tcptrace about TCP RTT calculation when packet truncation happens

From: Minghua Chen (minghua@eecs.berkeley.edu)
Date: 02/24/03

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    Date: Mon, 24 Feb 2003 14:44:41 -0800 (PST)
From: Minghua Chen <minghua@eecs.berkeley.edu>
Subject: tcptrace about TCP RTT calculation when packet truncation happens
Message-ID: <Pine.SOL.4.44.0302241437010.4734-100000@nima.EECS.Berkeley.EDU>

    Hi,

    I am dumping and analyzing the TCP packets from a fixed host to a mobile
    host connected via Verizon wireless network using 1xRTT CDMA data service.
    I run tcpdump on the mobile host, and try to DL some file from the
    fixed host using FTP service.

    When I look into the RTT raw file, I saw some packet with RTT 0, while
    some with RTT != 0, which makes the RTT statistics not make sense (only
    54.3 ms roundtrip!)

    I also notice all the packets from the fixed host to the mobile host is
    truncated. So it might be the calculation bug (?) when calculating the
    RTT of packets that get truncated?

    Any suggestions on how can i get the correct RTT in my senario?

    Thanks

    Minghua

    -------------- examples of RTT raw file of the FTP data packets:
    2629228319 196
    2629230103 0
    2629231563 0
    2629234483 0
    2629235943 0
    2629238863 0
    2629240323 0
    2629243243 0
    2629244703 102
    2629246487 0
    2629247947 0
    2629250867 0
    2629252327 0
    2629255247 0
    2629256707 0
    2629259627 0
    2629261087 107
    2629262871 0
    2629264331 0
    2629265791 174
    2629268711 0
    2629270171 136
    2629271631 157
    2629273091 0
    2629274551 117
    2629277471 0
    2629277795 100
    2629279255 120
    2629280715 0
    2629283635 0
    2629285095 0
    2629286555 164
    2629289475 0
    2629290935 126
    2629293855 0
    2629294179 108
    2629295639 126
    2629297099 0
    2629298559 170
    2629301479 0
    2629302939 152
    2629304399 173
    2629305859 0
    2629307319 114
    2629310239 0
    2629312023 0
    2629313483 0
    2629316403 0
    2629317863 0
    2629320783 0
    2629322243 0
    2629325163 0
    2629326623 177
    2629328407 0
    2629329867 0
    2629332787 0
    2629334247 0
    2629337167 0
    2629338627 0
    2629341547 0
    2629343007 142

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