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Change to the Very Distant Host specification (RFC0547)

IP.com Disclosure Number: IPCOM000006034D
Original Publication Date: 1973-Aug-13
Included in the Prior Art Database: 2001-Nov-28
Document File: 4 page(s) / 6K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D.C. Walden: AUTHOR

Abstract

Attached is a new version of figure F-4 for BBN Report 1822, Specification for the Interconnection of a Host and an IMP. Also attached is replacement text for the paragraph beginning at the bottom of page F-7 and continuing through page F-8.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 50% of the total text.

Network Working Group                                          D. Walden

Request for Comments: 547                                        BBN-NET

NIC: 17793                                                13 August 1973

             Change to the Very Distant Host Specification

   Attached is a new version of figure F-4 for BBN Report 1822,

   Specification for the Interconnection of a Host and an IMP.  Also

   attached is replacement text for the paragraph beginning at the

   bottom of page F-7 and continuing through page F-8.

   Please put this RFC with your copy of 1822 pending update of 1822.

   DCW/ph

                   SPECIAL PACKET BIT ___

                                         |

                                         |

      ___HELLO/I-HEARD-YOU BIT           |      ___ UNUSED __

     |                                   |     |             |

     |                                   |     |             |

     V                                   V     V             V

    _______________________________________________________________

   |   |   |                       |   |   |///////|   |   |///|   |

   |   |   |                       |   |   |///////|   |   |///|   |

   |___|___|___|___|___|___|___|___|___|___|///|///|___|___|///|___|

     ^   ^     PACKET WORD COUNT     ^               ^   ^       ^

     |   |         ( 6 BITS )        |               |   |       |

     |   |                           |               |   |    CHANNEL

     |   |                           |               |   |    NUMBER

     |   |                           |               |   |

     |  PACKET                  HOST/IMP BIT         |  CHANNEL ZERO

     |  ODD/EVEN BIT                                 |  ACKNOWLEDGE BIT

     |                                               |

    LAST PACKET BIT                                CHANNEL ONE

                                                   ACKNOWLEDGEMENT BIT

                          FIG. F-4   CONTROL WORD FORMAT

Walden                                                          [Page 1]

RFC 547      Change to the Very Distant Host Specification13 August 1973

   The following algorithm is used to decide whether the circuit between

   an IMP and a very distant Host is dead or alive.  We first define

   what we call a special packet -- this is (logically) a one word

   packet consisting of only the control word and having the SPECIAL

   PACKET bit set to one.  All packets which are not special packets

   (i.e., which are regular data packets or null packets) have the

   SPECIAL PACKET bit set to zero.  In a special packet, none of the

   control word fields or bits have their usual meanings; consequently,

   a special packet cannot be used to acknowledge data packets or send

   data.  In a special packet, only one bit other than the SPECIAL

   PACKET bit has any meaning, the HELLO/I-HEARD-YOU bit.

   Every r seconds both IMP and Host (independently) send a HELLO

   packet, a special packet with the HELLO/I-HEARD-YOU bit set to zero.

   When either IMP or Hosts receives a HELLO packet, it must promptly

   (with highest priority) send the other an I-HEARD-YOU packet, a

   special packet with the HELLO/I-HEAR-YOU bit set to one.  In other

   words, the I-HEARD-YOU packet is an acknowledgement of the periodic

   HELLO packet, and a I-HEARD-YOU packet must only be sent as

   acknowledgement for a HELLO packet.  If either IMP or Host sends more

   than t HELLO packets without receiving an I-HEARD-YOU packet in

   acknowledgemen...