Skip to content

What Is Demarcation Point? Definition & How to Use It



What Is Demarcation Point Definition & How to Use It

Today, with the availability of internet connection and other advanced technology, it has become easier to communicate and keep in touch with others who are miles far away from us.

But have you ever thought about the point at which your internet and telephone network service ends and the service provider begins?

That point is called the Demarcation point. It can really affect how well your connection works and who is responsible for problems.

Learning about Demarc will help you understand your internet and phone service better.

In this article, we’ll focus on what a Demarcation point, aka Demarc, is, its history, and its extensions. We’ll also talk about how Demarcs are used and their different types.

What is Demarcation Point?

The demarcation point or Demarc, refers to the specific location or physical point within a  physical wiring at which the responsibility of telecommunication companies ends for providing their network services, including telephone network and the responsibility for the customer premises equipment begins.

Suppose you’re at your home and have an internet connection from a service provider. You have your own device, access point, and router, and the service provider has their own network. But, there is a line that comes from the service provider, such as fiber optic internet lines, to your home. The point where this responsibility of the service provider ends and the responsibility of your network begins is basically the Demarcation point. 

Inside your home, all of the responsibility is up to you. Your devices belong to you, and if something goes wrong with your devices, you have to take responsibility. From the demarcation point to the other side, if anything goes wrong, if the service provider network goes down, for example, or if there are other types of failure, all of those failures are basically the service provider’s responsibility. 

That’s what defines the Demarcation point: the responsibility on your part and the responsibility on the service provider’s part.

Telcom History of Demarcation Point 

The concept of the demarcation point originated due to AT&T’s long-held monopoly over the U.S. telecommunications industry in the late 19th/early 20th century. 

As the dominant provider at that time, phone companies like AT&T owned customers’ entire telephone systems through subsidiaries, from the network to the customer’s network termination unit. 

However, beginning in the 1950s, various lawsuits challenged this monopoly power. Ultimately, a 1974 antitrust case led to a 1982 settlement requiring AT&T to divest its ownership of local telephone networks. 

As a result of this breakup of the Bell System taking effect in 1984, customers could now obtain service and equipment from alternative providers besides AT&T. 

This need to distinguish responsibility boundaries between the networks and property of telecom providers versus subscribers gave rise to the demarcation point. 

It served to clearly define where a company’s infrastructure ends and customer premises began, now that the industry was open to free market competition.

The emergence of integrated services digital network (ISDN) technology in the 1980s further increased demands on clearly defining network boundaries at the demarc point.

Uses of a Demarcation Point

The key purpose of a demarcation point is to clearly define responsibilities between the service provider and customer networks. It determines whether issues are the customer or provider’s responsibility to fix. 

Additionally, it has other uses, such as:

  • It terminates incoming communication lines from services like phone, internet, fiber, VoIP, etc.
  • It separates public infrastructure from customer premises for legal and liability clarity.
  • It allows for third-party device connections and choice of multiple providers.
  • It enables isolated access for maintenance/upgrades without disrupting full network operations.
  • It facilitates performance monitoring, security implementation, and network optimizations.
  • It protects customer equipment and wiring from electrical surges.
  • It provides flexibility for repairs, upgrades, and reconfigurations when needed.
  • It aids in troubleshooting by allowing easy disconnection from provider networks.
  • It provides a standard interface point for connecting various local access providers like cable Internet, fiber networks, etc.
  • It provides flexibility for a business or individual customer to make repairs, upgrades, or reconfigurations as needed.

Different Types of Demarcs

The three most common Demarcs for business phones are Network Interface Devices, Smartjacks/Intelligent Network Interface Devices, and Optical Network Terminals. 

Listed below are each of their features and benefits:

  1. Network Interface Device (NID)
  • Basic outdoor box for weather protection that the telephone company would install.
  • Contains wiring termination, surge protection, and test jacks
  1. Smartjack/Intelligent Network Interface Device (INID)
  • Slightly more advanced than a NID
  • Features digital circuit boards to boost signal strength
  • Enables remote alarms and monitoring
  • Enables companies to easily add new business phone system features without costly construction work.
  1. Optical Network Terminal (ONT)
  • Used for fiber optic network connections
  • Transmits signals using light over fiber optic cables
  • Provides much faster transmission speeds than copper
  • Requires external power source but includes battery backup
  • Converts light signals to electrical for connection to the customer’s private network devices

Key Differences:

  • NID is the most basic, while ONT supports the highest speeds
  • INIDs and Smartjacks offer some digital enhancements
  • Technology choice depends on network services and capabilities needed

Overall, the demarcation point type selected will vary based on installation requirements for business telephone and data communication networks.

What are Demarcs Extension?

Demarc extension involves physically connecting a business’s internal network to the demarcation point where a telecom provider’s services are delivered. This is necessary for organizations requiring internet and phone connectivity both within and outside the company. 

Demarc extensions are commonly needed when constructing new buildings or offices or bringing network services to tenants. 

The process involves installing cables to bridge the gap between the demarcation point and customer equipment when they are not co-located, such as in high-rise buildings or large commercial campuses where the demarc may be farther from the network.

Proper demarc extensions ensure reliable transmission and isolate any issues to the correct network domain, either the provider side or the customer side.

As mandated by federal law, all telecommunication carriers must hand off their circuits to each subscriber, leaving their service at the building’s demarcation point, usually, a ground floor telecom room.

From this point, the demarc extension is the subscriber’s responsibility to extend their telecommunications circuit to their suite or network room and begin using the circuit.


In the end, having a clear demarcation point ensures there is no confusion over whether the customer or service provider needs to address and resolve problems with the network, wiring, devices, etc.

It started because things used to be only one company running everything, but then other companies wanted to compete too. 

So they needed to make clear rules about what each company and customer owns. Whether it’s a basic cable box outside, a fancy fiber box, or running new wires inside a big building, keeping the demarc point simple is key. It helps services work right, protects people from legal trouble, and lets new tech keep getting better as networks evolve. 

As long as everyone understands where the network ends and the network boundary point lies, users can keep full control over their connections while taking advantage of deals from providers through this standard process. The demarcation point makes communications fair and reliable for all.


What do you call the demarcation point for fiber technologies?

The demarcation point or demarc for a fiber optic network is typically a device called an optical network terminal (ONT) or optical line terminal (OLT).

How much does it cost to extend a demarcation point?

Demarcation point extension cost typically costs around $300 or more, depending on the complexity of the extension and local rates.

What do you mean by Demarcation Point?

The demarcation point denotes the precise physical location (physical point) where a telecommunications service provider’s public network infrastructure stops and a customer’s private internal wiring and devices start.

What is Global Demarcation?

A demarcation point is the boundary between a telecommunications provider’s network and a customer’s private internal wiring and equipment.

Global demarcation points can vary by country and region depending on local telecommunications regulations. For example, in the UK, the demarcation point is within a phone jack jointly owned by the provider and customer, while in Canada, it is typically a junction block connecting phone extensions within the customer’s premises.

To maintain the demarcation point, who is responsible?

The typical arrangement is that the service provider is responsible for maintaining the demarcation point until connection to the customer’s network. Once past the demarcation point and into the customer’s network, any maintenance activities or problems that arise will be the responsibility of the customer, not the service provider.

How can I find my Demarc?

Some locations commonly used as demarcation points include:

  • Outside the building, near the electric meter, for easy access by technicians.
  • Inside, near the electrical panel, providing an easily accessible area for supplier maintenance. 
  • Inside the wall where the telephone line first enters the house/building, providing a central location near the entry point.

The exact demarcation location can vary depending on the structure, but these areas are often chosen because they are accessible to technicians to work on the connection between the supplier and customer networks.

Follow our newsletter !
Subscribe to our newsletter & stay updated for the latest news.
Dinesh Silwal Co-Founder KrispCall

Dinesh Silwal

Dinesh Silwal is the Co-Founder and Co-CEO of KrispCall. For the past few years, he has been advancing and innovating in the cloud telephony industry, using AI to enhance and improve telephony solutions, and driving KrispCall to the forefront of the field.

Dinesh Silwal

Dinesh Silwal

Dinesh Silwal is the Co-Founder and Co-CEO of KrispCall. For the past few years, he has been advancing and innovating in the cloud telephony industry, using AI to enhance and improve telephony solutions, and driving KrispCall to the forefront of the field.

Related Blogs