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1 Nokia Siemens Networks Presentation / Author / Date / CN3410-30N

For public use IPR applies

Message Transfer Part (MTP)Switching Core Network Signalling

M14/U4

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Nokia Siemens Networks Academy

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Siemens Networks has the sole right to copy, distribute, amend, modify, develop, license,sublicense, sell, transfer and assign the Nokia Siemens Networks training material. Individualscan use the Nokia Siemens Networks training material for their own personal self-developmentonly, those same individuals cannot subsequently pass on that same Intellectual Property toothers without the prior written agreement of Nokia Siemens Networks. The Nokia SiemensNetworks training material cannot be used outside of an agreed Nokia Siemens Networkstraining session for development of groups without the prior written agreement of NokiaSiemens Networks.

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Document change history

Date Version Name Change comment

Jan 14, 2008 1.0 Noppamat Poonyarat Update to NSN template, more slides

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Introduction

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Introduction to MTPLevel 1: SIGNALLING DATA LINK

Defines the physical characteristics towards the transmissionmedium, a PCM link.

Level 2: SIGNALLING LINK

Defines message structure, framing, error detection andcorrection, alignment procedures, and so on.

Level 3: SIGNALLING NETWORK

2 parts: message handling function (includes messagerouting and distribution to the respective user parts) andnetwork management function.

F CK SIF SIO LI

F

I

B

FSN

B

I

B

BSN F

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Introduction to MTP

MTP2

MTP3Layer 4(User Part) ISUP TUP SCCP Other User Parts

Signalling

MTP2

MTP1Signalling Link

FunctionSignalling Data Link

Function

Signalling MessageHandlingSignalling NetworkManagement

Control signals Signalling message flow

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7/507 Nokia Siemens Networks Presentation / Author / Date / CN3410-30N


Component of a signalling network

SEP

STP

Signalling link

Signalling link

SEP

SEP SEP

Signalling

end point

Signalling

end point

Signalling

end point

Signalling

end point

Signalling

transfer point

DPC = X

Signalling link

DPC = X

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SPC and network indicator

Signalling Point Codes

National useLength: 14 bits (ITU-T SS7 standard), 16 bits (Japan SS7 standard), or 24bits (China or ANSI SS7 standard )

Format: can be allocated into subfields

International use (ITU-T Q.708)

3bit-8bit-3bitmeaning: Zone-Area-Signalling point

Network Indicator

NA0 National network 0

NA1 National network 1IN0 International network 0

IN1 International network 1

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MTP Level 2Signalling link function

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MTP Level 2

Signalling Link Function

To provide reliable transfer of signalling messages

Functions:

Delimitation of signal unit- by means of flagsFlag imitation prevention- by bit stuffing

Error detection- by means of check bits (CRC16)

Error correction- by retransmission

Signal unit sequence control- by sequence numbers in SUSignalling link failure detection- by SUERM

Signalling link recovery- by level 2 procedures

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User Part

Level1

Flag Detectionand Bit-stuffing

Controller

RetransmissionBuffer

Message LengthCheck

Checksum

Generation andComparison

Sequence Number

Check

Received Buffer

Flag Generationand Bit-stuffing

ChecksumGeneration

Sequence Number

Generation

Transmit Buffer

Level 1

FSN BSN

BIB

MTP Level 2 Functions

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MTP Level 2

Creates signalling units of variable length:

1. Message signal units (MSU)

used for the transport of the user part messages.

2. Link status signal units (LSSU)

contain information about state of the signalling link.

3. Fill-in signal units (FISU)contain no additional information. Used when there is nomessage to be sent on the link.

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Signal units

F CK SIF SIO LIFIB

FSNBIB

BSN F

8 16 8n, n>2 8 2 6 1 7 1 7 8 [bit]

MSU First bittransmitted

length indicator >2 and 63

F CK SF LIFIB

FSNBIB

BSN F

8 16 8 or 16 2 6 1 7 1 7 8 [bit]

LSSU First bittransmitted

length indicator = 1 or 2

F CK LIFIB

FSNBIB

BSN F

8 16 2 6 1 7 1 7 8 [bit]

FISU First bittransmitted

length indicator = 0

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Link Status Signal Unit (LSSU)

Bit 000 Status indication O (SIO) Link out of alignment

Bit 001 Status indication N (SIN) Normal alignment

Bit 010 Status indication E (SIE) Emergency alignment

Bit 011 Status indication OS (SIOS) Link out of service

Bit 100 Status indication PO (SIPO) Processor outage

Bit 101 Status indication B (SIB) Busy

F CK SF LIFIB

FSNBIB

BSN F

8 16 8 or 16 2 6 1 7 1 7 8 [bit]

LSSU First bittransmitted

D C B A

X X X X X 0 0 0

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Error correction method

Retransmission Buffer

Signalling TerminalSignalling Terminal

MSU

Basic error correction method (Tansmission time15ms)

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Example:Basic error correction

SP A SP BLast Seq. # sent : 30

Last Seq. # recd. : 40

Last FIB/BIB : 1

FI

B

FSNBI

B

BSN

1 31 1 40

BSNBIB

30 0 41 1

FSNFIB

Negative Acknowledgement

Retransmission

Positive Acknowledgement

F

IB FSN

B

IB BSN0 31 1 41

BSNBIB

31 0 42 1

FSNFIB

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Signalling link failure detection

Signalling Unit Error Rate Monitoring (SUERM)

If SUERM counter reaches the threshold, the link is declaredFAULTY and the CHANGEOVER procedure takes place to aworking link.

+1 for every SU in error

-1 for 256 correctly received SUs

Alarm level

ZNOI:0,A:;

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Initial alignment procedure

Initial alignment procedure is used for link activation or

restorationActivate link

SIO

SIO

SIN/SIE

SIN/SIE

FISU

FISU

FISU

FISU

MSU (SLTM)

MSU (SLTA)

Link Idle

Link out of service

Link Aligned

Link Proving

Link In Service

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Link Proving

Normal Proving (LSSU=SIN)

216 octects of FISU are sent in 8.2 sec

If FISUs in error 4 use of AERM(Alignment Error Rate Monitoring)

Emergency Proving (LSSU=SIE)

212 octects of FISU are sent in 0.5 sec

If FISUs in error 1 use of AERM(Alignment Error Rate Monitoring)

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Signalling link failure detection

Alignment Error Rate Monitoring (AERM)

This counter is set to zero to mark the beginning of analignment period.

Every SU in error increments the counter by 1.

If AERM5 (2) the link is marked faulty

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MTP Level 3Signalling network function

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F CK SIF SIO LIFIB

FSNBIB

BSN FFirst bit

transmitted8 16 8n, n>2 8 2 6 1 7 1

7 8

User Data

SIO

SIO

SIODPCOPCSLC

User Data DPCOPCSLS

User Data DPCOPCSLS

CIC

SIOUser Data DPCOPCCICTUP

ISUP

Network Management

SCCP

Structure of messages from MTP users

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MTP3 message structure

[bit]

SLS OPC DPC

User InformationRouting

LabelSIO

Subservice

Field (SSF)

Service

Indicator (SI)

Signalling Information Field (SIF)

4 14 14 4 4

First bittransmitted

OPC Originating Point CodeDPC Destination Point CodeSLS Signalling Link Selection

0000 (0H): SNM

0001 (1H): SNT

0011 (3H): SCCP

0100 (4H): TUP

0101 (5H): ISUP

1101 (DH): BICC

00XX (0H) : IN0

01XX (4H) : IN1

10XX (8H) : NA0

11XX (CH) : NA1

ZNPI;

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Signalling network function

2 functions:

Signalling message handling Discrimination (using DPC)

Distribution (using SIO)

Routing (using DPC and network indicator)

Signalling network management Signalling traffic management (changeover procedure, changeback

procedure, and so on)

Signalling route management (TFP, TFA, and so on) Signalling link management (link activation, deactivation, restorationprocedure)

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Signalling message handling

Messagediscrimination

Message

distribution

Messagerouting

DPC = own SPC

MTP2

MTP3User Part

DPC own SPC

ISUP TUP SCCP Network ManagementSignalling message handling

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Signalling Link Selection (SLS)

To control the LOAD Sharing the selection of a Signalling Link

in a Signaling Route Set, giving the corresponding SLC

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Load sharing within a linkset1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

- - - - - - - - - -- -- -- -- -- -- --

0000 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

0001 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

0010 1 1 3 3 3 3 3 3 3 3 3 3 3 3 3 3

0011 1 2 1 4 4 4 4 4 4 4 4 4 4 4 4 4

0100 1 1 2 1 5 5 5 5 5 5 5 5 5 5 5 5

0101 1 2 3 2 1 6 6 6 6 6 6 6 6 6 6 6

0110 1 1 1 3 2 1 7 7 7 7 7 7 7 7 7 7

0111 1 2 2 4 3 2 1 8 8 8 8 8 8 8 8 8

1000 1 1 3 1 4 3 2 1 9 9 9 9 9 9 9 9

1001 1 2 1 2 5 4 3 2 1 10 10 10 10 10 10 10

1010 1 1 2 3 1 5 4 3 2 1 11 11 11 11 11 11

1011 1 2 3 4 2 6 5 4 3 2 1 12 12 12 12 12

1100 1 1 1 1 3 1 6 5 4 3 2 1 13 13 13 13

1101 1 2 2 2 4 2 7 6 5 4 3 2 1 14 14 141110 1 1 3 3 5 3 1 7 6 5 4 3 2 1 15 15

1111 1 2 1 4 1 4 2 8 7 6 5 4 3 2 1 16

SLS

LINK

ZNEO:NA0,XXXX;

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Load sharing between link sets

1 2 3 4 5 6 7 8- - - - - - - -

0000 1 1 1 1 1 1 1 1

0001 1 1 1 1 1 1 1 1

0010 1 1 1 1 1 1 1 2

0011 1 1 1 1 1 2 2 2

0100 1 1 1 2 2 2 2 3

0101 1 1 1 2 2 2 2 3

0110 1 1 2 2 2 3 3 4

0111 1 1 2 2 3 3 3 4

1000 1 2 2 3 3 3 4 5

1001 1 2 2 3 3 4 4 5

1010 1 2 2 3 4 4 5 6

1011 1 2 3 3 4 4 5 6

1100 1 2 3 4 4 5 6 7

1101 1 2 3 4 5 5 6 7

1110 1 2 3 4 5 6 7 8

1111 1 2 3 4 5 6 7 8

LINK SET

SLS

ZNRI:NA0,XXXX;

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Signalling network management messagesThe SIO in MSU classifies two groups:

Signalling network management (SNM)

SI in SIO=0000

Signalling network testing and maintenance (SNT)

SI in SIO=0001

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SNM structure

F CK SIF SIO LIFIB

FSNBIB

BSN F

4 4 4 14 14 4 4 [bit]

MSU First bittransmitted

User Information H1 H0 SLS OPC DPC SSFSI

0000

SSF Subservice FieldH0 Heading code indicating which message group the message belong toH1 Heading code indicating the message within the group in question

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Heading code for SNM messages

GROUPH0 H1

0001 0010 0011 0100 0101 0110 0111 10000000

CHM 0001 COO COA CBD CBA

ECM 0010 ECO ECA

FCM 0011 RCT TFC

TFM 0100 TFP TFR TFARSM 0101 RST RSR

MIM 0110 LIN LUN LIA LUA LID LFU LLT LRT

TRM 0111 TRADLM 1000 DLC CSS CNS CNPUFC 1010 UPU

SNT

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SNT messagesThere are only two SNT messages:

Signalling Link Test Message (SLTM)

Signalling Link Test Acknowledge (SLTA)

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Signalling traffic management procedures-Changeover-Changeback

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Changeover procedure

In case of a signalling link failure, the signalling traffic from a failed link is

diverted to one alternative signalling link using a changeover message.

Procedure1. The signalling traffic from a faulty link is stopped. New signalling

messages for this link are buffered in the transmission buffer of

signalling link X.2. An alternativesignalling link (link Y) is chosen.

3. A changeover message (COO)is sent to the remote end. Thischangeover message contains the signalling link code (SLC) of thefaulty link and the FSN of the last successfully transmitted MSU.

4. The reception of COO message is acknowledged by sending achangeover acknowledgement (COA)message.

5. The signalling link selection table is changed.

Ch t ll l li k

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Changeover to a parallel link

A B

SLC = X

SLC = Y

1) COO (SLC=X, FSN)

2) COA

0) Faulty link

3) Change SLS table in CCSU

H1=0001=COO Changeover order signal

H1=0010=COA Changeover acknowledgement signal

1

0FSN of last

accepted MSUH1

H0=0001

(CMN)Routing Label

7 4 4 32

Ch b k d

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Changeback procedure

The objective of the changeback procedure is to ensure that the

transfer of the signalling from the alternative signalling link toa signalling link that has become available again issuccessful.

Procedure1) Automatically the traffic is returned to the now available

signalling link.

2) The signalling link selection (SLS) table is updated and the

new information is distributed to all CCSUs.3) A changeback message(CBD)is sent to the remote end

and acknowledged with a changeback acknowledgementmessage (CBA)

Ch b k t d li k

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Changeback to a recovered link

A B

SLC = X

SLC = Y

1) CBD (SLC=X)

2) CBA

0) Recovered link

H1=0101=CBD Changeback declaration signal

H1=0110=CBA Changeback acknowledgement signal

Changeback code H1H0=0001

CHMRouting Label

8 4 4 32

3) Update SLS table in all CCSUs

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Signalling route management procedures-Transfer-prohibited-Forced rerouting-Signalling-route-set-test-Transfer-allowed-Controlled rerouting

T f hibit d d

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39 Nokia Siemens Networks Presentation / Author / Date / CN3410-30NFor public use IPR applies

Transfer-prohibited procedure

This procedure informs the adjacent network elements about

the unavailability of a destination

Procedure1) In case of unavailability of a signalling route set (e.g. the

route between B and D is no longer available and neither Bnor D have any alternative route to reach the destination), Band D send a transfer-prohibited message (TFP)includingthe DPC of the network element which is no longerreachable to the adjacent signalling points.

2) The reception of a transfer-prohibited message (TFP)causes a forced rerouting procedure

Transfer prohibited procedure

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Transfer-prohibited procedure

2) TFP (DPC=D)

2) TFP (DPC=D) 2) TFP (DPC=B)

1)

TFP Transfer-prohibited Message

2

00 DestinationH1=0001

TFP

H0=0100

TFMRouting Label

14 4 4 32

SP A

SP B

SP C

SP E

SP D

F d ti d

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Forced rerouting procedure

On reception of a transfer-prohibited message (TFP), the

forced rerouting procedure is activated.

Procedure

1) An alternative route to the destination which was named in

the received TFP is searched and the traffic is rerouted viathe new route

F d ti g d

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Forced rerouting procedure

1) TFP (DPC=D)

1) TFP (DPC=D) 1) TFP (DPC=B)

2) FRR:

Signalling traffic to D via C2) FRR:

Signalling traffic to D via E

2) FRR:

Signalling traffic

to B via C

SP A

SP B

SP C

SP E

SP D

Signalling route set test procedure

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Signalling-route-set-test procedure

Test procedure for checking the availability of a signalling route.

Procedure

1) On reception of a TFP message, the signalling point initiatesthe signalling-route-set-test procedure.

2) A, C and E send periodically a signalling-route-set-test(RST) to B respectively to D. This message contains thesame DPC like in the received TFP message.

3) The reception of a RST message causes B respectively D tocheck the availability of the route.

4) In case the signalling route is still unavailable, noacknowledgement is sent.

5) In case the signalling route is available again, a transfer-allowed (TFA) message is sent back

Signalling route set test procedure

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Signalling-route-set-test procedure

RST (DPC=D)

RST (DPC=D)

RST (DPC=B)

RST Signalling-route-set-test message

2


RST

H0=0101

RSMRouting Label

14 4 4 32

SP A

SP B

SP C

SP E

SP D

Transfer allowed procedure

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Transfer-allowed procedure

Procedure to inform the adjacent signalling points that a

destination is available again

Procedure

1) If the route set becomes available again, B and D send a

transfer-allowed (TFA) message including the DPC of thenetwork element which is available again to the adjacentsignalling points.

B sends the DPC of D

D sends the DPC of B

2) The reception of a TFA message may cause a controlledreroutingprocedure

Transfer allowed procedure

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Transfer-allowed procedure

2) TFA (DPC=D)

2) TFA (DPC=D)2) TFA (DPC=B)

1)

TFA Transfer-allowed Message

2


TFA

H0=0100

RSMRouting Label

14 4 4 32

SP A

SP B

SP C

SP E

SP D

Controlled rerouting procedure

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Procedure to restore the optimal signalling routing

3 different cases to distinguished:

1) In the case the route that become available again has ahigher prioritythan the route actually used, the controlled

rerouting procedure is performed.2) In the case the route that becomes available again has the

same priorityas the route actually used and load sharing isallowed, the traffic is spread over both routes.

3) In the case the route that become available again has thesame priorityas the route actually used and load sharing isdenied, the traffic is still sent over the actually used route.


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TFA (DPC=D)

TFA (DPC=D)

TFA (DPC=B)

SP A

SP B

SP C

SP E

SP D

MTP in a nutshell

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MTP in a nutshellCCS7 Transport over TDM

Message delimitation (F)

Error detection and correction (CK)

Sequence control (FSN, BSN, BIB, FIB)

Message Routing (Network + DPC)

Message Distribution (SIO)

Load sharing (SLS)

Signaling network management

Creating MTP< ZNCN< ZNSC

< ZNRC

Activating MTP< ZNLA + ZNLC

< ZNVA + ZNVC

Checking MTP< ZNET

MTP in a nutshell

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MTP in a nutshell

FBSN

BIB

FSN

FIB

LICKF MTP-3DATA

First bit transmitted

SIODPCOPC

SL

x

MTP USER

DATA

To upper layer

protocols

MTP-3

MTP-2

Documents

MTP_slide