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No.7 Common Channel Signaling
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1 The relationship between signalingnetwork and telecom network
Overview
2 The development of No.7 signalingsystem
3 The development goal of No.7
signaling system
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No.7 are common channel signaling systems .
The No.7 signaling system (abbreviated as SS7) was first stipulated by
the CCITT in 1980 (in the orange cover book), and was twice
modified and supplemented in 1984 (blue book) and in 1988 (white
book). The general goal of the No.7 signaling system is to suggest an
internationally standardized common channel signaling system with
general applications fields so that the digital communication networks
with digital SPC switches can work in the best status. Furthermore,
such networks can provide sequential and highly reliable transmission
with no loss and no repetition.
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You will study
1 Basic conception
1 Basic conception
2NO.7 signaling system
2NO.7 signaling system
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signalingsignaling
It is the dialog language for the communication
between various parts of the telecom network. It ensures the
network to operate normally as an integer.
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Classification of signaling
Subscriber signaling:between sub. and switch:between sub. and switch
Inter-office control the setup and release of callWorking areaWorking area
Monitoring signals: monitor the changes of: monitor the changes of
call states or conditions in the linescall states or conditions in the lines
Selection signals in routingin routing
Operation signals management andmanagement and
maintenance of telecom networksmaintenance of telecom networks
SignalingSignalingfunctionfunction
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Common channel signalingCommon channel signaling
Channel associated signalingChannel associated signaling
TransmissioTransmissio
n pathn path
Line signalingmonitors the states of inter-office
calls
Register signaling also selection signals and network
management signals
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Opposite end alarming
code for out of frame
16 frames,125 s !16=2ms
F0F15
0 1 15 16 17 30 31
32 slots ,256bit,125s, 1frame
Reserved for
international
(presently 1)
Synchronization
time slot
Voice channel time slot
TS1-TS15
Voice channel time slot
TS17-TS31
Frame synchronous code
D1 D2 D3 D4 D5 D6 D7 D8Even
frame
Odd
frame
F1 a b c d a b c d
Signaling code for
voice channel 16
Signaling code
for voice
channel 1
1 1 A1 1 1 1 1 1
Reserved for
international
(presently 1)
a b c d a b c d
Signaling code
for voice
channel 15
Signaling code for
voice channel 30
Synchronization:A1=0; A2=0
Out of sync:A1=1; A2=1
Figure 1.3.4-1 PCM 30/32 frame format
1 0 0 1 1 0 1 1 0 0 0 0 1 A2 1 1
Multi-framesynchronous
code
Multi-frame alarmand reserved bit
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v+s
s
v
s
v
LineLineterminalterminal
ExchangeA
ExchangeA
Register
Register
ExchangeB
ExchangeB
v+s
ISDNISDNlineline
terminalterminal
LineLineterminalterminal
ISDNISDNlineline
terminalterminal
Register
Register
SignalingSignaling
terminalterminal
S
v
vvv
SignalingSignaling
terminalterminal
Common Channel Signaling System
p54
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ExchangeA
RegisterRegister
Exchan
geB
Lineter
minal
Lineter
minal
v+sv+s
v+s
v+sv+s
v+s
Subscriber Line Signaling
associated channel signaling
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4.3.1 Overview
1. Advantages of Common channel signalingCompared with associated channel signaling, common channel
signaling has many important advantages:
1) Information can be switched between processors much faster
than in channel-associated signaling.2)With a huge signal capacity, it can hold dozens or even hundreds
of different kinds of signals, thus providing more new services.
3)With a great flexibility, it can provide more new services simply
by modifying software to increase signals.4)Line signaling device is not needed any more at any trunk station,
which shall greatly reduce investment costs.
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Um
MSC/VLRMSC/VLR
HLR/AUCHLR/AUC MSC/VLRMSC/VLR
SMCSMC
MAP
C
DMAP
MAP
E
PLMNPSTN
ISDN
PSPDN
TUP ISUP
OMC S Network Management Center Q3
TCP/IP X. 25
BSC
BTS
BTS
BSSAP
A
Abis
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5) Since line signaling is no longer needed, trunk devices can beused both in calls from A to B, and in calls from B to A.
In such bi-directional working modes, even less circuits arerequired than when trunk circuits are respectively used in single calldirections.6) When a call is being set up, signals related to this call can be sent.In this way, the subscribercan change the already setup connections.For example, the subscriber can transfer one call to another place, or
request a third party to join the present connections.7) Signals can be switched between processors so as to be used formaintenance or network management.8) The No.7 line signaling can provide powerful support for ISDN,IN, TMN and cellular mobile communication systems, as this
signaling is their basis.9) The signaling system is not restricted by the voice channelsystem, thus making it very flexible to add and change signal types.
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Disadvantage A contradictory phenomenon
1)The error rate of the common channel signaling system must be
very low.
2) Its reliability must be much higherthan the channel associated
signaling system. This is because once the data link fails, all related
calls between the two related switches shall be affected.
3 bi-directional trunk working modes existconflict of seizure.
4) The SS7 systems that every transnationalcorporation produces are having some problems
in compatibleness.
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Signaling systemSignaling system
signaling system includes a set of integrated signaling
and operation procedure.
Signaling system is the collection of software and
hardware which generate transmit receive and
recognize the signaling.
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NO.7 signalingNO.7 signaling
protocol systemprotocol system
structurestructure1 System structure and the
function of every layer
2Message structure
2 The introduction of signaling system
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2a The earliest structure of No.7 signaling protocol
system
2a The earliest structure of No.7 signaling protocol
system
SCCPMTP3 network layer
MTP2 Data link layer
MTP1 Physical layer
TUPISUP DUP User part
Message
transfer part
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4 The structure of No.7 signaling protocol system
OSI model
MTP1MTP2MTP3
MAP
TCAP
TCAP
Intermediate
service part
ISP
SCCP
OMAP
TCAP
CCITT No.7 Signaling functional class
TUP DUP
ISUP
Transport layer,
session layer and
presentation
layer
Applicationlayer
Physical
layer, datalink layer andnetwork layer
Figure 4.3.1-1 The relationship between No.7 signaling and OSI model
OSI 1,2,3
OSI 4,5,6
OSI 7
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User part
Signal network
function
Signaling link
function
Signaling data
link function
L4
L3
L2
L1Physical path
Logical path
Logical path
Logical path
User part
Signal network
function
Signaling link
function
Signaling data
link function
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For example, the President of a Chinese company is
communicating with the President of a Pakistan company ,
however neither speaks the others language. Each employs an
English translator and the translated messages are sent by the Faxoperator over physical communication channel. Thus, the two
presidents are communicating with each other through five layers
below them.
Give an example
Eff i
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Company A
(in China)
physical communication channel
Company B
(in Pakistan)
Chinese President
Translator
Fax Operator
Write to paper
Print to paper
President
Translator
Fax Operator
Write to paper
Print to paper
Effective
Communications
telegraph
talk
English
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(1) Use structure of function level. Between
function levels they have relation and also
independent. The change of certain level willnot change another level.
(2) Use the special interface between function
levels to communicate with each other.(3) For two signaling systems, L1 is the only
physical path. All the signaling messages are
sent through L1. At same time ,L2 L3 L4only process the message sent by same function
level of the another system.
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4.3.2 Common channel signaling network
Since in common channel signaling systems, the signalingsignals and voice signals are separately transmitted, so a
dedicated common channel signaling network can be composed.
Base of CCSN is Data Communication Network.The common-channel signaling network consists of the
following parts.
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The common-channel signaling network consists of the following
parts.
1)Signaling point (SP)
It refers to the node in the signaling system that provides commonchannel signaling. SP can also be divided into source points (the SP
that generate signaling messages)OPC(Originating points code) and
destination points (i.e.,the SP that receives signaling
messages)DPC(destination point code). Actually, SP is part of aswitching system.
2)Signaling transfer point (STP)
It refers to SP that transfer signaling messages from one signaling link
to another. They are neither source points, nor destination points. That
is, they are the middle node points during signaling transfer.
OPC or DPC is 14-bit address for CCITT (24-bit for China)
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B
Voice channels
A
Signaling link
C
SP ASP B
STP
2_2_2 3_3_3
8_8_5
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OPC or DPC is not absolute. OPC and DPC are relative, the OPC of
certain Office, for other Offices, is DPC.
for example, the SP of switch A is 2_2_2, and SP of switch B is
3_3_3. If you work in switch A then 2_2_2 is OPC for A, and 3_3_3
is DSP for A. If other work in switch B, then 3_3_3 is OPC for B, and
2_2_2 is DPC for B.
B
Voice channels
A
Signaling link
C
2_2_2 3_3_3
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switches A
OPC is 2_2_2
DPC is 3_3_3
switches B
OPC is 3_3_3
DPC is 2_2_2
B
Voice channels
A
Signaling link
C
2_2_2 3_3_3
3)Signaling link( N7 SLK)
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3)Signaling link( N7_SLK)It refers to the signaling message channel that connects an SP andanother SP( or STP).
Signaling link set( N7_SLS)
A bunch of signaling links directly connecting two SP (includingSTP) form one signaling link set.
ROUTE ( N7_ROUTE)One such set usually includes all parallel signaling links.
ROUTE SET ( N7_RS)It is also possible to set several routes between two SP.
LINK
LINK SETROUTE
ROUTE SET
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LinkLink Set 1
Link Set 2
ROUTE1
ROUTE2
ROUTE3
ROUTE SET
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the signaling mode
1)The associated mode
In this mode, messages related to the voice channel connecting
two switches are sent on the signaling link that directly connects
two switches, as shown in the Figure.
B
Voice channels
ASignaling link
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2)Non-associated mode
This is as shown in Figure 4.3.2-1 (b). Signaling messages between A
and B are transferred by several signaling links according to the
current network status, but the voice circuit is the direct route betweenA and B. In other cases, the common channel signaling messages are
transferred on different paths.
B
Voice channels
A
Signaling link
This mode is normally not used, as it is rather difficult to exactly
identify a route at any given time.
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3)The quasi-associated mode (Figure 4.3.2-1(c)
This can be called a special case of the non-associated mode. In this mode,
signaling messages between switches A and B go through the severalpreset concatenated signaling links, but voice signalsgo through the direct
channels between A and B. Normally, different transmission carriers are
used in the common channel signaling systems and their related voice
links.
B
Voice channels
A
Signaling link
CSTP
SP SP
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Now, modern telecommunications networks include:
1. Telecommunications basic network;
2. Signal supports network;
3. Digital clock synchronization network;
4. telecommunications manage network;
p5
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B2
A2
A1
LSTP
HSTP
HSTPHSTP
D DD
DDD
DD
B1
C1
C2
A B
C
A
C
B
B
BB
B
SP
SP
SP
SP
A
A A
A
A
C
B
HSTP-LSTP: DLINK
LSTP :CLINK LSTP :BLINKSP-LSTP ||:ALINK
The 3-level signaling network
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1) Functions of the signaling data link level(1st level)
The 1st level defines the physical, electrical, and
functional features of the signaling data link, and is
thus similar to the OSI physical layer. It determines the connection method with the data
link, and provides an information carrierfor the
signaling link. In digital transmission, signaling
data links are usually digital channels at 64kbit/s.
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2) Functions of the signaling link level
(the second -level) The second level defines the signaling
message transmission functions andprocedure related to its transfer on asignaling data link.
The second level and the first signalingdata link used as a whole as an information
carrier, provide a signaling link betweentwo signaling points for the reliable transferof messages.
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signal unit demarcation and localization
error check 16 bit check code
error correction FSN;BSN;FIB;BIB; basic error correction and
preventive cyclic retransmission(PCR)
initial localization when recovering links after the firststarting and the link is failed
error monitoring of signaling link prevent the overmuch
retransmission when error occurs
flow control prevent the link congestion if the load on the link
is too heavy
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3) The signaling network function level
(the third level)
Within a signaling network, each switching
node is allocated a signaling point code,which is 14-bit address (24-bit for China).
Every CCITT No.7 message then contains
the point code of the originating node
(OPC) and the destination point code
or( DPC).
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message routing selecting the signaling link that is used by each
signaling message to be transmitted
message distribution send the message to a user part or level-
3functions after receiving the message
message authentication to determine whether a signaling point is
the destination point of a message after the signaling point receives the
message.
signaling service management control message routing
etc.signaling link management control the locally connected
link
groupsignaling route
management
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Messageidentification
Messagechanneling:
Messagedistribution:
Come from the second levelGo to the fourth level
Go to the second lever
Come from the fourth level SLS and DPC
DPC and SI
LINK BY LINK
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4) The user part (the fourth level)
The user part is the fourth function level of
the NO.7 signaling system. Its main
function is to control the setup and releaseof various basic calls.
The major user parts include the telephone
user part (TUP), the ISDN user part (ISUP)and the signaling connection control part
(SCCP).
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transmission system DTDT
2048kb/s
Level 1
Signaling link
Level 2
MPMP
Level 3
Message transfer part
Level 4
STBSTB
semi-permanent connecting
64kb/s
NET NET
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The signaling messages structure of TUP
The NO.7 signaling are sent in unequal message units. And the MTP
mainly controls the message transfer. The three signal units of the CCITTstipulated NO.7 signaling include the message signal unit (MSU), the link
status signal unit (LSSU) and the filling-in signal unit (FISU). Their
formats are as shown in Figure 4.4.2-1.
MSU
LSSU
FISULI
0
The first transmitted bit
F LI FIB FSN BIB BSN FCK
LI
1~2
Note: SF---- Status Field The first transmitted bit
F CK SF LI FIB FSN BIB BSN F
LI>2The first transmitted bit
F CK SIF SIO LI FIB FSN BIB BSN F
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The main meanings of 3 signal units:
The fill-in signal unit (FISU)
Just as its name implies, when no other signaling units need to be senton the signal link, the FISU shall be sent.
It is used to give positive or negative acknowledgement
to the received MSU,
to show whether the local signal link is working normally,to detect the error rates of the remote signaling link.
FISU is used to keep the synchronization of signal links, so it is also
called the synchronization signal unit.
The first transmitted bit
F LI FIB FSN BIB BSN FCK
LI
0Generate by MTP2
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The link status signaling unit (LSSU)
At the initialization of the signal link, to control the flow of
MSU,and the link failure status, LSSU is continuously sent from one
end to the other reciprocally, to show the adjustment status information
of each other.
The format of the SF field in LSSU is as shown in Table 4.4.2-1.
LSSULI
1~2
Note: SF---- Status Field The first transmitted bit
F CK SF LI FIB FSN BIB BSN F
Generate by MTP2
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Ta b le 4 .4 . 2 - 1 C o d e a n d m e a n i n g o f t h e S F f ie l d
H G F E D C B A sta tu s m e a n in g
0 0 0 sta tu s 0 T h e l i n k i s o u t o f o r d e r.
0 0 1 sta tu s N T h e l i n k i s a t n o r m a l a d j u s t in g s ta t u s .
re se rv e d 0 1 0 sta tu s E T h e l in k i s a t e m e r g e n t a d j u s ti n g s t a t u s .
0 1 1 sta tu s O S T h e l i n k f a i l s, se r v i c e s i n te r r u p t
1 0 0 sta tu s P O T h e P r o c e s s o r o r u p l a y e r m o d u l e f a i ls . , ,se r v i
1 0 1 sta tu s B T h e l i n k i s b u s y.
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The message signaling unit (MSU)
The message signaling unit(MSU) is related to user part, and used
to send the user part messages. The length of MSU is variable, with
a maximum length of 272 bytes.
MSULI>2 The first transmitted bit
F CK SIF SIO LI FIB FSN BIB BSN F
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The meanings of the various fields are as follows:
1) Flag (F):the starting flag indicates the start of a signal unit. The start
flag of a signal unit is usually the ending flag of the preceding signal
unit. The ending flag indicates the end of a signal unit, and has a flag
code type of01111110.
F F F F F
signal unitssignal unitssignal unitssignal units
01111110
start
start end
delimitation
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F F F01111110
01111110 01111110
F F F010111110
In order to ensure that 01111110 code do not appear in other parts
of the unit, after fifth 1 (with more than 6 continuous 1s) we
appended a 0 in outgoing end, and remove it in receive end.
desequencing code
F
??
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2) Length indication code (LI): the length indication code indicates the
quantity of octets located after the length indication code and before the
check bits, is a number within 0 63 represented by a binary. The
length indication codes of 3 forms of signal units are respectively:
octets byte 1 byte = 8 bit
LI 0 byte: filling-in signal unit (FISU)
LI 1 byte or 2: link status signal unit (LSSU)
LI>2 byte: message signal unit (MSU)
In message signal unit, when the signaling information field has
tets more than 62, LI =63.
3) The status field (SF): if the length indication code is 1, (LI=1)then the
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The first transmitted bit
Standby
5
Status
indication3
C B A
F CK SF LI FIB FSN BIB BSN F
status field is one octet; if the length indication code is 2, then the status
field is two octets. The code of the link status indicator is shown in Table
4.4.2-1.
HGFED C B A status meaning
0 0 0 status 0 The link is out of order.
0 0 1 status N The link is at normal adjusting status.
reserved 0 1 0 status E The link is at emergent adjusting status.
0 1 1 s t a t u s O S The link fails, services interrupt
1 0 0 s t a t u s P OThe Processor or up layer modulefails. , ,services interrupt
1 0 1 status B The link is busy.
1
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4) Sequence number (FSN, BSN):
the forward sequence number (FSN) is the No. of the signal unit
itself.
the backward sequence number (BSN) is the No. of theacknowledged signal unit.
Both forward sequence number and backward sequence number are
binary numbers with a length of 7 bits, in the cycling sequence from0 to 127.
The first transmitted bit
F LI FIB FSN BIB BSN FCK
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The first transmitted bit
F LI FIB FSN BIB BSN FCK
5) The indication bits (FIB, BIB): together with FSN and BSN, the
forward indication bit (FIB) and the backward indication bit (BIB)
are used forbasic error control, with a length of 1 bit, so as to
perform the signal unit sequence number control and
acknowledgment.
6) The check code (CK): each signal unit has the 16-bit check
code for error detection.
7) The service information octet (SIO): in the message signal unit, the
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service information octet includes the Service Indication Code and sub-
service field. The structure of the service information octet is shown in
Figure 4.4.2-2.
Figure 4.4.2-2 SIO formatThe service indication codes used in the international signaling network
are as follows:
DCBA
Sub-service
field
Serviceindication
code
DCBAThe first transmitted bit
F CK SIF SIO LI FIB FSN BIB BSN F
8 16 8n(n2) 8 2 6 1 7 1 7 8
SSF SI
Bit: DCBA(SI)
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0000 signaling network management message
0001 signaling network test and maintenance message
0010 reserved
0011 SCCP0100 the telephone user part (TUP)
0101 the ISDN user part (ISUP)
0110 the data user part (messages related to call and circuit)
0111 the DUT (performance registration and canceling message)
1000 reserved for MTP to test the user part
1001
1010
1011
1100 reserved1101
1110
1111
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The sub-service field (SSF) includes the indication code (bits C and D)
and two reserved bits (bits A and B). The network indication codes are
distributed as follows:
bit:
DC
00 international network
01 reserved (for international use only)
10 domestic network
11 reserved for domestic use
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The first transmitted bit
F CK SIF SIO LI FIB FSN BIB BSN F
8) The signaling information field (SIF): the signaling information
field consists of an integral number of [2, 272] octets. The format and
code of the signaling information field is stipulated in detail in each
user part. The signaling information of the TUP user part shall be
illustrated with examples in the following sections.
4 5The Telephone User Part (TUP)
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4.5The Telephone User Part (TUP)
In the No.7 signaling system, all phone signals shall be sent throughthe message signal unit. In the phone message signal unit, only thesignal information field (SIF) is related with the phone control signal ofthe telephone user part, and handled by thetelephone user part.
The signaling program of the TUP is similar to the channelassociated signaling, except that the signal content is much more thanchannel associated signaling, the representation of signaling
information and transfer is also different. Besides, ordinary phoneconnections, it can also provide a part of subscribers withsupplementary services, such as calling back busy, call transfer, andmalicious call tracing.
The length of the signal information field (SIF) is variable, and is
related to the phone call control signals of the telephone user part. Itnormally consists of three parts: the label, the head code and signalinginformation.
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F FCK SIF SIO LI FIB FSN BIB BSN
The first transmitted bit
8 16 8n 8 2 6 1 7 1 7 8n>2
Signalingmessage
labelH1 H0
DPCCIC OPC
4 12 24 24
8n 4 4 64
Format of TUP message units
in national networks
4 5 1 The label of phone signaling message
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4.5.1 The label of phone signaling message
Each signaling message is a set of information used separately by
the different No.7 signaling user part. To label the original and
destination point of each signaling message, in each signalingmessage unit there is the messages channeling label with a fixed
length.
The label of telephone signaling messages is as shown in Figure 4.5.1-
1. It includes three fields: the destination signaling point code (DPC),
the originating signaling point code (OPC), and the circuit
identification code (CIC).
CIC OPC DPC
The first transmitted bit4 12 14/24 14/24
Figure 4.5.1-1 Flag in the signaling message
2) The circuit identification code CIC
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2) The circuit identification code CICThe circuit identification code is distributed to each phone circuit, by
bilateral agreement or preset principles:
(1) The 2048kb/s digital channelFor the 2048kb/s digital channel, the 5 lowest bits in the 12-bit CIC is
the time slot code of the voice channel.
the other7 bits represent the codes of the PCM systems between DPC
and OPC.
Primary group (E1) consists of 32 time slots, 25=32so that 5 bits are enough.
27=128
128*32=4096 voice channels
one 64kb/s No 7 link is able to service for 4096 trunks.
7 bits 5 bits
32 TS
128 E1
(2) The 8448Kb/s digital channel
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(2) The 8448Kb/s digital channelFor the 8448Kb/s digital channel, the 7 lowest bits in the 12-bit CIC is
the time slot code of the voice channel, and the other 5 bits represent
the codes of the PCM systems between DPC and OPC.Second order group consists of 4 Primary group 32*4=128
27=128
7 lowest bits for E2 are enough.
5 bits 7 bits
128 TS
32 E2
27=128 and25=32
128*32=4096 voice channels
one 64kb/s No 7 link is able to service for 4096 trunks.
4.5.2 Title code distribution
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LEAD CODES
SI H1 H0 LABEL
8n 4 4 64
CIC OPC D PC
4 12 14 14
F CK SIF SIO LI FIB FSN BIB BSN F
8 16 8n(n2) 8 2 6 1 7 1 7 8 The first transmitted bit
SSI SI
All phone signaling messages contain a title that consists of thehead code H0 and H1.
H0 marks the message group, and H1 contains one message code,
or, marks the format of these messages in case of complex messages.
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Table 4.5.2-1 Distribution of the head codes in the TUP messages
messagegroup
H1
H00000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
0000 Reserved for dom esticFAM 0001 IAM IAI SAM SAO
FSM 0010 GSM COT CCF
BSM 0011 GRQ
SBM 0100 ACM CHG
UBM 0101 SEC CGC NNC ADI CFL SSB UNN LOS SST ACB DPN MPR EUM
CSM 0110 ANU ANC ANN CBK CLF RAN FOT CCL
CCM 0111 RLG BLO BLA UBLU BA CCR RSC
GRM 10 00 M G B M B A M G UM U AH GB H BA H GU H UA G RS G RA S GB S BA S GU S U A
1001 reservedCNM 1010 ACC
1011
Reserved for international anddomestic
NSB 1100 MPMNCB 1101 OPR
NUB 1110 SLB STB
NAM 1111 MAL
Reserved for dom estic
4 5 3 M i f i l i TUP
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4.5.3 Meanings of signal messages in TUP
1) The forward address message (FAM)
(1) The initial address message (IAM)
CIC OPC D PC
SI H1 H0 LABEL
0001 0001
Address Address Number Signaling Flag R e s e r v e dcaller type
LKJHGFEDCBA FEDCBA
F A M 0 0 0 1 I A M I A I S A MS A O
H1 0001 0010 0011 0100H0 0001
IA
MSignal
information
Bit 8n 4 12 2 6 4 4LKJIHGFEDCBA FEDCBA 0001 0001
The number
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Address digital(in binary)
of address
digital (in
binary)
Signaling flagNot in
useCaller type H1 H0
0000-1001: standfor numbers 0-9
1010, 1101, 1110:reserved
1011, 1100: used inthe internationalcall connection
ST: = 1111(end of the address)
0000: filling code(to guarantee thelength of the
variable field lengthis integral multipleof 8bit. )
BA: address character00 local call subscriber number01 reserved10 domestic valid number11 international number
DC: circuit character00 connection without satellite circuit01 connection with satellite circuit10 reserved11 reservedFE: continuity test00 need not continuity test01 continuity test isrequired in this section10 continuity test isdemanded in the previous
section11 reservedG: phone echo canceller0 excluding phone echo canceller
1 including phone echo canceller
H: international incoming call0 not international incoming call1 international incoming callI: changing into issuing a call0 not changing into issuing a call
1 changing into issuing a call
J: complete digital channel
is demanded.0 normal call1 complete digital channelis demandedK: signal communicationschannel0 any channel1 all No.7 signalingchannels are demandedL: reserved
FEDCBA000001 operator, French000010 operator, English000011 operator, German000100 operator, Russian
000101 operator, Spanish000110 language negotiated by both sides
(Chinese)
000111 language negotiated by both sides
001000 language negotiated by both sides
(Japanese)001001 domestic operator (with the function
of interpolation )001010 ordinary subscriber, used in the
toll(international)-toll and toll(international)-
local offices.
001011 priority subscriber, used in thetoll(international)-toll and toll(international)-
local offices.
001100 data call001101 test call001110-001111 reserved010000 common, billing free010001 common, regular001010 common, subscriber table,immediate010011 common, printer, immediate010100 priority, billing free
010101 priority, regular010110-010111 reserved011000 common, used in the local-local offices.011001-111111 reserved
Figure 4.5.4-1 IAM format
p341
(2) The initial address information (IAI) with additional information
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(2) The initial address information (IAI) with additional information
For a call between local and toll switches, or for a special service call,
additional information such as the caller number is required, thus the
initial address message (IAI ) with additional information is used.CIC OPC D PC
HGFEDCBA LK BA
first presentation Adress Number of address Signaling flag
FEDCBA 0010 0001
Reserved Calling user type H1 H0 Flag
2 6 4 4
Billing
informati
on
Original
callee
address
Caller
line
label
Additional
route
information
Additional
caller
information
Close user
group
information
Network capability or user
performance information
(optional)
8n 8 8n 8n 8n 40 8
p342
Bit 8n 4 12 2 6 4 4LKJIHGFEDCBA FEDCBA 0001 0001
The number
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Address digital(in binary)
of address
digital (in
binary)
Signaling flagNot in
useCaller type H1 H0
0000-1001: standfor numbers 0-9
1010, 1101, 1110:
reserved
1011, 1100: used inthe internationalcall connection
ST: = 1111(end of the address)
0000: filling code(to guarantee the
length of thevariable field lengthis integral multipleof 8bit. )
BA: address character00 local call subscriber number01 reserved10 domestic valid number
11 international numberDC: circuit character00 connection without satellite circuit01 connection with satellite circuit10 reserved11 reservedFE: continuity test00 need not continuitytest01 continuity test isrequired in this section10 continuity test is
demanded in the previoussection11 reservedG: phone echo canceller0 excluding phone echo canceller
1 including phone echo canceller
H: international incoming call0 not international incoming call1 international incoming callI: changing into issuing acall0 not changing into issuing acall
1 changing into issuing a call
J: complete digital channelis demanded.0 normal call1 complete digital channelis demandedK: signal communicationschannel0 any channel1 all No.7 signaling
channels are demandedL: reserved
FEDCBA000001 operator, French000010 operator, English000011 operator, German
000100 operator, Russian000101 operator, Spanish000110 language negotiated by both sides(Chinese)000111 language negotiated by both sides001000 language negotiated by both sides(Japanese)001001 domestic operator (with the functionof interpolation )001010 ordinary subscriber, used in thetoll(international)-toll and toll(international)-
local offices.001011 priority subscriber, used in thetoll(international)-toll and toll(international)-local offices.
001100 data call001101 test call001110-001111 reserved010000 common, billing free010001 common, regular001010 common, subscriber table,immediate010011 common, printer, immediate010100 priority, billing free010101 priority, regular010110-010111 reserved011000 common, used in the local-local offices.011001-111111 reserved
-
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(3) The subsequent address message (SAM) with multiple addresses
After sending the IAM message in the OVERLAP mode, if the least
sent code bits (except the number bits sent in the IAM message) isgreater than 1, then the subsequent address message (SAM ) with
multiple caller address figure shall be used.
(4) The subsequent address message (SAO) with one address figure
After sending the initial address message, all the remaining calleesubscriber numbers can be sent in SAO.
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Local exchange Local exchangeTandem exchange
IAM
SAM
SAO IAM
ACM
Ringing
ANCANCCLF CLFTalking
RLGRLG
CBKCBK Callee
release first CLFCLF
RLG RLG
Si li t i i th ZXJ10 it h N 7 i li t
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No.: 000061 sequence number: 6403 code: SHOW_SIGNAL_TRACEdate: Dec.10, 1997 time: 14h 51m 05s
Man-machine command output content
tracing mode common channel outgoing callee number4560034
time DPC OPC CIC H1H0 DATA14:50:44:100 1-1-1 2-2-2 63 IAM 18 00 74 54 06 30 04
14:50:44:350 2-2-2 1-1-1 63 ACM 25
14:50:46:160 2-2-2 1-1-1 63 ANC
14:50:49:230 1-1-1 2-2-2 63 CLF
14:50:49:360 2-2-2 1-1-1 63 CBK
14:50:49:470 2-2-2 1-1-1 63 RLG
Signaling tracing in the ZXJ10 switch No.7 signaling system
p378
IAM carries the called number,and caller type.
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IAM carries the called number,and caller type.
The DATA stands for the concrete information carried by the
messages. The first byte (octet) is caller type: 18 is decimal system.
It can divide into two BCD codes.
18 0001 1000
F E D C B A
0 1 1 0 0 0
From Figure 4.5.4-1 we find out that is common, used in the
local-local offices.
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The second byte is Signaling Flag (00 74)
BA--00 local call subscriber number
DC--00 connection without satellite circuit
FE--00 need not continuity test
G----0 excluding phone echo canceller
H----0 not international incoming call
I---- 0 not changing into issuing a call
J---- 0 normal call
K--- 1 all No.7 signaling channels are demanded
L--- 0 reserved
Second
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18 00 74 54 06 30 04
Digit ofcallee
is seven
First
number
Second
number third
number
fourth
number
fifthnumber
sixth
number
callee number is 4560034
last
number
2) Th f d (FSM)
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2) The forward setup message (FSM)
(1)General forward signal message (GSM).
GSM is a responding message to general request messages GRQ.
(2) Continuity test message
The continuity test message includes the continuity signal message
(COT) and the continuity failure signal message (CCF).
As common channel signals are not signals sent in voice channels, but
are signaling signals for a group of voice channels via one or several
concentrated signal links, the continuity test of voice channels are
needed to ensure the correct connection and smooth transmission of
voice channels.
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3) The backward setup request message (BSM)The general request message GRQ
GRQ contains the request type indicators, indicating that the requested
service is:
x requesting caller type
x requesting caller line label
x requesting original callee address
requesting malicious call tracingrequesting holding
requesting echo suppressor
In the process of connection, the above requests are made according
to service needs to the originating switch, which answers with GSM.
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4) The successful backward setup message (SBM)
The address complete message (ACM)
ADC: address complete, billing required;
ADN: address complete, billing free;
ADX: address complete, payphone;
AFC: address complete, subscriber idle, billing required;
APN: address complete, subscriber idle, billing free;AFX: address complete, subscriber idle, payphone.
After receiving all the called subscriber numbers and recognizing the
called subscriber status, the incoming switch immediately sends abackward setup message. In normal call connections, if the callee
subscriber is idle status, the backward address complete message ACM
shall be sent.
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8 4 40001 0100HGFEDCBA
H1 H0
BA:
00 Address complete
01 Address complete, billing
10 Address complete, billing free11 Address complete, payphone
C:
0 Callee terminal has no indication
1 Callee terminal idle
Others Not in use
Figure 4.5.4-5 Address complete signal format
E:
0 : No forward transfer for call
1 : forward transfer for call
F:
0 : any channel
1: all No.7 signaling channel
ACM 25
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ACM 25
25--------00100101
Address complete, billing
Callee terminal idle
all No.7 signaling
channels are demanded
standby
H G F E D C B A H1 H0
0 0 1 0 0 1 0 1 0001 0100
5) The unsuccessful backward setup message (UBM)
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5) The unsuccessful backward setup message (UBM)
switching equipment congestion signal SEC
circuit group congestion signal CGC
address incomplete signal ADI call failure signal CFL unallocated number signal UNN line does not service signal LDS send special information tone signal SST
access barred signal ACB digital path not provided signal DPN national network congestion signal NNC subscriber busy signal (electrical) SSB expanded unsuccessful backward setup message EUM
When the whole callee subscriber number reaches the incomingswitch, after number analysis, if the callee number is unallocatednumber, then the UNN message will be sent back.
6) Th ll i i (CSM)
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6) The call supervision message (CSM)
It includes the following signals:
answer signals, unclassified ANU
answer signal, billing required ANC
answer signal, billing free ANN
callee backward release CBK
clear forward signal CLF re-answer signal RAN
forward transfer signals (semi-automatic international call
signals) FOT
calling party clear signal CCL
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7) The circuit supervision message (CCM)
It contains the following signals:
release-guard signal RLG
blocking signal BLO
blocking acknowledgement signal BLA
unblocked signal UBL
unblocking acknowledgement signal UBA
continuity-check-request signal CCR
reset circuit signal RSC
8) The circuit group supervision message (GRM)I i l d h f ll i i l
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It includes the following signals:maintenance oriented group blocking signal MGBmaintenance oriented group blocking ack. signal MBA
maintenance oriented group unblocking signal MGUmaintenance oriented group unblocking ack. Signal MUA hardware failure oriented group blocking signal HGB hardware failure oriented group blocking ack. message HBA
hardware failure oriented group unblocking message HGU
hardware failure oriented group unblocking ack. message HUA circuit group rest GRS circuit group recovery ack GRA software generation group blocking ack. message SGB software generation group unblocking message SGU
software generation group unblocking ack. (domestic optional)SUA
9) Domestic unsuccessful backward setup message (NUB)
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9) Domestic unsuccessful backward setup message (NUB)
Subscriber local busy SLB
Subscriber toll busy STB
10) Node-to-node message (NNM)11) Circuit network management message (CNM)
The automatic congestion control message ACC12) Domestic successful backward setup message (NSB)
13) Domestic call supervision message (NCB) Traffic and signal OPR14) Unsuccessful backward setup message (NUB)
Subscriber local busy signal SLB Subscriber toll busy signal STB
15) Domestic area message (NAM) The malicious call identification signal MAL The caller re-off-hooking signal CRA
ISUP signaling message and parameter
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ISUP signaling message and parameter
ISUP provides signaling basic support service and supplementservice for voice service and non-voice service.
ISUP can use MTP also can use SCCP to send message
between ISUP.
ISUP can realize all the function of TUP.
All the messages can be classified into the
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All the messages can be classified into the
following kinds according to the function:
1.call setup message : includes the request for call setup, information transferof supplementary call setup, information transfer during call setup process,
response from called user, transfer of line continuity test results when necessary,
etc.
2. In-communication message : includes call suspension, recovery,conversion in calls, messages used by operators during communication, etc.
3.call release message : the message used to release calls upon call completion.
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4.line monitoring message : includes monitoring messages used when line(suspend the use of line temporarily) is blocked for maintenance and test, when circuit is
initialized (compelled release) in case of failure, and when continuity test is performed.
5.line group monitoring message : includes messages of simultaneous blockingof line groups (up to 256 lines can be specified), initialization preset and line state detection
on a timing-basis.
6.supplementary service and other messages : includes using the messagesrelated to the request, acknowledgement, and rejection of supplementary services, transferringthe end-to-end signaling messages and user-to-user signaling.
Type Message name Code Basic function
Call
Initial address message (IAM) 00000001 The request for call setup
Subsequent address message (SAM) Inform subsequent address information
Continuity message (COT) 00000101 Inform the information channel continuity test is
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establishment completedInformation request message (INR) 00000011 The request for additional call setup information
Information message (INF) 00000100 The additional call setup information
Address complete message (ACM) 00000110 The notice of address message receiving complete
Call progress message (CPG) 00101100 The notice of call setup process
Answer message (ANM) 00001001 The information of answer from called user
Connection message (CON) 000000111 With the ACM+ANM function
In
communicatio
n
Suspend message (SUS) 00001101 The request for call suspension
Recover message (RES) 00001110 The request for recovering suspended calls
Call modification request message (CMR) 00011100 The request for modifying call features in a call
Call modification complete message (CMC) 00011101 The information of completing to modify call features
Call modification rejected message (CMRJ) 00011110 The information of rejecting to modify call features
in a callForward information (FOT) 00001000 The call request from operator
Call release Release message (REL) 00001100 The request for call release
Release complete message (RLC) 00010000 The request for call release complete
Line
monitoring
Continuity check request message (CCR) 00010001 The request for continuity testRestore circuit message (RSC) 00010010 The request for circuit initialization
Block message (BLO) 00010011 The request for circuit blocking
Unblock message (UBL) 00010100 The request for unblocking circuit
Block acknowledgement message (BLA) 00010101 Circuit blocking acknowledgement
Unblock acknowledgement message (UBA) 00010110 Circuit unblocking acknowledgement
Line group
monitoring
Circuit group block message (CGB) 00011000 The request for circuit group blocking
Circuit group unblock message (CGU) 00011001 The request for circuit group unblocking
Circuit group blockacknowledgement message 00011010 Circuit group blocking acknowledgement
Circuit group unblockacknowledgement Circuit group unblocking acknowledgement
Circuit group restoration message (GRS) 00010111 The request for circuit group initialization
Circuit group restoration acknowledgement 00101001 Circuit group initialization acknowledgement
Circuit group query message (CQM) 00101010 The message of querying circuit group state
Circuit group query response message (CQR) 00101011 The notice of circuit group state
Suppliementar
y services and
others
Performance acceptance message (FAA) 00100000 The request for allowing supplementary services
Performance request message (FAR) 00011111 The request for supplementary services
Performance rejection message (FRJ) 00100001 The request for rejecting supplementary services
Passing message (PAM) 00010100 Transfer information along with signal routeUser-to-user message USR 00101101 User-to-user signaling transfer
ISUP signaling message and parameter
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ISUP signaling message and parameter
For TUPD C B A
0 1 0 0
D C B A
0 1 0 1
F CK SIF SIO LI FIB FSN BIB BSN F
8 16 8n(n2) 8 2 6 1 7 1 7 8 The first transmitted bits
SSI SI
SI H1 H0 label
CIC SLS OPC D PC7 Route label 0
CIC
Message type code
Necessary fixed part
Necessary variable part
Random part
integer multiples of octets
For ISUP
Routing label
Circuit identification code
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Compulsory fixed part
Compulsory variable part
Optional part
Optional part
Message type cpde
Compulsory fixed parameter A
Mandatory fixed parameter F
Pointer to variable parameter M (point to parameterM)
Pointer to variable parameter P (point to parameter P)
Pointer to start of optional part (point to the first optional parameter)
Length indicator of variable parameter M
Variable parameter M
Length indicator of variable parameter P
Variable parameter P
Variable parameter name X
Length indicator of optional parameter X
Optional parameter X
Optional parameter name Z
Length indicator of optional parameter Z
Optional parameter Z
End of optional parameters
General format of ISUP message
Route label
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SLS OPC DPC
8 24/14 24/14
DPC: destination point code OPC
SLS: signaling link select, selection for signaling link of load
share,presently only lower 4 bits used, higher 4bits standby
Route label
CIC
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7 6 5 4 3 2 1 0
CIC lowest efficient bits
Standby CIC highest efficient bits
ISUP has 2 octets to be as CIC
It is identification code for the circuits between OPC and
DPC only use lower 12 bits now higher 4 bits
standby . (coding method same as TUP )
1
2
Message type code
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g yp
defines the label of each ISUP message in a unified
mannerCompulsory fixed part
Compulsory variable part
be compulsory for a specific message and the length of
parameter should be fixed.
compulsory for specific messages but the lengths of
parameters are variable. So pointer must be used to
indicate the number of octet between the pointer and the
first octet given by each parameter value.
optional part
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optional part
For a specific message, optional part may or may not exist. If it
exists, each parameter should include parameter name, lengthindicatorand parametercontents.
Length indicator code
Indicating the byte number of parameter.
Pointer code
Occupy 1 octet indicate the number of octet between the
pointer and the first octet pointed by the pointer (included)
given by each parameter value.
ISUP message example---IAM
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ISUP message example IAM
IAM00 60 00 0A 03 02 08 06 81 90 54 48 41 03 0A 07 83 13 52
54 08 50 06 08 01 80 00
(Parameters) (type)
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(Parameters)
()(type)
(Octet)
Message type 2.1 F 1
Nature of connection indicators 2.34 F 1
Forward call indicators 2.22 F 2
Calling party's category 2.10 F 1
Transmission medium requirement 2.53 F 1
Called party number (Note 2) 2.8 V 4-?(4-11)
Transit network selection (nationaluse)
2.52 O 4-?
Call reference (national use) 2.7 O 7(8)
Calling party number (Note 2) 2.9 O 4-?(4-12)
Optional forward call
indicators
2.37 O 3