Experiences Supporting By-Request Circuit-Switched T3 Networks
RFC 1306

Document Type RFC - Informational (March 1992; No errata)
Last updated 2013-03-02
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Network Working Group                                       A. Nicholson
Request for Comments: 1306                                      J. Young
                                                     Cray Research, Inc.
                                                              March 1992

     Experiences Supporting By-Request Circuit-Switched T3 Networks

Status of this Memo

   This RFC provides information for the Internet community.  It does
   not specify an Internet standard.  Distribution of this memo is
   unlimited.

Abstract

   This memo describes the experiences of a project team at Cray
   Research, Inc., in implementing support for circuit-switched T3
   services.  While the issues discussed may not be directly relevant to
   the research problems of the Internet, they may be interesting to a
   number of researchers and implementers.

   Developers at Cray Research, Inc. were presented with an opportunity
   to use a circuit-switched T3 network for wide area networking.  They
   devised an architectural model for using this new resource.  This
   involves activating the circuit-switched connection when an
   application program engages in a bulk data transfer, and releasing
   the connection when the transfer is complete.

   Three software implementations for this feature have been tested, and
   the results documented here.  A variety of issues are involved, and
   further research is necessary.  Network users are beginning to
   recognize the value of this service, and are planning to make use of
   by-request circuit-switched networks.  A standard method of access
   will be needed to ensure interoperability among vendors of circuit-
   switched network support products.

Acknowledgements

   The authors thank the T3 project team and other members of the
   Networking Group at Cray Research, Inc., for their efforts: Wayne
   Roiger, Gary Klesk, Joe Golio, John Renwick, Dave Borman and Craig
   Alesso.

Nicholson & Young                                               [Page 1]
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                                               [Page 2]
RFC 1306          Experiences with Circuit-Switched T3        March 1992

   to make a network connection it will do so (if possible), and breaks
   the connection when requested.  The switch will not activate
   automatically if there is an attempt to transfer data over an
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