X.25 Cause and Diagnostic Bytes

X.25 Cause Bytes

Diagnostic, Registration, Restart, Clear, and Reset Request packets that are sent to the X.25 link have the cause byte set to zero if the configuration parameter zerocause is set to YES (default). Otherwise, the cause bytes described below can be sent. The optional diagnostic byte is always included in these packets to assist in problem diagnosis. In reporting these events to the operating system, zerocause does not zero the cause byte.

Following the decimal byte value is the hexadecimal byte value, using the C language "0x" prefix. Following that is the packet type in which the value may occur.

Decimal byte	Hexadecimal byte	Packet	Description
3	0x03	Clear	Illegal facility code or parameter. Always accompanied by 66 or 65 as the diagnostic byte. See definition of those diagnostic bytes below.
5	0x05	Reset	Local Procedure Error for Reset. This is the default Reset Cause byte for any error in a packet from the X.25 link causing a reset.
11	0x0B	Clear	Incoming call is rejected due to link configuration option Incoming Calls Barred.
19	0x13	Clear	Local Procedure Error for Clear. This is the default Clear Cause byte for any error in a packet from the X.25 link that causes a clear.
		Registration	Local Procedure Error for Registration. This is produced with diagnostic 42 as prescribed by the CCITT when the system has not been configured for registration support and receives a registration packet. This applies also if XIP's registration support has been compiled out.
25	0x19	Clear	An incoming call specified Reverse Charging and the link options are configured to refuse incoming reverse charged calls.
41	0x29	Clear	An incoming call specified the Fast Select facility, and the link options are configured to refuse such calls.
127	0x7F	Registration	This is the cause code set in all Registration Confirmation packets sent by XIP, unless the Request had a format error, in which case, Restart is sent.

XIP Causes

Whenever an SVC is cleared or a circuit is reset, SyncServer provides a third cause byte to assist in problem diagnosis: the xip_cause byte.

When xip_cause is less than 128, the Clear or Reset was received from the X.25 link. Its value is a translation of the original incoming cause byte value. The purpose of this is to provide an index to a character string table that is independent of the packet type. For example, in a Reset, Remote Procedure Error is 3 while the same condition is 17 in a Clear; the xip_cause for Remote Procedure Error is always 4.

The following table shows the CCITT causes that are associated with xip_causes less than 128.

cause field translations to xip_cause values

Reset	Clear	xip_cause	CCITT description
0	0	0	Remote DTE Initiated
7	5	1	Network Congestion
15		2	Network Operational (PVCs only)
5	19	3	Local Procedure Error
3	17	4	Remote Procedure Error
17	33	5	Incompatible Destination
	1	6	Number Busy
1	9	7	Out of Order
	25	8	No Reverse Charging
	3	9	Invalid Facility Request
	11	10	Access Barred
	13	11	Number Invalid
9		12	Remote DTE up (PVCs only)
	41	13	No Fast Select
x	x	15	Unknown Cause Field

When xip_cause is 128 and over, an error condition has been detected within the driver software. For most of these, the xip_cause value itself is used as the diagnostic code in an outgoing Clear or Reset on the X.25 link. This is because the error condition is entirely an internal matter. However in some cases, notably for xip_cause 129, the diagnostic code presented to the link is in fact one of the CCITT defined values for the condition.

In the Diagnostic Bytes section below, diagnostics 128 and will be seen in xip_cause bytes.

X.25 Diagnostic Bytes

Standard CCITT Diagnostic Bytes (Range 0x00 to 0x7F)

These diagnostic bytes are CCITT (ITU) defined diagnostics. They are part of the X.25 specification and therefore mean the same thing to all equipment following this standard.

Decimal byte	Hexadecimal byte	Packet	Description
0	0x00	Clear, Reset	Value for "no additional information". This diagnostic is only used when selected by an X.25 API program, or for a Clear caused by a UNIX Close of a tty device with HUPCL also set. The latter is the normal action after you have logged off, which is why its diagnostic should indicate a normal clearing.
1	0x01	Reset	Bad P(S) in a packet from the X.25 link. Most likely due to a mismatch of default packet window sizes on a non-negotiating link.
2	0x02	Reset	Bad P(R) in a packet from the X.25 link.
17	0x11	Restart	Restart Confirmation received when packet level is in Level Ready state.
20	0x14	Clear	Illegal packet (anything besides Call) on an Idle channel.
21	0x15	Clear	Illegal packet for Calling state of a channel.
22	0x16	Clear	Illegal packet for Accepting state of a channel.
23	0x17	Clear	Illegal packet for Data Transfer state of a channel.
25	0x19	Clear	Illegal packet for Clearing state of a channel.
27	0x1B	Reset	Reset Confirmation on a channel in Data Transfer state.
33	0x21	Clear, Reset	Unrecognized Packet Type Identifier on a configured logical channel, including the Reject Packet when XIP has not been compiled for Packet Reject support.
34	0x22	Clear	Incoming call on a logical channel reserved for Outgoing Calls Only.
35	0x23	Reset	Incoming Call, Call Accept, Clear Request, or Clear Confirm on a logical channel reserved for operation as a PVC.
36	0x24	Diagnostic, Clear	A packet on an non-configured logical channel. If the incoming packet was an Incoming Call, a Clear is issued with this diagnostic.
37	0x25	Reset	Produced when a Packet Reject packet is received and packet reject support is not an option in the link configuration.
38	0x26	Diagnostic, Clear, Reset	Packet was too short for the packet type. This applies to Call or Clear packets with Address Length or Facilities Length fields that are greater than the length of the packet. If an individual facility length exceeds the Facility Length, diagnostic 64 is produced.
39	0x27	Clear, Reset	Packet was too long for the packet type. This applies to Call or Clear packets with User Data fields that are too long. If no User Data field is allowed, diagnostic 42 is produced instead.
40	0x28	Diagnostic	Packet had a General Format Identifier (the first 4 bits of the packet header) that was illegal for the packet type.
41	0x29	Clear, Reset	Packet was on a configured Logical Channel Identifier, but it was a Restart or Restart Confirmation packet. These packets must have a zero LCI.
42	0x2A	Clear	Illegal facility specified for the packet type. Specifically, User Data was found in Clear, Clear Confirm, or Call Connect when the call is not a Fast Select call, or an attempt was made to Accept a Fast Select Restricted Response call.
43	0x2B	Reset	Interrupt Confirmation received when an unconfirmed Interrupt is not outstanding.
44	0x2C	Reset	Interrupt received when an Interrupt Confirmation was not sent to the last Interrupt packet.
49	0x31	Clear	T21 (outgoing Call Request timer) expired while waiting for Call Connect or Clear. Check "bwc_num" in link configuration file.
50	0x32	Clear	T23 (outgoing Clear Request timer) expired while waiting for Clear Confirm from the X.25 link. XIP will retry the Clear a specified number of times (default 20), and then consider the logical channel unavailable.
51	0x33	Reset	T22 (outgoing Reset Request timer) expired while waiting for Reset Confirmation.
52	0x34	Restart	T20 (Restart Request timer) expired while waiting for Restart Confirmation.
64	0x40	Clear	Facilities Length exceeds 63 bytes on a 1980 link, or facilities found exceed Facilities Length.
65	0x41	Clear	Bad facility code, or illegal facility code for the link options, or illegal facility code for the packet type.
66	0x42	Clear	Illegal value found in a facility parameter field.
67	0x43	Clear	Invalid/Non-configured Called Network Address.
68	0x44	Clear	Invalid/Non-configured Calling Network Address.
69	0x45	Clear	On CCITT 1984 links, the facilities length exceeded 109 bytes.
70	0x46	Clear	Incoming call barred.

XIP Packet Level Diagnostic Bytes and xip_causes (Range 0x80 to 0xE7)

Diagnostics values 0x80 and greater are in the implementation specific range, and not standardized by the CCITT. This means that the following definitions are only applicable if the clear or reset was sent by TSG software. For diagnostics sent by other X.25 vendor equipment, refer to their manuals.

Decimal byte	Hexadecimal byte	Packet	Description
128	0x80	Clear, Reset	Sent to the operating system on all permanent virtual circuits (PVCs) when Packet Level Ready is lost. Sent to the operating system on all active SVCs when Packet Level Ready is lost.
129	0x81	Clear, Reset	Sent to the operating system whenever an error in a packet from the X.25 link occurs, for which the accompanying cause and diagnostic to the X.25 link have been issued.
132	0x84	Clear	Internal error - the operating system issued a message type out of context.
133	0x85	Reset	Internal error - Attempt by the operating system to acknowledge too many packets, or to send packets when the window was closed.
134	0x86	Reset	Occurs when an X.25 IOCTL API program issues Interrupt Request before the network Confirmed the previous one, or the program issues Interrupt Confirmation when no Request from the network is outstanding.
135	0x87	Clear	Channel is out of order due to failure of the X.25 link to return a Clear Confirmation within the T23 timeout.
137	0x89	Reset	Internal error - operating system driver specified a bad length packet to be transmitted.
		Clear	The operating system specified a bad length Call Progress Structure to a Call Accept.
138	0x8A	Clear	Call Collision when the system is DCE. The same logical channel as the DTE was chosen The call is cleared internally, and when complete, the incoming call is permitted to come through.
139	0x8B	Clear	Returned to the operating system if the facilities specified in an outgoing call request were incompatible with the link configuration or illegal for the packet type. Also sent if a Call Acceptance from the operating system is similarly in error.
140	0x8C	Clear	The packet level is attempting to quiesce use of an old configuration in order to install a new one due to a Registration or an X_NEWCONFIG request, and so is not accepting new incoming calls.
141	0x8D	Clear, Reset	If a Restart Request is received when the system was already in Packet Level Ready, all SVCs are Cleared to the operating system with this diagnostic. Always sent in a Reset to the operating system on PVCs whenever the packet level comes Ready.
142	0x8E	Reset	Sent to the OS upon an attempt to send any call establishment or call teardown packets on a PVC. Also, the xip_cause of the automatic Reset sent to the OS upon a PVCATTACH.
144	0x90	Clear	The Clear Confirm timer T23 expired.
145	0x91	Clear, Reset	Sent if unrecoverable buffer shortage occurs.
146	0x92	Reset	For the BX.25 Data Packet Acknowledgement timer. An acknowledgement for a data packet was not received within the T25 time limit.
147	0x93	Clear	The operating system sent a bad format Call Progress Structure for a Clear Request, or it was incompatible with the call's options or link configuration.
148	0x94	Clear	The operating system sent a bad format Call Progress Structure with a Clear Confirm. The operating system is actually re-cleared for this error.
149	0x95	Reset	The operating system has not yet attached to this PVC. This Reset is produced for all packets sent by the X.25 link (unless the system is waiting for Reset Confirm) until the OS executes X_PVCATTACH for this PVC. It is also produced when a the OS program detaches from a PVC to clean up any outstanding acknowledgements.
150	0x96	Registration	An incoming Registration Request attempted to configure a group of SVCs at logical channels that have been reserved for PVCs. That group has been deleted from the Request.
		Reset	This diagnostic is sent on PVCs for the automatic Reset that is generated upon PVCATTACH.
151	0x97	Registration	An incoming Registration Request attempted to configure a packet or window size greater than the currently configured maximums. The request is modified to be the maximum.
152	0x98	Registration	An incoming Registration Request attempted to configure a number of logical channels, or Packet Reject support, for which XIP needs to be recompiled.
153	0x99	Restart	Sent in order to install a dynamic reconfiguration request from the OS for which all SVCs must be down.
154	0x9A		Modem has CTS OFF and is unable to dial the call (X.32 only).
155	0x9B	Clear	Device closed while SVC was still up.
156	0x9C		Modem has dropped DSR, connection cleared (X.32 only).
157	0x9D		Modem reports "No Dialtone" and is unable to dial the call (X.32 only).
158	0x9E		Modem has not been able to complete the call. Some possible causes are no answer, line busy, unable to synchronize with remote system or the dial timeout has expired (X.32 only).
159	0x9F		No listener for incoming call.
164	0xA4	Clear	An X.25 Invitation to Clear was received from the remote system.
165	0xA5	Clear	Stream associated with VC is closed, or X25clear() called and diagnostic was not specified with either a T_DIAG or T_PCPS tag.
168	0xA8	Clear	IP router idle timer expired (no traffic).
169	0xA9	Clear	The call was rejected because the IP address is not in the local configuration, or because the IP router software is shut down.
170	0xAA	Clear	The IP router interface was shut down (tcp shutdown) or a configuration change requiring circuits be re-established occurred.
171	0xAB	Clear	The IP router refused the call because it did not contain the calling address field.
172	0xAC	Clear	The IP router refused the call because the maximum number of virtual circuits allowed by the configuration are already in use.
176	0xB0	Clear	Incoming call did not match any x25incalls entries and there is no "ANY" entry in the file.
177	0xB1	Clear	Incoming call was cleared due to a specific directive in the x25incalls file. There are two scenarios here: the x25incalls either directed that all such calls be cleared, or the x25incalls would not allow reverse charging on this call.
178	0xB2	Clear	Incoming call was cleared because the daemon failed to execute the process to handle the call.
179	0xB3	Clear	x25daemon failed to fork a child process in preparation for executing a new process. This will be very rare. It should probably only happen if the system wide maximum number of processes (NPROC) is exceeded (UNIX only).
180	0xB4	Clear	Incoming call was cleared because the x25daemon failed to open the STC module (UNIX only).
181	0xB5	Clear	Incoming call was cleared because the x25daemon failed to push on the STC module (UNIX only).
182	0xB6	Clear	Incoming call was cleared because the x25daemon failed to send STC the incoming call (UNIX only) (putmsg failure).
193	0xC1		Modem timeout.
194	0xC2		The modem reported a bad command.
195	0xC3		Modem timeout.
197	0xC5	Clear	Internal problem - driver made an illegal request.
199	0xC7	Clear	An outgoing call failed because the packet level is not Ready. This is probably due to the HDLC link being down.
200	0xC8	Clear	An outgoing call specified a Call Progress Structure with an incorrect length.
201	0xC9	Clear	An outgoing call failed because the link is currently being reconfigured - try again in a few minutes.
202	0xCA	Clear	An outgoing call failed because Outgoing Calls are Barred as per the link configuration.
203	0xCB	Clear	An outgoing call failed because no SVC logical channels are available.
224	0xE0	Clear	User cleared PAD connection.
225	0xE1	Clear	PAD received invitation to clear.
226	0xE2	Clear	X.29 received invitation to clear.

Reserved Diagnostic Bytes (Range 0xE8 to 0xFF)

This range is available and reserved for use by user software.

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