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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 k

S i g n a l l i n g

S u b s c r i b e r

S i g n a l l i n g

S u b s c r i b e r

S i g n a l l i n gccs

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 NH 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 Trunk

Signaling 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 Network

A 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 Code

OPC: Originating Point Code

A 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 Network

Working 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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HUAWEI

When 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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HUAWEI

When 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 Type

0 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 A

International NetworkInternational ReservedNational NetworkNational Reserved

0 00 11 01 1

Spare

D C B A

0 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 LIErrorCorrection F

MSU - Message Signal Unit

ROUTING LABEL

OPC 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 8

Transmission Direction

Signal Infor H1 H0 Label

CIC

SLSOPC 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

CLFCLF

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

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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 ISUPTCAP

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

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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.

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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)

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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)

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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-Begin

TC-Invoke (Invoke)

TC-Continue

TC-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.

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HUAWEI

Intelligent Network Application Part

Chapter Seven

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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.

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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.

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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 DP

Request Report BCSM Event

Apply Charging

Apply Charging Report

BCSM Event Report

Release 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 !