megaco h248 slide

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

For public use IPR applies

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


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Nokia Siemens Networks Academy

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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*




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)




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




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




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




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

megaco h248 slide

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