0aa000008 ss7 protocol issue2.0

7/30/2019 0aa000008 Ss7 Protocol Issue2.0

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ISSUE

Fixed Network Curriculum

Development Section

OAA000008 Call Control Protocol --SS7

2.0


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Confidential Information of Huawei.No Spreading without Permission. Security Level: Internal

2

Objective

SS7 system principle

Message transfer part (MTP) principle

ISDN user part (ISUP) message and

application

After this session, you will learn:


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3

References

Product Manual -- Technical Manual -- Signaling and

Protocols Chapter 5 SS7


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Contents

Section 1 MTP

Section 2 ISUP


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5

Signaling System No.7 (SS7)

Signaling is used for connection control, work

coordination and session between communication

devices

SS7 is formulated by CCITT and is widely applied inswitched circuit networks (e.g. PSTN).

SoftX3000 supports SS7 and implements interworking

with the existing switched circuit networks.


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SS7 Functional Structure in SoftX3000

MACMTP1

MTP2

MTP3

SCCP

TCAP

TUP

ISUP

M3UA

IP

INAP

User part

MessageTransfer Part

M2UASCTP


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SoftX3000 SS7 Functional Structure

SS7 has two parts:

User Part (UP)

Message Transfer Part (MTP).

MTP : enables reliable transfer of signaling messages

between user functions.

SS7 messages can be transmitted over

narrowband TDM transmission network (i.e. MTP),

over broadband IP network (the protocol used for transmitting SS7

over IP network is SIGTRAN.)

UP :

the independent user part of different users

it is the functional entity for various call services


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MTP

Overview, MTP1, MTP2

MTP3


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MTP - Overview

The main function

to provide reliable signaling message transfer in the

signaling network

Feature : has measures to avoid or reduce

message loss

repetition

loss of sequence

MTP consists of three function levels:

signaling data link (MTP1)

signaling link function (MTP2)

signaling network function (MTP3).


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MTP1

MTP1 definition:

Defining the physical, electric and functional characteristics

of signaling data link, as well as access methods.

Equivalent to the physical layer of OSI seven-layer protocol

structure, and used to generate and receive the signals

over physical channels

Signaling Data Link :

A bidirectional transmission channel for a signaling.

Composed of two-way data channels.

The standard bit-rate is 64kbit/s

which also can be applied to the transmission link with lower rate

(such as 4.8kbit/s) or that with higher rate (2048kbit/s)


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MTP2

MTP2 definition:

Having Signaling link function .

It is used to transmit signaling to data link, and cooperates with MTP1

to ensure reliable signaling link between two directly connected

signaling points.

Signaling link function can be sub-divided into

signaling unit delimitation

signaling unit location

error detection

error correction,

initial location

processor failure

level-two flow control

and signaling link error rate monitoring functions.


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MTP

Overview, MTP1, MTP2

MTP3


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MTP3

Definition : Network layer

It implements the functions of the third layer of OSI

used to transmit management messages to ensure reliable

transmission of signaling messages in case of faults in

signaling link or signaling transfer point


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Functions

Message

allocation

Signal message processing

Message

identificationMessage

routing

Out

In

Signal Traffic

management

Signal network management

Signal route

management

Signal link

management

Signal network functions

The fourth level The third-level MTP The second level

Test and maintenanceSignal message stream

Indication and control


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Signaling Message Processing

Message routing function:

To determine the outgoing signaling link for transmitting

messages to destination point

Message identification function:

To check whether the destination signaling point in

received message is a local office signaling point

Message allocation function:

To distribute received messages (sent to the point) to

corresponding UPs


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Signaling Network Management

Signaling service management:

To transfer signaling service from one link or route to one

or multiple different links or routes, reset MTP in a signaling

point or slow down the traffic in case of congestion

Signaling link management:

To recover faulty signaling link, activate idle (non-arranged)

links, and deactivate arranged signaling links.

Signaling route management:

To distribute the messages related to signaling network

status, block or unblock signaling routes


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Message Format

MTP has three basic signaling unit formats:

Message Signaling Unit (MSU)

To transmit messages of respective UPs, signaling network

management messages as well as signaling network test and

maintenance messages.)

Link Status Signaling Unit (LSSU)

LSSU provides the link status information to perform the connection

and recovery of signaling links

Fill-In Signaling Unit (FISU)

FISU is used to maintain normal operation of the signaling link and

implement fill-in function when no MSU or LSSU is transmitted over

the signaling link.


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Message Format

MSU F CK SIF SIO LI FIB FSN BIB BSN F

8 16 8N(N2) 8 2 6 1 7 1 7 8

Message signaling unit format

First transmitted bit

LSS U F CK SF LI FIB FSN BIB BSN F

8 16 816 2 6 1 7 1 7 8

Link status signaling unit format


FISU F CK LI FIB FSN BIB BSN F

8 16 2 6 1 7 1 7 8

Fill-in signal unit format



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Mandatory Part for MTP Processing

This part mainly includes the following fields:

flag (F)

forward sequence number (FSN)

forward indicator bit (FIB)

backward sequence number (BSN)

backward indicator bit (BIB)

length indicator (LI)

check bit (CK)

status field (SF)

service information octet (SIO).


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Meanings of SF status indication:

SF CBA Indicator Indication Meaning

000 SIO Status indication

"O"

Loss of alignment

001 SIN Status indication

"N"

Normal alignment

010 SIE Status indication

"E"

Emergency

alignment

011 SIOS Status indication

"OS"

Break of Service,

100 SIOP Status indication

"OP"

Processor fault


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Service Information Octet SIO

SISSF

MeaningDCBA

International

network message

Reserved

(International)

Domesticmessage

Reserved

(Domestic)

0 0 0 0

0 1 0 0

1 0 0 0

1 1 0 0

MeaningDCBA

Signaling network management message

Signaling network test and maintenance messages

Reserved

Signaling connection control part

Telephone user partISDN user part

Data user part

Reserved

0 0 0 0

0 0 0 1

0 0 1 0

0 0 1 1

0 1 0 00 1 0 1

0 1 1 0

0 1 1 1

1 0 0 0

1 1 1 1

F CKSIF SIO


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SIF to be Processed by UP

F CK SIF FIBLI FSNSIO BIB BSN

Management messages SLC OPC DPC

Type A: Signaling network

management message

Type B TUP message

Type C ISUP message

Type D SCCP message

Signaling messageCIC

OPC DPCSLS

Signaling message OPC DPCCIC SLC

F

SSCP subscriber data SLS OPC DPC


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Assignment of Signaling Network Management

Message Label Codes

MessageGroup

H1

H00000 0001 0010 0011 0100 0101 0110 0111 1000

0000

CHM 0001 COO COA CBD CBA

ECM 0010 ECO ECA

FCM 0011 RCT TFC

TFM 0100 TFP * TFR TFA *

RSM 0101 RST RSR

MIM 0110 LIN LUN LIA LUA LID LFU LLT LRT

TRM 0111 TRA

DLM 1000 DLC CSS CNS CNP

1001

UFC 1010 UPU


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Signaling procedure

Message routing

Changeover

Changeback

Signaling link activation

Signaling link recovery

Signaling link deactivation

Signaling route manager Transfer prohibited


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Contents

Section 1 MTP

Section 2 ISUP


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ISUP Signaling

Overview

Message structure

Call process


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ISUP - Overview

ISUP is one of UPs of Common Channel Signaling

System No.7.

It provides necessary signal functions for supporting

basic bearer services and supplementary services ofvoice and non-voice purposes in the Integrated Service

Digital Network (ISDN).


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Applications in SoftX3000


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Protocol Stack

MACMTP1

MTP2

MTP3

ISUP

M2UA

M3UA

IP

SCTP

User part

Message transfer part


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ISUP Signaling

Overview

Message structure

Call process


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Message Type Codes

Co

de

Abbre

viation

Meaning

0000

0001

IAM Initial address message: A message sent in the forward direction to

initiate occupancy of an outgoing circuit and to transmit number and

other information relating to the routing and handling of a call.

0000

0010

SAM Subsequent address message: A message that may be sent in the

forward direction following an initial address message, to convey

additional called number information.

0000

0011

INR Information request: A message sent by an exchange to request for

channel associated information of a call.

0000

0100

INF Information: A message sent to convey channel associated

information of a call, which may have been requested in an

information request message.


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Message Type Codes (Cont.)

Cod

e

Abbrevia

tion

Meaning

0000

0101

COT Continuity message: A message indicating whether or

not there is continuity on the preceding circuit as well

as of the selected circuit to the following exchange,including verification of the communication path

across the exchange with the specified degree of

reliability.

0000

0110

ACM Address complete message: A message indicating that

all the address signals required for routing the call to

the called party have been received.

0000

0111

CON Connect message: A message indicating that all the

address signals required for routing the call to the

called party have been received and that the call has


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Code Abbreviation Meaning

0000

1000

FOT Forward transfer: A message sent in the forward

direction on semi-automatic calls when the outgoing

international exchange operator wants the help of an

operator at the incoming international exchange. The

message will normally serve to bring an assistance

operator into the circuit if the call is automatically set

up at the exchange.When the call is completed via an

operator at the incoming international exchange, the

message should preferably cause this operator to be

recalled.

0000

1001

ANM Answer message: it indicates that the call has been

answered. In semi-automatic phone set, this message

has a supervisory function. In automatic phone set,

this message is used in conjunction with charging

information.


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Code Abbreviatio

n

Meaning

0000

1100

REL Release message: A message sent in either forward or

backward direction to indicate that the circuit is being

released due to the cause supplied and is ready to be put

into the idle state on receipt of the release complete message.

Where the call is to be redirected the message will also carry

the redirection number.

0000

1110

RES Resume message: A message sent in either direction

indicating that the calling or called party, after having been

suspended, is reconnected.

0001

0000

RLC Release complete message: A message sent in either

direction in response to the receipt of a release message, or

if appropriate, to a reset circuit message, when the circuit

concerned has been brought into the idle condition.


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Code Abbre

viation

Meaning

0001

0001

CCR Continuity check request message: A message sent by an

exchange for a circuit on which a continuity check is to be

performed, to the exchange at the other end of the circuit,

requesting for continuity checking equipment to be attached.

0001

0010

RSC Reset circuit message: A message sent to release a circuit, due

to memory failure or other causes.

0001

0011

BLO Blocking: A message sent only for maintenance purposes to the

exchange at the other end of a circuit, to cause an engaged

condition of that circuit for subsequent calls outgoing from that

exchange. When a circuit is used in the dual-circuit mode of

operation, an exchange receiving the blocking message must be

capable of accepting incoming calls on the concerned circuit

unless it has also sent a blocking message. Under certain

conditions, a blocking message is also a proper response to a


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Cod

e

Abbre

viatio

n

Meaning

0001

0101

BLA Blocking acknowledgement: A message sent in response

to a blocking message, indicating that the circuit has beenblocked.

0001

0111

GRS Circuit group reset: A message sent to release an identified

group of circuits.

00011000

CGB Circuit group blocking message: A message sent to theexchange at the other end, indicating the specified circuit

group has been blocked.

0001

1001

CGU Circuit group unblocking: A message sent to the exchange

at the other end of an identified group of circuits to cause

cancellation in that group of circuits of an engaged


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Code Abbre

viation

Meaning

0001

1010

CGBA Circuit Group Blocking Acknowledgement: A message

sent in response to a circuit group blocking message

to indicate that the requested group of circuits has

been blocked.

0001

1011

CGUA Circuit group unblocking acknowledgement: A

message sent in response to a circuit group

unblocking message to indicate that the requested

group of circuits has been unblocked.

0001

1111

FAR Facility request: A message sent from an exchange to

another exchange to request for activation of a facility.

0010

0000

FAA Facility accepted: A message sent in response to a

facility request message indicating that the requested

facility has been activated


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Code Abbre

viatio

n

Meaning

0010

0001

FRJ Facility rejected: A message sent in response to a facility request

message to indicate that the facility request has been rejected.

0010

0100

LPA Loop-back acknowledgement message: A message sent in the

backward direction in response to a continuity check request

message indicating that a loop (or transceiver in the case of a 2-

wire circuit) has been connected.

00101000

Handoffs

0010

1001

GRA Circuit group reset acknowledgement: A message sent in response

to a circuit group reset message and indicating that the requested

group of circuits has been reset.The message also indicates the

maintenance blocking state of each circuit.


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Code Abbreviation

Meaning

0010

1010

CQM Circuit group query message: A message sent on a

routine or demand basis to request the far-end exchange

to give the states of all circuits in a particular range.

0010

1011

CQR Circuit group query response: A message sent in

response to a circuit group query message to indicate

the states of all circuits in a particular range.

0010

1100

CPG Call progress: A message sent in either direction during

the set-up or active phase of the call, indicating that an

event, which is of significance, and should be relayed to

the originating or terminating access, has occurred.


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Code Abbre

viation

Meaning

0010

1111

CFN Confusion message: A message sent in response to

any message (other than a confusion message) if the

exchange does not recognize the message or detects

a part of the message as being unrecognized.

0011

0000

OLM Overload message: A message sent in the backward

direction, on non-priority calls in response to an IAM,

to invoke temporary trunk blocking of the circuit

concerned when the exchange generating the

message is subject to load control.

0011

0001

CRG Charging information: Information sent in either

direction for accounting and/or call charging purposes.


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Code Abbre

viation

Meaning

00110010 NRM Network resource management message: A

message sent in order to modify network

resources associated with a certain call.The

message is sent along an established path in

any direction in any phase of the call.

00110011 FAC Facility: The message is sent at any stage of

a call in the forward or backward direction to

request for an action at the peer end. This

message is used to carry the previous

request result, error or rejected information.

00110110 Identification request


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Code Abbre

viation

Meaning

00110111 Identification response

00111000 SGM Segmentation message: A message thatmay be sent in the forward direction

following an initial address message, to

convey additional called party number

information.

00011101 Reserved

00011100

00011110

00100111


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ISUP Signaling

Overview

Message structure

Call process


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Successful Call Setup

Calling PartyOriginationg

ExchangeTransit

Destination

ExchangeCalled Party

Setup IAMIAM

Setup

Address Complete

(no indication)

Address Complete

(no indication)

Alerting

Alerting

Call Progress

(Alerting)Call Progress

(Alerting)

ANM

ANMConnect

Connect Answered(off hook)

Dial

Ring

Ring

Connect Ack

Connect Ack

Speech or Data


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Successful Call Release (1)

Calling Party Originationg

ExchangeTransit Destination

ExchangeCalled Party

Disconnect

REL REL

RLC

Release

RLC

RLC

DisconnectOnHook


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Successful Call Release (2)

Calling Party OriginationgExchange

Transit DestinationExchange

Called Party

DisconnectREL REL

RELEASEDisconnectRLC

RLC

OnHook


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Summary

SS7 signaling includes two parts: Message Transfer Part

(MTP) and User Part (UP).

The MTP consists of MTP1, MTP2 and MTP3

ISUP is one of UPs of SS7. It provides necessary signalfunctions for supporting basic bearer services and

supplementary services of voice and non-voice purposes

in the integrated service digital network.


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0aa000008 ss7 protocol issue2.0

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