Reliable Data Protocol
RFC 908

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Reliable Data Protocol

                                  RFC-908

                               David Velten

                               Robert Hinden

                                 Jack Sax

                      BBN Communications Corporation

                                July 1984

Status of This Memo

   This RFC specifies a proposed protocol for the ARPA Internet
   community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.






     RDP Specification                           

                             Table of Contents

     1   Introduction.......................................... 1

     2   General Description................................... 3
     2.1   Motivation.......................................... 3
     2.2   Relation to Other Protocols......................... 5

     3   Protocol Operation.................................... 7
     3.1   Protocol Service Objectives......................... 7
     3.2   RDP Connection Management........................... 7
     3.2.1   Opening a Connection.............................. 8
     3.2.2   Ports............................................. 8
     3.2.3   Connection States................................. 8
     3.2.4   Connection Record................................ 11
     3.2.5   Closing a Connection............................. 13
     3.2.6   Detecting an Half-Open Connection................ 14
     3.3   Data Communication................................. 14
     3.4   Reliable Communication............................. 15
     3.4.1   Segment Sequence Numbers......................... 15
     3.4.2   Checksums........................................ 16
     3.4.3   Positive Acknowledgement of Segments............. 16
     3.4.4   Retransmission Timeout........................... 17
     3.5   Flow Control and Window Management................. 17
     3.6   User Interface..................................... 19
     3.7   Event Processing................................... 20
     3.7.1   User Request Events.............................. 21
     3.7.2   Segment Arrival Events........................... 24
     3.7.3   Timeout Events................................... 29

     4   RDP Segments and Formats............................. 31
     4.1   IP Header Format................................... 31
     4.2   RDP Header Format.................................. 32
     4.2.1   RDP Header Fields................................ 33
     4.3   SYN Segment........................................ 36
     4.3.1   SYN Segment Format............................... 36
     4.3.2   SYN Segment Fields............................... 37
     4.4   ACK Segment........................................ 38
     4.4.1   ACK Segment Format............................... 38
     4.4.2   ACK Segment Fields............................... 39
     4.5   Extended ACK Segment............................... 40
     4.5.1   EACK Segment Format.............................. 40
     4.5.2   EACK Segment Fields.............................. 40

                                                                Page i




     RFC-908                                                 July 1984

     4.6   RST Segment........................................ 42
     4.6.1   RST Segment Format............................... 42
     4.7   NUL Segment........................................ 43
     4.7.1   NUL segment format............................... 43

     5   Examples of Operation................................ 45
     5.1   Connection Establishment........................... 45
     5.2   Simultaneous Connection Establishment.............. 46
     5.3   Lost Segments...................................... 47
     5.4   Segments Received Out of Order..................... 48
     5.5   Communication Over Long Delay Path................. 49
     5.6   Communication Over Long Delay Path With Lost
       Segments
          .................................................... 50
     5.7   Detecting a Half-Open  Connection  on  Crash
       Recovery
          .................................................... 51
     5.8   Detecting a Half-Open  Connection  from  the
       Active Side
          .................................................... 52

     A   Implementing a Minimal RDP........................... 53

     Page ii




     RDP Specification                           

                                  FIGURES

     1  Relation to Other Protocols............................ 5
     2  Form of Data Exchange Between Layers................... 6
     3  RDP Connection State Diagram.......................... 10
     4  Segment Format........................................ 31
     5  RDP Header Format..................................... 32
     6  SYN Segment Format.................................... 37