Ethereal-users: Re: [Ethereal-users] "TCP Segment of a Reassembled PDU" vs. "Continuation or non

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From: Guy Harris <gharris@xxxxxxxxx>
Date: Tue, 18 Apr 2006 10:51:36 -0700
Feeny, Michael (TD&DS, Applications Infrastructure Svcs.) wrote:

I have 2 different trace files, each of which contains an HTTP �POST� request that is split across 2 packets. In one of the traces, Ethereal displays "TCP Segment of a Reassembled PDU" for the 1^st of these 2 packets, and in the other, it displays "Continuation or non-HTTP traffic" for the 2^nd of the 2 packets.

Can someone explain the distinction?

"TCP Segment of a Reassembled PDU" means that Ethereal's doing reassembly, which means that

1) TCP's "Allow subdissector to reassemble TCP streams" preference is turned on;

	2) HTTP's reassembly preferences are turned on;

3) the POST body is either not split across segments or has a Content-Length header (currently, HTTP bodies aren't reassembled if they don't have a Content-Length header).

"Continuation or non-HTTP traffic means Ethereal's not doing reassembly. Unless you changed the preference settings between the two traces, it might be that the second POST doesn't have a Content-Length header.

One difference in the 2 traces: In the first trace, HTTP is sent over a non-standard TCP port (3139), and so I have to use �Analyze/Decode as�� to force Ethereal to interpret the traffic as HTTP. Does that explain the difference in diagnostic messages?

Probably not - the HTTP code path should work the same in either case.