out of order packets

From: "Raja Epsilon" <raja_epsilon@hotmail.com>
Subject: out of order packets
Date: Thu, 01 Mar 2001 11:55:20 -0000
Message-ID: <F279SAsRFmrLbcfmINl00003100@hotmail.com>

Hello,

 

I have a question regarding the out of order packets calculated by Tcptrace. To plot out-of-order packets as a function of time, I calculated out of order packets using the following logic:

 

-- variable "highest_sequence" is  initialized to zero

--first sequence # is assigned to it (which is the highest sequence number seen so far)

--subsequent sequence numbers are compared to it to always maintain the highes sequence number

--any number less than it willl result in "highes_sequence" - "small sequence number just seen" out-of-order packets

But this script is resulting more "out-of-order: packets than what is reported by Tcptrace.

I am not sure what part of my logic is wrong. Has it something to do with "SACK"?

 

My second question is again about out-of-order packets. I have a dedicated network where two computers are connected using a hub where one connection is wireless. Is it possible to get out of order packets in this scenario? I am getting lots of out-of-order packets from my experiments using Tcptrace. In INTERNET it is common to have out of order packets since packets are routed through different routers. But how can this happen on a dedicated network? Is it because of bit errors in the wireless medium that forces corrupted packets to spend more time in data link layer employing FEC whereas uncorrupte packets are processed quicker and passed on the transport layer?

 

Thanks in advance,

Raja