Wireshark-users: [Wireshark-users] "TCP Segment of a reassembled PDU" from a NetApp filer

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From: lemons_terry@xxxxxxx
Date: Tue, 18 Mar 2008 21:22:36 -0400
Hi

I've read previous posts regarding "TCP Segment of a reassembled PDU", but I still can't figure out why it is happening in my environment.

I'm using NDMP between a Windows 2003 system and a NetApp filer.  I'm able to have a problem-free NDMP conversation between this same Windows 2003 system and another NDMP-capable system.  But the packets sent from the NetApp to the Windows 2003 system all have the "TCP Segment of a reassembled PDU".  Not only does this smack of a network problem, but Wireshark can not decode the NDMP of the packets sent from the NetApp.

Here are the first few frames of the conversation.  Any thoughts?

No.     Time        Source                Destination           Protocol Info
    213 18.582986   192.168.11.115        192.168.11.250        TCP      epp > ndmp [SYN] Seq=0 Win=65535 Len=0 MSS=1460

Frame 213 (62 bytes on wire, 62 bytes captured)
Ethernet II, Src: tivo1.backup (00:11:43:32:05:93), Dst: Intel_dd:61:b4 (00:03:47:dd:61:b4)
Internet Protocol, Src: 192.168.11.115 (192.168.11.115), Dst: 192.168.11.250 (192.168.11.250)
Transmission Control Protocol, Src Port: epp (3044), Dst Port: ndmp (10000), Seq: 0, Len: 0
    Source port: epp (3044)
    Destination port: ndmp (10000)
    Sequence number: 0    (relative sequence number)
    Header length: 28 bytes
    Flags: 0x02 (SYN)
    Window size: 65535
    Checksum: 0x3420 [validation disabled]
    Options: (8 bytes)

No.     Time        Source                Destination           Protocol Info
    214 18.583098   192.168.11.250        192.168.11.115        TCP      ndmp > epp [SYN, ACK] Seq=0 Ack=1 Win=8760 Len=0 MSS=1460

Frame 214 (62 bytes on wire, 62 bytes captured)
Ethernet II, Src: Intel_dd:61:b4 (00:03:47:dd:61:b4), Dst: tivo1.backup (00:11:43:32:05:93)
Internet Protocol, Src: 192.168.11.250 (192.168.11.250), Dst: 192.168.11.115 (192.168.11.115)
Transmission Control Protocol, Src Port: ndmp (10000), Dst Port: epp (3044), Seq: 0, Ack: 1, Len: 0
    Source port: ndmp (10000)
    Destination port: epp (3044)
    Sequence number: 0    (relative sequence number)
    Acknowledgement number: 1    (relative ack number)
    Header length: 28 bytes
    Flags: 0x12 (SYN, ACK)
    Window size: 8760
    Checksum: 0x1c92 [validation disabled]
    Options: (8 bytes)
    [SEQ/ACK analysis]
        [This is an ACK to the segment in frame: 213]
        [The RTT to ACK the segment was: 0.000112000 seconds]

No.     Time        Source                Destination           Protocol Info
    215 18.583113   192.168.11.115        192.168.11.250        TCP      epp > ndmp [ACK] Seq=1 Ack=1 Win=65535 Len=0

Frame 215 (54 bytes on wire, 54 bytes captured)
Ethernet II, Src: tivo1.backup (00:11:43:32:05:93), Dst: Intel_dd:61:b4 (00:03:47:dd:61:b4)
Internet Protocol, Src: 192.168.11.115 (192.168.11.115), Dst: 192.168.11.250 (192.168.11.250)
Transmission Control Protocol, Src Port: epp (3044), Dst Port: ndmp (10000), Seq: 1, Ack: 1, Len: 0
    Source port: epp (3044)
    Destination port: ndmp (10000)
    Sequence number: 1    (relative sequence number)
    Acknowledgement number: 1    (relative ack number)
    Header length: 20 bytes
    Flags: 0x10 (ACK)
    Window size: 65535
    Checksum: 0x98d8 [validation disabled]
    [SEQ/ACK analysis]
        [This is an ACK to the segment in frame: 214]
        [The RTT to ACK the segment was: 0.000015000 seconds]

No.     Time        Source                Destination           Protocol Info
    216 18.584792   192.168.11.250        192.168.11.115        TCP      [TCP segment of a reassembled PDU]

Frame 216 (60 bytes on wire, 60 bytes captured)
Ethernet II, Src: Intel_dd:61:b4 (00:03:47:dd:61:b4), Dst: tivo1.backup (00:11:43:32:05:93)
Internet Protocol, Src: 192.168.11.250 (192.168.11.250), Dst: 192.168.11.115 (192.168.11.115)
Transmission Control Protocol, Src Port: ndmp (10000), Dst Port: epp (3044), Seq: 1, Ack: 1, Len: 4
    Source port: ndmp (10000)
    Destination port: epp (3044)
    Sequence number: 1    (relative sequence number)
    [Next sequence number: 5    (relative sequence number)]
    Acknowledgement number: 1    (relative ack number)
    Header length: 20 bytes
    Flags: 0x18 (PSH, ACK)
    Window size: 8760
    Checksum: 0xc925 [validation disabled]
    [SEQ/ACK analysis]
        [This is an ACK to the segment in frame: 215]
        [The RTT to ACK the segment was: 0.001679000 seconds]
    TCP segment data (4 bytes)

No.     Time        Source                Destination           Protocol Info
    219 18.767903   192.168.11.115        192.168.11.250        TCP      epp > ndmp [ACK] Seq=1 Ack=5 Win=65531 Len=0

Frame 219 (54 bytes on wire, 54 bytes captured)
Ethernet II, Src: tivo1.backup (00:11:43:32:05:93), Dst: Intel_dd:61:b4 (00:03:47:dd:61:b4)
Internet Protocol, Src: 192.168.11.115 (192.168.11.115), Dst: 192.168.11.250 (192.168.11.250)
Transmission Control Protocol, Src Port: epp (3044), Dst Port: ndmp (10000), Seq: 1, Ack: 5, Len: 0
    Source port: epp (3044)
    Destination port: ndmp (10000)
    Sequence number: 1    (relative sequence number)
    Acknowledgement number: 5    (relative ack number)
    Header length: 20 bytes
    Flags: 0x10 (ACK)
    Window size: 65531
    Checksum: 0x98d8 [validation disabled]
    [SEQ/ACK analysis]
        [This is an ACK to the segment in frame: 216]
        [The RTT to ACK the segment was: 0.183111000 seconds]

No.     Time        Source                Destination           Protocol Info
    220 18.768162   192.168.11.250        192.168.11.115        TCP      [TCP segment of a reassembled PDU]

Frame 220 (90 bytes on wire, 90 bytes captured)
Ethernet II, Src: Intel_dd:61:b4 (00:03:47:dd:61:b4), Dst: tivo1.backup (00:11:43:32:05:93)
Internet Protocol, Src: 192.168.11.250 (192.168.11.250), Dst: 192.168.11.115 (192.168.11.115)
Transmission Control Protocol, Src Port: ndmp (10000), Dst Port: epp (3044), Seq: 5, Ack: 1, Len: 36
    Source port: ndmp (10000)
    Destination port: epp (3044)
    Sequence number: 5    (relative sequence number)
    [Next sequence number: 41    (relative sequence number)]
    Acknowledgement number: 1    (relative ack number)
    Header length: 20 bytes
    Flags: 0x18 (PSH, ACK)
    Window size: 8760
    Checksum: 0x1d2a [validation disabled]
    [SEQ/ACK analysis]
        [This is an ACK to the segment in frame: 219]
        [The RTT to ACK the segment was: 0.000259000 seconds]
    [PDU Size: 40]
    TCP segment data (24 bytes)
    [Reassembled PDU in frame: 220]
    TCP segment data (28 bytes)
    [Reassembled PDU in frame: 224]
    TCP segment data (12 bytes)
[Reassembled TCP Segments (28 bytes): #216(4), #220(24)]



Thanks!
tl

Terry Lemons
Backup Platforms Group
EMC² 
where information lives
4400 Computer Drive, MS D239
Westboro MA 01580
Phone: 508 898 7312
Email: Lemons_Terry@xxxxxxx