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Switched Multi-megabit Data Service (SMDS) was a connectionless service used to connect LANs, MANs and WANs to exchange data, in early 1990s. In Europe, the service was known as Connectionless Broadband Data Service (CBDS).[1]

SMDS was specified by Bellcore,[2] and was based on the IEEE 802.6 metropolitan area network (MAN) standard, as implemented by Bellcore, and used cell relay transport, Distributed Queue Dual Bus layer-2 switching arbitrator, and standard SONET[3] or G.703 as access interfaces.

It is a switching service that provides data transmission in the range between 1.544 Mbit/s (T1 or DS1) to 45 Mbit/s (T3 or DS3). SMDS was developed by Bellcore as an interim service until Asynchronous Transfer Mode matured.[1] In the mid-1990s, SMDS was replaced, largely by Frame Relay.

SMDS was notable for its initial introduction of the 53-byte cell and cell switching approaches, as well as the method of inserting 53-byte cells onto G.703 and SONET.[4] Note that the abbreviation searched for was SMD not SMDS


  1. ^ a b McDysan (1999), p. 510  Missing or empty |title= (help)
  2. ^ TA-TSY-000772, TA-TSY-000773 and TA-TSY-000774.
  3. ^ GR-253
  4. ^ McDysan (1999), p. 214  Missing or empty |title= (help)


  • McDysan, David E.; Darren L. Spohn (1999). ATM Theory and Applications. Montreal: McGraw-Hill. ISBN 0-07-045346-2. 
  • Bellcore. Generic System Requirements in Support of a Switched Multi-Megabit Data Service. Technical Advisory, TA-TSY-000772; October 1989.
  • Bellcore. Local Access System Generic Requirements, Objectives, and Interface Support of Switched Multi-Megabit Data Service. Technical Advisory TA-TSY-000773, Issue 1; December 1985.
  • Bellcore. Switched Mutli-Megabit Data Service (SMDS) Operations Technology Network Element Generic Requirements. Technical Advisory TA-TSY-000774.
  • Telcordia. Generic Requirements for SONET. GR-253

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