ADSL vs SDSL
ADSL (Asymmetric Digital Subscriber Line) and SDSL (Symmetric Subscriber Digital Subscriber Line) are the two major groups when it comes to broadband internet connections. The most major difference between these two groups is in how much bandwidth they allocate to the user. Since SDSL is symmetric. It offers equal download and upload speeds to the user while, although the download speed is also very high for ADSL, the upload speed can be significantly slower. Some people, especially those who upload videos or other content, may prefer the high upload bandwidth of SDSL, but for most people, ADSL provides sufficient upload speed since we download much more information than we upload while browsing the internet, watching videos, and downloading files.
The most major advantage that ADSL has is the ability to have the DSL and a telephone unit on the same two wires and they can be used simultaneously. This is because ADSL does not take up the entire bandwidth. SDSL uses the whole bandwidth and leaves no room for a telephone unit. The bandwidth for the telephone is allocated to the upload speed and explains the much higher bandwidth despite using the same two wires.
ADSL is a standardized technology and as such, most devices that can operate with ADSL can be used interchangeably. They adapt to the standard and are therefore compatible. SDSL is proprietary and was never standardized, leaving manufacturers to implement their own standards in how their devices are supposed to operate. This meant that most SDSL devices would only work when they are from the same company. Using devices from different companies would not ensure that your network would as intended.
ADSL is currently the technology that is deployed in most parts of the world where high speed internet connectivity is being enjoyed. SDSL on the other hand, is considered as a legacy technology. It is no longer used in modern deployments as it has been succeeded by G.SHDSL and is largely considered as obsolete.
Summary:
1. ADSL is asymmetric while SDSL is symmetric
2. The upload and download speeds of SDSL are equal while that of ADSL are not
3. ADSL can have a telephone unit on the same line while SDSL cannot
4. ADSL is a standardized technology while SDSL is proprietary and was never standardized
5. ADSL is the current technology used today while SDSL is considered as legacy technology