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New cloverleaf is sending TCP PSH flags, 2 receiveing system have problems

› Clovertech Forums › Cloverleaf › New cloverleaf is sending TCP PSH flags, 2 receiveing system have problems

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  • March 25, 2024 at 6:40 am #121267
    J.S.
    Participant

      Hi

      Last month we upgraded to 2022.09 rev2 on a RH linux system 9.3. (from a 6.2 on RH 7)

      When during the day, when there is more traffic, wireshark/tcpdump show that PSH flags are beeing sent, telling the receiver to push it right away to the application layer. There the HL7 message is nog yet complete so it is erroring because of not correct start/end characters of the message.

      Anyone also encoutered this behaviour? Any settings known we can adjust?

      Thanks..

      Jessica

      Regards
      J.S.

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      • March 26, 2024 at 2:21 am #121268
        Charlie Bursell
        Participant

          Must be large messages where multiple packets are received.  Should it be inherent on the receiving application to buffer those packets until a complete message is received? For example, assuming MLP HL7 data, Cloverleaf noting a packet with a start character of x0b (vertical Tab),  would buffer the message until 1c0d (File separator/Carriage Return)  is received

          Am I missing something?

        • March 28, 2024 at 3:09 am #121269
          J.S.
          Participant

            Yes we use MLP, and yes, with MTU of 1500 also this is sometimes in multiple packets. But this is not different from the old system, sending the PSH is.

            PSH means transmit to the application immediate, and that seems to be in case of our PACS system not a complete segment.

            Maybe they could improve something, but the change on cloverleaf side triggers this behaviour, hence the question if we could change settings on that side making sure PSH is not sent. There are quite some tcp settings involved.

            I’m not completely sure but I think MLP is already a layer up on tcp.

             

            Regards
            J.S.

          • April 8, 2024 at 6:44 am #121300
            Robert Kersemakers
            Participant

              Hi Jessica,

              We just installed CL 2022.09.03 on a new RHEL9.3 cluster in Azure.
              Our Dutch reseller (you know them/him…) told us that there was a problem with 2022.09 on RHEL9 regarding this PSH flag that is suddenly being send.

              Problem occurs only with 2022.09 on RHEL9; on RHEL7 it worked without a problem. And only certain systems are affected; probably those that actually adhere to the PSH flag and try to process the data when the PSH flag is sent.

              Call was made for Infor to check this out. Not a nice thing to know as we just installed on RHEL9. And we also have Sectra as PACS, which is one of the offending systems.
              I can’t find anything quickly about this PSH flag and how to disable it. Will research some more.

              Zuyderland Medisch Centrum; Heerlen/Sittard; The Netherlands

            • April 11, 2024 at 8:35 am #121313
              Sandy McQuay
              Participant

                This is great information.  We’re just starting to plan our upgrade from 6.2.2 on RHEL 7.9 to 2022.09.03 on RHEL x.x (not sure yet, whatever is certified).  We also have Sectra PACS.

                We’ll keep this in mind as we move forward.

              • August 29, 2024 at 9:42 am #121581
                Marc Pleijers
                Participant

                  Hi all,

                  Infor has done research on this issue together with Redhat.

                  In RHEL 7 and 8 there was a bug in the TCPIP stack that was fixed in RHEL9 and now the TCIP stack is completely according to the specifications.

                  This fix adds the PSH flags in HL7 messages of a certain minimum size, when Cloverleaf sends them to Sectra and other systems. This is exactly according to the TCPIP specifications.

                  For HL7 messages the MLP protocol is used on top of the TCPIP protocol. Receiving system Sectra should  buffer the message until  according to MLP protocol 1c0d (File separator/Carriage Return)  is received. They should not start processing once they get a PSH flag inside the message body.

                  Conclusion is that this is not a Redhat 9 /Cloverleaf 2022.09 issue but is an MLP implementation problem at the receiving Sectra System. Sectra has been informed about this.

                  Kind regards,

                  Marc Pleijers

                   

                  • This reply was modified 3 months, 3 weeks ago by Marc Pleijers.

                  Marc Pleijers
                  Senior Integration Consultant
                  Enovation BV
                  The Netherlands

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