1 Signalling, SIP, SIGTRAN Overview -1- Name: Bartlomiej Puchalski (Bartek) Country: Poland Education: PhD in Optimization of analogue Circuit Testing at Silesian University of Technology in Poland MsC in Telecommunications (Silesian University of Technology, Bournemouth University UK) Professional Experience: Instructor, Leliwa – training for /// Ericsson Manager, Orange Poland Consultant, Kennedy Information -2- Course Agenda • SS7 Signalling Overview ~ 3,5 Days • SIGTRAN ~ 1 Days • SIP 0,5 Days Daily Agenda Introduction to the Signaling Architecture Vertically Integrated and Horizontally Integrated network Figure 1-1: Vertically Integrated and Horizontally Integrated network design models Old approach PCM IP PPP ATM SDH New approach AMR GPRS PPP SDH IP AAL2 AAL5 SDH ATM AMR GPRS Synchronous Digital Hierarchy
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1
Signalling, SIP,
SIGTRAN Overview
- 1 -
Name: Bartlomiej Puchalski (Bartek)
Country: Poland
Education:PhD in Optimization of analogue Circuit Testing at Silesian University of Technology in Poland
MsC in Telecommunications (Silesian University of Technology, Bournemouth University UK)
Professional Experience: Instructor, Leliwa – training for /// Ericsson Manager, Orange PolandConsultant, Kennedy Information
- 2 -
Course Agenda
• SS7 Signalling Overview ~ 3,5 Days
• SIGTRAN ~ 1 Days
• SIP 0,5 Days
Daily Agenda
Introduction to the Signaling Architecture
Vertically Integrated and Horizontally Integrated network
Figure 1-1: Vertically Integrated and Horizontally Integrated network design models
Old approach
PCM
IP
PPP ATM
SDH
New approach
AMR GPRS
PPP
SDH
IPAAL2 AAL5
SDH
ATM
AMR GPRS
Synchronous Digital Hierarchy
2
Figure 1-3: Monolithic Architecture vs Layered Architecture
Handout: Classical (monolithic) architecture and Mobile Network Development
Figure 1-2: Layered Core Network Model Showing the Logical Network Nodes
Vertical architecture protocol stack.
Control Layer
ISDNMSC
HLR
GMSCBSC
AUCIN
BSSAP ISUP ISUP
MAPINAPCAP
Figure 1-5: Protocols used in the Mobile Core Network for Circuit Mode services
BICC – Used by /// only (all other vendors use SIP-T)
ITU /// IETFH248 = GCP = MEGACO
/// uses GCP because complete H248 functionality was not implemented in R1
Future ….
Figure 1-6: The access signaling in the common GSM and WCDMA systems Network
Figure 1-7: User plane protocol stacks for IP and ATM backbones
Figure 1-8: PCM encoded vs. Compressed speech in the Core Network
Figure 1-9: TrFO for WCDMA and TFO for GSM
Figure 1-10: Target architecture for the Mobile Core Network
Introduction to Signaling
Signalling and network activities
Traffic control
Database communication
Network management
B-numberAddress complete
Clear forwardB-answer
data base 1
data base 2 MS=‘X’
MS=‘X’ is now in my area!
OK, I have updated!
Trunk seizure!
Trunk blocked!
O&
M
Trunk group ‘Y’ blocked!
Redirect traffic …, etc.!
Figure 2-1: Signaling in Telecommunication Networks
Signalling:
• Access signalling (or subscriber signalling), between a subscriberterminal and the local exchange.
In practice CAS is not implementednowadays. However some old PSTN exchanges still use it andmust be supported in MSC.
Figure 2-2: CCITT R2 Signals (MFC)
Figure 2-3: Simplified Call Setup using the CAS System
Signalling Terminal
Computer
Signalling Terminal
Computer
ExchangeExchange
Signalling link
Data packet
Signalling message
Common Channel Signalling (CCS)
Figure 2-4: OSI Reference Model
Figure 2-5: Schematic figure of Information added in each Layer
L1
L2
L3
Service Access Point
Signalling entity
Primitive
Characteristics
High flexibility
Many different types of telecommunication services can use SS7.
High capacity
A single signalling link can support several thousand traffic circuits.
High speed
Setting up a call through a number of exchanges takes less than a second.
High reliabilityThe system contains powerful functions for elimination of disturbances in the signalling network. One example is the possibility of choosing alternative links for signalling.
Economical
Wide range of telecommunication services and connections can use one and the same signalling system. is an important economical aspect.
Signalling System No. 7 Signalling System No. 7Figure 2-8: Relationship between OSI and CCITT SS7
Figure 2-7: ETSI / ITU-T Protocols in the Mobile Core Network
4
SS7 Terminology
SP
(SPC=10)
SP
(SPC=20)
SL (SLC=1)
SL (SLC=0)
circuit (CIC=1) circuit (CIC=29)
LS
0 311 2
circuit (CIC=2)
SP - Signalling Point – sender/receiver of signalling messageSPC - Signalling Point Code – address of the SPSL - Signalling Link – 64 kbps TS carrying SS7 signalling between two SPsSLC - Signalling Link Code – SL identifier (4 bits)LS - Link Set – set of SLs connecting two SPs. Max 16 SLs/LSCIC - Circuit Id. Code – Connection Id. Standard 12b (4000 connections)
may be extended to 16b (65 000 connections)Figure 2-9: Signaling Network Elements
SS7 Signalling LinksProblem with capacity – 16 Signalling Links/Link Set not enough for GSM
Solution 1. Allocation of 2 logical signalling points to one physical node.
SPC=A
SPC=A’
SPC=B
SPC=B’
1 LS
16 SLs
16 SLs
Solution 2.Proprietary modification (e.g. CISCO, not supported by ///).
SPC=B32 SLs
SPC=A
Solution 3. HSL – High Speed Signalling Link. Whole E1 allocated for SS7.
SPC=B16 HSLsSPC=ASS7oATMoE11 SL has 2Mbps capacityIn practice 50% is wasted by ATM1 HSL = 16 SL
SS7 Addressing
International level
National level
SP
2-20
SP
2-10
SP
2-10
SP
2-32
NI Network Indicator
0 – international net. 2 – national net.1 – not used3 – operator network (e.g. in Russia 2 – whole federation,
3 – whole republic)
SP
0-12 2-28
SP
0-10 2-23
SPC Signalling Point Code
SS7 Signalling Point Types Figure 2-10: Associated and Quasi-associated Signaling Modes
Topology guidelines
• Each SP that is not an STP is connected to at least two STPs of thelower level.
• Each STP of the lower level is connected to at least two STPs of thehigher level.
• STPs in the higher level are fully meshed (all STPs have direct link toeach other).
Figure 2-11: A Hierarchically Structured Network
SS7 Signalling Link Types (ANSI)
SP
STP
STP
STP
SP
SP
STP
STP
SP
STP
F
A
A
E
CB
B
D
D
CA – AccessB – BridgeC – Cross
D – DiagonalE – ExtendedF – Fully associated
Figure 2-12: North American Signaling Network Link Types
Message Transfer Part - MTP
5
SS7 Protocol Stack
MTP
TUP
SCCP
BSSAP ISUP
TCAP
MAP CAP/INAP
Figure 3-1: Functional Levels of the Message Transfer Part
MTP1
MTP2
MTP1
MTP2
MTP1
MTP2
MTP1
MTP2MTP1
MTP2
MTP1
MTP2
MTP1
MTP2
MTP1
MTP2
MTP 3LS
SL
Relations between MTP entities and SL
Regional Hardware& Software
Central Software
Figure 3-2: MTP Connections in an AXE Exchange
Figure 3-3: Traditional MTP versus ATM-based MTP
Figure 3-4: Message Processing on High-speed Signaling Links
Signal UnitFigure 3-5: MTP Signal Unit Formats
• MSU - Message Signal Unit
(LI = 3 ÷ 63) is used to carry upper layer messages protocol messages.
• LSSU - Link Status Signal Unit
(LI = 1 or 2) is used to start up the link and in case of failures.
• FISU - Fill-In Signal Unit
(LI = 0) is used for error supervision (it carries only error correction fields. It is sent when in the transmission buffer there is nothing else to be sent to keep the link running.
Figure 3-6: Bit Stuffing and De-stuffing
MTP L2: FSN, BSN, FIB and BIB usage
request for retransmission
retransmission
FSN=1 BSN=1 FIB=0 BIB=0
FSN=2 BSN=1 FIB=0 BIB=0
FSN=3 BSN=3 FIB=0 BIB=1
FSN=3 BSN=1 FIB=0 BIB=0
FSN=2 BSN=3 FIB=0 BIB=0
FSN=4 BSN=2 FIB=0 BIB=0
FSN=5 BSN=2 FIB=0 BIB=0
FSN=4 BSN=3 FIB=1 BIB=1
FSN=5 BSN=3 FIB=1 BIB=1
sequence error
positive ack.
MTP L2: FSN, BSN, FIB and BIB usageBackward Indicator Bit (BIB)
The BIB (1 bit) marks the signal unit as:
• Positive acknowledged if the logical value of the BIB bit is the same as that received in the latest signal unit.
• Negative acknowledged if the value of BIB is not equal to the value in the latest received signal unit.
Forward Indicator Bit (FIB)
• If the logical value of the FIB is equal to the one in the previous signal unit, the receiver is informed that the signal unit is sent for the first time.
• If the logical value of FIB is not equal to the one in the previous signal unit, the receiver is informed that it is a repetition of a previously sent signal unit.
Service Information OctetFigure 3-7: Service Information Octet
Signalling Information Field
DPC
CKF SIO LI FSN BSN FSIF
OPCCICISUP message
OPC Originating Point Code
DPC Destination Point Code
SLS Signalling Link Selection -> SLC (used for load sharing)
CIC Circuit Identity Code
ISUP ISDN User Part
routing label
SLS
6
MTP routing labels
Signalling information CICSLS OPC DPC
14 bits 14 bits
Management information SLS OPC DPC
4 bits
12 bits
Signalling information CIC OPC DPCSLS
Signalling information OPC DPCSLS
4 bits
MTP management messages (label type A):
TUP messages (label type B):
ISUP messages (label type C):
SCCP messages (label type D):
Status Field in the LSSU Figure 3-7: Service Information Octet
Alignment procedure
LSSU (SIO)
LSSU (SIN/SIE)
LSSU (SIOS)
Out of alignment (HELLO)
Normal/Emergency (faster) alignment
Proving period
Normal Operation
Out of Service (e.g. link failure, cannot transmit/receive MSU, due to other
reasons than processor outage)
FISU
Alignment Error Rate Monitor
AERM
Emergency 0.5s ≤1 error
Normal 8.2s ≤4 errors
If proving is aborted M (M=5) times, the link is returned to the out-of-service state.
Recommendation:
In each LS one SL shouldoperate in emergency mode.At restart of the SP, all routesbecome available very quickly
SP SP
SP
LS SIO
SIE
Figure 3-12: Signal Unit Error Rate Monitor
Processor outage Problems at a functional level higher than MTP level 2 preclude utilisation of the link.
MSU/FISU
MTP3
MTP2← LSSUs (SIPO)
FISUs →
MTP3
MTP2MSU/FISU
RxTx RxTxLSSU (SIB)
Re-Tx Re-Tx
BSN, BIB - stop
LSSU (SIB)RxTx Re-Tx
BSN, BIB - stop
link faulty
First SIB reception T6 (3-6s)
SIB reception -> restart T7 0,5÷2s)
T5 (80-120ms)
T5 (80-120ms)
Congestion in the receiver buffer
Figure 3-9: Overview of the Signaling Link Functions (level 2)
Figure 3-10: SU Acceptance Procedure
Signalling Network – MTP 3
Signalling Network functions
• Signaling Message Handling
• Signaling Network Management
Traffic handling sub-functions
• Message Routing
• Message Discrimination
• Message Distribution
Figure 3-13: Overview of the Signaling Network Functions
Figure 3-14: Signaling Message Handling Overview
Figure 3-15: MTP SIF Fields: Routing Labels and User Information
7
International Signalling Point Codes (ISPC)
Zone identification Area/network identification Signalling point identification
3 bits 8 bits 3 bits
Signalling Area/Network Code (SANC)
Zone identification
•7 – South America•5 – Australia, South East Asia•3 – North and Central America
•6 – Africa•4 – Asia and Middle East•2 – Europe
7-096 – Uruguay3-136 – Cuba
7-060 – Chile3-128 – Bahamas
7-048 – Brazil3-020 to 3-059 – USA
2-144 – Ireland
5-102 – Tuvalu6-110 – South Africa4-120 – China2-124 to 2-131 – Germany
5-050 – Singapore6-092 – Madagascar4-108 – Hong Kong2-080 to 2-081 – Sweden
5-040 – Thailand6-078 – Kenya4-080 – Japan2-072 – UK (Mercury)
5-010 – Australia6-010 – Tunisia4-040 Saudi Arabia2-068 – UK (BT)
Load SharingLoad sharing within a LS - Always applied, uses the least significant part of the SLS field.
Load sharing between LSs - one method, commonly used, can be applied by using a specific Load SHaring Bit (LSHB) in the SLS field (each signalling route set usually needs no more than two LSs).
Load SharingSLS is selected by upper layer protocols (ISUP, SCCP) that control load Sharing. Often SLS values are changed one-by-one.
In case of „sequence-sensitive” protocol Load Sharing is disabled in orderto cope with variable delays in different Signalling Links (loss of sequence)
Congested Signalling Route Set (international network)
A
B
C
D
Route #1
Route #2
SL congested
SR congested
SRS congested
SL congestion -> SR congestion -> SRS congestion
Congested Signalling Route Set (international network)
A
B
C
D
Route #1
Route #2
SL congested
TFC
L4 SRS towards D congested
(congestion status not retained at level 3)
TFC Transfer Control
Signalling Link Changeover
COA SLC=0 FSN=123
Re-TxTx
MSU 123
MSU 124
MSU 125
MSU 126
Re-TxTx
MSU 72
MSU 73
MSU 74
MSU 75
MSU 76
MSU 77
MSU 78
Re-TxTx
MSU 81
MSU 82
MSU 83
Re-TxTx
MSU 64
MSU 65
MSU 66
MSU 67
MSU 68
unavailable
COO SLC=0 FSN=81
MSU 69
Changeover Order (CCO) Changeover Acknowledgement (COA)Diverted traffic has no priority in relation to normal traffic already conveyed on the SL.
Figure 3-21: Changeover Procedure
Figure 3-20: Fault in Local Signaling Link (SL)
Emergency Signalling Link Changeover Due to Signalling Terminal failure it may be impossible to determine FSN of the last MSU accepted over the unavailable link.
COA SLC=0 FSN=123
Re-TxTx
MSU 123
MSU 124
MSU 125
MSU 126
Re-TxTx
MSU 72
MSU 73
MSU 74
MSU 75
Re-TxTx
MSU 81
MSU 82
MSU 83
Re-TxTx
MSU 64
MSU 65
MSU 66
MSU 67
MSU 68
unavailable
ECO SLC=0
Figure 3-22: Emergency Changeover Procedure
9
Time-controlled changeover
Time-controlled changeover is initiated f any (or several) of the
following cases apply:
• No signalling path exists between the two ends of the unavailable link, so that the exchange of changeover messages is impossible.
• Processor outage indication is received on a link. In this case, if the remote processor outage condition is only transitory, sending of a changeover order could result in failure of the link.
• A SL currently carrying traffic has been marked (locally or remotely) inhibited. In this case, time controlled changeover is used to divert traffic for the inhibited link without causing the link to fail.
Traffic is transmitted via a new SL after expiry of a time T1 (500 to 1200 ms) in order to reduce the probability of message mis-sequencing.
If no changeover message in response to a CC0 is received within a timer T2 (700 to 2000 ms), new traffic is started on the alternative SL.
Figure 3-23: Changeover Procedure on No Response to COO
Signalling Link Changeback
CBA
CBDSPSP
ChangeBack Declaration (CBD)
ChangeBack Acknowledgment (CBA)
Forced Rerouting Procedure
A
Y
Z
X
�
�
�
� TFP (x)
� Destination X:
Route Y, unavailable
Route X, available
Figure 3-24: Fault on SL between A and B
Transfer Prohibited (TFP)
Case 1
RST every30s
Route Set Test (RST)
Figure 3-25: Forced Rerouting Procedure
TFP procedure (case 2 –broadcast method)
X
Destination X:
Route Y, unavailable
Route Z, available
B
A
C
Y
Z
TFP (x)
TFP procedure (case 3 – response method)
A
Y
Z
X
MSU X
Destination X:
Route Y, unavailable
Route Z, available
TFP (x)
Controlled Rerouting (case 1)
A
Y
Z
X
�
�
�
Destination X:
Route Y, available
Route X, available
Figure 3-26: Fault on SL between A and B Repaired
Figure 3-27: Controlled Rerouting Procedure
� TFA (x)
Transfer Allowed (TFA)
RST
10
Controlled Rerouting (case 2)
A
Y
Z
X
�
�TFR (x)
�
Destination X:
Route Y, restricted
Route Z, available
Link Management Procedure• Signaling link activation
Activates the SL at the operator’s request.
• Signaling link restoration
Performs an attempt to restore (activate) a faulty SL.
• Signaling link deactivationDeactivates the SL at the operator’s request. Can be performed even if the SL is in service.
•· Signaling link emergency restart
If the entire LS fails, the resource management indicates an “emergency” situation for all links in the group. In this case a restoration of each link is started and level 2 uses the short alignment period.
Link inhibiting
X Y
SL 0 unavailable, locally inhibited
SL 1 available
management system
LIN
LIA
SL 0 unavailable, remotely inhibited
SL 1 available
Inhibiting – disabling traffic for testing/troubleshooting purposes.e.g. too many changeovers and changebacks in a short time
Link Inhibit Message (LIN)
Link Inhibit Acknowledgement (LIA)Link Inhibit Denied (LID) - inhibiting will result in a destination becoming inaccessible
Link uninhibiting
X Y
SL 0 unavailable, locally inhibited available
SL 1 available
management system /
signalling routing control function
LUN
LUA
SL 0 unavailable, remotely inhibited available
SL 1 available
Link Uninhibit (LUN)
Link Uninhibit Acknowledgement (LUA)
Link Forced Uninhibit (LFU) - Signalling routing control will initiate SL uninhibit if an inhibited link is found to be a member of a LS in a route to a destination which has become inaccessible.
Signalling Link Test
SLTM
SLTA
A B
Signalling Link Test Message (SLTM) – initiates test. Sent every T2 (30-90s)
Signalling Link Test Acknowledgement (SLTA)
Fault Indication
A test run is unsuccessful if the following events occur:
• SLTA is not received within 10 seconds on the SL that has sent the corresponding SLTM.
• The bit pattern in the received SLTA does not agree with thebit pattern in the sent SLTM.
• The SL is indicated faulty if two consecutive tests fail.
Policing
STP Policing
• OPC restricted, all DPCs allowed• DPC restricted, all OPCs allowed• Both OPC and DPC restricted
SNM Policing – support for STM Policing. Limits the use of SNM messages.
Figure 3-28: Communication between Layers and Nodes
11
Signaling Transport in ATM Networks - SAAL
Figure 4-1: Broadband and Narrowband SS7 protocol stacks
Asynchronous Transfer Mode ATM
Figure 4-2: ATM cell format
Figure 4-3: The use of AALs
Figure 4-4: ATM Adaptation Layer type 1
Figure 4-5: ATM Adaptation Layer type 5
Figure 4-6: Message Transfer Part Functional Levels
Figure 4-7: AAL Architecture
• Segmentation and Reassembly sublayer (SAR)The SAR is responsible for the segmentation of the CS ProtocolData Unit (PDU) into 48 octet ATM SDUs.
• Convergence Sublayer (CS)The CS is responsible for adding information to the user-data,allowing acceptable recovery at the exit point of the ATMnetwork.
ATM Adaptation Layer for Signaling on the Network-to-Network Interface, (SAAL-NNI)
Figure 4-7: AAL Architecture
Common Part Convergence Sublayer (CPCS)
Performs functions that are common to all users of the specificAAL type (e.g. compressed voice and compressed video)
Service Specific Convergence Sublayer (SSCS)
Performs functions that are specific to the user application.
In SAAL – NNI the two lower sublayers SAR & CPCS are the same as inAAL5
SERVICE SPECIFIC CONNECTION-ORIENTED PROTOCOL (SSCOP)
SSCOP – almost the same capabilities as MTP-2, adaptedto broadband ATM transport
Figure 4-8: SSCOP Functions
Figure 4-9: SSCOP PDUs
Figure 4-10: Sequenced Data PDU
Invalid PDU :
· Has an unknown PDU type code· Is not 32 bit aligned.· Is not the proper length for a PDU of the stated type.
and should be discarded.
SSCOP PDU fieldsN(S) - functionally similar to the MTP-2 Forward Sequence Number (FSN).
Information field - in SD, MD or UD PDUs (upper layer info).
N(PS) - in POLL PDU, incremented each time a POLL PDU is sent
N(R) - although there is no explicit field like (BSN) receiver still maintains a variable containing the next in-sequence N(S) expected. Sent in STAT and USTAT PDUs
N(MR) - receiver window advertisement. Sent in STAT, STAT, RS, RSAK, ER, ERAK, BGN and BGAK
Source (S) bit - set (1) when the connection was released by the SSCOP entity. Sent in END PDU.
N(SQ) - incremented every time a new connection is initiated. Used by SSCOP entities to detect duplicate BGN, RS, or ER PDUs.
PDU Type field, PAD, Pad Length (PL)
SSCOP FUNCTIONSFigure 4-11: Connection Establishment and Release
Figure 4-12: SSCOP Error Free Operation
Figure 4-13: Error Correction using USTAT
Figure 4-14: Error correction using STAT
Figure 4-15: Coding of STAT element lists
Flow Control
N(MR) - For example, if the sender’s N(S) is 23 and the receiver Sets N(MR) to 87, the sender is permitted to send PDUs 23..86 Without further acknowledgement.
Keep Alive
No FISU. Heartbeat mechanism POLL->STAT
12
SERVICE SPECIFIC CONTROL FUNCTION (SSCF)
Figure 4-16: SSCF Functions
ISDN User Part - ISUP
ISUP Function
Figure 6-8: ISUP Message Structure Overview
ISUP is responsible for providing the necessary signalingcapability between exchanges in order to support the handling of the basic and supplementary ISDN services.
ISUP Message structure
Optional Part
Mandatory Variable Part
Mandatory Fixed Part
Message Type Code
Circuit Identification Code (CIC)
Routing label
CIC and SLS
CIC
SLS
4 bits
LSB
Ensures the in-sequence delivery of all messages related to a particular connection
Interaction between ISUP and MTP loadsharing
2-20
2-30
2-31
2-50
12-31
12-302-50
PriorityLSDPC
SLS=x0xx
SLS=x1xx
LSHB
SLS=xx00 SLS=xx01 SLS=xx10 SLS=xx11
path (message with SLS=1010)
CIC=0x1010
All the messages related with connection on CIC=0x1010 between exchanges 2-20 and 2-50 are exchanged under normal conditions over the same SLs and LSs.
Circuit Identity Code (CIC) format
CIC (most sig. bits)octet 2
CIC (least significant bits)octet 1
12345678Bit
Spare
For international applications, the four spare bits of the CIC field are reserved for CIC extension, provided that bilateral agreement is obtained before any increase in size is performed. For national applications, the four spare bits can be used as required.
13
Handout: ISUP message types
Formatting Principles
Figure 6-9: An IAM Example Message
Figure 6-3: Information Elements in an IAM Message
Call Setup
BA
Setup
CICB-no
IAM
Selection of outgoing route
BA
SetupB-no ?
called party numberconnection type required,network signalling capability required
CIC allocation (example)
CIC
=1
CIC
=2
CIC
=3
1
CIC
=3
2
CIC
=6
2
A B
A’B’
IAM (CIC=54)
2-11 2-10IAM (CIC=54)
ACM (CIC=54)
IAM (CIC=22)
Dual Seizure
Automatic repeat attempt
A B
�IAM�IAM
�!#$??
�IAM
�ACM�ACM
Params. in Initial Address Message -National/international call indicator
A B
IAM IAM IAM
national nationalinternational international
nat/international nat/international international
End-of-pulsing signal
IAM
A
Called Address Signals:
48323764433F
Removal of CC at last international exchange
A B
IAM IAM IAM
national nationalinternational international
48323766305 32376630548323766305
Network protection timerIAM
A
T7 (20-30s)ind.
no ACM/CON/…
Completion of transmission path
� IAM
A B
� Setup� Setup
� ACM � Alerting� Alerting
� Answer� ANM Connect
� �
�
Figure 6-2: En-bloc, Non-auto Answer Call Set-up and Disconnection
14
Subsequent Address Messages (SAM)
A B
IAM(48)
national nationalinternational international
004832376630
5
national
IAM(4832)SAM(32)IAM(4832)
SAM(3766) SAM(3766) SAM(3766)IAM
(48323766)
SAM(305) SAM(305) SAM(305) SAM(305)
Figure 6-4: Overlap, Non-auto Answer Call Set-up and Disconnection
Echo (acoustic feedback) & (crosstalk in the handset cord)
IHECD and OHECD
2
2
2 2
trunk networkaccess network access network
A B
OHECD
IHECD
Incoming Half Echo Control Device IHECD
Outgoing Half Echo Control Device
Echo control procedure (decision in originating exchange)
A B
OHECD
IHECD
�
IHECD may be needed
IAM(OHECD included)
IAM(OHECD included)
IAM(OHECD included)
�
IHECD may be needed
IHECD may be needed
�
ACMACMACM �
�
(IHECD included, OHECD not included, OHECD requested)
(IHECD included, OHECD not included, OHECD requested)
(IHECD included, OHECD not included, OHECD requested)
16
Echo control procedure (decision in terminating exchange)
A B
OHECD
IHECD
IAM(OHECD not included)
IAM(OHECD not included)
IAM(OHECD not included)
� �
ACM(IHECD included, OHECD included,
OHECD requested)
ACMACM ��
OHECD may be needed
(IHECD included, OHECD included,
OHECD requested)
(IHECD included, OHECD included,
OHECD requested)
NRM(OHECD included)
NRM(OHECD included)
�
�
�(OHECD released)
�
�
�
�
�
�
(OHECD released)
NRM�
(OHECD released)
(OHECD included)
Continuity check
� IAM
continuity check required
TX
RX�
� COT
continuity check successful
�
�COT
�
Continuity check test call
� CCR
TX
RX� �
CIC mismatch
CIC
=1
CIC
=2
CIC
=0
CIC
=3
CIC
=4
CIC
=1
CIC
=2
CIC
=3
Swapped cables
DIP #1
DIP #2
Tx
Rx
TxRx
Reset of circuits
RSC
REL
GRS
GRA
Reset Circuit (RSC) – acknowledged with Release
Circuit Group Reset (GRS)Circuit Group Reset Acknowledgement (GRA)
Unreasonable messages
When a message format error (e.g. improper length, mandatory variable or start of optional parameter’s pointer points beyond themessage length) the message is discarded.
Unrecognized messages and parameters
release callXX1
discard message and send notification110
pass on message010
discard message100
pass on message000
discard message
indicator
send notification
indicator
release call
indicator
Required action
Instruction indicator
Message compatibility information parameter
Unrecognized messages and parameters
release callXXX1
1110discard message and send notification
0110
discard parameter and send notification1010
pass on parameter0010
1100discard message
0100
discard parameter1000
pass on parameter0000
discard parameter indicator
discard message indicator
send notification
indicator
release call
indicator
Required actionInstruction indicator
Parameter compatibility information parameter
17
Compatibility information missing
XXX
CFN
Message compatibility: - do not release call, - send notification, - discard message
message type non-existent or not implemented – discarded, diagnostic field = XXX
Confusion message
Signaling Connection Control Part - SCCP
Call related and call non-related signalling
Figure 12-1: Circuit-related vs. Non-circuit-related Signaling
AddressingNormally exchanges analyse B-number, which is a problem with the call non-related signalling (no B-number).
The only address available in MTP is DPC. Problem with mobilesubscribers, as national DPCs are not unique.
Additionally, to enable routing based on DPC each SP should know the routes to all SPs worldwide. Any network reconfigurationrequires updates in routing tables (manually configured).
Figure 12-14: SCCP Address Elements
Figure 12-3: SCCP in the Mobile Core Network
Global TitleE.164 numbering plan address.
GT = 46 501 563 432
SPC = 2-2745
GT = 46 501 456 501
SPC = 2-1024
GT = 46 501 767 453
SPC = 2-7038
GT = 46 501 273 454
SPC = 2-6053
2-70382-102446 501 456...
2-10242-703846 501 273...
SSPPSPGT series
Figure 12-15: Global Title Translation
SCCP & Load SharingHow to exceed LS above 16 SLs?
SPC=ASPC=B
SPC=B’
16 SLs
16 SLs
How to implement Load Sharing over 32 links?
MTP – impossibleSCTP – possible with GTT
GT48 607 0
48 607 148 607 2
48 607 348 607 448 607 4
GTRC = 1
GTRC = 2
GTRC PSP SSP1 B B’
2 B’ B
MGT Mobile Global Title
MSC HLRIMSI MGT
GT = 48 607 000 000
IMSI 260 01 221954
MGT 48 607 21954
MCC MNC MSIN
CC NDC SN
• Used in the GSM network during the registration procedure.• One-to-one relation between MCC Mobile Country Code (IMSI) and the CC Country Code.
• In MNC to NDC translation a first digit of the MSIN is taken into account because operator can use more than one NDC.
STP on the way are only analysing MGT series
In home network IMSI is used.
International STPsdo not
understand IMSI
18
SSN Subsystem Number
SPC = 2-2381GT = 49 601 000001
VLR
GMSC, MSC
HLR
AUC SSN = 10
SSN = 6
SSN = 7
SSN = 8
Result of GT translation
Termination indication (OWNSP) - The message terminates in this node.
DPC with intermediate indication - The message is sent to the next SCCPnode. The next SCCP node re-routes the message further. The DPC is used In the routing label of the message to route the message to another node forfurther GT translation. The GT is left unchanged for translation in the nextnode.
DPC with termination indication - The message is sent to the next SCCPnode. The message terminates in the next SCCP node. The DPC is used inthe routing label of the message together with the SSN of the called party address to route the message to its final destination.
Figure 12-16: Connectionless Signaling Sequence
SCCP exemplary proceduresFigure 12-26: SCCP Addressing during a Call to an MS
Figure 12-27: SCCP Addressing during Location Updating
Figure 12-28: SCCP Addressing between the MSC and the BSC
SCCP service classesFigure 12-4: SCCP Protocol Classes
Connectionless Connection oriented
SCCP CL 0 (MAP example)
This class of operation is used for ‘window size = 1’ procedures, i.e. there is never more than one message send in particular direction before the result or answer message is received from the opposite side.
MSCVLRHLR
SEND ROUTING INFORMATION PROVIDE ROAMING NUMBER
PROVIDE ROAMING NUMBERSEND ROUTING INFORMATION
GMSC
IAM
SCCP class 0, called address,
calling address
SCCP class 0, called address,
calling address
SCCP class 0, called address,
calling address
SCCP class 0,
called address, calling address
SCCP CL 0 & MTP load sharing
SCCP
MTP
00SCCP message
10SCCP message
20SCCP message
30SCCP message
40SCCP message
………
150SCCP message
00SCCP message
SLSClass
19
SCCP CL 1 (MAP example)This class of operation is used for ‘window size > 1’ procedures, i.e. there are multiple messages send in particular direction before the result or answer message is received from the opposite side (bigger portion of data).
VLR HLRMSC
UPDATE LOCATION
INSERT SUBSCRIBER DATA
INSERT SUBSCRIBER DATA
UPDATE LOCATION
INSERT SUBSCRIBER DATA
INSERT SUBSCRIBER DATA
INSERT SUBSCRIBER DATA
INSERT SUBSCRIBER DATA
Class 0, called and calling address
Class 1, called and calling address
Class 1, called and calling address
Class 1, called and calling address
Class 0, called and calling address
Class 0, called and calling address
Class 0, called and calling address
Class 0, called and calling address
The sameSLS
SCCP CL 1 & MTP load sharing
SCCP
MTP
40SCCP message
51SCCP message
31SCCP message
20SCCP message
10SCCP message
00SCCP message
60SCCP message
31SCCP message
51SCCP message
70SCCP message
31SCCP message
51SCCP message
80SCCP message
SLSClassoperations executed in
sequence
SCCP Class 2 is used across BSC-MSC interface in order to make relation between identity of the dedicated channelallocated to the MS, known by the BSC, and the identity of the MS (IMSI/TMSI), known by the MSC.
SCCP CL 2 & (BSSAP example)
Figure 12-19: Connection Establishment
Figure 12-21: Data Transfer Phase
Figure 12-23: Connection Release Phase
Figure 12-9: SCCP Messages
Figure 12-10: Parameters of Some SCCP Messages
Figure 12-11: Overview of the Structure of an SCCP Message
Figure 12-5: SCCP Service Primitives
Figure 12-6: Peer-to-peer Communication
Figure 12-7: Service Primitive - General Syntax and Examples
Figure 12-12: Detailed Structure of an SCCP Message
Figure 12-13: Unitdata (UDT) Message
Figure 12-20: Connection Establishment Data Flow
Figure 12-22: Data Transfer Data Flow
Figure 12-24: Connection Release Data Flow
SCCP CL 2 & MTP load sharing
SCCP
MTP
32SCCP message
42SCCP message
22SCCP message
22SCCP message
10SCCP message
00SCCP message
50SCCP message
22SCCP message
42SCCP message
32SCCP message
22SCCP message
42SCCP message
60SCCP message
SLSClassmessages belonging to
the same connection
SCCP Subsystem Status Management • Signalling Point status management (SSN=1 the whole SCCP)