Pi Digit Generation Protocol
RFC 3091

Document Type RFC - Informational (April 2001; Errata)
Last updated 2017-03-14
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Network Working Group                                         H. Kennedy
Request for Comments: 3091                        University of Michigan
Category: Informational                                     1 April 2001

                      Pi Digit Generation Protocol

Status of this Memo

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

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This memo defines a protocol to provide the Pi digit generation
   service (PIgen) used between clients and servers on host computers.

Introduction

   This protocol is intended to provide the Pi digit generation service
   (PIgen), and be used between clients and servers on host computers.
   Typically the clients are on workstation hosts lacking local Pi
   support, and the servers are more capable machines with greater Pi
   calculation capabilities.  The essential tradeoff is the use of
   network resources and time instead of local computational cycles.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Note

   All digits supplied by implementations of this service are ASCII
   [US-ASCII] representations of decimal (base 10) numbers following the
   decimal point in values or approximations of Pi.  There MUST be an
   implied decimal value of 3 (three) preceding the values provided by
   the service defined by this protocol.

1.     TCP Based Digit Generator Service

   One REQUIRED PIgen service is defined as a stateless TCP service.  A
   server listens on TCP port 314159.  Once a connection is established
   the server sends a stream of data, one digit of Pi at at time,

Kennedy                      Informational                      [Page 1]
RFC 3091              Pi Digit Generation Protocol          1 April 2001

   starting with the most significant digit following the decimal point.
   Any incoming data MUST be discarded.  This continues until the client
   closes the connection.

   The data flow over the connection is limited by the normal TCP flow
   control mechanisms, so there is no concern about the server sending
   data faster than the client can process it.

   Servers MAY use any appropriate method of Pi digit generation to
   provide this service, including (but not limited to) table lookup
   [DIGITS], numerical calculation [FIBPI,PIFFT] and statistical
   sampling [MCM].  However, the method chosen SHOULD provide a precise
   value for the digits of Pi generated.

   Implementors of PIgen MUST provide this service to be conditionally
   compliant with this RFC.

1.1.   Approximate Service

   An OPTIONAL PIgen service is defined as a stateless TCP service.  A
   server listens on TCP port 220007.  Once a connection is established
   the server sends a stream of data, one digit of the rational number
   22/7 at a time, starting with the most significant digit following
   the decimal point.  Any incoming data MUST be discarded.  This
   continues until the client closes the connection.

2.     UDP Based Digit Generator Service

   An OPTIONAL PIgen service is defined as a stateless UDP service.  A
   server listens on UDP port 314159.  When a datagram requesting a
   specific digit of Pi is received, an answering datagram is sent
   containing the value of the requested digit of Pi according to the
   format defined in sections 2.1.1. and 2.1.2.

   The requested digit value MAY be determined by any appropriate method
   of Pi digit generation.  RECOMMENDED methods include table lookup
   [DIGITS], or numerical calculation [BBPPA].

2.1.   Packet Format

   The datagram-based components of the PIgen protocol suite all share
   the following UDP data payload formats (defined in the ABNF of RFC
   2234 [RFC2234]).

Kennedy                      Informational                      [Page 2]
RFC 3091              Pi Digit Generation Protocol          1 April 2001

2.1.1. Request Payload Format

   request   = nth_digit

   nth_digit = 1*DIGIT  ; specifying the n-th digit following the
                        ; decimal point

2.1.2. Reply Payload Format

   reply  = nth_digit ":" DIGIT ; where DIGIT is the value of the n-th
                                ; digit following the decimal
                                ; point

2.2.   Approximate Service

   An OPTIONAL PIgen service is defined as a stateless UDP service.  A
   server listens on UDP port 220007.  When a datagram requesting a
   specific digit of the rational number 22/7 is received, an answering
   datagram is sent containing the value of the requested digit of 22/7
   according to the format defined in sections 2.1.1. and 2.1.2.

3.     IP Multicast Based Digit Generator Service

   An OPTIONAL PIgen service is defined as a stateless UDP service.  A
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