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  1. Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU
  2. Path: sparky!uunet!gatech!udel!darwin.sura.net!paladin.american.edu!auvm!DJUKFA11.BITNET!ZDV104
  3. Organization: Forschungszentrum Juelich GmbH
  4. Message-ID: <IBMTCP-L%92122207222010@PUCC.PRINCETON.EDU>
  5. Newsgroups: bit.listserv.ibmtcp-l
  6. Date:         Tue, 22 Dec 1992 13:18:52 +0100
  7. Sender:       IBM TCP/IP List <IBMTCP-L@PUCC.BITNET>
  8. From:         ZDV104@DJUKFA11.BITNET
  9. Subject:      Problems with ftp via RS6000-BMPX
  10. Lines: 44
  11.  
  12. Hello all,
  13.  
  14. Using an RS6000 as a gateway between ES9000/620 VM-system and the KFA-wid
  15. FDDI network, I get an error using binary FTP transfer.
  16.  
  17. The scenario is the following:
  18.  
  19.                           ==========================
  20.                          //                        \\
  21.                     +------------+            +------------+
  22.     +----+   BMPX   |            |            |            |
  23.     | VM |----------| RS6000/350 |  FDDI-net  | RS6000/350 |
  24.     +----+          |  rs-host-1 |            |  rs-host-2 |
  25.                     +------------+            +------------+
  26.                           \\                       //
  27.                            ====.. other hosts ..====
  28.  
  29. Transferring a binary file with e.g. 4040 Bytes from rs-host-2
  30. to the VM-system (PUT from rs-host-2), the ftp command is hanging.
  31.  
  32. Binary files with less than 4030 bytes are working fine.
  33.  
  34. I assume that 4030 bytes + IP-, TCP- and other headers add up
  35. to less than 4096 bytes(max-seg-size for BMPX-adapter). FDDI does
  36. support a max-segment-size of up to 4500.
  37.  
  38. It seems to me that the VM-TCP/IP-software and the rs-host-2 software
  39. (AIX-TCP/IP) do not agree on the max-seg-size.
  40.  
  41. Setting the "MAXIMUM IP PACKET SIZE (Default:4352)" for the RS6000-fddi
  42. interface to e.g. "4000" (lower than 4096), the file was transfered
  43. correctly. But the decreased packetsize in general has effect to the
  44. throughput to other hosts.
  45.  
  46. Has anyone else seen this behavior? Any remarks?
  47.  
  48. Thank in advance, Marry Christmas and a happy new year.
  49.  
  50. Ralph Niederberger             Research Center Juelich (KFA)
  51.                                Central Institute for Applied Mathematics
  52.                                P.O.BOX 1913
  53.                                D-5170 Juelich
  54.                                Tel.: +49 2461 61 4772
  55.                                INTERNET: R.Niederberger@kfa-juelich.de
  56.