Trunks and SIP Lines and which option will benefit your customers or company better.


Chetu, Inc. does not affect the opinion of this article. Any mention of specific names for software, companies or individuals does not constitute an endorsement from either party unless otherwise specified. All case studies and blogs are written with the full cooperation, knowledge and participation of the individuals mentioned. This blog should not be construed as legal advice.

Chetu was incorporated in 2000 and is headquartered in Florida. We deliver World-Class Software Development Solutions serving entrepreneurs to Fortune 500 clients. Our services include process and systems design, package implementation, custom development, business intelligence and reporting, systems integration, as well as testing, maintenance and support. Chetu's expertise spans across the entire IT spectrum.

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