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4.1 Transmission


Transmission technology was fundamental to the establishment of the gigabit testbeds. The emergence of SONET/SDH standards for high speed transmission over wide area optical fiber in the late 1980s, and of HIPPI for local high speed connectivity in the same time frame, provided an opportunity both to construct experimental testbed facilities using prototype equipment and to accelerate that equipment's path to successful use in operational networks.

While SONET and HIPPI were the dominant transmission technologies used in the testbeds, other technologies were also used. These included wide area all-optical links using optical amplifier repeaters and new local area gigabit technologies such as Glink, which became available during the course of the project.

An important research focus in this area was the exploration of striping techniques to derive gigabit user rates from multiple lower-speed SONET channels. This was necessitated by the fact that most of the early SONET equipment available to the testbeds provided only 155 Mbps user ports -- however, striping was also pursued as a research topic in its own right, since the aggregation of multiple lower speed network channels to achieve higher bandwidths becomes increasingly attractive as user data rate requirements increase and multichannel technologies such as all-optical WDM are introduced.

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