03/02 Level 2 Troubleshooting
WorkCentre Pro 423/428 2-93 CHAPTER 2 TROUBLESHOOTING
2.3.2.5 B channel troubleshooting
If origination or termination is completed through the D channel, the channel is switched to B
for fax signal transmission. In G3 communication through ISDN, the CED, DIS, and PIX
signals of G3 fax are sent through B channels. In B-channel troubleshooting, therefore, it is
necessary to locate a fault in the local or remote terminal.
From the B channels, the protocol trace data of Layers 2 (Network) to 6 (Presentation) can be
collected individually. Seemingly necessary layers should be set before communication.
Even when the protocol layer is changed after communication, its trace data is not recorded.
The default is Layer 5 (Session).
The protocols of Layers 2 (Network) and 5 (Session) are used for troubleshooting the B
channels and that of Layer 6 (Presentation) is used for checking the document size. This
section explains the Network, Session, and Presentation protocols.
2.3.2.5.1 Network Protocol (Layer 3 of B channel)
For the normal sequence of the Network protocol, see "Network" in the B-channel sequence.
In case of a communication fault in the Network layer, one of the packet signals (CQ, CI, SQ,
SI, RQ, and RI) is sent. The cause of the fault can be confirmed by analyzing the cause and
diagnostic information contained in this signal.
Table 1 Packet Signals Used in Network Protocol (Layer 3 of B channel)
Packet
signal
Meaning Description
CR Call request 10 01 0B (Origination number) (Termination number)
(Packet size etc.)
CN Termination 10 01 0B (Origination number) (Termination number)
(Packet size etc.)
CA Call acceptance 10 01 0F (Origination number) (Termination number)
(Packet size etc.)
CC Connection
complete
10 01 0F (Origination number) (Termination number)
(Packet size etc.)
CQ Recovery request 10 01 13 (Cause) (Diag)
CI Disconnection
indication
10 01 13 (Cause) (Diag) *See Tables 2 and 3
CF Disconnection
confirmation
10 01 17
SQ Restart request 10 00 FB (Cause) (Diag)
SI Restart indication 10 00 FB (Cause) (Diag) *See Tables 4 and 5
SF Restart confirmation 10 00 FF
RQ Reset request 10 01 1B (Cause) (Diag)
RI Reset indication 10 01 1B (Cause) (Diag) *See Tables 6 and 7
RF Reset confirmation 10 01 1F
DT Data 10 01 (Packet number etc.)
RR RECEIVE READY 10 01 (Packet number etc.)
RNR
RECEIVE NOT READY
10 01 (Packet number etc.)
Table 2 Causes of CI Packet Disconnection (Cause)
Code value Description
01 Remote terminal busy or no free channel
03 Invalid request by CR packet
05 Network congestion
09 Connection failure because remote terminal is faulty or power-off
0B Connection to remote terminal not permitted
0D Missing
11 Remote procedure error or illegal packet received
13 Local procedure error or illegal packet sent
19 Termination side not permitting charging on termination
29 Termination side not permitting fast selection
80-FF Normal disconnection
Table 3 Diagnostic Results of CI Packet (Diag)
Code
value
Description Code value Description
11 Packet level ready 31 Timeout in CA packet wait
12 Terminal restart request 32 Timeout in CF packet wait
14 Empty 41 Illegal signal
15 CC packet wait 42 Illegal parameter
16 CA packet wait 43 Invalid termination address
17 Data transfer in progress 44 Invalid origination address
18 Origination-termination
collision
45 Illegal signal length
19 CQ packet wait 46 Termination rejected
21 Packet type unknown 47 No free channel
22 Origination through
termination-only channel
48 Collision of origination and
termination
26 Packet too short 49 Duplicate request
27 Packet too long 4A Illegal signal length (address
length)
29 Illegal SQ, SI, or SF packet 4B Illegal signal length (facility
length)
2A Illegal packet type 00 Other
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