ISDN vs DSL: Here Are The Key Differences Between Them

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ISDN vs DSL: Here Are The Key Differences Between Them

According to Statista, there are more than 4.66 billion active internet users across the world – that’s about 60% of the global population. There’s no denying that everybody needs a fast connection to gain smooth access to the Internet. So, for you to determine the best “Internet speed” and “Internet connection,” one of the best approaches is to get yourself familiar with all the connections, understanding the distinction between them.

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In today’s world, there are several different connections that you can opt for, to connect your PC, mobile devices, or other devices to the internet. Two of the most widely used Internet connection options are ISDN and DSL. But here’s a question; what is the difference between these two internet connections?

ISDN is an acronym for Integrated Services Digital Network; it utilizes phone lines already in use to deliver data, voice, and video content over the digital phone lines. On the other hand, DSL, which stands for Digital Subscriber Line, uses existing telephone lines to deliver data to users at high speeds.

To fully understand which of the two internet connection options; ISDN and DSL, is better for you, it’s essential that you deeply understand the difference between them. In the rest of this post, I’ll make things easier for you by performing a detailed comparison between the two options using different factors, such as Internet speed, installation, and technology.

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What Is ISDN and What Benefits Does It Offer?

As you already know, ISDN or Integrated Services Digital Network is a type of connection that relies on phone lines in use to deliver data, voice, fax transmissions, etc., through digital copper telephone wires. The primary aim of the phone system is to help replace analog landline technology, making them more digital for human use.

The ISDN internet connection was first talked about in 1988. At the time, the UN-based International Telecommunications Union recommended it as a new system for companies to deliver data. However, it wasn’t until the 1990s before the first ISDN (National ISDN 1 or N1-2) was created.

Types of ISDN

There are mainly two different types of Integrated Services Digital Network out there; they are:

  • Basic Rate Interface (BRI)
  • Primary Rate Interface (PRI)

Since the BRI and PRI are the two types of ISDN, it’s safe to say that they have a lot of things in common. However, you need to understand that they also differ by a couple of factors.

As the name suggests, BRI is the lower tier of ISDN service; it only helps to address the basic needs – of course, at a lower cost. On the other hand, PRI represents the main ISDN service. Unlike the former, it offers much better connections and faster internet speeds.

Furthermore, BRI is only capable of delivering an internet speed of 128 Kbps over a standard copper line. However, that’s further broken down into 16 Kbps over the D channel and 64 Kbps over the B channel. On the other hand, if perfectly set up, the PRI service is capable of delivering twice the speed mentioned above.

What Is DSL and What Benefits Does It Offer?

Today, DSL or Digital Subscriber Line is one of the broadband internet access connections that replaces the ISDN connection. It is a digital transmission system that utilizes already installed copper telephone lines to deliver voice and data packets – usually at high speeds.

If you don’t know, the purpose of the high speed in the DSL technology is to prevent data from interfering with voice data. To make things simpler, the high frequency makes it possible for DSL users to utilize the phone and internet at the same time.

Pros & Cons of DSL


Digital Subscriber Line offers its users a lot of benefits. One of them, which I already pointed out earlier, is the ability to keep the Internet connection open while stile using your phone line for voice calls. Apart from that, DSL offers a very high internet speed.

Furthermore, DSL or asymmetric digital subscriber line (ADSL) as many people will call it, is widely available. Of course, that’s possible because the technology is built on existing phone lines.


Like every other type of internet connection out there, DSL also has its weaknesses. One of them is that you’ll most likely be able to enjoy the connection better when you’re pretty much closer to the provider’s central office. What that means is that the signal tends to become weak as you get farther away from the source.

Types of DSL

There are two main types of Digital Subscriber Line out there; asymmetric DSL (ADSL)  and symmetric DSL (SDSL).

The asymmetric DSLs, which are the most popular of all DSL connections, comes with a higher speed. However, they offer more network bandwidth for downloading data instead of sending data over the Internet. Furthermore, ADSL is available in various forms, such as ADSL,  ADSL 2+, ADSL Lite, R-ADSL (rate-adaptive digital subscriber line), and VDSL (very high bit-rate digital subscriber line).

On the other hand, the symmetric DSLs come with equal bandwidth for both uploads and downloads. It’s available in three different forms; SDSL, SHDSL (symmetrical high-speed digital subscriber line), and HDSL (high bit-rate digital subscriber line).

What Are the Differences Between ISDN and DSL


While there are several differences between ISDN and DSL, the key factor that differentiates the two of them is that DSL uses existing telephone lines alongside a modem. However, ISDN lines need to be installed since they require an adapter at each end of the wire.


Apart from their mode of installation, ISDN and DSL are also different because of the type of speed they deliver.

In case you don’t know, DSL Is a lot faster than ISDN. It’s capable of sending and receiving data with speeds as low as 128Kbps and as high as 100 Mbps. On the other hand, ISDN is only capable of delivering a maximum speed of 128Kbps.

The bottom line is, even the slowest DSL internet connection is faster than any ISDN connection.

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