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    1 Nokia Siemens Networks Presentation / Author / Date / Document Number

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    MEGACO/H.248Switching Core Network Signalling - M14/U4

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    Nokia Siemens Networks Academy

    Legal notice

    Intellectual Property Rights

    All copyrights and intellectual property rights for Nokia Siemens Networks trainingdocumentation, product documentation and slide presentation material, all of which are forthwithknown as Nokia Siemens Networks training material, are the exclusive property of NokiaSiemens Networks. Nokia Siemens Networks owns the rights to copying, modification,translation, adaptation or derivatives including any improvements or developments. Nokia

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

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    Document change history

    Date Version Name Change comment

    Mar 3, 08 1 Pubate Satienpoch Revised and update from M13 to M14/U4

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    Introduction

    Megaco/H.248 has been jointly developed by IETF and ITU-T

    Support separation of: Call control entity (MSS) from Bearer Control entity (MGW)

    Bearer Control entity (MGW) from transport entity (eg. ATM or IP)

    First defined in RFC3525 and H.248.1 version1

    Updated in H.248.1 v.2&3 RFC5125 (Feb 08)

    Media

    Gateway

    Controller

    Media

    Gateway

    Controller

    Media

    Gateway

    Media

    Gateway

    BICC

    IP/ATM

    Megaco/ H.248

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    H.248 based Call Bearer Control Protocol concept

    With the concept of separation of Call Control and Bearer Control entity, Call

    Bearer Control is a protocol (CBC) used between them Different applications (eg VoIP, UMTS R4&R5) have different requirements for

    CBC

    Main tasks of CBC are for example: Control bearer connection setup, modification and release

    Indication of events concerning the bearer connection

    Trigger and detection of tones and signals on the bearer

    Retrieval of statistics about the bearer connection

    IETF/ITU-T defined a basic framework for CBC based on Megaco/H.248 to avoidthe need to defined different CBC for different applications

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    CBC component

    For a CBC the following are needed:

    Framework: functional architecture, interfaces andabstract models.

    Commands: the basic communication units exchangebetween functional units defined in the framework.

    Properties: parameters and their values typically usedto describe bearers

    Events: what is detectable by MGW and reportable to

    the MSS Signals: various indications running on the bearer such

    as busy tone, dialling tone

    Statistics: describes which information is to be collected

    by the MGW about the bearer termination

    H.248 defined Framework, commands, and basic

    properties, Events, Signals and Statistics Properties, Events, Signals, and Statistics are

    defined in Packages

    Framework

    Commands

    PropertiesEvents

    SignalsStatistics

    Call Bearer Control Protocol

    H.248

    H.248Packages

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    Connection Model : Main concept for H.248

    Termination : Source or Sink ofmedia flows, it represent one ormore stream entering or leavingMGW

    Physical : Associated withphysical resource TDM

    Ephemeral : Created when

    needed such as ATM, IP

    Context :An association within thecollection of terminations

    Possible to have one or moreterminations depends onscenario such as multiparty

    call, normal 2 party call, or acall in the beginning of setupphase

    Null Context : Pools of TDMtermination which are not used

    RTP Port

    Termination

    TDM TSL

    Termination

    AAL2channel

    Termination

    TDM TSL

    Termination

    *

    Context

    Context

    Null Context

    Context

    RTP Port

    Termination

    AAL2Channel

    Termination*

    AAL2Channel

    Termination*

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    Context and its attributes

    Context ID, may be wildcarded

    Context ID 0x0 is used to indicate the NULL Context

    Context ID 0xFFFFFFFE is used to indicate a CHOOSE wildcard

    Context ID 0xFFFFFFFF is used to indicate an ALL wildcard

    Topology

    (T1,T2,Bothway)

    (T1,T2,Oneway)

    (T1,T2,Isolate)

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    Termination attributes

    Termination ID : 4 octets

    000 Reserved

    001 Ephemeral termination

    010 TDM termination

    011 - 110 Reserved

    111 Reserved for ROOT termination Id (ROOT termination ID =0xFFFFFFFF)

    Wildcarding field (1 octet) can be used in front of termination ID

    Bit 7 = 1 : All

    Bit 7 = 0 : Choose

    Descriptors which describe

    Characterizing properties of a termination (parameter of bearer)

    Signals to apply to a termination

    Event to detect and report by a termination

    Statistics accumulated on a termination

    These descriptors are manipulated by a command in the form of command parameter

    Termination Type: 3 bits X : 29 bits

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    Command

    H.248 commands are used to manipulate context and termination.

    Parameters of a command which consists of a name and a list of items Example structure of command

    Command name

    Termination id

    Local termination state descriptor

    Local Termination Descriptor, Remote Termination Descriptor

    Event descriptor

    Signal descriptor

    MGC

    MGW

    MGC

    MGW

    MGC

    MGW

    AddSubtract

    Move

    Notify ServiceChangeModifyAuditValue

    AuditCapability

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    Command

    Add: add a termination to a context and may be used to create a new context.

    Modify : modify properties, events and signals of a termination

    Subtract : remove a termination from a context. The command disconnects a Termination from itsContext. The Subtract command on the last termination in a context deletes the context.

    Move : moves a termination from one context to another

    AuditValue : return information about the current state of properties, events, signals and statistics ofTerminations

    AuditCapabilities : return information about all the possible values for Termination properties, events andsignals allowed by the MGW

    Notify : allow the MGW to informs the MGC of the occurrence of event in the MGW

    ServiceChange : allow the MGW to notify the MGC that a Termination or group of Terminations is aboutto be taken out of service or has just been returned to service, and allow MGW to announce its availabilityto an MGC (registration). The MGC may also use ServiceChange to instruct the MGW to take a

    termination or group of terminations in or out of service

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    Descriptors

    Descriptor name Description

    Media A list of media stream specifications.

    TerminationState Properties of a Termination (which can be defined in Packages) that are not stream specific.

    Stream A list of remote/local/localControl descriptors for a single stream.

    Local Contains properties that specify the media flows that the MG receives from the remote entity.

    Remote Contains properties that specify the media flows that the MG sends to the remote entity.

    LocalControl Contains properties (which can be defined in packages) that are of interest between the MG and the MGC.

    Events Describes events to be detected by the MG and what to do when an event is detected.

    Signals Describes signals applied to Terminations.

    Audit In Audit commands, identifies which information is desired.

    Packages In AuditValue, returns a list of Packages realized by Termination.

    ServiceChange In ServiceChange, what, why service change occurred, etc.

    ObservedEvents In Notify or AuditValue, report of events observed.

    Statistics In Subtract and Audit, report of Statistics kept on a Termination.

    Error Contains an error code and optionally error text; it may occur in command replies and in Notify requests.

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    Media Descriptor

    Media Descriptor : specifies parameters for all the media streams

    Termination state descriptor Stream descriptor

    Local Control descriptor

    Local descriptor

    Remote descriptor

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    Termination State descriptor

    Termination state descriptor : properties that are not stream dependent

    The ServiceStates Property describes the overall state of the termination (notstream specific)

    "Test" indicates that the termination is being tested

    "OutOfService indicates that the termination cannot be used for traffic

    "InService" indicates that a termination can be used or is being used for normal traffic

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    Stream descriptor

    Stream descriptor : parameter of a single bidirectional stream

    Local Control descriptor :

    Mode property : Inactive: The termination does not pass any media for the stream.

    SendOnly: The termination passes media for the stream from the interior to the exterior of the context.

    RecvOnly: The termination passes media for the stream from the exterior to the interior of the context.

    SendRecv:The termination passes media for the stream both into and out of the context.

    LoopBack:The termination loops received media for the stream back to the sender.

    Local /Remote descriptor : reserve and commit MGW resources for media decoding and encoding for the given stream and

    termination

    MGW includes these descriptors in its response to indicate what it is actually prepared to support.

    Local refers to the media received by the MGW and Remote refers to the media sent by the MGW

    main goal of local and remote descriptors is to define the address information where we want toreceive the media (Local) or where we will send the media (Remote).

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    Event Descriptor

    Event Descriptor :

    contains Request ID + list of events for MGW to detect and report

    Events can have parameters

    To allow an event description to have variation in meaning without creating largenumber of event

    When an event is processed and found to be present in that descriptor ("recognized"), thedefault action of the MG is to send a Notify Command to the MGC

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    Observed Event descriptor

    Observed Event descriptor

    Supplied with Notify command to inform MSS of event detected in MGW Request ID of the triggered Event Descriptor + event detected

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    Signal descriptor

    Signals descriptor

    Contain the set of signals that MGW is asked to apply to a Termination

    Signal possibly have parameters

    There are three types of signals: OnOff (OO): the signal lasts until it is turned off;

    TimeOut (TO): the signal lasts until a specific period of time expire;

    Brief (BR): the signal will stop on its own unless a new Signals Descriptor is applied that causes it to stop.

    Signal direction: Indicates the directionality applied to a termination

    External:The signal is applied on a termination so that none of the other terminations in the context hear it.

    Internal:The other terminations in the context hears it.

    Bothway:All the terminations in the context hears it as well as it being sent external to the MGW.

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    Audit descriptor

    Audit descriptor

    specifies what information is to be audited

    specifies the list of descriptors and/or individual properties to be returned

    Possible items in Audit Descriptors are:

    Events

    Media

    Signals

    ObservedEvents

    Statistics

    Packages

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    ServiceChange descriptor

    ServiceChange descriptor contains, for example

    ServiceChange Method eg. Graceful, Force, Restart

    ServiceChange Reason eg. Cold boot, MG impending failure, MGC impending failure

    ServiceChange Delay

    ServiceChange Profile, specify the profile of the protocol supported

    ServiceChange Version, contains protocol version

    Timestamp

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    Statistics descriptor

    Statistics descriptor

    provides information describing the status and usage of a termination

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    Package descriptor

    Package descriptor

    Used only with the AuditValue command

    Returns a list of packages realized by the termination

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    Error descriptor

    Error descriptor

    If a responder encounters an error when processing a transaction request, it must include anError Descriptor in its response

    It consists of an IANA-registered error code, optionally accompanied by an error text

    ITU-T Rec. H.248.8 contains a list of valid error codes and error descriptions

    IANA (Internet Assigned Numbers Authority)

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    Transaction and Message

    Commands are grouped into Transaction each of which identified by Transaction ID.

    Transaction contains one or more Actions.

    An Action consists of a list of Commands that are limited to operating within a single Contextwhich are specified by a ContextID.

    All commands within the same actions will be executed sequentially in the order described inthe transaction.

    Several transactions can be later concatenated into a message. Such transactions remainindependent though and no order is implied by such a concatenation.

    A Transaction can be: TransactionRequests

    TransactionReply (corresponding responses to a TransactionRequest are received in a single reply)

    TransactionPending (is used to periodically notify the receiver that a Transaction has not completed yet

    Example form a Transaction:

    TransactionRequest (TransactionId=12345

    ContextId=* Add(T3, )

    ContextId=C1 Modify(T1 ) )

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    Transaction and Message

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    Transport and Codes

    -NSN support both SCTP and TCP for Transport-SCTP Server port number

    - 2944 : Text Encoding (ABNF: Augmented Backus-Naur form)

    - 2945 : Binary Encoding (ASN.1 : Abstract Syntax Notation 1)

    M3UA

    IP

    SCTP

    H.248

    UDPTCP

    IP

    SCTP

    H.248

    IP

    SCTP

    H.248

    MTP3b

    ATM

    SAAL

    H.248

    Possible transports defined

    in H.248/Megaco

    3GPP defined stack

    for pure IP

    3GPP defined stack

    for pure ATM

    3GPP defined stack

    for mixed IP&ATM

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    Non Call-Related Transaction

    Transaction used in ITU-T Recommendation Q.1950 Procedure defined in 3GPP TS 23.205

    BIWF_Service_Cancellation_Indication MGW Out of Service

    BIWF_Lost_Communication MGW Communication Up

    BIWF_Service_Restoration_Indication MGW Restoration

    BIWF_Registration MGW Register

    BIWF_Re-Registration MGW Re-register

    CCU Ordered BIWF Re-Registration (G)MSC Server Ordered Re-register

    CCU Initiated Service Restoration (G)MSC Server Restoration

    CCU Initiated Service Cancellation (G)MSC Server Out of Service

    BIWF_Service_Cancellation_Indication Termination Out-of-Service

    BIWF_Service_Restoration_Indication Termination Restoration

    Audit_Values Audit Value

    Audit_Capabilities Audit Capability

    BIWF_Capability_Change Capability Update

    MGW Resource Congestion Handling - Activate

    MGW Resource Congestion Handling - Indication

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    Call-Related Transaction

    Transaction used in ITU-T Recommendation Q.1950 [23] Procedure defined in 3GPP TS 23.205 [2] and 3GPP TS 23.153 [1]

    Change_Topology Change Flow Direction

    Join Join Bearer Termination

    Isolate Isolate Bearer Termination

    Establish_BNC_Notify+(tunnel) Establish Bearer

    Prepare_BNC_Notify+(tunnel) Prepare Bearer

    Cut_Through Change Through-Connection

    Not defined in Q.1950 Activate Interworking Function

    Cut_BNC (include several procedures). Release Bearer (Release Bearer and Release termination)

    BNC Established Bearer Established

    BNC Release Bearer Released

    Insert_Tone Send Tone

    Insert_Annoucement Play Announcement

    Signal Completion Announcement Completed

    Detect_Digit Detect DTMF

    Insert_Digit Send DTMF

    Detected digit(BIWF) Report DTMF

    Confirm_Char Confirm Char

    Modify_ Char Modify Char

    Reserve_Char_Notify Reserve Char

    BNC Modified Bearer Modified

    Echo Canceller Activate Voice Processing Function

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    Call-Related Transaction (Cont.)

    Transaction used in ITU-T Recommendation Q.1950 [23] Procedure defined in 3GPP TS 23.205 [2] and 3GPP TS 23.153 [1]

    BNC Connected No definition yet

    BNC Modification failure Bearer Modified Failed

    Tunnel (MGC-MGW) Tunnel Information Down

    Tunnel (MGW-MGC) Tunnel Information Up

    Insert Tone Stop Tone

    Insert Announcement Stop Announcement

    Detect Digits Stop DTMF Detection

    Insert Digit Stop DTMF

    Signal.Completion Tone Completed

    Not defined Reserve Circuit

    Not defined Command Rejected

    Not defined TFO Activation

    Not defined Codec_Modify

    Not defined Optimal Codec and Distant List_Notify

    Not defined Distant Codec List

    Modify Char Modify Bearer Characteristics

    Not defined IWF Protocol Indication

    Not defined Bearer Modification Support

    Not defined CTM repor

    Not defined Prepare IP transport

    Not defined Modify IP transport address

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    Packages

    Properties, Events, Signals, and Statistics are defined in the Package

    PackageID uniquely identifies the package and the ID of the item uniquelyidentifies the item in that package

    Packages can also be defined by any organisation; a vendor could even

    define its own packages to adapt the functionality to its architecture. Thisis regarded as private packages.

    Private packages are required to either support proprietary functionalityand/ or to enhance existing defined public functionality. For example,

    NokiaTrace package has been proposed to the 3GPP. It enablesactivation of GSM/UMTS trace from Nokia MSC Server to Nokia MGW

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    Package ID are reserved by IANA, can be found on

    http://www.iana.org/assignments/megaco-h248

    Public package : defined in H.248, ITU-T Q.1950, and 3GPP TS 29.232 specification

    Private package : Nokia, Ericsson,

    Private Packages

    http://www.iana.org/assignments/megaco-h248http://www.iana.org/assignments/megaco-h248http://www.iana.org/assignments/megaco-h248http://www.iana.org/assignments/megaco-h248
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    Profiles

    Defines how the H.248 protocol is used and what functionality is supported by the MGW

    Specifies what options associated with H.248 have been used:

    Naming Convention: Addressing associated with the name of MGC/MG

    Termination Names: The termination identity structure

    Topology Descriptor: The topology descriptor used by one profile

    TimeStamps: Specifies whether timestamps will be used in the ServiceChange and/or Notifycommands

    Transport: Specifies what transport are supported by the profile

    Encoding: Specifies what encoding is supported by the profile

    Packages: Specifies the packages that are supported in this profile

    Procedure: Specifies the procedures that are associated with the profile

    A profile is identified by a Name (IANA registered) and a Version