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ANNEX A
(to Recommendation Q.714)
State diagrams for the signalling connection
control part of Signalling System No. 7
A.1 Introduction
This Annex contains the definitions for the symbols used and defines the
states of the signalling point X/Y interface and the transitions between states
in the normal case.
Annex B contains the full definition of actions, if any, to be taken on
the receipt of messages by a signalling point.
A.2 Symbol definition of the state diagrams at the message interface between
two nodes (signalling points: X and Y) (see Figures A-1/Q.714 and
A-2/Q.714)
Figure A-1/Q.714 CCITT 19172
Figure A-2/Q.714 - CCITT 73120
A.3 Order definition of the state diagrams
For the sake of clarity, the normal procedure at the interface is
described in a number of small state diagrams. In order to describe the normal
procedure fully, it is necessary to allocate a priority to the different figures
and to relate a higher order diagram with a lower one. This has been done by the
following means:
- Figures A-3/Q.714, A-4/Q.714, A-5/Q.714 and A-6/Q.714 are arranged in
order of priority, with Figure A-3/Q.714 having the highest priority
and subsequent figures having lower priority. Priority means that when
a message belonging to a higher order diagram is transferred, that
diagram is applicable and the lower order one is not.
- The relation with a state in a lower order diagram is given by
including that state inside an ellipse in the higher order diagram.
- The message abbreviations are those defined in Recommendation Q.712.
Figure A-3/Q.714 - CCITT 19192
Fascicle VI.7 - Rec. Q.714 PAGE33
Figure A-4/Q.714 - CCITT 19201
Figure A-5/Q.714 - CCITT 73131
Figure A-6/Q.714 - CCITT 19210
ANNEX B
(to Recommendation Q.714)
Action tables for the signalling connection
control part of Signalling System No. 7
B.1 Introduction
This Annex contains the definitions for the symbols used and contains the
full definition of actions, if any, to be taken on the receipt of messages by a
signalling point (node).
Annex A contains the full definition of states of the signalling point X/Y
interface and the transitions between states in the normal case.
B.2 Symbol definition of the action tables
The entries given in Table B-1/Q.714 and B-2/Q.714 indicate the action, if
any, to be taken by a SP on receipt of any kind of message, and the state the SP
enters, which is given in parentheses, following the action taken.
PAGE96 Fascicle VI.7 - Rec. Q.714
In any state it is possible to receive an Error message (ERR). The
reaction, if any, depends on the contents (error cause and possible diagnostics)
of the message and is specified in Q.714, S 3.10.3.
The reaction on messages received with procedure errors (e.g. too long,
invalid P(R), not octet aligned, etc.) are normal actions and will be described
in the text. So they are covered by the actions indicated as NORMAL.
B.3 Table of contents
Table B-1/Q.714 Actions taken by SP-Y on receipt of messages.
Table B-2/Q.714 Actions taken by SP-Y on receipt of messages with known
message type and containing mismatch information.
Table B-3/Q.714 Actions taken by SP-Y on receipt of messages during
connection establishment and release phases.
Table B-4/Q.714 Actions taken by SP-Y on receipt of messages during the
data transfer phase in a given state: reset.
Table B-5/Q.714 Actions taken by SP-Y on receipt of messages during the
data transfer phase in a given state: data expedited
data, flow control.
TABLE B-1/Q.714
Action taken by SP-Y on receipt of messages
State of the interface as perceived by node Any state
SP-Y
Message received by node SP-Y
Any message with unknown message type (see DISCARD
Note)
Any message with known message type and: See Table B-2/Q.714
a)unassigned destination local
reference number, or
b)Originating Point Code received
not equal to the PC stored
locally, or
c)source local reference number
received not equal to the remote
local reference number stored
locally
Any other message See Table B-3/Q.714
DISCARD: SP-Y discards the received message and takes no subsequent action
Note - This notion of unknown message type depends upon the protocol class
TABLE B-2/Q.714
Action taken by SP-Y on receipt of messages with known message type and
containing mismatch information as in Table B-1/Q.714 in any state
Type of mismatch
information Unassigned Source local Originating Point
Message destination local reference number Code received not
received by node PS-Y reference number received not equal equal to the PC
to the one stored stored locally
locally (see Note 1)
CR (X) N.A. N.A. N.A.
Fascicle VI.7 - Rec. Q.714 PAGE33
CC (Y, X) Send ERR (X) (see N.A. N.A.
Note 2)
CREF (Y) DISCARD N.A. N.A.
RLSD (Y, X) Send RLC (X, Y) Send ERR (X) Send ERR (X)
(see Note 2) (see Note 2) (see Note 2)
RLC (Y, X) DISCARD DISCARD DISCARD
DT1 (Y) DISCARD N.A. C.O.N.P.
DT2 (Y) DISCARD N.A. C.O.N.P.
AK (Y) DISCARD N.A. C.O.N.P.
ED (Y) DISCARD N.A. C.O.N.P.
EA (Y)
PAGE96 Fascicle VI.7 - Rec. Q.714
DISCARD N.A. C.O.N.P.
RSR (Y, X) Send ERR (X) Send ERR (X) Send ERR (X)
(see Note 2) (see Note 2) (see Note 2)
RSC (Y, X) Send ERR (X) Send ERR (X) Send ERR (X)
(see Note 2) (see Note 2) (see Note 2)
ERR (Y) For further study For further study For further study
IT (Y, X) DISCARD RELEASE C.O.N.P
DISCARD: SP-Y discards the received message and takes no subsequent action.
C.O.N.P. Check Optionally Not Performed.
N.A. Not Applicable
NAME (d, s): NAME = abbreviation of message
d = destination local reference number
s = source local reference number.
Note 1 - Performing this check is a national option.
Note 2 - In this situation no action is taken locally on any existing connection section.
Information in any message sent back is taken from the received message.
Fascicle VI.7 - Rec. Q.714 PAGE33
TABLE B-3/Q.714
Action taken by SP-Y on receipt of messages during connection establishment and release
phases
State of the
interface Signalling connection control ready: r1
as perceived by
node SP-Y
Message Ready SP-X SP-Y Data SP-X SP-Y
received connecti connecti transfer disconne disconne
by note SP-Y c1 on on ct ct
pending pending c4 pending pending
c2 c3 c5 c6
Connexion request NORMAL See Note
(CR) (c2)
Connection confirm DISCARD NORMAL DISCARD ERROR 1 DISCARD
(CC) (c2) (c4) (c4) (c6) (c6)
Connection refused DISCARD NORMAL DISCARD ERROR 1 DISCARD
(CREF) (c2) (c1) (c4) (c6) (c6)
Released (RLSD) See DISCARD ERROR 2 NORMAL DISCARD
Table (c2) (c3) (c5)
B-2/Q.71
4
PAGE96 Fascicle VI.7 - Rec. Q.714
(c5) NORMAL
(c1)
Released complete DISCARD ERROR 3 DISCARD ERROR 1 NORMAL
(RLC) (c2) (c1) (c4) (c6) (c1)
Other messages DISCARD ERROR 3 See ERROR 1 DISCARD
(c2) (c1) Table (c6) (c6)
B-4/Q.71
4
NORMAL: The action taken by SP-Y follows the normal procedures as defined in the
appropriate sections of the procedure text.
DISCARD: SP-Y discards the received message and takes no subsequent action.
ERROR 1: SP-Y discards the received message and initiates a connection release by
sending a RLSD message with proper invalid type cause.
ERROR 2: SP-Y returns a Released complete message using information contained in the
message and takes no subsequent action.
ERROR 3: SP-Y discards the received message and releases locally.
Note - Reception of CR in these states is note possible because CR does not contain a
destination local reference number (no search is performed).
Fascicle VI.7 - Rec. Q.714 PAGE33
TABLE B-4/Q.714
Action taken by node SP-Y as receipt of messages during the data transfer state
State of the interface as Data transfer: c4
perceived by node SP-Y
Data SP-X SP-Y
Message received by node SP-Y control reset reset
ready request request
(d1) (d2) (d3)
Reset request (RSR)(see Note 2) NORMAL DISCARD NORMAL
(d2) (d2) (d1)
Reset confirmation (RSC)(see Note 2) ERROR ERROR NORMAL
(d3) (d3) (d1)
Other messages See ERROR DISCARD
Table (d3) (d3)
B-5/Q.71 (see
4 Note 1)
NORMAL:The action taken by SP-Y follows the normal procedures as defined in
the appropriate sections of the procedure text.
DISCARD:Signalling point Y discards the received message and takes no
subsequent action.
ERROR:Signalling point Y discards the received message and initiates a reset
by transmitting a reset request message with the appropriate cause
indication.
Note 1 - If signalling point Y issues a reset by transmitting a reset request
message as a result of an error condition in state d2, it should eventually
consider the interface to be in the Data control ready state (d1).
Note 2 - Reception of these messages for a class 2 connection section may
trigger the sending of an ERR message back if these message types are known by
the receiving SCCP.
TABLE B-5/Q.714
Action taken by SP-Y on receipt of messages during the data control ready state
State of the interface
as perceived by node SP-Y Data control ready: d1
Normal SP-X SP-Y SP-X and
data expedite expedite
Message received by node SP-Y flow d data d data
e1 e2 e3
PAGE96 Fascicle VI.7 - Rec. Q.714
SP-Y
expedite
d data
e4
Expedited data (ED) NORMAL ERROR NORMAL ERROR
(d2) (d3) (d4) (d3)
Expedited data (EA) acknowledgement DISCARD DISCARD NORMAL NORMAL
(e1) (e2) (e1) (e2)
Data (DT), data acknowledgement (AK) and NORMAL NORMAL NORMAL NORMAL
Inactivity Test (IT) (e1) (e2) (e3) (e4)
NORMAL:The action taken by signalling point Y follows the normal procedures as defined
in the appropriate sections of the procedure text.
DISCARD:Signalling point Y discards the received message and takes no subsequent
action as direct result of receiving that message.
ERROR:Signalling point Y discards the received message packet and indicates a reset
by transmitting a reset request message with the appropriate cause indication
(e.g. procedure error).
Note - Reception of an ED, EA, DT2 or AK message for a class 2 connection section will
cause the receiving SCCP to DISCARD any of these messages. A DT1 message received for a
class 3 connection section will also be discarded.
Fascicle VI.7 - Rec. Q.714 PAGE33
ANNEX C
(to Recommendation Q.714)
State transition diagrams (STD) for the signalling connection
control part
of Signalling System No. 7
C.1 General
This annex contains the description of the main SCCP functions (except
SCCP management (SCMG) which is contained in annex D to Recommendation Q.714)
according to the CCITT Specification and Description Language (SDL).
For the SCCP as a whole, Figure 1/Q.714 illustrates a subdivision into
functional blocks, showing their functional interactions as well as the
functional interactions with the other major functions of signalling system No. 7
(e.g. MTP).
The functional breakdown shown in this diagram is intended to illustrate a
reference model, and to assist interpretation of the text of the SCCP procedures.
The state transition diagrams are intended to show precisely the behaviour of the
signalling system under normal and abnormal conditions as viewed from a remote
location. It must be emphasized that the functional partitioning shown in the
following diagrams is used only to facilitate understanding of the system
behaviour, and is not intended to specify the functional partitioning to be
adopted in a practical implementation of the signalling system.
C.2 Drafting conventions
Each major function is designated by its acronym (e.g. SCOC = SCCP
connection-oriented control).
External inputs and outputs are used for interactions between different
functional blocks. Included within each input and output symbol in the state
transition diagrams are acronyms which identify the functional blocks which are
the source and the destination of the message, e.g.:
SCRC « SCOC indicates that the message is sent from SCCP routing control to
SSCP connection-oriented control
Internal inputs and outputs are only used to indicate control of timers.
C.3 Figures
The list of figures is as follows:
Figure C-1/Q.714 SCCP routing control procedures (SCRC).
Figure C-2/Q.714 Connection establishment and release procedures at
originating node for SCCP connection-oriented control
(SCOC).
(Sheets 1 to 3: connection establishment, and sheets 4 to
6: connection release procedures)
Figure C-3/Q.714 Connection establishment and release procedures at
destination node for SCCP connection-oriented control
(SCOC).
(Sheets 1 to 2: connection establishment, and sheets 3 to 5:
connection release procedures)
Figure C-4/Q.714 Data transfer procedures at originating and destination
nodes for SCCP connection-oriented control (SCOC).
Figure C-5/Q.714 Expedited data transfer procedures at originating and
destination nodes for SCCP connection-oriented control
(SCOC).
Figure C-6/Q.714 Reset procedures at originating and destination nodes for
SCCP connection-oriented control (SCOC).
PAGE96 Fascicle VI.7 - Rec. Q.714
Figure C-7/Q.714 Connection establishment and release procedures at
intermediate node for SCCP connection-oriented control
(SCOC).
(Sheets 1 to 4: connection establishment, and sheets 5 to 9:
connection release procedures)
Figure C-8/Q.714 Data transfer procedures at intermediate node for SCCP
connection-oriented control (SCOC).
Figure C-9/Q.714 Expedited data transfer procedures at intermediate node
for SCCP connection-oriented control (SCOC).
Figure C-10/Q.714 Reset procedures at intermediate node for SCCP
connection-oriented control (SCOC).
Figure C-11/Q.714 Restart procedure for SCCP connection-oriented control
(SCOC).
Figure C-12/Q.714 SCCP connectionless control (SCLC).
C.4 Abbreviations and timers
Abbreviations and timers used in Figures C-1/Q.714 to C-11/Q.714 are
listed below.
Abbreviations
CR Connection Request
DPC Destination Point Code
GT Global Title
IT Inactivity Test
MSG Message
MTP Message Transfer Part
NPDU Network Protocol Data Unit
NSDU Network Service Data Unit
PC Point Code
SCCP Signalling Connection Control Part
SCLC SCCP Connectionless Control
SCMG SCCP Management
SCOC SCCP Connection-Oriented Control
SCRC SCCP Routing Control
SLS Signalling Link Selection
SS Sub-System
SSN Sub-System Number
SSPC Sub-System Prohibited Control
Timers
T(conn est) Waiting for connection confirm message.
T(ias) Delay to send a message on a connection section.
T(iar) Waiting to receive a message on a connection section.
T(rel) Waiting for release complete message.
T(int) Waiting to report abnormal release to maintenance function.
T(guard) Waiting to resume normal procedures for temporary connection
Fascicle VI.7 - Rec. Q.714 PAGE33
sections during the restart procedure
PAGE96 Fascicle VI.7 - Rec. Q.714
Figure C-1/Q.714 (feuillet 1 sur 3) - T1114960-88
Figure C-1/Q.714 (feuillet 2 sur 3) - T1114970-88
Figure C-1/Q.714 (feuillet 3 sur 3) - T1114980-88
Figure C-2/Q.714 (feuillet 1 sur 6) - T1114990-88
Figure C-2/Q.714 (feuillet 2 sur 6) - T1115000-88
Figure C-2/Q.714 (feuillet 3 sur 6) - T1115010-88
Figure C-2/Q.714 (feuillet 4 sur 6) - T1115020-88
Figure C-2/Q.714 (feuillet 5 sur 6) - T1115030-88
Figure C-2/Q.714 (feuillet 6 sur 6) - T1115040-88
Figure C-3/Q.714 (feuillet 1 sur 5) - T1115050-88
Figure C-3/Q.714 (feuillet 2 sur 5) - T1115060-88
Figure C-3/Q.714 (feuillet 3 sur 5) - T1115070-88
Figure C-3/Q.714 (feuillet 4 sur 5) - T1115080-88
Figure C-3/Q.714 (feuillet 5 sur 5) - T1115090-88
Fascicle VI.7 - Rec. Q.714 PAGE33
