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End-to-End DSL Architectures by Wayne C. Vermillion

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xDSL Varieties

There are two broad divisions of xDSL—asymmetric (ADSL) and symmetric (SDSL). Current and future types are summarized in Table 1-1.

Table 1-1. Summary of xDSL Types and Standards
Asymmetric DSLSymmetric DSL (Multiple Varieties of Symmetric DSL Are Marketed as “SDSL”)

CAP— No standard

SDSL— No standard

G.DMT— (Worldwide) ITU G.992.1

HDSL— No standard

ADSL/ISDN (ADSL over ISDN)— No standard

HDSL2— (North America) ANSI T1.418

DMT2-(North America) ANSI T1.413.2

“G.Lite” or “half-rate DMT”— (Worldwide) ITU G.992.2

IDSL— ISDN over DSL

G.dmt.bis (ADSL2)— (Worldwide) G.992.3

SHDSL— (Worldwide) ITU G.991.2

G.lite.bis (half-rate ADSL2)— (Worldwide) G.992.4

 

VDSL— No standard

 

The difference between asymmetric and symmetric service is simple: Either the ...

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