Wireshark · Ethereal-dev: Re: [Ethereal-dev] OSI Session dissector in the works

[Guy Harris <guy@xxxxxxxxxxxx>]

On Sep 9, 2003, at 1:34 AM, Sid Sid wrote:

> Now I've got recent version. But something is still wrong with 
> reassembling segmentent COTP PDUs.
> Please, have a look to attached capture file - clnp_.I mean frames 
> 8-16.Frame 8 is the first and frame 16 last COTP segmented PDUs.

No, frames 10, 12, 14, and 16 are the segments of a segmented PDU to 
dst-ref 0x0001.  Frame 8 is a non-segmented PDU to dst-ref 0x0101 
(i.e., it's going in the other direction).

The problem is that the reassembly code assumes that sequence numbers 
in a segmented packet start at 0; unfortunately, the sequence numbers 
in COTP are PDU numbers, and those are connection sequence numbers that 
increase sequentially, so the first segment of a segmented PDU doesn't 
have a sequence number that starts at 0.

That will require more work in the reassembly code to fix.