RFC 1306 (rfc1306) - Page 2 of 10

Experiences Supporting By-Request Circuit-Switched T3 Networks

RFC 1306          Experiences with Circuit-Switched T3        March 1992


Overview

   Users of wide-area networks often must make a compromise between low
   cost and high speed when accessing long haul connections.  The high
   money cost of dedicated high speed connections makes them
   uneconomical for scientists and engineers with limited budgets.  For
   many traditional applications this has not been a problem.  Datasets
   can be maintained on the remote computer and results were presented
   in a text-only form where a low-speed connection would suffice.
   However, for visualization and other data transfer intensive
   applications, this limitation can severely impact the usability of
   high performance computing tools which are available only through
   long-haul network connections.

   Supercomputers are one such high performance tool.  Many users who
   can benefit from access to supercomputers are limited by slow network
   connections to a centrally located supercomputer.  A solution to this
   problem is to use a circuit-switched network to provide high speed
   network connectivity at a reduced cost by allocating the network only
   when it is needed.

   Consider how a researcher using a visualization application might
   efficiently use a dedicated low speed link and a circuit switched
   high speed link.  The researcher logs in to the remote supercomputer
   over the low speed link.  After running whatever programs are
   necessary to prepare the visualization, the high speed connection is
   activated and used to transfer the graphics data to the researcher's
   workstation.

   We built and demonstrated this capability in September, 1990, at the
   Telecommunications Association show in San Diego, using this type of
   visualization application.  Further, it will be available in a
   forthcoming release of our system software.

Architectural Model

   We developed our support for circuit switched services around a
   simple model of a switched network.  At some point in the path
   between two hosts, there is a switched network connection.  This
   connection is likely to connect two enterprise networks operated by
   the same organization.  Administrative overlap between the two
   networks is useful for accounting and configuration purposes.  We
   believe that with further investigation circuit switched network
   support could be extended to multiple switched links in an internet
   environment.

   The switch which makes the network connection operates on a "by-
   request" basis (also called "on-demand").  When it receives a request



Nicholson & Young