Download - Kommunikationsnetze I v10c Ws1112 Ss7 Org

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.(Zeichengabesystem Nr. 7)

SS#7, SS7, ...

Common Channel Signaling System No. 7,

C7, CCS7, ...- r.

www.comnets.uni-bremen.de SS7 - 10 - 1


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Terms (Begriffe)

Communication Networks I + IIi i +

http://www.lkn.e-technik.tu-muenchen.de/itg/empfehlung.html

(old: http://www.comnets.rwth-aachen.de/~itg/FG521/home_ger.html)

http://www.comnets.uni-bremen.de/itg/itgfg521/FG521/home_ger.html

German Version o Scri t: see web site



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Signaling System No. 7

global standard for telecommunications definedby the International Telecommunication Union

e eco ca o a ar za o ec or(ITU-T) (Q.700-Q.795)

by which network elements in the publicswitched telephone network (PSTN) exchange

n orma on over a g a s gna ng ne wor oeffect wireless (cellular) and wireline call setup,routin and control

ITU definition of SS7 allows for national

variants such as the American Nationalan ar s ns u e use n orAmerica and the European TelecommunicationsStandards Institute ETSI standard used in

www.comnets.uni-bremen.de SS7 - 10 - 3Europe


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SS7 network and protocol used for:

basic call setup, management, and release

mobile services mobile roamin and mobilesubscriber authentication

local number portability (LNP) toll-free (800) and toll (900) wireline services

enhanced call features such as call forwardin ,

calling party name/number display, and three-way calling, conference calls

assures efficient and secure worldwide

telecommunications



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Advantages of SS7

faster call setup times(compared to in-band signaling using multi-frequency (MF) signaling tones)

more efficient use of voice circuits support for Intelligent Network (IN) services

which require signaling to network elements

w ou vo ce run s e.g., a a ase sys ems improved control over fraudulent network usage



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Protocol Architecture SS7

User of SS#7

OSIlayers

ser(e.g., MAP, INAP)

Transaction ISDN7

Capabilities ApplicationPart (TCAP)

ser

Part(ISDN-UP,

e ep oneUser Part

(TUP)level 44-6

Signalling Connec-tion Control Part

(level 4)

empty

3

2

MTP (level 1-3)



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Message Transfer Part The Message Transfer Part (MTP)

is divided into three levels (Ebenen). The lowest level MTP Level 1 is e uivalent to the OSI Ph sical

Layer. MTP Level 1 defines the physical, electrical, andfunctional characteristics of the digital signaling link. Physical

interfaces defined include E1 (2048 kbit/s; 32 x 64 kbit/sc anne s , - s; x s c anne s , .(64 kbit/s), DS-0 (64 kbit/s), and DS-0A (56 kbit/s).(64 kbit/s -> 2 Mbit/s)

signaling link. Level 2 implements flow control, message sequencevalidation, and error checking. When an error occurs on asignaling link, the message (or set of messages) isretransmitted. MTP Level 2 is equivalent to the OSI Data LinkLayer (Frame similar to HDLC).

MTP Level 3 provides message routing between signaling points ine ne wor . eve re-rou es ra c away romfailed links and signaling points and controls traffic whencongestion occurs. MTP Level 3 is equivalent to the OSI

-


communication).


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ISDN User Part (ISUP)

The ISDN User Part (ISUP) defines theprotocol used to set-up, manage, and releasetrunk circuits that carry voice and data between

terminating line exchanges (e.g., between aca ng par y an a ca e par y .

Today ISUP is usedTCAP User

non-ISDN calls. TCAP (L7) ISUP

(L4)TUP(L4)

,originate and terminate

at the same switch do

SCCP (L4)

not use ISUP signaling.Why?

MTP (level 1-3)



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Telephone User Part (TUP)

In some parts of the worldC i i

the Telephone User Part (TUP) is used toi -

TUP handlesTCAP User.

In many countries, TCAP (L7) ISUP(L4)

TUP(L4)

TUP for call SCCP (L4)

. MTP (level 1-3)



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Signaling Connection Control Part (SCCP)

SCCP provides connection-less and connection-oriented network services and global title trans-lation (GTT) capabilities above MTP Level 3.

A global title is an address (e.g., a dialed 800num er, ca ing car num er, or mo i esubscriber identification number) which is

and subsystem number.A subs stem number uni uel TCAP User

identifies an application at

the destination signaling point.

TCAP (L7)

ISUP(L4)

TUP(L4)

s use as t e transportlayer for TCAP-based services.

MTP (level 1-3)


r y se y .


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Transaction Capabilities Applications Part (TCAP)

suppor s e exc ange o non-c rcu re a e a abetween applications across the SS7 network using theSCCP connectionless service (connection-less).

Queries and responses sent between SSPs (Service

Switching Point) and SCPs (Service Control Point) in the

For example, a switching point (SP)sends a TCAP query to determine

TCAP User

e rou ng num er assoc a ewith a dialed 800 number or tocheck the personal identification SCCP (L4)

(L4) (L4)

num er PIN o a ca ing car user.

In obile networks IS-41 and GSM TCAP carries

MTP (level 1-3)

Mobile Application Part (MAP) messages sent betweenmobile switches and databases to support user


, , .


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Signaling Network and Bearer Network

SP A SP CSignaling Network

Switch B

Switch CSwitch A

Traffic/BearerNetwork



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Network Nodes SS7

SP: Signaling Point(Zeichengabeknoten)

layer 1-7, , ...

co-located or part of a switching node

STP: Signaling Transfer Point(Transit-Zeichengabeknoten)

layer 1-3



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a)

0 STP Signaling Transfer Point (STP)

Traffic Channel

2 SS#7 channels per traffic channel1 STP

c) d)

3 SS#7 channels per traffic channel

4 SS#7 channels per traffic channel



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Number ofswitching nodes (Vermittlungsknoten)

for a typical ISDN end-to-end connection

localconnection

nationalconnection

internationalconnection

Number of switching nodes 1-4 5-7 8-10



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SS7 message types for ISDN

connection setup and release IAM Initial Address Messa e

sent to install a traffic channel between A and B,

Parameters: calling and called numberress omp e e essage

signals that the informationfor connection setup is complete

CPG Call Progress Messagesignals state of connection set-up,e. . that B is bein alerted

ANM Answer Messagesignals that traffic channel can be activated

e ease essagesignals that traffic channel can be released

RLC Release Complete Message

www.comnets.uni-bremen.de SS7 - 10 - 19sent after release of the traffic channel


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Callingsubscriber A

SubscriberLocal Exchange A

Transit Exchange SubscriberLocal Exchange B

Calledsubscriber B

SetupIAM

IAMACM Setup

Alerting

CPG

ACM

ANMAlerting

ANM

Traffic Channel

Disconnect

Release REL

RLC Disconnect

Success ul ISDN


connection set-up


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T e Code ISUP: Messa e t e

ACM 06 Address Complete

BLA 15 Blocking Acknowledgement

CCR 11 Continuity Check Request

on us on

CGB 18 Circuit Group Blocking

CGBA 1A Circuit Group Blocking Acknowledgement



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CGU 19 Circuit Group Unblocking

CGUA 1B Circuit Group Unblocking Acknowledgement

CMC 1D Call Modification CompletedCMR 1C Call Modification Request

CMRJ 1E Call Modification Reject

CON 07 ConnectCOT 05 Continuity

CPG 2C Call Progress

C M 2A Circuit Grou uer

CQR 2B Circuit Group Query Response



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CRG 31 Charge information

DRS 27 Delayed Release

FAA 20 Facility AcceptedFAR 21 Facility Request

FOT 08 Forward Transfer

FRJ 1F Facility RejectGRA 17 Circuit Group Reset Acknowledgement

GRS 29 Circuit Group Reset

IAM 01 Initial Address Messa e

INF 04 Information



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INR 03 Information Request

LPA 24 Loop Back Acknowledgement

OLM 30 OverloadPAM 28 Pass Along

REL 0C Release

RES 0E ResumeRLC 10 Release Complete

RSC 12 Reset Circuit

SAM 02 Subse uent Address Messa e

SUS 0D Suspend



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UBA 16 Unblocking Acknowledgement

UBL 14 Unblockin

UCIC 2E Unequipped Circuit Identification Code

0A Reserved

0F Reserved

eserve

23 Reserved

25 Reserved

26 Reserved



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Callingsubscriber

SubscriberLocal Exchange

Transit Exchange SubscriberLocal Exchange

Calledsubscriber

SetupIAM

IAMACM Setup

Alerting

CPG

ACM

Alerting

Disconnect

Release REL

RLC Disconnect


connec on se -up su scr er oes no answer


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QoS circuit switched ISDN services

Quality of serviceparameter (ITU-T E.721)

Normal load (100%) Higher load (115%)

mean 95 % mean 95%

D-channel

0.6 s 1.0 s 1.0 s 2.0 saccess me

Connection setup time

local connection

3.0 s na ona connec on

international connection

5.0 s8.0 s

.8.0 s11.0 s

Time of answer delay

local connectionnational connection

international connection

0.75 s1.5 s2.5 s

local connectionnational connection

2%3%5%



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Maximum time allowed for

total connection set-up time according to I.352

connec on se -up me

mean 7.5 s

95 % 8.45 s

I.352 (03/93) Network performance objectives



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MPT MPI MPI MPT

T or S/T T TTransit AE(nat. part)

Transit AE(nat. part)

User User AE Transit AE

User AE User.

AE Access Element

n erna ona or er

MPT Measurement Point

i



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-

connection set-up delay

mean 1.7 s

95 % 2.3 s

connection set-up delay

Connection set-up delay of international network part

mean 2.9 s

. s

Connection set-up delay of national network part



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MPI1 ISCISC MPI2ISC

easurement o nt nternat onaISC International Switching Center

Worst-Case Reference Connection for international network art

MPT LE MPIPC SC ISC

MPT Measurement Point - TerminalLE Local Exchange

PC, SC Transit Switchin NodesISC International Switching CenterMPI Measurement Point - International

- i i



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um er o s um er o s

International NetworkPart

3 4

National

4 5e wor ar


Parameters for the calculation


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Parameters for the calculationo connection rocessin dela s



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Current "SS7" Developments

Fixed and mobile telephone network operators are designing a so-called AllIP architecture including support for signaling system 7SS7 si nalin rotocols

The benefits of using an IP network in comparison to a legacy TDM-(time division multiplex)based network include:

Ease of deploymentWhen using signaling gateways, there is no need toisrupt t e existing SS7 networ , an uture en ancements are

transparent. Less costly equipmentThere is no need for further expensive

invest ents in the le ac si nalin ele ents.

Better efficiencySignaling over an IP network does not require thephysical E1/T1 over synchronous digital hierarchy (SDH) rings. Using newtechnologies like IP over SDH and IP over fiber, for instance, can

. Higher bandwidth Signaling information over IP does not constrain link

capacity as it does in the SS7 network. The IP network is much more

flexible than the TDM-based legacy network. Enhanced servicesImplementing a core IP network facilitates avariety of new solutions and value-added services (VAS).

see e.g. SIGTRAN IETF group


l


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Current "SS7" Developments

SIGTRAN (Signaling Transport) is aworking group within the IETFstandard organization. Its primarypurpose is to address the transportof packet-based public switched

telephone network (PSTN) signaling,account the functional andperformance requirements of thePSTN signaling.

In order to interwork with thePSTN, IP networks need totransport signaling such asn egra e serv ce g a ne(ISDN) (e.g. Q.931) or SS7 (e.g.ISDN user part (ISUP), SCCP, and

such as a signaling gateway (SG), amedia gateway controller (MGC), amedia gateway (MG), or an IP


ase ata ase.


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- . - .

CC NDC SN

CC Country Code, defined in E.164 (Landeskennzahl)

NDC National Destination Code Ortsnetzkennzahl

SN Subscriber Number (Teilnehmernummer)

+49 421 2182277


R f


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References

http://www.pt.com/tutorials/ss7/
