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Seminar - An Overview of Communications Technologies


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Module 5 - SONET, WDM, DWDM and B-ISDN Technologies                                                             Slide 39 of 76 _________________                                                                                  __________

                                                   Virtual Tributaries

VT Levels Line Rate
(M bps)		 Standard
VT-1.5 1.728 DS-1
VT-2 2.304 SEPT-1.520
VT-3 3.456 DS1-C
VT-6 6.912 DS-2
VT-6-N NX6.9 Future
Async DS3 44.736 DS-3

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The North American tributary (DS-1 at 1.544 M bps) and the European tributary (E-1 at 2.048 M bps) have defined VT mappings. SONET defines the tributaries which have not yet been defined. Virtual Tributaries carry the DS-1, DS-2 and DS-3 signals within the Synchronous Payload Envelope (SPE).