Black Box 5000 series Reference Manual page 259

Format:
Receive frames (r) are indented.
Transmit frames (x) are not.
Valid frames are as follows:
I - Information
RR - Receiver Ready
RNR - Receiver Not Ready
REJ - Reject
SABM - Set Asynchronous Balance Mode
DM - Disconnect Mode
DISC - Disconnect
UA - Unnumbered Acknowledgment
FRMR - Frame Reject
Information (I) Frame traces will be displayed with the following:
Link (L1/L2)(x/r)I
As much of the Data Field as will fit on one line will be displayed if hex or ASCII format is specified. If off is specified, only
the Data Field Length is given.
Supervisory (S) frame traces will be displayed with the following:
Link (L1/L2)(x/r)(RR / RNR / REJ)
Unnumbered (U) frame traces will be displayed with the following:
Link (0/1) (x/r)
Any illegal or unknown frame will be completely dumped in hex. Note that any frame with a CRC error will not be displayed
and a Level 2 error will be output.
LAPB control field formats:
Three types of Link Access Procedures (Balanced) LAPB control field formats are used to perform:
1) numbered information transfer (I format),
2) numbered supervisory functions (S format) and
3) unnumbered control functions (U format).
The numbered I format is used to perform information transfer.
The numbered S format is used to perform data link supervisory control functions such as:
- acknowledge I frames,
- request transmission of I frames, and
- to request a temporary suspension of I frames.
The unnumbered U format is used to provide additional data link control functions.
Menus Reference Manual: WAN Trace Menu
N(r), N(s)
N(r)
(SABM / DM / DISC / UA / FRMR)
Data Field Length Data Field (hex)
259