Movatterモバイル変換

Network Working Group                                      David WaldenRFC # 533                                                  BBN-NETNIC # 17452                                                July 17, 1973MESSAGE-ID NUMBERS    It has been noted that the IMP message format (specified in BBNReport 1822) constrains network users to low throughputs if messages areto be uniquely identified via the link number.  We have recentlyimplemented a change in the IMP/Host protocol which alleviates thisdifficulty.  The link field in the IMP/Host and Host/IMP leaders hasbeen extended to the right by four bits (in other words, it now usesbits 17 to 28 of the leader), and the name of the link field has beenchanged to the _message-id field_.  We expect this field to be used touniquely identify messages between the IMPs and the Hosts.  All 12 bitsin the message-id will be returned to the Host in RFNMs, INCOMPLETETRANSMISSIONs, etc.  Note that no ordering is implied by the use of themessage-id field.    Given that the Host/Host protocol uses the old link field toidentify connections, the additional four bits in the new message-idfield might well be used to uniquely identify messages on a givenconnection (i.e., over a given link).  Of course, there is no obligationfor Hosts to uniquely identify their messages (the IMP subnetworkcertainly doesn't care), so this change in the IMP/Host message formatis completely backward compatible.  In fact, since the receiving Hostdoes not have to look at these extra four bits on arriving messages, thechange is completely backward compatible even when senders of messagesdo use the extra four bits to uniquely identify messages.    Please store this RFC with your copy of BBN Report 1822 until 1822is updated.       [ This RFC was put into machine readable form for entry ]       [ into the online RFC archives by Alex McKenzie with    ]       [ support from GTE, formerly BBN Corp.            10/99 ]Walden                                                          [Page 1]