signaling system
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1
HUAWEI
By Common Technologies Department
SS7 Signaling System
Course Code: OIA0005
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HUAWEI Objectives
Understand the basic concepts in SS7
Understand the important composition of SS7 signalling units
Understand the basic signalling procedures of SS7
Upon completion of this course,you will be able to:
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HUAWEI
Chapter 1 Fundamentals of SS7 Chapter 2 Message Transfer Part Chapter 3 Telephone User Part Chapter 4 ISDN User Part Chapter 5 Signaling Connection Control Part Chapter 6 Transaction Capabilities Application Part Chapter 7 Intelligent Network Application Part
Contents
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HUAWEI
Fundamentals of SS7
Chapter One
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HUAWEI An Introduction to Signaling
In a telephony context, signaling means the passing of information and instructions from one point to another relevant to the setting up and supervision of a telephone call.
By tradition, Signaling has been divided into two types: Subscriber Signaling i.e. signaling between a subscriber terminal (telephone) and the local exchange, and Trunk Signaling i.e. signaling between exchanges.
L o c a lE x c h a n g e
L o c a lE x c h a n g e
T r u n kS i g n a l l i n g
S u b s c r i b e rS i g n a l l i n g
S u b s c r i b e rS i g n a l l i n g
ccs
cas
ccs
cas
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HUAWEI Subscriber Signaling
H O O K O F F
D I A L T O N E
N U M B E R
R I N G I N G T O N E R I N G I N G S I G N A L
B A N S W E R
C O N V E R S A T I O N
H O O K O N H O O K O N
Calling PartyA_Number
Called PartyB_Number
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HUAWEI Channel Associated Signaling (CAS)
Characteristic for CAS is that for each speech channel there is one unambiguously defined signaling path, either On-speech-path, i.e. the signals are transferred in the speech channel (in-band signaling) or Channel-associated, i.e. the signals are transferred in a separate signaling channel, for example the line signals are transferred in time slot 16 in PCM system.
All of these signaling systems have a number of limitations like: Relatively slow, Limited information capacity, etc.
Switch1
Switch2
Voice TrunkSignaling Link
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HUAWEI Common Channel Signaling (CCS)
In type of CCS, signaling for numerous circuits can be handled by a few fast signaling data links. The signaling is performed in both directions, with one signaling channel in each direction.
The signaling information that will be transferred is grouped into signal units (data packets). Besides the signaling information itself, there is also need for speech circuit identification and address information (label) and information for error control.
SS7 is a kind of CCS signaling system.
SP SP
STP STP
Voice Trunk
Signaling Link
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HUAWEI Evolution of SS7
Common Channel Signaling System No. 7 (i.e., SS7 or C7), which was specified in 1979/80, is intended primarily for digital networks, both national and international, where the high transmission rate (64 kb/s)can be exploited. It may also be used on analog lines.
SS7 signaling has not only been designed to control the setting up and supervision of telephone calls but of non -voice services also.
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HUAWEI Advantages of Using SS7
SS7 has several advantages compared with traditional signaling systems. Some obvious advantages are the following:
FAST - the time for call set up is reduced to less than one second in most cases.
HIGH CAPACITY - each signaling link can handle the signaling for several thousand simultaneous calls.
ECONOMICAL - much less signaling equipment is required, compared to traditional signaling systems.
RELIABLE - by using alternate signaling routes, the signaling network can be made very secure.
FLEXIBLE - the system can contain many more signals, for example, and can be used for other purposes than telephony.
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HUAWEI Definition of CCS7 Signalling System
In CCS7, signalling links are independent of voice channels. These signalling links form a network dedicated to the transmission of signalling, which is called CCS7 signalling network.
It is a multifunctional supporting network, can be used in telephone network, circuit-switch data network, ISDN network, and intelligent network, etc.. Fundamentally, CCS7 signalling network is a packet switching data network used for dedicated purpose.
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HUAWEI Three Elements in CCS7 Signalling NetworkA CCS7 signalling network is composed of three elements:
signalling Point (SP), signalling Transfer Point (STP) and signalling Link.
Link Voice Channel
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HUAWEI Three Elements in CCS7 Signalling Network
SP is the originating or destination point of a CCS7 message. In each signalling network, a SP has an exclusive signalling point code: SPC (14 bits). Since the four signalling networks assign the SPCs independently, only NI+SPC can uniquely locate a SP.
SP (Signalling Point)
Notes: In data setting we usually describe SPC in Hex. Following are some examples of SPC shown in binary and hex. SPC (binary) SPC (Hex) 00 0000 1011 0101 00b5 10 0011 1101 0111 23d7
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HUAWEI OPC and DPC ( I )
DPC: Destination Point CodeOPC: Originating Point CodeA message going from one SP to another SP should bear the SPC of the originating SP and the terminating SP, which are called OPC and DPC respectively. If we compare sending a message to sending a letter, OPC and DPC are similar to the sender's address and receiver's address.
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HUAWEI Three Elements in CCS7 Signalling Network
Link is the data channel which connects the nodes (SPs and STPs) in CCS7 signalling network.Digital link, 64 kb/s
STP is the network node which transfers CCS7 messages.
STP (Signalling Transfer Point)
Link
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HUAWEI Signaling Route & Signaling Route Set
The pre-determined path, that a message takes through the signaling network between the origination point and the destination point is called a Signaling Route. It may consist of a succession of SP/STPs and the interconnecting SLs.
All the Signaling Routes that may be used between an origination point and a destination point by a message traversing the signaling network is the Signaling Route Set for that signaling relation.
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HUAWEI Working Modes of CCS7 Signalling NetworkWorking mode refers to the relationship between the signalling link and the voice channels the link serves.Presently two modes are in use:Associated mode
The messages between two adjacent points are conveyed over a link-set directly interconnecting those signalling points, i.e., the link is parallel to the voice path.
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HUAWEI Working Modes of CCS7 Signalling Network
Quasi-associated mode In the quasi-associated
mode the message which is going to arrive at a SP goes through a path which is predetermined and via one or more STPs.
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HUAWEIWhen the links between any two offices are transferred by a STP, how will be the link path?
Note: the sole purpose of using signalling is to serve the voice path.
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HUAWEIWhen the links between any two offices are transferred by a STP, how will be the link path?
Note: the arrows show the paths that signalling messages go through. Remember, a signalling path always starts from one end of the voice path it is going to serve, and ends up at the other end of the voice path.
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HUAWEI An Example of Signaling Network
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HUAWEI SS7 Protocol Stack
The OSI Reference Model and the SS7 Protocol Stack
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HUAWEI
Message Transfer Part
Chapter Two
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HUAWEI MTP Level 1
The lowest level, MTP Level 1 defines the physical, electrical, and functional characteristics of the digital signaling link. Physical interfaces defined include E-1 (2048 kb/s; 32 64 kb/s channels), DS-1 (1544 kb/s; 24 64 kp/s channels), V.35 (64 kb/s), DS-0 (64 kb/s), and DS-0A (56 kb/s).
MTP Level 1 is equivalent to the OSI Physical Layer.
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HUAWEI MTP Level 2
MTP Level 2 ensures accurate end-to-end transmission of a message cross a signaling link. Level 2 implements flow control, message sequence validation, and error checking. When an error occurs on a signaling link, the message (or set of messages) is retransmitted.
MTP Level 2 is equivalent to the OSI Data Link Layer.
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HUAWEI MTP Level 3
MTP Level 3 provides message routing between signaling points in the SS7 network. MTP Level 3 re-routes traffic away from failed links and signaling points and controls traffic when congestion occurs.
MTP Level 3 is equivalent in function to the OSI Network Layer.
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HUAWEI Signaling Unit (SU)
An SS7 message is called a signal unit (SU).
There are three kinds of signal units: Fill-In Signal Units (FISUs), Link Status Signal Units (LSSUs), and Message Signal Units (MSUs)
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HUAWEI Fill-in Signal Units (FISUs)
Fill-In Signal Units (FISUs) are transmitted continuously on a signaling link in both directions unless other signal units (MSUs or LSSUs) are present. FISUs carry basic level 2 information only (e.g., acknowledgment of signal unit received by a remote signaling point). Because a CRC checksum is calculated for each FISU, signaling link quality is checked continuously by both signaling points at either end of the link.
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HUAWEI
Link Status Signal Units (LSSUs) carry one or two octets (8-bit bytes) of link status information between signaling points at either end of a link. The link status is used to control link alignment and to indicate the status of a signaling point (e.g., local processor outage) to the remote signaling point.
Link Status Signal Unit (LSSUs)
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HUAWEI Message Signal Units (MSUs)
Message Signal Units (MSUs) carry all call control, database query and response, network management, and network maintenance data in the signaling information field (SIF). MSUs have a routing label which allows an originating signaling point to send information to a destination signaling point across the network.
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HUAWEI Length Indicator (LI)
LI Value Signal Unit Type0 Fill-In Signal Unit (FISU)1..2 Link Status Signal Unit (LSSU)3..63 Message Signal Unit (MSU)
The value of the LI (Length Indicator) field determines the signal unit type. The 6-bit LI can store values between zero and 63. If the number of octets which follow the LI and precede the CRC is less than 63, the LI contains this number. Otherwise, the LI is set to 63. An LI of 63 indicates that the message length is equal to or greater than 63 octets (up to a maximum of 273 octets). The maximum length of a signal unit is 279 octets: 273 octets (data) + 1 octet (flag) + 1 octet (BSN + BIB) + 1 octet (FSN + FIB) + 1 octet (LI + 2 bits spare) + 2 octets (CRC).
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HUAWEI Flag
The flag indicates the beginning of a new signal unit and implies the end of the previous signal unit (if any). The binary value of the flag is 0111 1110. Before transmitting a signal unit, MTP Level 2 removes "false flags" by adding a zero-bit after any sequence of five one-bits. Upon receiving a signal unit and stripping the flag, MTP Level 2 removes any zero-bit following a sequence of five one-bits to restore the original contents of the message. Duplicate flags are removed between signal units.
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HUAWEI CRC (Cyclic Redundancy Check)
The CRC value is used to detect and correct data transmission errors.
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HUAWEI BSN, BIB, FSN & FIB
BSN (Backward Sequence Number) is used to acknowledge the received signal units by the remote signaling point. The BSN contains the sequence number of the signal unit being acknowledged.
BIB (Backward Indictor Bit) indicates a negative acknowledgment by the remote signaling point when toggled.
FSN (Forward Sequence Number) contains the sequence number of the signal unit.
FIB (Forward Indicator Bit) is used in error recovery like the BIB.
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HUAWEI Basic Error Correction Method
A B
FSN
BSN
Positive Acknowledgement
FSN=63
BSN=63 BIB=FIB
A B
FSN
BSN
Negative Acknowledgement
FSN=63
BSN=62 BIB=Toggled Value of FIB
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HUAWEI SIO (Service Information Octet)
Service Indicator
D C B AInternational NetworkInternational ReservedNational NetworkNational Reserved
0 00 11 01 1
Spare
D C B A0 0 0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 0
0 1 1 1to
1 1 1 1
Signaling Network ManagementMaintenance Test MessageSpareSCCPTelephone User PartISDN User PartData User Part
Spare
Service Information Octet
SubService Field
Network Indicator
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HUAWEI SIF (Signaling Information Field)
The SIF in an MSU contains the routing label and signaling information (e.g., SCCP, TCAP, and ISUP message data).
LSSUs and FISUs contain neither a routing label nor an SIO as they are sent between two directly connected signaling points. For more information about routing labels, refer to the description below.
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HUAWEI MTP Level 3 Routing Label
MTP Level 3 routes messages based on the routing label in the signaling information field (SIF) of MSUs. The routing label is comprised of the destination point code (DPC), originating point code (OPC), and signaling link selection (SLS) field.
Signaling Points Codes are numeric addresses which uniquely identify each signaling point in the SS7 network.
The DPC in a message indicates the receiving signaling point, and the OPC in a message indicates the originating signaling point.
The message is distributed to the appropriate user part (e.g., ISUP or SCCP) indicated by the service indicator in the SIO.
The selection of outgoing link is based on information in the DPC and SLS.
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HUAWEI
F CK SIF SIO LI ErrorCorrection F
MSU - Message Signal Unit
ROUTING LABELOPC NI (Spare) SISLS DPC
MTP Level 3 Routing Label
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HUAWEI MTP Level 3 Routing Label
ITU-T point codes are pure binary numbers which may be stated in terms of zone, area/network, and signaling point identification numbers.
For example, the point code 5557 (decimal) may be stated as 2-182-5 (binary 010-10110110-101). The point code always uses 3-segment format.
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HUAWEI Signaling Link Selection (SLS)
The selection of outgoing link is based on information in the DPC and Signaling Link Selection field. The SLS is used to:
Ensure message sequencing. Any two messages sent with the same SLS will always arrive at the destination in the same order in which they were originally sent.
Allow equal load sharing of traffic among all available links. In theory, if a user part sends messages at regular intervals and assigns the SLS values in a round-robin fashion, the traffic level should be equal among all links (within the combined linkset) to that destination.
MTP Level 3 re-routes traffic away from failed links and signaling points and controls traffic when congestion occurs.
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HUAWEI OPC and DPC ( II )
In the following two figures, what's the DPC and OPC of the messages?
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HUAWEI Answer
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HUAWEI
Telephone User Part
Chapter Three
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HUAWEI
The Telephone User Part defines the necessary telephone signaling functions in SS7 for international as well as national telephone traffic. It provides the same features for telephone signaling as other ITU-T signaling systems.
The telephone signals are transferred in the signaling network as the form of signaling messages, which are the contents in the SIF field in the Message Signal Units (MSUs).
Overview of TUP
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HUAWEI TUP Message Structure
MSU of TUP
F CK SIF SIO LI ErrorCorrection F
8 16 8n,n¡ Ý2 8 2 6 16 8Transmission Direction
Signal Infor H1 H0 Label
CICSLS OPC DPC
12 14 14
Routing Label
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HUAWEI
Message Group
H1H0
0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
0000 Spare, reserved for national use
FAM 0001 IAM IAI SAM SAO
FSM 0010 GSM COT CCF
BSM 0011 GRQ
SBM 0100 ACM CGH
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 UBL UBA CCR RSC
GRM 1000 MGB MBA MGU MUA HGB HBA HGU HUA GRS GRA SGB SBA SGU SUA
1001 Reserved
CNM 1010 ACC Spare, reserved for international and national use1011
NSB 1100
Spare, reserved for national useNCB 1101
NUB 1110
NAM 1111
TUP Signals
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HUAWEI An Example of TUP Signals
0001 0001
Address signals
Number ofaddresssignals
MessageIndicators
SPARE
A-Category H1 H0 Routing Label
TransmissionDirection
n¡ Á8 4 12 2 6 4 4 40
IAM -- Initial Address Message
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HUAWEI Commonly Used TUP Signals
IAM or IAI
The Initial Address Message (IAM) is the first message of a call set -up. It generally includes all of the information required to route the call. IAI is the same as IAM, but IAI has the caller identification. Generally, IAI is sent from LS to TS.
SAM or SAO
The remaining digits, if any, may be sent individually (SAO - Subsequent Address Message with One digit) or grouped together (SAM - Subsequent Address Message). Efficiency can be gained by grouping together as many digits as possible.
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HUAWEI
ACM
The Address Complete Message will be originated by the last Signaling System No. 7 exchange. It is sent as an acknowledgment signal if the B -subscriber is free and contains information like charging, echo suppresser information etc.
ANC or ANN
The signals Answer Charge and Answer No Charge are sent as a result of the first off-hook signal from the B -subscriber. In the case of ANC signal, the charging process should be initiated after receiving the ANC signal.
Commonly Used TUP Signals
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HUAWEI Commonly Used TUP Signals
CBK
A Clear Back signal is sent if the B -subscriber hooks on first. This signal does not disconnect the established speech channel.
CLF
The Clear Forward signal is sent when the A -subscriber hooks on. All exchanges must respond by releasing the speech (or data) circuit and send a Release Guard (RLG) as an acknowledgment.
RLG
The Release Guard signal is the last signal in the signaling procedure of a call. After this signal has been sent, the speech circuit will be released and available for new traffics again.
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HUAWEI An Example of a Toll Call (A Hooks on)
LSA TSA LSB
IAI IAM
SAM SAM
SAO SAO
ACM ACM
ANCANC
CLF CLF
RLGRLG
Ringing
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HUAWEI
LSA TSA LSB
IAI IAM
SAM SAM
SAO SAO
ACM ACM
ANCANC
CLF CLF
RLGRLG
Ringing
CBKCBK
An Example of a Toll Call (B Hooks on)
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HUAWEI An Example of Requesting Calling Number
LSA LSB
IAM
GRQ
GSMACM
ANC
CBKCLF
RLG
GRQ: General Request MessageGSM: General Group Reset Message
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HUAWEI
ISDN User Part
Chapter Four
56
HUAWEI
The ISDN User Part (ISUP) defines the protocol and procedures used to set-up, manage, and release trunk circuits that carry voice and data calls over the public switched telephone network (PSTN) or ISDN network. ISUP is capable of processing ISDN specific information which is more complex than telephony signaling.
ISUP is used for both ISDN and non-ISDN calls. Calls that originate and terminate at the same switch do not use ISUP signaling.
Overview of ISUP
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HUAWEI ISUP Message Structure
Unlike TUP, SLS is an independent 4-bit, no longer part of CIC. And ISUP uses Message Type instead of H1 and H0.
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HUAWEI Commonly Used ISUP Signals
Initial Address Message (IAM)An IAM is sent in the "forward" direction by each switch needed to complete the circuit between the calling party and called party until the circuit connects to the destination switch. An IAM contains the called party number in the mandatory variable part and may contain the calling party name and number in the optional part.
Address Complete Message (ACM)An ACM is sent in the "backward" direction to indicate that the remote end of a trunk circuit has been reserved. The originating switch responds to an ACM message by connecting the calling party's line to the trunk to complete the voice circuit from the calling party to the called party. The originating switch also sends a ringing tone to the calling party's line.
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HUAWEI Commonly Used ISUP Signals
Answer Message (ANM)When the called party answers, the destination switch terminates the ringing tone and sends an ANM to the originating switch. The originating switch initiates billing after verifying that the calling party's line is connected to the reserved trunk.
Release Message (REL)A REL is sent in either direction indicating that the circuit is being released due to the cause indicator specified. An REL is sent when either the calling or called party "hangs up" the call (cause = 16). An REL is also sent in the backward direction if the called party line is busy (cause = 17).
Release Complete Message (RLC)A RLC is sent in the opposite direction of the REL to acknowledge the release of the remote end of a trunk circuit and end the billing cycle as appropriate.
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HUAWEI Basic ISUP Call Control
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HUAWEI
Signaling Connection Control Part
Chapter Five
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HUAWEI Where is SCCP?
INAP: IN Application Protocol MAP: Mobile Application PartCAP: CAMEL Application Part TCAP: Transaction Capability Application PartTUP: Telephone User Part ISUP: ISDN User PartMTP: Message Transfer Part SCCP: Signaling Connection Control Part
TUP ISUP TCAP
INAP CAP MAP
MTP
SCCP
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HUAWEI What is SCCP?
In SS7 signaling system , SCCP and MTP layer three together are responsible for signaling network layer function. SCCP expands the MTP functions in the following points:
Enable to convey various non-circuit-related signaling message.
Provide enhanced addressing and routing function, and enable to achieve the direct global transmission between different SS7 networks by using GT addressing.
Expand the user part of MTP. SCCP supports up to 256 kinds of sub systems in stead of 16 in MTP.
Enable to provide connectionless service and connection-oriented service.
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HUAWEI Service Functions of SCCP Network
According to the various service requirements, SCCP provides four classes of service: two connectionless services and two connection-oriented services. The four classes are:
Class 0: Basic connectionless class.
Class 1: In-sequence delivery connectionless class.
Class 2: Basic connection-oriented class.
Class 3: Flow control connection-oriented class.
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HUAWEI Addressing and Routing Functions of SCCP
The SCCP routing provides a powerful addressing information translation function on behalf of its users. The routing function also responds to the MTP and SCCP congestion reports.
SCCP Addressing makes use of three separate elements:
DPC;
Global Title (GT);
Sub-System Number (SSN);
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HUAWEI Primitive
In SS7 system, the information exchange between two adjacent layers is called primitive which includes primitive name, primitive type and primitive parameters. There are four types of primitives:
Request Indication Response Confirmation
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HUAWEI Primitives between SCCP and SCCP-User
Primitives between SCCP and SCCP-User (TCAP) are N_Primitives. The connectionless services use the following N_Primitives:
N_UNITDATA_REQ : is used when SCCP-User requires SCCP to send data.
N_UNITDATA_IND : is used when SCCP reports the received data to SCCP-User.
N_NOTICE_IND : is used when SCCP reports the reason why the SCCP-User data cannot be sent to peer point.
N-Primitives can be traced on SSP maintenance terminals.
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HUAWEI N_UNITDATA Parameters
N-UNITDATA_IND and N-UNITDATA_REQ have the same parameters.
SCCP-USER Octet (83H)
Routing Label (DPC 、 OPC 、 SLS)
Sequence Control (SLS)
Protocol Class (81H)
Parameter Location Pointer (Called Address, Caller Address, User Data Pointer)
Called Address (Destination Address)
Caller Address (Originating Address)
User Data (SCCP-User Data to be sent by SCCP transparently, SCCP makes no change to them)
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HUAWEI
N_NOTICE has the same parameter structure with N_UNITDATA, but the Protocol Class is changed to return reason.
N_NOTICE Parameters
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HUAWEI SCCP Message Types
There are 17 kinds of SCCP messages. Among them UDT (Unit Data) and UDTS (Unit Data Service) are used for connectionless services. The codes for UDT and UDTS are 09H and 0AH.
INAP only uses UDT messages.
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HUAWEI
Transaction Capabilities Application Part
Chapter Six
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HUAWEI Applications of TCAP
Applications of TCAP:
Data Exchange between switching systems
Switching systems access network database center
Network databases establish remote operation dialogue
Examples of TCAP applications:
Mobile service applications
Free phone service (800-service)
Credit Card calling
Operation & Maintenance applications
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HUAWEI Dialogue
Dialogue is the association established between two TC -users exchanging data. Whenever two signaling points are going to exchange data, they will setup a dialogue via TCAP. It is TCAP that initiates, maintains and releases of a dialogue. But TCAP does not care the functions of the dialogue.
The procedure of message exchange between two signaling points is similar to man-machine dialogue mode, which involves all necessary messages such as BEGIN and END.
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HUAWEI Component
Component is the protocol data unit exchanged between TC –users. i.e. the information exchanged in a dialogue is just a set of components.
Components are defined by TC-Users. Components include the invoke operation by initiator and the returned result of the operation. The operation is decided by applications, e.g. number translation.
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HUAWEI
A dialogue has one or more components. A service procedure is just one dialogue. i.e. all the operations of a service procedure constitute a dialogue, the dialogue is the carrier of the operations.
The Relationship Between Dialogue and Component
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HUAWEI Categories of TCAP Components
Invoke (INV) is used to send an operation request to remote TC-User.
Return Result-Last (RR-L) is used to return the components of final result of last INV operation.
Return Result-not Last (RR-NL) is used to return the components of non-final result of last INV operation.
Return Error (RE) is used to return the components of error information, in which an error code is embedded.
Reject (RJ) is used to reject last INV operation, in which a reason code is embedded.
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HUAWEI
According to different requirements of operation results, TCAP are classified into 4 classes:
Class 1: Result will be returned no matter the operation is successful or not. i.e. a RR-L, RR-NL or RE must be returned.
Class 2: Only when the operation fails, a RE will be returned.
Class 3: Only when the operation succeeds, a RR-L or RR-NL will be returned.
Class 4: No result returned no matter the operation is successful or not.
Classes of TCAP Operations
78
HUAWEI
TCAP and TC-User exchange data via TC_Primitives.
There are 16 kinds of TC_Primitives, among them there 9 Component TC-Primitives which are related to components and 7 Dialogue TC-Primitives which are related to dialogues.
The TC_Primitives from TCAP to TC-User are Indication primitives, from TC-User to TCAP are Request primitives.
TC Primitives
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HUAWEI Component TC_Primitives (1)
TC- INVOKE is used to invoke an operation.
TC- RESULT- L is used to return the result of an operation.
TC- RESULT- NL is similar to TC - RESULT - L, but only returns the middle result.
Note: all above primitives have both Indication and Request types.
80
HUAWEI
TC- U- ERROR is a Request Primitive which is used to return the error code when the operation fails although TC-User has received the correct operation request.
TC- U- REJECT : is a Request Primitive which is used to return reject code when TC-User has received an incorrect operation request.
TC- U- CANCEL is a Request Primitive which is used for TC-User to request TCAP to cancel an operation.
Component TC_Primitives (2)
81
HUAWEI
TC- L- CANEL is an Indication Primitive which is used to notify TC-User an operation is overtime.
TC- L- REJECT is an Indication Primitive which is used to reject an operation by local TCAP.
TC- R- REJECT : is an Indication Primitive which is used to reject an operation when remote TCAP rejects the operation.
Component TC_Primitives (3)
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HUAWEI Types of TCAP Dialogues
There are two types of TCAP dialogues.
Unstructured Dialogue in which only unidirectional (UNI) messages are included. No response to be returned from opposite point in unstructured dialogue (e.g. a dialogue for sending an alarm message). Intelligent Network seldom uses this kind of dialogues.
Structured Dialogue has initiating, maintaining and ending processes. It has BEGIN, CONTINUE and END or ABORT messages. Intelligent Network just uses this kind of dialogues.
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HUAWEI
TC- UNI TC-User or TCAP request to begin a UNI dialogue.
TC- BEGIN Request or indicate to begin a dialogue.
TC- CONTINUE Request or indicate to maintain a dialogue.
TC- END Request or indicate to end a dialogue.
Dialogue TC_Primitives (1)
84
HUAWEI
TC- U- ABORT : Request to abort a dialogue.
TC- P- ABORT : Indicate TC-User to abort a dialogue because of the error in transaction layer.
TC- NOTICE : Indicate TC-User that the network service provider cannot provide the required service (e.g. STP does not support INAP).
Dialogue TC_Primitives (2)
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HUAWEI An Example of TCAP Process
TC-BeginTC-Invoke (Invoke)
TC-ContinueTC-Invoke (Invoke)
TC-Continue
TC-Result-L (RR-L)
TC-End
TC-Result-L (RR-L)
Node1 (SSP) Node2 (SCP)
SSP begins a dialogue to query the balance of a calling card subscriber.
SCP asks SSP to return the password.
SSP returns the password.
SCP returns balance of the subscriber.
86
HUAWEI
Intelligent Network Application Part
Chapter Seven
87
HUAWEI The Functions of INAP
INAP defines operation criterion among the IN functional entities SSF, SCF, SRF and SDF.
INAP is transmitted by SCCP UDT data, using connectionless services.
88
HUAWEI The Relationship Between INAP and SCCP
INAP usually uses DPC+SSN routing mode of SCCP.
INAP can also use GT routing mode of SCCP.
INAP uses class 0 and class 1 connectionless services of SCCP.
89
HUAWEI
Class 1: Result will be returned no matter the operation is successful or not. i.e. a RR-L, RR-NL or RE must be returned.Class 2: Only when the operation fails, a RE will be returned.Class 3: Only when the operation succeeds, a RR-L or RR-NL will be returned.Class 4: No result returned no matter the operation is successful or not.
INAP Operation Categories
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INAP is a kind of TC-User.
In INAP protocol, all INAP operations are also classified into 4 classes.
Class 1 Activate Service Filtering, P&C
Class 2 Initial DP, RRBE
Class 3 AT
Class 4 RC, BER
INAP Operations
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IDP is the first INAP message sent from SSP to SCP, requesting SCP to establish the control relationship for an IN call. The parameters included in IDP are: access code, service key (the unique identifier of an IN service), caller number, called number, number attributes, etc.
IDP: Initial DP
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RRBE is sent from SCP to SSP, requesting SSP to configure DP dynamically. When SSP meets these DPs in later call process, SSP will report call information to SCP. RRBE provides SCP the condition of controlling calls.The parameters of RRBE include DP type, DP condition, etc. One RRBE can configure several DPs.
RRBE: Request Report BCSM Event
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CTR is sent from SCP to SSP, requesting SSP to connect the user to IP. CTR provides the users the condition of using IP.If IP is integrated with SSP, SSP makes only the internal connection with IP. If IP is independent from SSP, SSP communicates IP via TUP messages, connecting the users to IP through PSTN voice channels.
CTR: Connect To Resource
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P&C is sent from SCP to SSP, requesting IP to play voice prompts the users and collect the users’ input.
P&C needs IP to return operation results.
P&C: Prompt & Collect User Information
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DFC is sent from SCP to SSP, requesting SSP to disconnect the connection between the users and IP.
DFC: Disconnect Forward Connect
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AC is sent from SCP to SSP, requesting SSP to charge the call.
The parameters of AC include: charge class, the balance of the subscriber, charging party, etc.
AC: Apply Charging
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Connect is sent from SCP to SSP, requesting SSP to connect the users to the designated number.
Connect
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ACR is sent from SSP to SCP, reporting the charge result.The parameters in ACR include: the call start time, call end time, call length, caller number, called number, charging number, fee, etc.
ACR: Apply Charging Report
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ERB is sent from SSP to SCP when SSP detects the DPs configured by SCP in last RRBE message, reporting the call information to SCP.
ERB: Event Report BCSM
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HUAWEI RC: Release Call
RC is sent from SCP to SSP, requesting SSP to release the occupied IN call resources.
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PA is sent from SCP to SSP, requesting IP to play voice prompts to the users.
PA does not need result return from IP.
PA: Play announcement
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SRR is sent from SSP to SCP, notifying SCP the end of playing announcement.
SRR: Specialized Resource Report
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SCP sends AT to SSP every 6 minutes when the call is established to check the communication between SSP and SCP. If SSP can return AT_ack, the communication is good. If no AT_ack returns to SCP, the communication is broken, and SCP will release the resources occupied this IN call.
AT: Activity Test
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Initial DPRequest Report BCSM Event
Apply Charging
Apply Charging ReportBCSM Event ReportRelease Call
Connect
SSP SCP
An Example of INAP (FPH Service)
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HUAWEI An Example of INAP (Continue)
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AP: Application Process, which processes IN calls in SSP.
InitialDP
Request Report Bcsm Event
Apply Charging
Connect
Apply Charging Report
Event Report BCSM
Release Call
AP
TC-BEGIN-REQ
TC-INVOKE-REQ
TC-CONTINUE-IND
TC-INVOKE-IND
TC-CONTINUE-IND
TC-INVOKE-IND
TC-CONTINUE-IND
TC-INVOKE-IND
TC-CONTINUE-REQ
TC-INVOKE-REQ
TC-CONTINUE-REQ
TC-INVOKE-REQ
TC-END-IND
TC-INVOKE-IND
TCAP
N_UNITDATA-REQ
N_UNITDATA-IND
N_UNITDATA-IND
N_UNITDATA-IND
N_UNITDATA-REQ
N_UNITDATA-REQ
N_UNITDATA-IND
UDT
UDT
UDT
UDT
UDT
UDT
UDT
MSU
MSU
MSU
MSU
MSU
MSU
MSU
SCCP MTP SCPINAP
SCCP 、 TCAP and INAP (FPH Service)
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Chapter 1 Fundamentals of SS7 Chapter 2 Message Transfer Part Chapter 3 Telephone User Part Chapter 4 ISDN User Part Chapter 5 Signaling Connection Control Part Chapter 6 Transaction Capabilities Application Part Chapter 7 Intelligent Network Application Part
Summary
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Thank you !
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