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

    www.comnets.uni-bremen.de SS7 - 10 - 2

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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

    www.comnets.uni-bremen.de SS7 - 10 - 4

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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

    www.comnets.uni-bremen.de SS7 - 10 - 5

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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)

    www.comnets.uni-bremen.de SS7 - 10 - 6

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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

    -

    www.comnets.uni-bremen.de SS7 - 10 - 7

    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)

    www.comnets.uni-bremen.de SS7 - 10 - 9

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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)

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

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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)

    www.comnets.uni-bremen.de SS7 - 10 - 11

    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

    www.comnets.uni-bremen.de SS7 - 10 - 12

    , , .

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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

    www.comnets.uni-bremen.de SS7 - 10 - 14

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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

    www.comnets.uni-bremen.de SS7 - 10 - 15

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    www.comnets.uni-bremen.de SS7 - 10 - 16

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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

    www.comnets.uni-bremen.de SS7 - 10 - 17

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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

    www.comnets.uni-bremen.de SS7 - 10 - 20

    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

    www.comnets.uni-bremen.de SS7 - 10 - 21

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    CGU 19 Circuit Group Unblocking