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Visual Packet Builder is a
tool designed for facilitating packet editing and generation in
the
Packet
Generator. This tool allows you to
quickly and correctly create a new packet or modify an existing one
using ready-made templates. Once created or edited, a packet can be
injected into the network using the
Packet
Generator.
Standard TCP, UDP, and
ICMP (based on the 4th
and
6th
versions of IP
protocol), and ARP packet generation is supported. To create a
packet, select its type from the Packet
Type drop-down list. The
default values of the packet fields will be automatically filled
in, but can be changed afterwards.
ICMP, TCP, UDP, and ARP
packets consist of several encapsulated layers, and the interface
of Visual Packet Builder is arranged the same way. Options that
correspond to the same layer are located on a separate panel. For
example, a TCP packet consists of 4 layers; the Source
MAC and Destination
MAC address fields are located
on the Ethernet
II panel (Data link layer),
and Src
Port and Dst
Port values are located on the
TCP panel (Transport layer). If you'd like to hide a panel, click
the Expand/Collapse
button located
in the right corner of the panel header.
Note that some "parental"
layer values affect the packet type on lower layers; hence
modifying upper layers may lead to rebuilding the lower layers of a
packet. Therefore, if you change the Protocol
type in
the Ethernet
II panel (Data link layer),
it will lead to rebuilding the whole packet. Another peculiarity
that you should keep in mind is that the values of some fields
depend on the contents of other fields, as well as the data
contents of the lower layers. Such fields are: checksums and header
lengths, and/or data of lower layers. Visual Packet Builder
calculates such values automatically. However, when creating
non-standard packets, you may want to specify different values
manually by checking the Override
default value box and specifying the
desired values.
Note:
Visual Builder helps you control the correctness of the packet
being built by highlighting the headers and fields with incorrect
or non-standard values in red.
Despite the fact that
Visual Packet Builder has internal support for TCP, UDP, ICMP and
ARP protocols only, you can still use it to edit packets that use
other protocols. For such packets, you can use the hex editor to
modify the data.
Once created, a packet can
be saved and subsequently loaded to Visual Packet Builder again.
Use the respective commands located in the File
menu of Visual
Packet Builder for loading/saving capture files. You can load any
CommView capture file (NCF); however, if the file contains more
than one packet, only the first one will be loaded.
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