Posted by Hemmi on February 18, 2004 at 03:25:38:
we have some problems with packet fragmentation in one of our plants.
there are two systems one Linux7.3(suse) and one OpenVMS. the application on OpenVMS-System sends a long telegram to the Linux-pc. Fact is that the application on Linux didn't receive the complete telegram and so application closes the connection. Here a TCPTrace of this case:
------------------ OpenVMS -> Linux
TCPtrace full display XMT packet 187 at 12-DEC-2003 19:38:43.38
IP Version = 4, IHL = 5, TOS = 00, Total Length = 1500
IP Identifier = ^x7FD6, Flags (0=0,DF=1,MF=0),
Fragment Offset = 0, Calculated Offset = 0
IP TTL = 60 , Protocol = 6, Header Checksum = ^x38AA
IP Source Address = ss.ee.xx.na OpenVMS
IP Destination Address = ss.ee.xx.nb Linux
TCP Source Port = 54976, TCP Destination Port = 4000
TCP Sequence Number = 775560913
TCP Acknowledge Number = 1436730459
Flags (URG=0,ACK=1,PSH=0,RST=0,SYN=0,FIN=0),
Window = 8760
TCP Checksum = ^x8804, Urgent Pointer = 0
---------- OpenVMS -> Linux
TCPtrace full display XMT packet 296 at 12-DEC-2003 19:38:43.38
IP Version = 4, IHL = 5, TOS = 00, Total Length = 224
IP Identifier = ^x8017, Flags (0=0,DF=1,MF=0),
Fragment Offset = 0, Calculated Offset = 0
IP TTL = 60, Protocol = 6, Header Checksum = ^x3DA5
Source Address = ss.ee.xx.na OpenVMS
IP Destination Address = ss.ee.xx.nb Linux
TCP Source Port = 54976, TCP Destination Port = 4000
TCP Sequence Number = 775562373
TCP Acknowledge Number = 1436730459
Flags (URG=0,ACK=1,PSH=1,RST=0,SYN=0,FIN=0),
Window = 8760
TCP Checksum = ^xA068, Urgent Pointer = 0
----------------- Linux -> OpenVMS
TCPtrace full display RCV packet 330 at 12-DEC-2003 19:38:43.88
IP Version = 4, IHL = 5, TOS = 00, Total Length = 40 IP Identifier = ^x8CE7, Flags (0=0,DF=1,MF=0),
Fragment Offset = 0 , Calculated Offset = 0
IP TTL = 64 , Protocol = 6 , Header Checksum = ^x2D8D
IP Source Address = ss.ee.xx.nb Linux
IP Destination Address = ss.ee.xx.na OpenVMS
TCP Source Port = 4000, TCP Destination Port = 54976
TCP Sequence Number = 1436730459
TCP Acknowledge Number = 775562373
Flags (URG=0,ACK=1,PSH=0,RST=0,SYN=0,FIN=0),
Window = 16352
TCP Checksum = ^x9C7A, Urgent Pointer = 0
-------------- OpenVMS -> Linux
TCPtrace full display XMT packet 420 at 12-DEC-2003 19:38:45.65
IP Version = 4, IHL = 5, TOS = 00, Total Length = 224
IP Identifier = ^x806F, Flags (0=0,DF=1,MF=0),
Fragment Offset = 0, Calculated Offset = 0
IP TTL = 60, Protocol = 6, Header Checksum = ^x3D4D
IP Source Address = ss.ee.xx.na OpenVMS
IP Destination Address = ss.ee.xx.nb Linux
TCP Source Port = 54976, TCP Destination Port = 4000
TCP Sequence Number = 775562373
TCP Acknowledge Number = 1436730459
Flags (URG=0,ACK=1,PSH=1,RST=0,SYN=0,FIN=0),
Window = 8760
TCP Checksum = ^xA068, Urgent Pointer = 0
------------------------ Linux -> OpenVMS
TCPtrace full display RCV packet 421 at 12-DEC-2003 19:38:45.66
IP Version = 4, IHL = 5, TOS = 00, Total Length = 40
IP Identifier = ^x8CFD, Flags (0=0,DF=1,MF=0),
Fragment Offset = 0 , Calculated Offset = 0
IP TTL = 64, Protocol = 6, Header Checksum = ^x2D77
IP Source Address = ss.ee.xx.nb Linux
IP Destination Address = ss.ee.xx.na OpenVMS
TCP Source Port = 4000, TCP Destination Port = 54976
TCP Sequence Number = 1436730459
TCP Acknowledge Number = 775562557
Flags (URG=0,ACK=1,PSH=0,RST=0,SYN=0,FIN=0),
Window = 16168
TCP Checksum = ^x9C7A, Urgent Pointer = 0
---------------- Linux sends FIN -> OpenVMS
TCPtrace full display RCV packet 422 at 12-DEC-2003 19:38:45.69
IP Version = 4, IHL = 5, TOS = 00, Total Length = 40
IP Identifier = ^x8CFE, Flags (0=0,DF=0,MF=0),
Fragment Offset = 0, Calculated Offset = 0
IP TTL = 64 , Protocol = 6, Header Checksum = ^x6D76
IP Source Address = ss.ee.xx.nb Linux
IP Destination Address = ss.ee.xx.na OpenVMS
TCP Source Port = 4000, TCP Destination Port = 54976
TCP Sequence Number = 1436730459 = ^x55A2C45B
TCP Acknowledge Number = 775562557 = ^x2E3A253D
Flags (URG=0,ACK=1,PSH=0,RST=0,SYN=0,FIN=1),
Window = 16352
TCP Checksum = ^x9BC1, Urgent Pointer = 0
-----------------------------------
Is there any specialist who has an idea why application on Linux don't get the complete telegram?
thanks in advance
Hemmi