SS7 Overview

Embed Size (px)

DESCRIPTION

SS7 Overview

Citation preview

  • 5/26/2018 SS7 Overview

    1/113

    111 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID 2002, Cisco Systems, Inc. All rights reserved.

  • 5/26/2018 SS7 Overview

    2/113

    2 2001, Cisco Systems, Inc. All rights reserved.

    Session Number

    Presentation_ID

    ITP Course

    ITP Product Team

  • 5/26/2018 SS7 Overview

    3/113

    333 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Section 1SS7 Overview

    2002, Cisco Systems, Inc. All rights reserved. 3

  • 5/26/2018 SS7 Overview

    4/113444 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Objectives

    Upon completing this module, you will be

    able to:

    Understand the role of SS7 in Telephony Networks.

    Have a High Level understanding of SS7 MTP, SCCP,ISUP and TCAP Protocol Layers.

    Get an General Introduction to SS7 NetworkArchitecture

    SCCP is also overed in another Section

  • 5/26/2018 SS7 Overview

    5/113555 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Agenda

    SS7 Architecture

    SS7 Protocol and Standards

    MTP L1, 2, 3

    ISUP

    SCCP

    TCAP

  • 5/26/2018 SS7 Overview

    6/113666 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling System 7 (SS7)

    An international standard Protocol to provide highlyreliable message transfer without duplication or loss

    for sending messages:Between switches for basic call control and callrelated services

    Between switches and databases for network

    based services (e.g.,free numbers ,portability)SS7 uses a logically separate, common channelpacket switched network .

  • 5/26/2018 SS7 Overview

    7/113777 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SS7 is widely deployed worldwide in Public

    Switched Telephone Networks Adopted by Mobile Operators, who are

    extensively implementing value added servicesusing SS7

    SS7 is emerging as the common thread to tietogether different transport networks forconvergence

    Signaling System 7 (SS7) Contd

  • 5/26/2018 SS7 Overview

    8/113888 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Many SS7 Protocol Standards

    SS7 was originally defined in the ITU (C7) :

    1980 Yellow Book

    1984 Red Book

    1988 Blue Book

    1992 White Book

    ANSI standard for US was developed from the Blue Book

    Bellcores version is based on the ANSI standard and hastoday become the standard in the US (with someexceptions)

    GR-246-CORE, Bell Communications ResearchSpecifications of SS7.

    China, Japan have their own flavors

  • 5/26/2018 SS7 Overview

    9/113999 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling Concept

    Switch to Switch

    Channel Associated Signaling

    SS7 (ISUP)

    Switch to Database

    SS7 (TCAP)

    Subscriber to Switch

    Dial PulseDTMF

    ISDN

  • 5/26/2018 SS7 Overview

    10/113101010 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Common Channel Signaling

    SSP CCSSO

    STP

    Conversation

    Signaling

    Channel Associated Signaling

    EO EO

    Signaling

    Conversation

    EO - End Office

    STP - Signaling Transfer

    Point

    CCSSO - Common Channel

    Signaling Switching office

    SSP - Service Switching Poi

  • 5/26/2018 SS7 Overview

    11/113111111 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling - Call Setup

    Switch SS7 Switch

    off hook

    dial tone

    digits IAM IAM setupalertingACMACMring tone

    off hookANMANMCONNECT

    CONN ACK

    DISCONN REL REL DISCONN

    RELEASERLCRLCRELEASE

    REL ACK

  • 5/26/2018 SS7 Overview

    12/113121212 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SS7 versus - OSI Model

    7 Application

    3 Network

    2 Data Link

    1 Physical

    ISUPTUP

    NUP

    MAP

    TCAP

    INAP

    TCAP

    SCCP

    MTP

    OMAP

  • 5/26/2018 SS7 Overview

    13/113131313 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SS7 Network Hierarchy

    Voice Trunks

    Signaling Links

    AINSCP

    SCP1Region X Region Y

    STP STP

    SSP

    SCP1

    STP STP

    CCSSO

    STP - Signal Transfer Point

    SSP - Service Switching Point

    SCP - Service Control Point

    AIN - Advanced Intelligent Network

    CCSSO - Common Channel Signaling Switching Office

  • 5/26/2018 SS7 Overview

    14/113141414 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    F

    The SS7 Terminology

    Tandem

    Switch

    Tandem

    Switch

    CO

    Switch

    SEP

    SSP = Service Switching Point

    CO

    Switch

    SSP

    STP

    STP

    SCP

    SSPSSP

    SCP SCP SCP

    F

    A A A A A A A A

    C

    B B B

    A A A A

    E

    SCP = Service Control Point

    STP = Signal Transfer Point

    F

    EE

    STP

    STP

    C

    STP

    STP

    C

    BBSTP

    STP

    C

    B

    D D D

    SEP = Signaling End Point

  • 5/26/2018 SS7 Overview

    15/113151515 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling Links

    CCS Network Elements are connected with dedicated 64Kbpsdigital, bidirectional transmission facilities. Links areEngineered at 40% of capacity and use diverse routes.

    Type of links:

    Access Links (A-links)

    Bridge Links (B-links)

    Cross Links (C-links)

    Diagonal Links (D-links)

    Extended Links (E-links)

    Fully Associated Links (F-links)

    Links that combined any two nodes are referred as being in a linkset.The size of any linkset can range from one to sixteen links. Eachlink is defined by its Signaling Link Code (SLC)

  • 5/26/2018 SS7 Overview

    16/113161616 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling Links (Continued)

    Associated - the signal links run directly in parallel with thebearer links. All connections are point-to-point, therefore routing

    is not required.

    Non-associated - there is a separate logical path for the signaland bearer links. Signal links generally go through multipleSTPs to get to their final destination.

  • 5/26/2018 SS7 Overview

    17/113171717 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    A

    Linksets

    F

    SLC=0

    SLC=1

    SLC=0SLC=1

    Combined

    Linkset

    SS7 Linksets & Link Codes

    C

    SLC=0

    SLC=1

    Linkset

    STP

    STP

    SSP

    SSP

  • 5/26/2018 SS7 Overview

    18/113181818 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling Transfer Point (STP)

    STPs are the heart of the CCS network. High speed,ultra-reliable special purpose packet switch forsignaling message in the SS7 network.

    They are responsible for routing messages.Messages can be routed in one of two ways:

    Information within the message (SCCP/GTT)

    Information within tables at the STP (MTP3 routing)

    STPs are deployed as geographically separate matedpairs for reliability and optimally loaded for 40%capacity for dependability.

  • 5/26/2018 SS7 Overview

    19/113191919 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ITU Signaling Point Code

    Network ID (NID)

    0--7(3bits)Cluster ID (CID)

    0 -- 255(8bits)Member ID (MID)

    0 7(3bits)

    All CCS network elements are assigned a unique number

    called a Point Code.ITU Point Codes are 14 bits, shown as decimal or 3-8-3 format

    ANSI Point Codes are 24 bits, shown as 8-8-8 Format

    Network ID are assigned by PTT- Authority

    (ANCR,Offtel,IBTT,etc..) on demand .The same entity

    from which the E164number ranges comes !!!

  • 5/26/2018 SS7 Overview

    20/113202020 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP3-STP Message Routing

    SS7 Link SS7 LinkSTP

    IncomingMessages

    OutgoingMessages

    DPC

    DPC X-Y-Z - Take Route 1

    DPC A-B-C - Take Route 2

    DPC is my own - Go to Global Title Translation Table

    Routing Tables

    DPC - Destination

    Point Code

  • 5/26/2018 SS7 Overview

    21/113212121 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP

    2002, Cisco Systems, Inc. All rights reserved. 21

  • 5/26/2018 SS7 Overview

    22/113

    222222 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SS7 Protocol Stack

    ISDN User

    Part (ISUP)TCAP

    INAPMAP

    Non-Circuit Applications

    SCCP

    MTP

    Enhanced addressing,

    Connectionless/connection oriented services

    Level 1

    Level 2

    Level 3

    Null Presentation, Session, Transport

    Application

    MAPMobile Application Part

    TCAP - Transaction Capabilities Application Part

    ISUP - Integrated Services Digital Network User Part

    Circuit-Related

    Services

    OSI Reference Model

    Network

    Message Discrimination/Distribution/Routing,

    Network Management

    Network

    Data LinkLinkSU Delimitation/Alignment, Error detection/Correction,

    retransmission, SUERM, Alignment, Flow Control

    PhysicalData Link Link connection, bit rate, voltages

    DTAP

    SCCP - Signaling Connection Control Part

    MTP - Message Transfer Part

  • 5/26/2018 SS7 Overview

    23/113

    232323 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Protocol - Network Elements

    ISUPTCAP

    SCCP

    MTP

    Null

    MTP L3

    MTPL2

    MTPL1

    STP

    SSP

    SCCP

    MTP

    MTP L3

    MTPL2

    MTPL1

    SCCP

    MTP

    MTP L3

    MTPL2

    MTPL1

    SCCP

    MTP

    MTP L3

    MTPL2

    MTPL1

    SCCP

    MTP

    MTP L3

    MTPL2

    MTPL1

    ISUP

    SCCP

    MTP

    MTP L3

    MTPL2

    MTPL1

    TCAP

    SCCP

    MTP

    Null

    MTP L3

    MTPL2

    MTPL1

    STP

    SCP

    STPSTP

    CCSSO

    STP

  • 5/26/2018 SS7 Overview

    24/113

    242424 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP Level 1

    There are two data channels in every link used for full duplextransmission. Common interface types are:

    - V.35(USA)

    -A single 64/56K channel (DS0) in a E1/T1 (DS1) interface

    -The specification for MTP L1 can be found in recomandationITU-T Q702

    - High-speed links

    - IP links

  • 5/26/2018 SS7 Overview

    25/113

    252525 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP Level 1

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 310

    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 2324

    SignalingFraming

    E1

    T1

    16

  • 5/26/2018 SS7 Overview

    26/113

    262626 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 2

    Signaling Unit delimitation

    Error detection & correction

    Initial Alignment

    Flow Control

    Signaling link Error monitoring

    Level 2 provides reliable transfer of signaling

    messages between two directly connectedpoints.

  • 5/26/2018 SS7 Overview

    27/113

    272727 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 2 (Signaling Unit Types)

    MSU - Transfer user information

    LSSU - Report change of linkstate

    FISU - Filler when no other SU to

    send

    3 Types of Signaling Units

  • 5/26/2018 SS7 Overview

    28/113

    282828 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    LSSU

    LSSULSSU

    MSUMSU

    MSU MSUFISU

    FISU FISU

    MTPL2 - SS7 Signal Units

    Message Signal Unit (MSU) - used to transmit user data fromSCCP layer, ISUP layer, or Network Management.

    Retransmitted if received in error

    Link Status Signal Unit (LSSU) - used to carry link status

    information between the two ends of a signaling link. LSSUs

    are used to restore a failed link, handle receive congestion, and

    communicate processor outage information to the far end

    Fill-In Signal Unit (FISU) - transmitted when there are not any

    MSUs or LSSUs. Used to maintain link integrity.

    6 - 279 bytes per SU

  • 5/26/2018 SS7 Overview

    29/113

    292929 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Message Formats

    FLAG BSN/BIB FSN/FIB Length Status

    FLAG BSN/BIB FSN/FIB Length CheckSvc Info Sig Info

    Fill-in Signal Unit

    Link Status Signal Unit

    Message Signal Unit

    1-2 bytes

    8-272 bytes

    BSN/BIBBBackward Sequence Number/Backward Indicator Bit

    FSN/FIBForward Sequence Number/Forward Indicator Bit

    LengthNumber of Octets Between Itself and the Check Sum

    Svc InfoIs Used to Indicate the Type of Signaling Message that Follows

    FLAG BSN/BIB FSN/FIB Length Check

    Check

  • 5/26/2018 SS7 Overview

    30/113

    303030 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTPL2 Data

    Flag = 0 1 1 1 1 1 1 0

    0 0

    PriorityN/I

    Length Indicator

    BIB

    FIB

    BSN

    FSN

    Service Indicator

    Signaling

    Information

    Field

    Check

    Bits

    MTPL2

    Data

    MTPL2

    Data

    Order of transmission

    Sequence Numbers and Indicator Bits - used to

    acknowledge the receipt of an MSU. Indicator

    bits are used to indicate that an MSU was received

    in error or has been retransmitted

    The Length Indicator implies the type of signal

    unit being transmitted:

    If LI = 0 FISU

    If LI = 1 or 2 LSSUIf LI > 2 MSU

    Service Information Octet defines the message

    priority, national or international indicator, and

    the service indicator. The service indicator indicates

    the upper level user who sent this information

    The Signaling Information Field contains the user

    data. This includes the following protocol layers:

    TCAP, ISUP, SCCP, MTPL3

    SIO

  • 5/26/2018 SS7 Overview

    31/113

    313131 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTPL2MSU - Service Information Octet

    The SIO contains 3 fields:

    Network Indicator- this says whether the messageconforms to National (2) or International (0) standards

    Priority(only USA)- All MSUs are assigned one of fourpriorities (0-3) with 3 being the highest. Only usedduring congestion (0-2 can be discarded)

    Service Indicator Code (SIC)- Upper level user

    0 - Information and status message 2 - Messages related to call in progress

    1 - Messages related to establishing a call 3 - Network Management messages

    0 - MTP Network Management 2 - Link Testing & Maintenance 5 - ISUP

    1 - Link Testing & Maintenance 3 - SCCP (TCAP, MAP, AIN)

  • 5/26/2018 SS7 Overview

    32/113

    323232 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Leaky Bucket - Link Failure

    A leaky bucket algorithm is used to fail a

    signaling link.

    1. When the signaling link is placed in service the bucket is

    empty.

    2. When a bad message is received (based on CRC), atoken is added to the bucket

    3. When 256 messages are received (good or bad), a tokenis removed from the bucket

    4. When the number of tokens in the bucket is equaled to 64the link is failed.

  • 5/26/2018 SS7 Overview

    33/113

    333333 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 2 (LSSU)

    SIOS - Out of Service

    SIO - Out of Alignment

    SIN - Normal Alignment

    SIE - Emergency Alignment

    SIPO - Process Outage

    SIB - Busy (Level 2 Congestion)

    Status Field Indicators

  • 5/26/2018 SS7 Overview

    34/113

    343434 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 2 (Link Alignment)

    T2 Start

    T2 Stop

    SIO

    SIO

    Not Aligned

    T3 Start

    T3 Stop

    SIN or SIE

    Aligned

    SIN or SIE

    SIOS

    Start Link Proving PeriodT4 Start

  • 5/26/2018 SS7 Overview

    35/113

    353535 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 3

    Level 3 is responsible for the reliable transfer of

    messages between SS7 network nodes.

    The Signaling Network functions fall into two

    major categories

    Signaling Message Handling

    Signaling Network Management

  • 5/26/2018 SS7 Overview

    36/113

    363636 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 3 (Routing Label)

    MSU

    SIF Field

    SIO

    Routing Label

    SIF

    User Specific Information

    Signaling Link

    Selector

    Origination Point

    Code

    Destination Point

    CodeRouting Label

  • 5/26/2018 SS7 Overview

    37/113

    373737 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP Level 3 - Routing Label

    4 octets field right after the SIO

    It is made of:

    Destination Point Code (DPC) - Identifies the node that the

    MSU is bound for. Not necessarily the ultimate destination ornext node-14 bits

    Originating Point Code (OPC) - Identifies the node that theMSU came from. Not necessarily the originator or previousnode14 bits.

    Signaling Link Selection (SLS) - Used to select a link andlinkset so that traffic is evenly distributed- 4 bits

  • 5/26/2018 SS7 Overview

    38/113

    383838 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP STP

    STP STP

    A

    B

    C

    D

    E

    F

    Load Sharing

    LS 1

    LS 0

    LS 1

    LS 0

    LS 1

    LS 0

    1. Node A assigns a unique 4 bit SLS code XXXX

    2. Node A uses the Bit number3(03) (LSB) to do the decision on link selection

    0->LS0 and 1->LS1 .The bit used for selection is configurable at each node.

    3 Node B and C will need to have make the decision on other bit (bit 2) to conserve

    the load sharing

    SLSXXXX

    SLSXXX1

    SLS -SLSXXX0 SLSXX00

    SLSXX10

  • 5/26/2018 SS7 Overview

    39/113

    393939 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Routesets

    3-3-21-1-31-1-2

    1-1-1

    3-3-0

    2-2-1

    2-2-0

    Alias 2-2-2

    1 2 3 4

    5

    6

    7

    1-1-0

    Point Code Linkset Cost

    1-1-1 LS1 00

    LS5 01

    1-1-2 LS2 00

    LS5 011-1-3 LS3 00

    LS5 01

    3-3-2 LS4 00

    LS5 01

    3-3-0 LS5 00

    2-2-0 LS6 00

    LS5 012-2-1 LS7 00

    LS5 01

    2-2-2 LS6 00

    LS7 00

    LS5 01

    Once a destination is known to an STP

    routing tables are consulted to determine the

    least cost route to get there.

  • 5/26/2018 SS7 Overview

    40/113

    404040 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 3 (SNM)

    Signaling Network Management

    Signaling Traffic Management

    Signaling Link Management

    Signaling Route Management

  • 5/26/2018 SS7 Overview

    41/113

    414141 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTPL3 - Network Management

    Traffic Management

    Slows or diverts traffic from or to an affected link or route

    Link Management

    Activates, deactivates or restores signaling links in response tofailures or changes in link status

    Route Management

    Distribute information about signaling network status

    Congestion Control (only used in USA)

    Control traffic based on message priority

  • 5/26/2018 SS7 Overview

    42/113

    424242 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP 3 (SNM)

    Signaling Traffic Management

    Changeover

    Changeback

    Forced Rerouting

    Controlled Rerouting

    Management Inhibiting

    Signaling traffic flow control

  • 5/26/2018 SS7 Overview

    43/113

    434343 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Traffic Management

    Slows or diverts traffic from or to an affected link or route

    Forced Rerouting - done when signaling route becomesunavailable. Procedure involves diverting traffic from one link

    set to another one. Result of TFP(Transfer Prohibited).Controlled Rerouting - used to divert traffic to a more efficient

    route. Result of TFR (Transfer Restricted).

    MTP Restart - used to avoid flooding node when it is goingthrough a restart. UsesTRW (Traffic Restart Waiting) and

    TRA(Transfer Allowed)

    Management Inhibiting - allows maintenance personnel toprevent MSUs from being transmitted on a link

  • 5/26/2018 SS7 Overview

    44/113

    444444 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Link Management

    Activates, deactivates or restores signaling links in response tofailures or changes in link status

    Signaling Link Activation - once a link is aligned and haspassed the link test, it is considered activated and ready tocarry traffic

    Signaling Link Changeover - diverts traffic from anunavailable link to one or more link without message loss,

    mis-sequencing or duplication. COO(Change Over Order) issent and COA(Change Over Acknowledgement) is returned.

  • 5/26/2018 SS7 Overview

    45/113

    454545 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Link Management (Cont)

    Activates, deactivates or restores signaling links in response tofailures or changes in link status

    Signaling Link Changeback - diverts traffic back to originallink. CBD ( Change Back Declaration) is sent and CBA(Change Back Acknowledge) is returned.

    Signaling Link Tests - done after initial alignment, periodicallybetween 2 nodes (30-90sec). SLTM (Signaling Link Test

    Message) is sent and SLTA (Signaling Link TestAcknowledge) is returned.

  • 5/26/2018 SS7 Overview

    46/113

    464646 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling Route Management

    Transfer Restricted (TFR)

    Transfer Prohibited (TFP)

    Transfer Allowed (TFA)

    Signaling Routeset Test (RST)

    Transfer Controlled (TFC)

    Signaling Routeset Congestion Test (RCT)

    Route Management

  • 5/26/2018 SS7 Overview

    47/113

    474747 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Route Management(cont)

    Distributes information about signaling network status

    Transfer-Restricted (TFR) - Notify a node to avoid sending messages tothe indicated PC through the STP that sent TFR

    Transfer-Prohibited(TFP) - Notify a node that an adjacent STP is unableto route to a specific signaling point in network

    Transfer-Allowed (TFA) - Notify a node that a signaling point is nowavailable through the STP that sent TFA

    Signaling-Route-Set-Test (RST) - Sent in response to a restricted or

    prohibited message (every 30 seconds)

  • 5/26/2018 SS7 Overview

    48/113

    484848 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Link Failure and Restoral

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link andrestoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    SLC=1

  • 5/26/2018 SS7 Overview

    49/113

    494949 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 eventsfor Out of service link and

    restoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    SLC=1

    COO

    COO

    Link Failure and Restoral

  • 5/26/2018 SS7 Overview

    50/113

    505050 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link and

    restoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sentfrom SSP2 to STP1 via STP2 with SLC=1

    SLC=1

    COA

    COA

    Link Failure and Restoral

  • 5/26/2018 SS7 Overview

    51/113

    515151 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link andrestoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sent

    from SSP2 to STP1 via STP2 with SLC=1

    4. Transfer Restricted (TFR) sent for SSP2

    to all signaling point connected to STP1

    SLC=1

    TFR

    TFR

    TFR

    TFR

    Link Failure and Restoral

  • 5/26/2018 SS7 Overview

    52/113

    525252 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link andrestoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sent

    from SSP2 to STP1 via STP2 with SLC=1

    4. Transfer Restricted (TFR) sent for SSP2

    to all signaling point connected to STP1

    5. Transfer Prohibited (TFP) sent by STP1

    to STP2

    SLC=1

    TFP

    Link Failure and Restoral

    i i

  • 5/26/2018 SS7 Overview

    53/113

    535353 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link andrestoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sentfrom SSP2 to STP1 via STP2 with SLC=1

    4. Transfer Restricted (TFR) sent for SSP2

    to all signaling point connected to STP1

    5. Transfer Prohibited (TFP) sent by STP1

    to STP2

    6. Route Set Test Restricted (RSR) sent for

    destination SSP2 to all signaling point to

    STP1 every 30 seconds

    SLC=1

    RSR

    RSR

    RSR

    RSR

    Link Failure and Restoral

    Li k F il d R l

  • 5/26/2018 SS7 Overview

    54/113

    545454 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link and

    restoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sentfrom SSP2 to STP1 via STP2 with SLC=1

    4. Transfer Restricted (TFR) sent for SSP2

    to all signaling point connected to STP1

    5. Transfer Prohibited (TFP) sent by STP1

    to STP2

    6. Route Set Test Restricted (RSR) sent for

    destination SSP2 to all signaling point toSTP1 every 30 seconds

    7. Link 1 is restored and aligned

    8. Change Back Declaration (CBD) send

    by STP1 and SSP2SLC=1

    CBD CBD

    Link Failure and Restoral

    Li k F il d R l

  • 5/26/2018 SS7 Overview

    55/113

    555555 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 eventsfor Out of service link and

    restoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sentfrom SSP2 to STP1 via STP2 with SLC=1

    4. Transfer Restricted (TFR) sent for SSP2

    to all signaling point connected to STP1

    5. Transfer Prohibited (TFP) sent by STP1

    to STP2

    6. Route Set Test Restricted (RSR) sent for

    destination SSP2 to all signaling point to

    STP1 every 30 seconds7. Link 1 is restored and aligned

    8. Change Back Declaration (CBD) send

    by STP1 and SSP2

    9. Change Back Acknowledge (CBA) sent

    by STP1 and SSP2SLC=1

    CBA

    CBA

    Link Failure and Restoral

    Li k F il d R t l

  • 5/26/2018 SS7 Overview

    56/113

    565656 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP1 STP2

    SSP1 SSP2

    SCP1 SCP2

    Sequence of Level 3 events

    for Out of service link andrestoral

    1. Link goes Status Indicator Out

    of Service (SIOS)

    2. Change Over Order (COO) sent from

    STP1 to SSP2 via STP2 with SLC=1

    3. Change Over Acknowledge (COA) sent

    from SSP2 to STP1 via STP2 with SLC=14. Transfer Restricted (TFR) sent for SSP2

    to all signaling point connected to STP1

    5. Transfer Prohibited (TFP) sent by STP1

    to STP2

    6. Route Set Test Restricted (RSR) sent for

    destination SSP2 to all signaling point to

    STP1 every 30 seconds

    7. Link 1 is restored and aligned8. Change Back Declaration (CBD) send

    by STP1 and SSP2

    9. Change Back Acknowledge (CBA) sent

    by STP1 and SSP2

    10. TFA sent by STP1 to all signaling

    points. RSR test suspended

    SLC=1

    TFA

    TFA TFA

    TFA

    Link Failure and Restoral

    3 (S )

  • 5/26/2018 SS7 Overview

    57/113

    575757 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Signaling Link Management

    Signaling link activation,

    restoration and deactivation

    Link set activation

    Automatic allocation of STs and

    data links

    MTP 3 (SNM)

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    58/113

    585858 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Link Inhibiting

    Link Inhibit (LIN)

    Link Inhibit Ack (LIA)Link Uninhibit (LUN)

    Link Uninhibit Ack (LUA)

    Link Force Uninhibit (LFU)

    Link Local Inhibit Test (LLI)

    Link Remote Inhibit Test (LRI)

    MTP 3 (SNM)

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    59/113

    595959 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    S.S.P.

    S.T.P.

    S.S.P.

    S.T.P.

    Link Inhibit

    LIN

    LIA

    MTP 3 (SNM)

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    60/113

    606060 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    S.S.P.

    S.T.P.

    S.S.P.

    S.T.P.

    Link Uninhibit

    LUN

    LUA

    MTP 3 (SNM)

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    61/113

    616161 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    S.S.P.

    S.T.P.

    S.S.P.

    S.T.P.

    Routing

    ControlledUninhibiting

    LUN

    (2)LUA

    (3)

    LFU(1)

    MTP 3 (SNM)

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    62/113

    626262 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Network Congestion

    Transmit Buffer Congestion (L3)

    3 Congestion Level Thresholds

    Handled by TFC,RCT messages

    Receive Buffer Congestion (L2)

    Congested/Not Congested (no levels)

    Handled by SIB LSSU

    MTP 3 (SNM)

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    63/113

    636363 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    S.S.P.

    B

    S.T.P.

    S.S.P.

    A

    S.T.P.

    Routeset

    Congestion (L3)

    MSU(B)

    Priority 1

    TFC(B)

    Priority 2

    Congestion

    Level 2

    MTP 3 (SNM)

  • 5/26/2018 SS7 Overview

    64/113

    646464 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ISUPCall Controll

    2002, Cisco Systems, Inc. All rights reserved. 64

    ISDN User Part (ISUP)

  • 5/26/2018 SS7 Overview

    65/113

    656565 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ISDN User Part (ISUP)

    The ISDN User Part (ISUP) defines the protocol used toset-up, manage, and release trunk circuits that carryvoice and data between terminating line exchanges (e.g.,between a calling party and a called party).

    ISUP is used for both ISDN and non-ISDN calls.

    Calls that originate and terminate at the same switch do

    not use ISUP signaling. The specification for ISUP can be found in ITU-T

    recomandations Q761-Q764

    ISUP M F t

  • 5/26/2018 SS7 Overview

    66/113

    666666 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MSU

    SIF Field

    SIO

    Routing Label

    SIF

    ISUP Message

    Optional

    Part CIC

    Message

    Type

    Mandatory

    Variable Part

    Mandatory Fixed

    Part

    ISUP Message Format

    Basic Tr nk Signaling

  • 5/26/2018 SS7 Overview

    67/113

    676767 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Basic Trunk Signaling

    Call Processing

    Software

    MTP L1, L2, L3

    ISUP

    Call Processing

    Software

    MTP L1, L2, L3

    ISUP

    MTP L1, L2, L3

    STP

    LEC Switch IXC Switch

    Voice Trunk

    A-LinkA-Link

    ISUP Message Format

  • 5/26/2018 SS7 Overview

    68/113

    686868 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ISUP Message Format

    Pointer to Variable Parameter 1

    Pointer to Variable Parameter n

    Pointer to Start of Optional Parameter

    Length of Variable Parameter 1

    Variable Parameter 1

    Length of Variable Parameter n

    Variable Parameter n

    Name of Optional Parameter m

    Length of Optional Parameter m

    Optional Parameter m

    Name of Optional Parameter 1

    Length of Optional Parameter 1

    Optional Parameter 1

    End of Optional Parameter

    Routing Label

    Trunk Circuit Identification Code (2)

    Message Type

    Mandatory Parameter 1

    Mandatory Variable Parameters

    Optional Parameters

    MTP

    MTP

    ISUP

    Data

    Mandatory Parameter p

    ISUP (Si l C ll)

  • 5/26/2018 SS7 Overview

    69/113

    696969 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ISUP (Simple Call)

    OriginateIAM

    ACM

    ANM

    Speech

    Ringback Ring

    SpeechREL

    Onhook

    RLC

    Sending an Initial Address Message

  • 5/26/2018 SS7 Overview

    70/113

    707070 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Sending an Initial Address Message

    STP STP

    SSP 1 SSP 2

    IAM

    1. SSP 1Connects via D-link

    SSP 1 Originated

    SSP 1 will set a time (TIAM20-30 seconds)

    and wait for a response

    2. SSP 2SSP will identify and busy the incoming trunk

    Translate the dialed digits

    (check the status of the called partys line)

    Encode and transmit an Address Complete Message (ACM)

    If a Continuity Check is to be done on the trunk, the ACM is delayed

    SS7 Voice Trunk

    Initial Address Message Format

  • 5/26/2018 SS7 Overview

    71/113

    717171 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SIODPC - OPC - SLS

    Circuit Identification Code

    Message Type (IAM)

    Nature of Connection Indicators

    Forward Call Indicators

    Calling party's Category

    Pointer to User Service Info

    Pointer to Called Party Number

    Length Indicator Called Party Number

    Pointer to Optional Part

    Length Indicator USI

    User Service Information

    Called Party Number

    Routing Label

    Mandatory Fixed Part

    Mandatory VariablePart

    End of Opt Parms

    Opt Parms

    Initial Address Message Format

    Initial Address Message

  • 5/26/2018 SS7 Overview

    72/113

    727272 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Initial Address Message

    Parameter Type Length

    Message Type

    Nature of Connection Indicators

    Forward Call Indicators

    Calling Partys Category

    User Service Information

    Called Party Number

    Calling Party Number

    Charge Number

    Originating Line Information

    Transit Network Selection

    Carrier SelectionService Code

    Carrier Identification

    Original Called Number

    Redirecting Number

    Redirection Number

    F

    F

    F

    F

    V

    V

    O

    O

    O

    O

    OO

    O

    O

    O

    O

    1

    1

    1

    2

    4

    4

    2-11

    6-12

    3-9

    33

    3

    5

    5

    6-9

    6-9

    Nature of Connection Indicators - Contains satellite

    indicator, continuity check indicator

    Forward Call Indicators - Information concerning

    the type of signaling used to this point (interworking

    or all SS7), and end to end transfer options

    Calling Partys Category- information concerningthe service category (ordinary/test) of the calling

    party

    User Service Information - describes the nature of

    the communication (i.e., voice, data, etc.)

    Called Party Number - contains address information

    for the calls destination

    Sending an Address Complete Message

  • 5/26/2018 SS7 Overview

    73/113

    737373 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP STP

    SSP 1 SSP 2

    IAM

    SS7 Voice Trunk

    Sending an Address Complete Message

    ACM

    4. Local Exchange will stop timer TIAM20-30

    3. SSP SSP sends the ACM in the backwards direction to indicate to the

    originating switch that all of the routing information required to

    complete the call has been received

    Address Complete Message

  • 5/26/2018 SS7 Overview

    74/113

    747474 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Address Complete Message

    Optional Backward Call IndicatorsCause Indicators O

    O5-6

    Parameter Type Length

    Message Type

    Backward Call Indicators F

    F

    2

    1

    3

    Backward Call Indicator - information consisting of the charge indicator, called partys status, interworking

    indicator

    Optional Backward Call Indicator - information of relevance to the originating exchange or calling party and

    consisting of the in-band information indicator and call forwarding may occur indicator

    Cause Indicators - information consisting of coding standard, location (international network, local private

    network, ), cause value (no route to destination, subscriber absent, ), and diagnostics.

    Sending an Answer Message

  • 5/26/2018 SS7 Overview

    75/113

    757575 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STP STP

    SSP 1 SSP 2SS7 Voice Trunk

    Sending an Answer Message

    IAM

    ACM

    6. SSP 1SSP 1 will begin any required billing

    on receipt of an ANM.

    Conversation begins

    5. SSP 2When called subscriber answers SSP 2 sends and answer message ANM .

    ANM

    Answer Message

  • 5/26/2018 SS7 Overview

    76/113

    767676 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Parameter Type Length

    Message Type

    Backward Call Indicators O

    F

    2

    1

    Answer Message

    Backward Call Indicator - information consisting of the charge indicator, called partys status, interworking

    indicator

    Release (REL) and Release Complete (RLC)

  • 5/26/2018 SS7 Overview

    77/113

    777777 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SSP 1 SSP 2

    STP STP

    SS7 Voice Trunk

    Release (REL) and Release Complete (RLC)

    1 or 2. SSP 1 or 2A REL message can be sent in either direction

    to indicate that the specified circuit (CIC) is being

    released from the connection. The circuit is

    released before the REL is sent but it not idleduntil a RLC is received

    2 or 1. SSP 1 or 2The RLC is sent in response to an REL to confirm that the indicated circuit has been

    placed in an idle state. The switch sets a guard timer (0.5 to 1 second). It will not seize

    that circuit until the guard timer expires.

    IAM

    ACM

    ANM

    RELRLC

    ISUP (REL Message Format)

  • 5/26/2018 SS7 Overview

    78/113

    787878 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ISUP (REL Message Format)

    SIO

    DPC - OPC - SLS

    Circuit Identification Code

    Message Type (REL)

    Pointer to Cause Indicators

    Pointer to Optional Part

    Length Indicator for Cause Indication

    Cause Indicators

    First Opt Parameter Name

    Length Ind. Last Optional Parm

    Length Ind. 1st Optional Parm

    1st Optional Parm

    Last Optional Parameter Name

    Last Optional Parm

    Routing Label

    Optional Part

    Mandatory VariablePart

    End of Opt Parms

    Release and Release Complete Messages

  • 5/26/2018 SS7 Overview

    79/113

    797979 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Parameter Type Length

    Message Type

    Cause Indicators V

    F

    3-4

    1

    Release and Release Complete Messages

    Release (REL)

    Parameter Type Length

    Message Type F 1

    Release Complete (RLC)

    Other messages, like the Reset Circuit (RSC) can also trigger an RLC

    Cause Indicators - information consisting of coding standard, location (international network, local private

    network, ), cause value (no route to destination, subscriber absent, ), and diagnostics.

    Sending a Continuity Check (COT)

  • 5/26/2018 SS7 Overview

    80/113

    808080 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Sending a Continuity Check (COT)

    STP STP

    SSP 1 SSP 2

    COT

    1. SSP 1The Nature of Connections Indicators in the IAM

    indicates whether a Continuity check is to be

    performed on this circuit, or if a Continuity check

    is being performed on some previous circuit

    2. SSP 2SSP 2 will not send an ACM until it has an indication that either:

    No Continuity checks are being done, or

    Any and all Continuity checks are successful.

    SS7 Voice Trunk

    IAM

    COT - a test used to verify that an SS7 bearer circuit is functioning correctly

    it generally involves a combination of tone generation, tone detection, and

    loopback circuitry to verify physical continuity of a circuit

    Continuity Message

  • 5/26/2018 SS7 Overview

    81/113

    818181 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Parameter Type Length

    Message Type

    Continuity Indicators F

    F

    1

    1

    Continuity Message

    Continuity check indicators - the value of the parameter is continuity check failed

    or continuity check successful

    Subscriber Busy

  • 5/26/2018 SS7 Overview

    82/113

    828282 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SSP 1 SSP 2

    STP STP

    SS7 Voice Trunk

    Subscriber Busy

    2. SSP 1The SSP will release the outgoing trunk, send an

    RLC to the distant end

    1. SSP 2Upon receiving an IAM the called partys line is checked for its busy/idle status.

    In the event that the called partys line is busy, a busy signal is returned to the

    calling party. The busy signal can be played from the terminating, intermediate, or

    originating switch

    The SSP releases the trunk that was indicated in the IAM. It sends a REL with a

    cause indicator of subscriber busy

    IAM

    REL

    RLC

    Release Message

  • 5/26/2018 SS7 Overview

    83/113

    838383 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Parameter Type Length

    Message Type

    Cause Indicators V

    F

    3-4

    1

    Release Message

    Diagnostic (if any)

    8

    1

    ext

    0/1

    ext

    Coding Standard Spare General

    Location

    Cause Value

    (class) (value in class)

    1234567

    Cause Indicators - information consisting of coding standard, location (international network, local private

    network, ), cause value (no route to destination, subscriber absent, ), and diagnostics.

    Trunk Release Procedure

  • 5/26/2018 SS7 Overview

    84/113

    848484 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SSP 1 SSP 2

    STP STP

    SS7 Voice Trunk

    Trunk Release Procedure

    1. SSPA REL has been sent, the SSP expects an RLC as a confirmation from the far end.

    The trunk is maintained in a software busy until an RLC is received.To guard against possibility of a lost RLC, 2 timers are started when the REL is sent.

    These are the TREL(4-6 seconds) and the TREL, 1(1minute).

    If timer TREL,1 expired before an RLC is received, the trunk will be removed from

    service and maintenance will be notified.

    An RSC is sent to the far end at one minute intervals until an RLC is received, or

    maintenance intervenes.

    REL

    RSC

    REL

    REL

    Glare

  • 5/26/2018 SS7 Overview

    85/113

    858585 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Glare

    STP STP

    SSP SSP

    IAM

    Two-way trunks are subject to occasional simultaneous seizures at both ends.

    This is called dual-seizure or glare.

    Switches have a glare bit in memory for each two-way trunk. The purpose of

    the glare bit is to determine which switch is in control and which switch must

    yield. Agreements between network operators need to be in place to determine

    control offices

    SS7 Voice Trunk

    IAM

    ISUP Call Set-up Example

  • 5/26/2018 SS7 Overview

    86/113

    868686 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Setup

    Call Proceeding

    Transit Exchange Destination ExchangeOriginating Exchange

    SU Ca Set up a p e

    ISUP Call Set-up Example

  • 5/26/2018 SS7 Overview

    87/113

    878787 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Setup

    Call Proceeding

    Transit Exchange Destination ExchangeOriginating Exchange

    IAM1IAM2

    Setup

    p p

    ISUP Call Set-up Example

  • 5/26/2018 SS7 Overview

    88/113

    888888 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Setup

    Call Proceeding

    Transit Exchange Destination ExchangeOriginating Exchange

    IAM1IAM2

    Setup

    Call Proceeding

    AlertingConnectACM1

    ANM1ACM1

    ANM1

    Connect

    Alerting

    End to End Connection

    p p

    ISUP Call Set-up Example

  • 5/26/2018 SS7 Overview

    89/113

    898989 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    p p

    Setup

    Call Proceeding

    Transit Exchange Destination ExchangeOriginating Exchange

    IAM1IAM2

    Setup

    Call Proceeding

    Alerting

    ConnectACM1

    ANM1ACM1

    ANM1

    Connect

    Alerting

    End to End Connection

    DisconnectREL2

    REL1Disconnect

    RLC2RLC1

    RELREL

    RLC RLC

  • 5/26/2018 SS7 Overview

    90/113

    909090 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SCCP

    2002, Cisco Systems, Inc. All rights reserved. 90

    SCCP

  • 5/26/2018 SS7 Overview

    91/113

    919191 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SCCP provides routing and management

    functions to subsystem instances.

    Connectionless Services

    Connection-oriented Services

    SCCP (Connectionless Services)

  • 5/26/2018 SS7 Overview

    92/113

    929292 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SCCP(Connectionless Services)

    Connection Class 0 & 1

    Unitdata (UDT)

    Unitdata Service (UDTS)

    Signaling Connection ControlPart (SCCP)

  • 5/26/2018 SS7 Overview

    93/113

    939393 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Part (SCCP)

    The primary function is to support the transfer of TCAPand OMAP data between network nodes. It also

    performs:Connectionless Transfer of Data - Class 0 and 1

    Specialized Routing Functions - Global TitleTranslation (GTT)

    Subsystem Management - record status of all primaryand secondary SCPs

    SCCP Routing

  • 5/26/2018 SS7 Overview

    94/113

    949494 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    E800 TCAP CLASS TCAPACCS TCAP AIN TCAP

    SCCP

    MTP

    Routes with Point Code

    Routes with

    SubsystemNumbers

    Specialized Routing

  • 5/26/2018 SS7 Overview

    95/113

    959595 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    p g

    SSPSTP STP

    GTT Changes DPC

    GTT Could change other MTP/SCCP Values

    GTT Does not change Calling Party Address or TCAP

    DPC is the STP where GTT will be done

    Service Indicator is a Value of 3 (SCCP)

    SCCP Routing Detail

  • 5/26/2018 SS7 Overview

    96/113

    969696 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Global TitleIndicatorRtgIndicator Point CodeindicatorNatl'/Int'lIndicator SSNIndicator

    CDPA & CGPA Address Indicator

    SCCP Routing Example

  • 5/26/2018 SS7 Overview

    97/113

    979797 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    S.T.P. AS.S.P. A S.C.P. A

    S.T.P. B

    Destination Point Code =2-2-2Route on GT

    Destination Point Code = 3-3-3

    SSN = 254

    Route on PC/SSN

    E800(254)

    Global TitleTranslations performed

    at STP

    1-1-1 2-2-1

    2-2-0

    3-3-3

    Alias

    2-2-2

    SCCP Management

  • 5/26/2018 SS7 Overview

    98/113

    989898 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    SCCP Management

    Messages

    Subsystem Allowed (SSA)

    Subsystem Prohibited(SSP)

    Subsystem Status Test (SST)

    Subsystem Out of Service Request (SOR)

    Subsystem Out of Service Grant (SOG)

    Subsystem Backup Routing (SBR)

    Subsystem Normal Routing (SNR)

    Subsystem Routing Status Test (SRT)

    SCCP Management

  • 5/26/2018 SS7 Overview

    99/113

    999999 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    S.T.P.

    S.T.P.

    S.C.P.

    ACCS

    PVN

    E800

    CLAS

    AIN

    S.C.P.

    1. SSP(E800)

    2. SST(E800)

    SCCP Management

    SCCP Data

  • 5/26/2018 SS7 Overview

    100/113

    100100100 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP Level 3 Data

    Options/Protocol Class

    SCCP Message Type

    SCCP

    Data

    MTP Level 3 Data

    Routing Label

    Pointers

    Called Party Address

    Calling Party Address

    Length of Data

    Optional SCCP Parameters

    SIFSCCP

    Data

    Message Type - There are 4 types

    UnitDaTa (UDT)

    UnitDaTa Service (UDTS)eXtended UnitDaTa (XUDT)

    eXtended UnitDaTa Service (XUDTS)

    The UDTS and XUDTS are options to return

    messages on error. XUDTS is similar to UDT

    but allow for optional SCCP parameters.

    Protocol Class - indicates the type of informationtransfer that is being requested:

    Protocol Class 0 - connectionless service without

    need for sequencing

    Protocol Class 1 - connectionless service with

    sequencing

    Protocol Class 2,3,4 - associated with connection

    oriented service

    CdPA - contains information about the destination

    node and the database or application for which

    the message is destined

    CgPA - contains information about the node that

    originated the transaction

    Options: The only available option is to return the

    message on error

    Routing Indicator

  • 5/26/2018 SS7 Overview

    101/113

    101101101 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP Link Level DataRouting Label

    SCCP Message Type

    Options/Protocol Class

    Pointers

    Called Party Address

    Calling Party Address

    Length of Data

    SIF

    MTP Link Level Data

    Length Indicator

    Address Type

    ABCDEFGH

    0

    1

    Route on DPC in routing

    label and SSN in CdPA

    Route on Global Title

    Bit G of the Address Type is the Routing

    Indicator (RI). If the RI is set to zero,

    routing is based on the Global Titledigits. If the RI is set to one, routing is

    based on the DPC in the routing label

    and the SSN in the CdPA field.

    Global Title Translations (GTTs)

  • 5/26/2018 SS7 Overview

    102/113

    102102102 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Global Title Translations allow for easy management of the network and flexibility in routing.

    Routing changes can be done at the STP pair, eliminating the need for knowing network

    addresses and applications at each network elements (SSPs).

    Global Title

    316285-316287

    316288-316292

    316230-316239

    3162599

    PPC - 1-1-5

    SPC - 1-1-6PPC-1-2-0

    SPC-1-2-1

    2-1-0

    0-50-5

    0-50-1

    Point Code SSN

    6

    6

    6

    6

    6

    6

    6

    RI

    D

    D

    D

    D

    G

    PPC - Primary Point Code

    SPC - Secondary Point Code

    RI - Routing Indicator

    D - Route on DPC/SSN

    G - Route on Global Title

    The application requesting GTT will indicate

    to the STP what table (Translation Table) to

    go to.

    The STP will go to the proper table and index

    the global title digits. Within that 6 or 10

    digit number (or range) will be the routing

    information required to send this message

    on its way.

    316240-316249

  • 5/26/2018 SS7 Overview

    103/113

    103103103 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    TCAP

    2002, Cisco Systems, Inc. All rights reserved. 103

    TCAP (Message Format)

  • 5/26/2018 SS7 Overview

    104/113

    104104104 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MSU

    SIF Field

    SIO

    Routing Label

    SIF

    SCCP

    Parameter

    Info Package Type

    Transaction

    InfoOperation Info Component Info

    TCAP

    TCAP Message Format

  • 5/26/2018 SS7 Overview

    105/113

    105105105 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    TCAP messages consist of two parts

    Transaction portion

    Component portion

    TCAP (Component Types)

  • 5/26/2018 SS7 Overview

    106/113

    106106106 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Invoke (Last/Not Last)

    Return Result (Last/Not Last)

    Return Error

    Reject

    Transaction CapabilitiesApplication Part (TCAP)

  • 5/26/2018 SS7 Overview

    107/113

    107107107 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    Application Part (TCAP)

    TCAP is an application level of the protocol Documents describing TCAP are specific to a

    particular service. TCAP follows guidelinesthat can be found in ITU-Q771-Q775, and

    Recommendation T1.114.1-5 (ANSI) All TCAP messages consist of 2 portions:

    Transaction Portion - contains protocol controlinformation

    Component portion - contains protocol controlinformation and data concerning the particularapplication

    TCAP (Messaging)

  • 5/26/2018 SS7 Overview

    108/113

    108108108 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    ( g g)

    Node A Node B

    Response

    Simple Query

    Query with

    Permission

    Node B

    Response

    ConversationQuery with

    Permission

    Node A

    Conversation with

    Permission

    Conversation withPermission

    TCAP Transaction Portion

  • 5/26/2018 SS7 Overview

    109/113

    109109109 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP

    MTP

    SCCP

    Transaction

    Portion

    Component

    Portion

    TCAP Package Type

    Total Length

    Transaction ID Identifier

    Transaction ID Length

    Transaction ID

    Component Sequence Identifier

    Component Sequence Length

    Package type - spells out what type of dialogue will

    exist between these 2 applications. There are 6 types:

    Unidirectional - One way, no reply expectedQuery With Permission - Sent from originating

    application. Will not send more than one message for

    transaction. Terminating application has permission

    to terminate

    Query Without Permission - Sent from originating

    application. Will send more messages for transaction.

    Response With Permission - Sent by terminating

    application In response to Query with or without

    Permission

    Response Without Permission - Sent by terminating

    application In response to Query with or without

    Permission

    Abort - Defined for use if protocol errors are

    received

    Transaction ID - Application use this unique

    random number to correlate messages within

    same transaction.

    TCAP Component Portion

  • 5/26/2018 SS7 Overview

    110/113

    110110110 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    MTP

    MTPSCCP

    Transaction

    Portion

    Component

    Portion Component Type IdentifierComponent Length

    Component ID Identifier

    Component ID Length

    Component IdsOperation Code Identifier

    Operation Code Length

    Operation Code

    Parameter Set Identifier

    Parameter Set Length

    Parameters

    800 Service - Query

  • 5/26/2018 SS7 Overview

    111/113

    111111111 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STPSSP

    GTT STP800 SCP

    DPC = STP Alias

    OCP = SSP

    SCCP

    CdPA

    Route on GT

    TT = 254SSN = 0

    GTA = 800234

    CgPA

    Route on Destination

    SSN = 254

    SPC = SSP

    TCAP

    Query with Permission

    Invoke

    8002341111

    ANI

    LATA

    OST

    MTP

    DPC = 800 SCP

    OCP = STP

    SCCP

    CdPA

    Route on Destination

    TT = 254SSN = 254

    GTA = 800234

    CgPA

    Route on Destination

    SSN = 254

    SPC = SSP

    TCAP

    Query with Permission

    Invoke

    8002341111

    ANI

    LATA

    OST

    MTP

    800 Service - Response

  • 5/26/2018 SS7 Overview

    112/113

    112112112 2001, Cisco Systems, Inc. All rights reserved.Presentation_ID

    STPSSP

    GTT

    800 SCP

    DPC = SSP

    OCP = SCP

    SCCP

    CdPA

    Route on Destination

    SSN = 254

    CgPA

    Route on Destination

    SSN = 254

    TCAP

    Response

    Invoke

    Carrier ID

    Routing Number

    AMA Call type

    MTP

    DPC = 800 SCP

    OCP = STP

    SCCP

    CdPA

    Route on Destination

    SSN = 254

    CgPA

    Route on Destination

    SSN = 254

    TCAP

    Response

    Invoke

    Carrier ID

    Routing Number

    AMA Call type

    MTP

    No GTTs are

    necessary

  • 5/26/2018 SS7 Overview

    113/113

    End Section

    Thank You