RFC 1235 (rfc1235) - Page 1 of 12
Coherent File Distribution Protocol
Alternative Format: Original Text Document
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.