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1. Load your capture file by choosing
Open
from the
File
menu on the
Control
window.
2. Select the file to load.
3. Choose
Protocol Stack
from the
Options
menu on the
Control
window
4. Select None from the list
5. Click Finish . The Protocol Stack Wizard asks you if you want to unframe your data and put it into a
new file.
6. Choose
Yes
.
The system removes the frame markers from your data, puts the unframed data into a new file, and opens
the new file. The original capture file is not altered.
See Reframing on page 73 for instructions on framing unframed data.
4.2.5 How the Analyzer Auto-traverses the Protocol Stack
In the course of doing service discovery, devices ask for and receive a Protocol Descriptor List defining which
protocol stacks the device supports. It also includes information on which PSM to use in L2CAP, or the channel
number for RFCOMM, or the port number for TCP or UDP. The description below talks about how the
analyzer auto-traverses from L2CAP using a dynamically assigned PSM, but the principle is the same for
RFCOMM channel numbers and TCP/UDP port numbers.
The analyzer looks for SDP Service Attribute Responses or Service Search Attribute Responses carrying
protocol descriptor lists. If the analyzer sees L2CAP listed with a PSM, it stores the PSM and the UUID for the
next protocol in the list.
After the SDP session is over, the analyzer looks at the PSM in the L2CAP Connect frames that follow. If the
PSM matches one the analyzer has stored, the analyzer stores the source channel ID and destination channel
ID, and associates those channel IDs with the PSM and UUID for the next protocol. Thereafter, when the
analyzer sees L2CAP frames using those channel IDs, it can look them up in its table and know what the next
protocol is.
In order for the analyzer to be able to auto-traverse using a dynamically assigned PSM, it has to have seen the
SDP session giving the Protocol Descriptor Lists, and the subsequent L2CAP connection using the PSM and
identifying the source and channel IDs. If the analyzer misses any of this process, it is not able to auto-traverse.
It stops decoding at the L2CAP layer.
For L2CAP frames carrying a known PSM (0x0001 for SDP, for example, or 0x0003 for RFCOMM), the analyzer
looks for Connect frames and stores the PSM along with the associated source and destination channel IDs. In
this case the analyzer does not need to see the SDP process, but does need to see the L2CAP connection
process, giving the source and destination channel IDs.
4.2.6 Providing Context For Decoding When Frame Information Is Missing
There may be times when you need to provide information to the analyzer because the context for decoding
a frame is missing. For example, if the analyzer captured a response frame, but did not capture the command
frame indicating the command.
The analyzer provides a way for you to supply the context for any frame, provided the decoder supports it.
(The decoder writer has to include support for this feature in the decoder, so not all decoders support it.
Note that not all decoders require this feature.)
If the decoder supports user-provided context, three items are active on the Options menu of the Control
window and the Frame Display window. These items are Set Initial Decoder Parameters ,
Automatically Request Missing Decoding Information , and Set Subsequent Decoder Parameters .
(These items are not present if no decoder is loaded that supports this feature.)
Chapter 4 Capturing and Analyzing Data TELEDYNE LECROY
Frontline BPA 600 Hardware & Software User Manual 74