RFC 1235 (rfc1235) - Page 1 of 12

Coherent File Distribution Protocol

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Network Working Group                                       J. Ioannidis
Request for Comments:  1235                              G. Maguire, Jr.
                                                     Columbia University
                                          Department of Computer Science
                                                               June 1991


                The Coherent File Distribution Protocol

Status of this Memo

   This memo describes the Coherent File Distribution Protocol (CFDP).
   This is an Experimental Protocol for the Internet community.
   Discussion and suggestions for improvement are requested.  Please
   refer to the current edition of the "IAB Official Protocol Standards"
   for the standardization state and status of this protocol.
   Distribution of this memo is unlimited.

Introduction

   The Coherent File Distribution Protocol (CFDP) has been designed to
   speed up one-to-many file transfer operations that exhibit traffic
   coherence on media with broadcast capability.  Examples of such
   coherent file transfers are identical diskless workstations booting
   simultaneously, software upgrades being distributed to more than one
   machines at a site, a certain "object" (bitmap, graph, plain text,
   etc.) that is being discussed in a real-time electronic conference or
   class being sent to all participants, and so on.

   In all these cases, we have a limited number of servers, usually only
   one, and  clients (where  can be large) that are being sent the
   same file.  If these files are sent via multiple one-to-one
   transfers, the load on both the server and the network is greatly
   increased, as the same data are sent  times.

   We propose a file distribution protocol that takes advantage of the
   broadcast nature of the communications medium (e.g., fiber, ethernet,
   packet radio) to drastically reduce the time needed for file transfer
   and the impact on the file server and the network.  While this
   protocol was developed to allow the simultaneous booting of diskless
   workstations over our experimental packet-radio network, it can be
   used in any situation where coherent transfers take place.

   CFDP was originally designed as a back-end protocol; a front-end
   interface (to convert file names and requests for them to file
   handles) is still needed, but a number of existing protocols can be
   adapted to use with CFDP.  Two such reference applications have been
   developed; one is for diskless booting of workstations, a simplified



Ioannidis & Maguire, Jr.
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