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  1. OASIS Message Queuing Telemetry Transport (MQTT) TC
  2. MQTT-89

Dup Flag consistency after issue 27

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    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 3.1.1
    • Fix Version/s: 3.1.1
    • Component/s: core
    • Labels:
      None
    • Proposal:
      Hide

      In the Subscribe Unsubcscribe and PubRel packets the Dup flag will be referred to as a reserved bit.

      So for subscribe line 956 WD13:

      Bit 7 6 5 4 3 2 1 0
      byte 1 MQTT Control Packet type (8) Dup flag Reserved
      1 0 0 0 0 0 1 0
      byte 2 Remaining Length

      See MQTT Issue-27
      Dup flag
      Set to zero (0). This means that the packet is being sent for the first time. See DUP, section 2.2.2.1 for more details.

      Bits 2,1 and 0 of the fixed header are reserved and must be set to 0,1 and 0 respectively. The server MUST treat any other value as malformed and close the Network Connection.

      Becomes

      Bit 7 6 5 4 3 2 1 0
      byte 1 MQTT Control Packet type (8) Reserved
      1 0 0 0 0 0 1 0
      byte 2 Remaining Length

      Bits 3,2,1 and 0 of the fixed header are reserved and must be set to 0,0,1 and 0 respectively. The server MUST treat any other value as malformed and close the Network Connection.

      Show
      In the Subscribe Unsubcscribe and PubRel packets the Dup flag will be referred to as a reserved bit. So for subscribe line 956 WD13: Bit 7 6 5 4 3 2 1 0 byte 1 MQTT Control Packet type (8) Dup flag Reserved 1 0 0 0 0 0 1 0 byte 2 Remaining Length See MQTT Issue-27 Dup flag Set to zero (0). This means that the packet is being sent for the first time. See DUP, section 2.2.2.1 for more details. Bits 2,1 and 0 of the fixed header are reserved and must be set to 0,1 and 0 respectively. The server MUST treat any other value as malformed and close the Network Connection. Becomes Bit 7 6 5 4 3 2 1 0 byte 1 MQTT Control Packet type (8) Reserved 1 0 0 0 0 0 1 0 byte 2 Remaining Length Bits 3,2,1 and 0 of the fixed header are reserved and must be set to 0,0,1 and 0 respectively. The server MUST treat any other value as malformed and close the Network Connection.
    • Resolution:
      Hide

      Fixed in WD14

      Show
      Fixed in WD14

      Description

      Issue 27 mandated that the Dup flag is zero in Subscribe Unsubcscribe and PubRel packets. Should the specification now show the Dup flag at all for these packets and should it be labeled as reserved rather than Dup?

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            • Assignee:
              andrew_banks Andrew Banks (Inactive)
              Reporter:
              andrew_banks Andrew Banks (Inactive)
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              Dates

              • Created:
                Updated:
                Resolved: