Capturing The Protocol Data - ZyXEL Communications omni TA128 User Manual

Capturing the Protocol Data

The data captured by the EPA can be classified into three
categories:
B-channel user data protocols.
D-channel signaling protocols.
DTE-DCE protocols.
The D-channel signaling protocols include layer 2 and layer 3 call
control protocols. Frames and messages exchanged via the D-
channel are all recorded for further analysis. These data messages
are essential to understanding interactive operations between an
ISDN TA and the ISDN network. They contain the compatibility
information for the Omni TA128 and your Central Exchange.
The B-channel user data protocols include X.75 and V.120. Only
the layer 2 header (addresses and control bytes) and layer 3 header
are captured. Since X.75 may be used with various layer 3
protocols (e.g. T.70, T.90, and ISO8208), only the first 8 octets of
the information field are recorded as the layer 3 header, and are
displayed in raw data form. The analysis of the protocol data will
be carried out by ZyXEL's Technical Support department.
The DTE-DCE protocols (at the R reference point according to the
ISDN nomenclature) include the AT commands/responses as well
as the CAPI internal interface. The CAPI internal interface is used
with the ZyXEL CAPI driver. The ZyXEL CAPI driver
communicates with the Omni TA128 through this internal
interface. It is not recommended that users get involved in this
internal interface. The AT commands/responses, on the other hand,
are in a standard user interface. An analysis of these commands
and responses might prove very informative. All messages
captured by the EPA are tagged with a time stamp according to a
free running timer that starts at the beginning of data capture. The
resolution of this timing information is in 0.01 second intervals.
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