NAME
    Net::Traces::TSH - Analyze IP traffic traces in TSH format

SYNOPSIS
      use Net::Traces::TSH qw(:traffic_analysis);

      # Enable progress information display
      #
      verbose;

      # process the trace in file some_trace.tsh
      #
      process_trace 'some_trace.tsh';

      # Then, write a summary of the trace contents to some_trace.csv, in
      # Comma-Separated Values (CSV) format
      #
      write_trace_summary 'some_trace.csv';

ABSTRACT
    Net::Traces::TSH provides methods to analyze IP packet traces in Time
    Sequenced Headers (TSH) format. Trace summary statistics are stored in
    comma separated values (CSV), a platform independent text format. Use
    Net::Traces::TSH to gather general information about a TSH packet trace,
    measure Transport protocol, DiffServ and ECN usage, and generate packet
    and segment size distributions. In addition, you can extract all TCP
    traffic present in a TSH trace in a tcpdump-like text format.

INSTALLATION
    To install "Net::Traces::TSH" type the following:

     perl Makefile.PL
     make
     make test
     make install

    Moreover,

     perldoc perlmodinstall

    provides more information and options about installing Perl modules.

DESCRIPTION
    With "Net::Traces::TSH" you can analyze IP packet traces in Time
    Sequenced Headers (TSH), a binary network trace format. Each 44-byte TSH
    record corresponds to an IP packet passing by a monitoring point.
    Although there are no explicit section delimiters, each record is
    composed of three rather distinct sections.

    Time and Interface
        The first section uses 8 bytes to store the time (with microsecond
        granularity) and the interface number of the corresponding packet,
        as recorded by the (passive) monitor.

    IP  The next 20 bytes contain the standard IP packet header. IP options
        are not recorded.

    TCP The third and last section contains the first 16 bytes of the
        standard TCP segment header. The TCP checksum, urgent pointer, and
        TCP options (if any) are not included in a TSH record.

    If a record does not correspond to a TCP segment, it is not clear how to
    interpret the last section. As such, "Net::Traces::TSH" makes no
    assumptions, and does not analyze in detail packets from protocols other
    than TCP. That is, "Net::Traces::TSH" reports on protocols other than
    TCP based on the second section (IP header) only.

    The following diagram illustrates a TSH record.

         0                   1                   2                   3
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  Section
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      0 |                      Timestamp (seconds)                      | Time
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      1 | Interface  No.|          Timestamp (microseconds)             |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      2 |Version|  IHL  |Type of Service|          Total Length         | IP
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      3 |         Identification        |Flags|      Fragment Offset    |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      4 |  Time to Live |    Protocol   |         Header Checksum       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      5 |                       Source Address                          |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      6 |                    Destination Address                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      7 |          Source Port          |       Destination Port        | TCP
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      8 |                        Sequence Number                        |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      9 |                    Acknowledgment Number                      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |  Data |       |C|E|U|A|P|R|S|F|                               |
     10 | Offset|RSRV-ed|W|C|R|C|S|S|Y|I|            Window             |
        |       |       |R|E|G|K|H|T|N|N|                               |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    This diagram is a modified version of the original TSH diagram (found on
    the NLANR PMA web site), which reflects the changes due to the addition
    of Explicit Congestion Notification (ECN) in the TCP header flags. Keep
    in mind that recent RFCs have modified the meaning of the IP header Type
    of Service field to accommodate Differentiated Services and Explicit
    Congestion Notification.

    For example, you can use "Net::Traces::TSH" to gather information from a
    TSH packet trace, perform statistical analysis on Transport protocol,
    DiffServ and ECN usage, and obtain packet and segment size
    distributions. The trace summary statistics are stored in comma
    separated values (CSV), a platform independent text format.

  Data Structures
    The data collected from a trace is stored is a hash called
    %Trace_Summary, the main data structure in "Net::Traces::TSH".
    %Trace_Summary is initialized and populated by process_trace. The
    recommended way to get the trace summary information is by calling
    write_trace_summary, which stores the contents of %Trace_Summary in a
    CSV-formated text file, as shown in SYNOPSIS.

    %Trace_Summary is not exported by default and it is not intended to be
    accessed directly by user code. However, if you know what you are doing,
    you can get a reference to %Trace_Summary by calling
    get_trace_summary_href. If you choose to do so, the following
    subsections explain how you can access some of the information stored in
    %Trace_Summary. See also Taking advantage of %Trace_Summary.

   General Trace Information
    $Trace_Summary{filename}
        The trace FILENAME.

    $Trace_Summary{log}
        The trace summary FILENAME.

    $Trace_Summary{starts}
        The first trace timestamp, in seconds.

    $Trace_Summary{ends}
        The last trace timestamp, in seconds.

    $Trace_Summary{records}
        Number of records in the trace.

    $Trace_Summary{unidirectional}
        True, if each interface carries unidirectional traffic.

        False, if there is bidirectional traffic in at least one interface.

        "undef" if traffic directionality was not examined.

    $Trace_Summary{Link Capacity}
        The capacity of the monitored link in bits per second (b/s).

   Internet Protocol
    $Trace_Summary{IP}{'Total Packets'}
    $Trace_Summary{IP}{'Total Bytes'}
        Number of IP packets and bytes, respectively, in the trace. The
        number of IP packets should equal the number of records in the
        trace.

   Fragmentation
    $Trace_Summary{IP}{'DF Packets'}
    $Trace_Summary{IP}{'DF Bytes'}
        Number of IP packets and bytes, respectively, requesting no
        fragmentation ('Do not Fragment').

    $Trace_Summary{IP}{'MF Packets'}
    $Trace_Summary{IP}{'MF Bytes'}
        Number of IP packets and bytes, respectively, indicating that 'More
        Fragments' follow.

   Differentiated Services
    $Trace_Summary{IP}{'Normal Packets'}
    $Trace_Summary{IP}{ 'Normal Bytes'}
        Number of IP packets and bytes, respectively, requesting no
        particular treatment (best effort traffic). None of the DiffServ and
        ECN bits are set.

    $Trace_Summary{IP}{'Class Selector Packets'}
    $Trace_Summary{IP}{'Class Selector Bytes'}
        Number of IP packets and bytes, respectively, with Class Selector
        bits set.

    $Trace_Summary{IP}{'AF PHB Packets'}
    $Trace_Summary{IP}{'AF PHB Bytes'}
        Number of IP packets and bytes, respectively, requesting Assured
        Forwarding Per-Hop Behavior (PHB).

    $Trace_Summary{IP}{'EF PHB Packets'}
    $Trace_Summary{IP}{'EF PHB Bytes'}
        Number of IP packets and bytes, respectively, requesting Expedited
        Forwarding Per-Hop Behavior (PHB)

   Explicit Congestion Notification
    $Trace_Summary{IP}{'ECT Packets'}
    $Trace_Summary{IP}{'ECT Bytes'}
        Number of IP packets and bytes, respectively, with either of the ECT
        bits set. These packets carry ECN-capable traffic.

    $Trace_Summary{IP}{'CE Packets'}
    $Trace_Summary{IP}{'CE Bytes'}
        Number of IP packets and bytes, respectively, with the CE bit set.
        There packets carry ECN-capable traffic that has been marked at an
        ECN-aware router.

   Transport Protocols
    Besides the summary information about the trace itself and statistics
    about IP, %Trace_Summary maintains information about the transport
    protocols present in the trace. Based on the IP header, %Trace_Summary
    maintains the same statistics mentioned in the previous section for TCP,
    UDP and other transport protocols with an IANA assigned number. For
    example,

    $Trace_Summary{Transport}{TCP}{'Total Packets'}
    $Trace_Summary{Transport}{TCP}{'Total Bytes'}
        Number of TCP segments and the corresponding bytes (including the IP
        and TCP headers) in the trace.

    $Trace_Summary{Transport}{UDP}{'Total Packets'}
    $Trace_Summary{Transport}{UDP}{'Total Bytes'}
        Ditto for UDP.

    $Trace_Summary{Transport}{ICMP}{'DF Packets'}
    $Trace_Summary{Transport}{ICMP}{'DF Bytes'}
        Number of ICMP packets and bytes, respectively, with the DF bit set.

  Taking advantage of %Trace_Summary
    The following example creates the trace summary file only if the TCP
    traffic in terms of bytes accounts for more than 90% of the total IP
    traffic in the trace.

     # Explicitly import process_trace(), write_trace_summary(), and
     # get_trace_summary_href():

     use Net::Traces::TSH qw( process_trace write_trace_summary
                              get_trace_summary_href
                            );

     # Process a trace file...
     #
     process_trace "some.tsh";

     # Get a reference to %Trace_Summary
     #
     my $ts_href = get_trace_summary_href;

     # ...and create a summary only if the condition is met.
     #
     write_trace_summary
        if ( ( $ts_href->{Transport}{TCP}{'Total Bytes'}
               / $ts_href->{IP}{'Total Bytes'}
             ) > 0.9);

FUNCTIONS
    "Net::Traces::TSH" does not export any functions by default. The
    following functions, listed in alphabetical order, are exportable.

  date_of
      date_of FILENAME

    Converts the epoch timestamp, typically part of a TSH trace FILENAME
    downloaded from http://pma.nlanr.net/Traces to a human readable date. If
    FILENAME contains a valid timestamp, date_of() returns the corresponding
    GMT date as a string. Otherwise, it returns an empty string, i.e.
    *false*.

    For example,

     date_of 'ODU-1073132115.tsh'

    returns "Sat Jan 3 12:15:15 2004 GMT".

  get_IP_address
     get_IP_address INTEGER

    Converts a 32-bit integer to an IP address. For example,

     get_IP_address(167772172)

    returns 10.0.0.12.

  get_trace_summary_href
     get_trace_summary_href

    Returns a hash *reference* to %Trace_Summary.

  process_trace
     process_trace FILENAME
     process_trace FILENAME, NUMBER
     process_trace FILENAME, NUMBER, TEXT_FILENAME

    If called in a void context process_trace() examines the binary TSH
    trace stored in FILENAME, and populates %Trace_Summary.

    NUMBER specifies the capacity of the monitored link in bits per second
    (b/s). If not specified, it defaults to 155,520,000.

    If called in a list context process_trace() gathers the same statistics
    and in addition it extracts all TCP flows and TCP data-carrying segments
    from the trace, returning two hash references. For example

     my ($senders_href, $packets_href) = process_trace 'trace.tsh';

    Here *$senders_href* is a reference to a hash which contains an entry
    for each TCP sender in the trace file. Each hash entry is a list of
    timestamps extracted from the trace record and stored after being
    "normalized" (start of trace = 0.0 seconds, always). In theory, all
    records should have different timestamps. In practice, although it is
    not very likely that two data segments have the same timestamp, I
    encountered a few traces that did have duplicate timestamps.
    process_trace() checks for such cases and implements a hash collision
    avoidance algorithm. If the collision threshold of trace records with
    the same timestamp is exceeded, process_trace() aborts as this is a hint
    that the trace is corrupted. The collision threshold is currently set to
    4.

    A TCP sender is identified by the ordered 4-tuple

     (src, src port, dst, dst port)

    where *src* and *dst* are the 32-bit integers corresponding to the IP
    addresses of the sending and receiving hosts, respectively. Similarly,
    *src port* and *dst port* are the sending and receiving processes port
    numbers. Senders are categorized on a per interface basis. For example,
    the following accesses the list of segments sent from 10.0.0.12:80 to
    10.0.0.14:1080 (in interface 1):

     $senders_href->{1}{167772172,80,167772174,1080}

    The second returned value, *$packets_href*, is another hash reference,
    which can be used to access any individual data-carrying TCP segment in
    the trace. Again, packets are categorized on a per interface basis.
    Three values are stored per packet: the total number of bytes in the
    packet (including IP and TCP headers, and application payload), the
    segment sequence number, and whether the segment was retransmitted or
    not.

    For example, assuming the the first record corresponds to a TCP segment,
    here is how you can print its packet size and the sequence number
    carried in the TCP header:

     my $interface = 1;
     my $timestamp = 0.0;

     print $packets_href->{$interface}{$timestamp}{bytes};
     print $packets_href->{$interface}{$timestamp}{seq_num};

    You can also check whether a packet was retransmitted or not:

     if ( packets_href->{$interface}{$timestamp}{retransmitted} ) {
       print "Packet was retransmitted by the TCP sender.";
     }
     else {
       print "Packet must have been acknowledged by the TCP receiver.";
     }

    Please note that process_trace() only initializes the "retransmitted"
    value to false (0). It is write_sojourn_times() that detects
    retransmitted segments and updates the "retransmitted" entry to *true*,
    if it is determined that the segment was retransmitted.

    CAVEAT: write_sojourn_times() has not been finalized yet, and as such it
    is not included in this version. Contact me if you want to to get the
    most recent version.

    If TEXT_FILENAME is specified, process_trace() generates a text file
    based on the trace records in a format similar to the modified output of
    tcpdump, as presented in *TCP/IP Illustrated Volume 1* by W. R. Stevens.
    The format is explained in more detail in *TCP/IP Illustrated Volume 1*,
    pp. 230-231.

    You can use such an output as input to other tools, present real traffic
    scenarios in a classroom, or simply "eyeball" the trace. For example,
    here are the first ten lines of the contents of such a file:

     0.000000000 10.0.0.1.6699 > 10.0.0.2.55309: . ack 225051666 win 65463
     0.000014000 10.0.0.3.80 > 10.0.0.4.14401: S 457330477:457330477(0) ack 810547499 win 34932
     0.000014000 10.0.0.1.6699 > 10.0.0.2.55309: . 3069529864:3069531324(1460) ack 225051666 win 65463
     0.000024000 10.0.0.5.12119 > 10.0.0.6.80: F 2073668891:2073668891(0) ack 183269290 win 64240
     0.000034000 10.0.0.7.4725 > 10.0.0.8.445: S 3152140131:3152140131(0) win 16384
     0.000067000 10.0.0.1.6699 > 10.0.0.2.55309: P 3069531324:3069531944(620) ack 225051666 win 65463
     0.000072000 10.0.0.11.3381 > 10.0.0.12.445: S 1378088462:1378088462(0) win 16384
     0.000083000 10.0.0.13.1653 > 10.0.0.1.6699: P 3272208349:3272208357(8) ack 501563814 win 32767
     0.000093000 10.0.0.14.1320 > 10.0.0.15.445: S 3127123478:3127123478(0) win 64170
     0.000095000 10.0.0.4.14401 > 10.0.0.3.80: R 810547499:810547499(0) ack 457330478 win 34932

    Note that the text output is similar to what tcpdump with options "-n"
    and "-S" would have produced. The only missing field is the TCP options
    negotiated during connection setup. Unfortunately, TSH records include
    only the first 16 bytes of the TCP header, making it impossible to
    record the options from the segment header.

  records_in
     records_in FILENAME

    Estimates the number to records in FILENAME and returns the "expected"
    number of records in the trace, which must an integer. If not an
    integer, records_in() returns *false*.

  verbose
     verbose

    As you might expect, this function sets the verbosity level of the
    module. By default "Net::Traces::TSH" remains "silent". Call verbose()
    to see trace processing progress indicators on standard error.

  write_trace_summary
     write_trace_summary FILENAME
     write_trace_summary

    Writes the contents of %Trace_Summary to FILENAME in comma separated
    values (CSV) format, a platform independent text format, excellent for
    storing tabular data. CSV is both human-readable and suitable for
    further analysis using Perl or direct import to a spreadsheet
    application. Although not required, it is recommended that FILENAME
    should have a *.csv* suffix.

    If FILENAME is not specified, write_trace_summary() will create one for
    you by appending the suffix *.csv* to the filename of the trace being
    processed.

    If you want FILENAME to contain meaningful data you should call
    write_trace_summary() *after* calling process_trace().

DEPENDENCIES
    Carp

EXPORTS
    None by default.

  Exportable
    date_of() get_IP_address() get_trace_summary_href() numerically()
    process_trace() records_in() verbose() write_trace_summary()

    In addition, the following export tags are defined

    :traffic_analysis
        verbose() process_trace() write_trace_summary()

    :trace_information
        date_of() records_in()

    Finally, all exportable functions can be imported with

     use Net::Traces::TSH qw(:all);

VERSION
    This is "Net::Traces::TSH" version 0.06.

SEE ALSO
    The NLANR MOAT Passive Measurement and Analysis (PMA) web site at
    http://pma.nlanr.net/PMA provides more details on the process of
    collecting packet traces. The site features a set of Perl programs you
    can download, including several converters from other packet trace
    formats to TSH.

    TSH trace files can be downloaded from the NLANR/PMA trace repository at
    http://pma.nlanr.net/Traces . The site contains a variety of traces
    gathered from several monitoring points at university campuses and
    (Giga)PoPs connected to a variety of large and small networks.

  DiffServ
    If you are not familiar with Differentiated Services (DiffServ), good
    starting points are the following RFCs:

    K. Nichols *et al.*, *Definition of the Differentiated Services Field
    (DS Field) in the IPv4 and IPv6 Headers*, RFC 2474. Available at
    http://www.ietf.org/rfc/rfc2474.txt

    S. Blake *et al.*, *An Architecture for Differentiated Services*, RFC
    2475. Available at http://www.ietf.org/rfc/rfc2475.txt

    See also RFC 2597 and RFC 2598.

  ECN
    If you are not familiar Explicit Congestion Notification (ECN) make sure
    to read

    K. K. Ramakrishnan *et al.*, *The Addition of Explicit Congestion
    Notification (ECN) to IP*, RFC 3168. Available at
    http://www.ietf.org/rfc/rfc3168.txt

AUTHOR
    Kostas Pentikousis, kostas@cpan.org.

ACKNOWLEDGMENTS
    Professor Hussein Badr provided invaluable guidance while crafting the
    main algorithms of this module.

    Many thanks to Wall, Christiansen and Orwant for writing *Programming
    Perl 3/e*. It has been indispensable while developing this module.

COPYRIGHT AND LICENSE
    Copyright 2003, 2004 by Kostas Pentikousis. All Rights Reserved.

    This library is free software with ABSOLUTELY NO WARRANTY. You can
    redistribute it and/or modify it under the same terms as Perl itself.

