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

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

      # Display progress indicators
      #
      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';

INSTALLATION
    "Net::Traces::TSH" can be installed like any CPAN module. In particular,
    consider using Andreas Koenig's CPAN module for all your CPAN module
    installation needs.

    To find out more about installing CPAN modules type

     perldoc perlmodinstall

    at the command prompt.

    If you have already downloaded the "Net::Traces::TSH" tarball,
    decompress and untar it, and proceed as follows:

     perl Makefile.PL
     make
     make test
     make install

DESCRIPTION
    "Net::Traces::TSH" can assist you in analyzing Internet Protocol (IP)
    packet traces in Time Sequenced Headers (TSH) format, a binary network
    trace format. Daily TSH traces are available from the NLANR PMA web
    site. Each 44-byte TSH record corresponds to an IP packet passing by a
    monitoring point. Although there are no explicit delimiters, each record
    is composed of three 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 the last section of a TSH record
    unless it corresponds to a TCP segment. In other words,
    "Net::Traces::TSH" reports on protocols other than TCP based solely on
    the first two sections.

    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 an adaptation 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. Also,
    keep in mind that recent Internet Engineering Task Force (IETF) Requests
    for Comments (RFCs) have deprecated the IP header *Type of Service*
    field in favor of Differentiated Services and Explicit Congestion
    Notification.

    You can use "Net::Traces::TSH" to gather information from a TSH packet
    trace, perform statistical analysis on Transport protocol,
    Differentiated Services (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
    A single TSH trace may contain records for packets observed on several
    different interfaces. For example, the daily TSH traces from the NLANR
    PMA repository typically contain records from two different interfaces.
    In such cases, incoming and outgoing traffic can be differentiated based
    on the interface number (despite the scrabbling of IP addresses to
    protect privacy). "Net::Traces::TSH" users may be interested in
    collecting statistical information for each interface separately or
    aggregating across the entire trace. "Net::Traces::TSH" uses two hashes
    to maintain these statistics: %Interfaces and %Trace.

    %Interfaces contains counts of several protocol particulars on a
    per-interface basis. For example, %Interfaces can tell you how many IP
    packets, TCP segments, and UDP datagrams were recorded in the trace for
    each interface.

    %Trace contains general information about the trace (date, number of
    records, duration, number of interfaces, etc.) as well as the aggregate
    data points across all interfaces. As such, %Trace will report the
    *total* number of UDP datagrams in the trace, the total number of TCP
    SYNs, and so on.

    Both %Trace and %Interfaces are *initialized and populated* by
    process_trace. The recommended way to get the trace summary information,
    after processing a trace is to call write_trace_summary, which stores
    the contents of %Trace in a CSV-formated text file, as shown in
    SYNOPSIS. Similarly, If you want summaries for the traffic on each
    interface, use write_interface_summaries.

    Neither %Trace nor %Interfaces are exported by default and are not meant
    to be accessed directly by user code. However, if you know what you are
    doing, you can get a reference to %Trace by calling
    get_trace_summary_href, and a reference to %Interfaces by calling
    get_interfaces_href. If you choose to do so, the following subsections
    explain how you can access some of the information stored in %Trace. The
    %Interfaces structure is virtually the same only lacking the "general
    trace information" part. See also Using the Net::Trace::TSH trace
    summary hashes.

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

    $Trace{date}
        The estimated date of the trace (see date_of).

    $Trace{summary}
        The trace summary FILENAME.

    $Trace{starts}
        The first trace timestamp, in seconds, as it is recorded in the
        trace.

    $Trace{ends}
        The last trace timestamp, in seconds, after being "normalized".
        Essentially, the number of seconds since $Trace{starts}.

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

        Similarly, if *$if* is the interface number,
        $Interfaces{$if}{records} contains the number or records
        corresponding to packets observed on interface *$if*.

    $Trace{interfaces}
        Number of interfaces recorded in the trace.

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

   Internet Protocol
    $Trace{IP}{Total}{Packets}
    $Trace{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.

        As mentioned earlier, %Trace has virtually the same structure as
        %Interfaces. Therefore, if *$if* is the interface number,
        $Interfaces{$if}{IP}{Total}{Packets} and
        $Interfaces{$if}{IP}{Total}{Bytes} contain the number of IP packets
        and bytes, respectively, observed on interface *$if*. The same
        "rule" applies to all %Trace fields presented below.

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

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

   Differentiated Services
    $Trace{IP}{Normal}{Packets}
    $Trace{IP}{Normal}{Bytes}
        Number of IP packets and bytes, respectively, requesting no
        particular treatment (best effort traffic). No DiffServ or ECN bits
        are set.

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

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

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

   Explicit Congestion Notification
    $Trace{IP}{ECT}{Packets}
    $Trace{IP}{ECT}{Bytes}
        Number of IP packets and bytes, respectively, with either of the ECT
        bits set. These packets should be carrying traffic from ECN-aware
        hosts.

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

   IP Options
    $Trace{IP}{'No IP Options'}{Packets}
    $Trace{IP}{'No IP Options'}{Bytes}
        Number of IP packets and bytes, respectively, carrying no IP header
        options.

    $Trace{IP}{'IP Options'}{Packets}
    $Trace{IP}{'IP Options'}{Bytes}
        Number of IP packets and bytes, respectively, carrying IP header
        options.

    The following diagram summarizes the %Trace data structure up to here.

     Trace
       - filename
       - summary
       - date
       - starts
       - ends
       - records
       - interfaces
       - unidirectional
       - 'Link Capacity'
       - IP
           - Total
               - Packets
               - Bytes
           - DF
               - Packets
               - Bytes
           - MF
               - Packets
               - Bytes
           - Normal
               - Packets
               - Bytes
           - 'Class Selector'
               - Packets
               - Bytes
           - 'AF PHB'
               - Packets
               - Bytes
           - 'EF PHB'
               - Packets
               - Bytes
           - ECT
               - Packets
               - Bytes
           - CE
               - Packets
               - Bytes
           - 'No IP Options'
               - Packets
               - Bytes
           - 'IP Options'
               - Packets
               - Bytes

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

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

    $Trace{Transport}{UDP}{Total}{Packets}
    $Trace{Transport}{UDP}{Total}{Bytes}
        Ditto, for UDP.

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

  Using the Net::Trace::TSH trace summary hashes
    The following example creates the trace summary file only if TCP
    accounts for more than 90% of the total IP traffic, in terms of bytes.

     # 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
     #
     my $ts_href = get_trace_summary_href;

     # ...and generate 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.

  configure
      configure %OPTIONS

    Used to specify verbosity, the link capacity, and the types of outputs
    requested. For example,

     configure(
               # Display progress information, equivalent to calling verbose()
               #
               Verbosity       => 1, # default is 0, no progress information

               'Link Capacity' => 100_000_000, # bits per second

               # Convert the TCP records in the TSH trace to tcpdump
               # format and store in 'trace.tcpdump'.
               #
               tcpdump         => 'trace.tcpdump',

               # Convert the TCP data-carrying segment records to binary
               # ns2 traffic trace format.  Create one binary file per
               # interface and use 'trace.ns2' as the file prefix.
               #
               ns2         => 'trace.ns2',

              );

  date_of
      date_of FILENAME

    TSH traces downloaded from the NLANR PMA trace repository typically
    contain a timestamp as part of their filename. date_of() converts the
    timestamp to a human readable format. That is, if FILENAME contains a
    valid timestamp, date_of() returns the corresponding GMT date as a human
    readable string. For example,

     date_of 'ODU-1073132115.tsh'

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

    If the FILENAME does not contain a timestamp, date_of() returns *false*.

    Note that there is nothing special about FILENAME: It can be any string.
    The goal here is to get an idea of the period the trace was collected.

  get_IP_address
     get_IP_address INTEGER

    Converts a 32-bit integer to an IP address in dotted decimal notation.
    For example,

     get_IP_address(167772172)

    returns 10.0.0.12.

  get_interfaces_href
     get_interfaces_href

    Returns a hash *reference* to %Interfaces.

  get_interfaces_list
     get_interfaces_list

    In list context returns a sorted list of all interfaces recorded in the
    trace. In scalar context returns the number of unique interfaces in the
    trace.

  get_trace_summary_href
     get_trace_summary_href

    Returns a hash *reference* to %Trace.

  process_trace
     process_trace FILENAME

    In a void context, process_trace() examines the binary TSH trace stored
    in FILENAME, and populates %Trace and %Interfaces.

    In a list context process_trace() in addition to collecting summary
    statistics, it extracts all TCP flows and TCP data-carrying segments
    from the trace, returning two hash references. For example,

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

    will process "trace.tsh" and return two hash references: *$senders_href*
    and *$segments_href*.

    *$senders_href* is a reference to a hash which contains an entry for
    each TCP sender in the trace file. 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 (on interface 1):

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

    Each hash entry is a list of timestamps extracted from the trace records
    and stored after being "normalized" (start of trace = 0.0 seconds,
    always).

    In theory, records corresponding to packets transmitted on the same
    interface 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 timestamp
    "collision avoidance" algorithm. A timestamp collision threshold is
    defined and is currently set to 3. Trace processing is aborted if the
    number of records with the same timestamp exceeds this threshold. If you
    encounter such traces, it is not a bad idea to investigate why this is
    happening, as the trace may be corrupted.

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

    For example, assuming 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 $segments_href->{$interface}{$timestamp}{bytes};
     print $segments_href->{$interface}{$timestamp}{seq_num};

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

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

    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() is not currently included in the stable,
    CPAN version of the module. Contact me if you want to get a copy of the
    bleeding edge version.

   Using a TSH trace in ns2 simulations
    In addition to extracting %senders and %segments, "Net::Traces::TSH"
    allows you to generate binary files suitable for driving ns2
    simulations. For example,

     configure(ns2 => 'some.tsh');

     process_trace 'some.tsh';

    After the call to configure(), process_trace() will generate a binary
    file for each interface found in the trace. For example, assume that
    some.tsh has recorded traffic from two interfaces, 1 and 2.
    process_trace() will generate two binary files:

      some.tsh-if1.bin
      some.tsh-if2.bin

    Each of these files can be used in ns2 simulations in conjunction
    Application/Traffic/Trace. For example, the following ns2 script
    fragment illustrates how to attach some.tsh-if2.bin to a traffic source

     # ...

     # Initialize a trace file
     #
     set tfile [new Tracefile]
     $tfile filename some.tsh-2.bin

     # Attach the tracefile
     #
     set trace [new Application/Traffic/Trace]
     $trace attach-tracefile $tfile

     # ...

    Note that both some.tsh-if1.bin and some.tsh-if1.bin include only the
    *TCP data-carrying segments* in the trace. If you want to convert the
    *entire* TSH trace to Traffic/Trace files, see "converters/tsh2ns2.pl".

   Converting TSH to tcpdump
    If you would like to extract the TCP traffic and store it in tcpdump
    format, use

     configure(tcpdump => 'tcpdump_filename');

    before calling process_trace(). process_trace() will 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 (see 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 this output is similar to what tcpdump with options "-n" and
    "-S" would have produced. The only missing fields are related to 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 based on its file size. It
    returns an integer corresponding to the "expected" number of records in
    the trace, or *false* if the file size does not seem to correspond to a
    legitimate TSH trace.

  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.

    As of version 0.13, verbose() is equivalent to

     configure(Verbosity => 1);

  write_interface_summaries
     write_interface_summaries
     write_interface_summaries FILE_PREFIX

    Writes a CSV summary similar to what write_trace_summary() generates for
    each interface in the trace (see %Interfaces). Each summary file has a
    ".if-X.csv" suffix, where X is the number of the interface. If
    FILE_PREFIX is provided, write_interface_summaries() will append to it
    this standard suffix (indicative of the interface).

  write_trace_summary
     write_trace_summary
     write_trace_summary FILENAME

    Writes the contents of %Trace 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
    Nothing non-standard: strict, warnings and Carp.

  EXPORTS
    None by default.

   Exportable
    configure() date_of() get_IP_address() get_interfaces_href()
    get_interfaces_list() 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_interface_summaries()
        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 0.16.

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.

    "Net::Traces::TSH" version 0.11 was presented in YAPC::NA 2004. The
    presentation slides are available at
    http://www.cs.stonybrook.edu/~kostas/art/yapc .

  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

  The ns2 network simulator
    "Net::Traces::TSH" can convert TSH traces to binary files suitable to
    drive simulations in ns2. More information about ns2 is available at
    http://www.isi.edu/nsnam/ns .

AUTHOR
    Kostas Pentikousis, kostas AT cpan DOT 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.