• 能達成高速通訊的技術之一，用以提供高速存取網際網路服務
• for faster long-distance commu #Overview⭐
• uses frequency above the audible range to transfer digital data while leaving the lower frequency spectrun for voice communication #overview ⭐
• 一組技術的集合：ADSL ; VDSL ; HDSL ; SDSY
• 可稱為 xDSL
• Asymmetric DSL 提供下載方向較高的資料傳輸速率 ⭐ ****
• 採用「無遮蔽」雙絞線傳送，易受到干擾，進而限制傳輸率的上限，改善方法為電纜網絡
• Two derivatives of PPP, Point-to-Point Protocol over Ethernet(PPPoE) and Point-to-Point Protocol over ATM (PPPoA),
  • are used most commonly by ISPs to establish a DSL