What is SDSL and SHDSL?
The terms Symmetric Digital Subscriber Line (SDSL) and Single-Pair High-Speed Digital Subscriber Line (SHDSL) mean the same thing. They refer to a specific type of internet connection where the same bandwidth is given to both uploads and downloads.

Note: The two different names exist because two separate organisations introduced their own standards for this technology. The SDSL standard was approved by the European Telecommunications Standards Institute (ETSI), and SDSL was approved by the International Telecommunication Union (ITU).


How is SDSL/SHDSL different to normal internet connections?

When we talk about standard internet connections, we are usually talking about Digital Subscriber Line (DSL) connections. DSL allows data to be transferred over existing wired telephone lines and is allocated to higher frequency bands to avoid conflicts with data from analog calls. 

The term DSL most commonly refers to Asynchronous Digital Subscriber Line (ADSL) technology. In this type of connection, more bandwidth is allocated for downloads from the internet service provider to the user, making downloads quicker than uploads. 

ADSL works like this because most users download more than they upload. In fact most common activities online, including web browsing and media streaming, only require a downstream data flow, making ADSL ideal for these use cases.
SDSL is different from ADSL in that bandwidth is split evenly between uploading and downloading flows.

What is SDSL used for?

[Translate to UK:]SDSL is used for applications where data has to flow quickly in both directions. A classic use case is Voice-over-IP (VoIP) telephony. Here, large amounts of data are being constantly downloaded and uploaded as the callers speak to one another. Assuming that both callers talk the same amount, the same amount of data needs to be sent and received. 

By providing equal speeds for data uploads and downloads, and with connection speeds that are typically much faster than ADSL, SDSL connections can greatly improve the quality of VoIP calls. This technology is used in the leading VoIP solutions, including the NFON Cloud Telephone System

To find out more about analog and VoIP telephone technologies and to understand the capabilities of the NFON Cloud Telephone System, please review the articles below: 


Further information

Voice over IP: The Art of Switching from PSTN to IP

What is VoIP?

The Voice over Internet Protocol, also called IP telephony, is a method of communication for making calls over a broadband Internet connection as an alternative to regular calls made…

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The abbreviation FMC stands for the technical phrase Fixed Mobile Convergence and describes the integration of mobile and fixed-line communication services within a complete solution. Whilst mobile…

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