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History

History

• Bellcore originally proposed SONET - Synchronous Optical NETwork

• 1985 ANSI T1X1 committee

• 1986 CCITT SDH standards published: G.707, G.708, G.709

• 1987 Bellcore submitted SONET to CCITT - much European opposition

• See table of existing PDH standards

• Note the various differences and hence the standardisation problem

• Compromises
  • Basic rate for SONET increased to 51.840 Mbs to permit more bandwidth for OAM (operation, administration and maintenance functions) - concession to Europeans - a good move

  • Europeans dropped demand for level 2 and 3 rates to be directly supported

  • SDH/SONET merged on DS-3 and CEPT-4 rates