SHDSL What is it?

A beginner's guide to SHDSL and SDSL

How does SHDSL differ from SDSL?

There is a lot of confusion about what differentiates SHDSL from SDSL but it's actually much easier to look at what they have in common.

Both are digital subscriber lines offering faster data speeds over traditional copper telephone lines than a voiceband modem.

Both are symmetric meaning that, unlike asymmetric lines, upstream and downstream bandwidth is identical.

And perhaps most importantly of all, both are significantly cheaper to implement than dedicated leased lines.

So those are the similarities but what about the differences?

Well, a Single-Pair High Speed Digital Subscriber Line or SHDSL is a standardised term that applies throughout Europe.

The Telecommunication Standardization Sector (ITU), the leading UN agency covering ICT issues, has been creating industry-accepted technology standards for more than 150 years.

It first set out what constitutes SHDSL in the ITU recommendation G.991.2.

Meanwhile, a Symmetric Digital Subscriber Line or SDSL is actually just a variation of SHDSL that is also used in Europe.

The European Telecommunications Standards Institute (ETSI), an EU-recognised organisation covering ICT issues, has been providing a separate set of technology definitions for more than two decades.

It standardised a subcategory of SHDSL under the name SDSL.

The key thing to note, however, is that SDSL is fully compatible with SHDSL.

So as you can see, there is plenty of common ground and businesses should not worry unduly about the minor differences between SHDSL and SDSL.