DSL – Broadband Technology


DSL - Digital Subscriber Line Technology is a copper loop transmission technology that achieves broadband speeds over the most universal network medium in the world – ordinary telephone line. DSL Technology is widely used most of countries because of its rich feature. Internet demand is growing rapidly year-on-year where every telco wanted to provide Internet as services to their customer and DSL is the best technology through which Telco can provide Internet to their customer using existing copper wire.    

  • Asymmetric – The data can flow faster in one direction than the other. Data transmission has faster downstream to the subscriber than upstream
  • Digital – No type of communication is transferred in an analog method. All data is purely digital, and only at the end, modulated to be carried over the line.
  • Subscriber Line – The data is carried over a single twisted pair copper loop to the subscriber premises.


DSL Picture




ADSL standards:



DSL Standard


ADSL Range – As distance decreases toward the telephone company office, the data rate increases. In general, the maximum range for DSL without a repeater is 5.5 km and ADSL other speed factors are – type and thickness of wires used, number and type of joins in the wire, proximity of the wires to radio transmitters.


Dsl p2

ADSL network components

  • The ADSL modem at the customer premises (ATU-R) – Session initiate.
  • DSL access multiplexer (DSLAM) -
  • Broadband Remote Access Server (B-RAS) – Remote session termination point.
  • Splitter – an electronic low pass filter that separates the analogue voice or ISDN signal from ADSL data frequencies DSLAM.

DSL Modulation-Discrete Multi Tone-DMT -

dsl 93

  • DMT has 224 downstream frequency bins and up to 31 upstream bins
  • Up to 15 bits per symbol can be encoded on each bin on a good quality line.
  • Uplink Speed = (15* 4.3125*31) = 2 Mbps
  • Down link Speed = (15* 4.3125*224) = 14.49 Mbps

PPP Broadband Access Methods –


DSL BB Drawing

  • PPPoA – PPP session initiated by CPE
  • PPPoE– PPP sessions initiated by the client

Akshay Sharma

AKshay has a rich experience of 10+ years in data and telecom domains. He is working as a solution architect in a reputed Telecom in India from the last 5 yrs and has diversified experience in providing robust network solution to SMB and enterprise segment. His core expertise is in DSL broadband/IP/MPLS/Routing and switching with hands on multiple telecom equipment’s and had done multiple certifications into his long career.

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