SIGTRAN Signaling Analysis

7/29/2019 SIGTRAN Signaling Analysis

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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

SIGTRAN SignalingAnalysis


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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page2

Foreword

With the development of softswitch network, there is a need

for media stream or signaling delivery across different

networks, such as TDM, ATM and IP network. How to

implement signaling transport across different networks isone topic of this course.


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Objectives

Upon completion of this course, you will be able to:

Know protocol stack and main functions of SIGTRAN

Know the basic concepts, signaling message and procedures

of SCTP

Know the procedures and implementation of M3UA and M2UA


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References

RFC 2960 Stream Control Transmission Protocol

RFC 3331 Signaling System 7 (SS7) Message Transfer

Part 2 (MTP2) User Adaptation Layer

RFC 3332 Signaling System 7 (SS7) Message Transfer Part

3 (MTP3) User Adaptation Layer (M3UA)


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Contents

1. SIGTRAN Introduction

2. SCTP Protocol

3. M2UA Protocol

4. M3UA Protocol


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Contents


2. SCTP Protocol

3. M2UA Protocol

4. M3UA Protocol


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Signaling Transport (SIGTRAN) protocol stack is defined by

the SIGTRAN workgroup of the Internet Engineering Task

Force (IETF) for interworking purposes between the

Signaling System No. 7 (SS7) and the IP.

It supports transmission of switched circuit network (SCN)

signaling across IP network.

It includes transport protocol and adaptation protocol.

SIGTRAN Introduction


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Traditional SS7 Signaling Protocol

Stack

MTP1

MTP2

BSSAP

SCCP

TCAP TUP

MAP/CAP

MTP3

ISUP

DSS1

Q.921 LAPV5

V5.2


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IP

MTP3

SCTP

M3UA

M2UA M2PA IUA V5UA

DSS1 V5.2

BSSAP

SCCP

TCAP TUP

MAP/CAP

ISUP

Adaptation Layer

Transport Layer

SIGTRAN Protocol Stack


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Contents


2. SCTP Protocol

3. M2UA Protocol

4. M3UA Protocol


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Contents

2 SCTP Protocol

2.1 SCTP Introduction

2.2 SCTP Terms

2.3 SCTP Functions

2.4 SCTP Message Format

2.5 SCTP Signaling Procedures


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SCTP overcome these

limitations of TCP to

match the requirements

of transport of SCN

signaling across the IPnetwork.

SCTPTCP

The limitations include the following:

-head-of-line blocking

-Poor Real time reliability

-Its difficult to support multi-homed hosts.

-Its vulnerable to denial of service (DoS)

attacks.

Motivation of SCTP development

SCTP (Streaming Control Transmission Protocol) is a reliable transport protocol operating on

top of a connectionless packet network such as IP.

Before SCTP, UDP or TCP is used to transfer signaling across IP network. UDP is one kind of

connectionless transport protocol. It can not match the transport quality requirements of PSTN

signaling.


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SCTP Features

Position in protocol stack

IP

SCTP

M3UA/M2UA/M2PA

Same as UDP and TCP, SCTP locates in

transport layer.

SCTP is based on TCP and overcomes its

limitations. SCTP provides services not only

for SIGTRAN.


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SCTP Features

SCTP advantages

reliability

security

Explicit packet-oriented delivery Sequenced or in-sequence delivery of user

message within streams

Support of multi-homing at either or both

ends of an association

A cookie mechanism is employed during

the association initialization to provide

protection against security attacks.

Multiple streams can be established in one

association. Each stream transfers user

message dependently.


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Contents

2 SCTP Protocol


2.2 SCTP Terms

2.3 SCTP Functions




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SCTP Transport Address

Transport Address = IP Address +

SCTP Port Number

Host A

IP

SCTP

SCTP Port

Number

IP Address

IP Address SCTP Port Number

10.105.28.92 3180

10.105.28.92 3181

10.105.28.93 3180

Examples: The following table lists three different transport addresses.


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Host and Endpoint

SCTP port 1 SCTP port 2

Host

IP1 IP2

User 1 User 2

IP Layer

SCTP

Layer

Application

Layer

Host: It is a physical entity that can configure one or more IP address,

such as a computer.

SCTP Endpoint: The logical sender/receiver of SCTP packets. It is

represented as a set of transport address with the same SCTP port

number.

Port 1

Port 2


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Association and Stream

Host 1 Host 2

Stream AStream B

Association:

A protocol relationship between two SCTP

endpoints is initiated by a four-way handshake.

Stream:

A uni-directional logical channel established from

one to another associated SCTP endpoint.

Endpoint

AEndpoint

B

Association

One association

includes one or more

streams. One stream

only belongs to oneassociation.


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Path and Primary Path

MGC SG

Path 0

Path 1

Path 2Path 3

10.11.23.14:3180

10.11.23.15:3180

10.11.23.16:3181

10.11.23.17:3181

Primary Path: The primary path is the destination and source

address that will be put into a packet outbound to the peer

endpoint by default. Other paths will be selected only when

the primary path is faulty.

Path: The route taken by the SCTP packets sent by one

SCTP endpoint to a specific destination transport address of

its peer SCTP endpoint. An association includes multiple path.

There are 4 path between MGC and SG in the above figure.


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Notes:

TSN and SSN are allocated independently.

TSN and SSNTSN

Transmission Sequence Number

SSN

Stream Sequence Number

Definition An sequence number is attached to

each chunk by sender SCTP endpoint

in association.

An sequence number is attached to

each chunk by sender SCTP

endpoint in stream.

Function It ensures data reliability by permitting

the receiving SCTP endpoint to

acknowledge its receipt and detect

duplicate deliveries.

It ensures data sequence in a

stream.

Validity association stream

Value Range 32 bits and unique inside association 16 bits and unique inside stream


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There are two streams between SCTP endpoint A and B. The chunks A, B, C,

D should be sent and A, B should be in sequence. A, B, C are sent through

stream 1 and D through 2. TSN and SSN are listed in the following table:

Suppose:

Example: TSN and SSN Allocation

Chun

k

TSN SSN Stream

A 1 1 1

B 2 2 1

C 3 3 1

D 4 1 2


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Congestion Window (CWND)

An SCTP variable that limits the data, in number of bytes, a sender can send to

a particular destination transport address before receiving an acknowledgement.

Transmission Control Block (TCB)

An internal data structure created by an SCTP endpoint for each of its existingSCTP associations to other SCTP endpoints. TCB contains all the status

and operational information for the endpoint to maintain and manage the

corresponding association.

An SCTP variable a data sender uses to store the most recently calculated

receiver window of its peer, in number of bytes. This gives the sender an

indication of the space available in the receivers inbound buffer. During theinitialization of association, two endpoints will exchange their RWND.

Receiver Window (RWND)


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Contents

2 SCTP Protocol


2.2 SCTP Terms

2.3 SCTP Functions




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Functional View of SCTP

Association

Startup

And

Takedown

Path Management

Packet Validation

Chunk Bundling

Acknowledgementand

Congestion Avoidance

User Data

Fragmentation

Sequenced deliverywithin streams


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SCTP Functions

Association Startup and Takedown

Function: initializing association before data delivery

Startup: cookie mechanism, four-way handshake

Takedown: graceful close, ungraceful close


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SCTP Functions

Sequenced delivery within streams

Function: delivering user message in sequence

Mechanism: transmission in stream, SSN


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SCTP Functions

User Data Fragmentation

Function: SCTP fragments user messages to ensure that the

SCTP packet passed to the lower layer conforms to the path MTU.

Mechanism: sender fragment, receiver reassemble.

Acknowledgement and Congestion Avoidance

Function: It is used to provide transmission reliability and

congestion avoidance.

Mechanism: TSN keeps reliability, window mechanism avoid

congestion


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SCTP Functions

Chunk Bundling

Function: transmitting upper user message more effectively in

SCTP level

Mechanism: bundling many user messages into a single SCTP

packet.Packet Validation

Function: detecting packet validation and provide protection against

attacks and data corruption in network.

Mechanism: verification tag, checksum


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SCTP Functions

Path Management

Function: monitoring path reachability

Mechanism: heartbeat


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Contents

2 SCTP Protocol


2.2 SCTP Terms

2.3 SCTP Functions




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Notes: The total length of a chunk (including Type, Length and Value fields) MUST be

a multiple of 4 bytes. If the length of the chunk is not a

multiple of 4 bytes, the sender MUST pad the chunk with all zero

bytes and this padding is not included in the chunk length field.

SCTP Packet Format16bit16bit

Source Port Destination Port

Verification Tag

Checksum

Type Flags Length

Chunk Value

Type Flags Length

Chunk Value

Chunk n

Chunk 1

Common

Header


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SCTP Chunk Type 1Chunk Type (ID) Explanation

DATA (0) Payload DataINIT (1) This chunk is used to initiate a SCTP association between two

endpoints.

INIT ACK (2) The INIT ACK chunk is used to acknowledge the initiation ofanSCTP association.

COOKIE ECHO (10) This chunk is used only during the initialization of an association.It is sent by the initiator of an association to its peer to complete

the initialization process.

COOKIE ACK (11) It is used to acknowledge the receipt of a COOKIE ECHO chunk.

SACK (3) This chunk is sent to the peer endpoint to acknowledge receivedDATA

chunks and to inform the peer endpoint of gaps in the received

subsequences of DATA chunks as represented by their TSNs.


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SCTP Chunk Type 2Chunk Type (ID) Explanation

HEARTBEAT (4) An endpoint should send this chunk to its peer endpoint to probethe reachability of a particular destination transport address

defined in the present association.

HEARTBEAT ACK (5) a response to a HEARTBEAT chunkABORT (6) Close the association.SHUTDOWN (7) An endpoint in an association use this chunk to initiate a

graceful close of

the association with its peer.

SHUTDOWN ACK (8) This chunk MUST be used to acknowledge the receipt of theSHUTDOWN chunk at the completion of the shutdown process.

SHUTDOWN COMPLETE (14) This chunk MUST be used to acknowledge the receipt of the

SHUTDOWN

ACK chunk at the completion of the shutdown process.


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Format of INIT Chunk

32bit

Type=1 Length

Initial Tag

Number Of

Outbound Streams

Initial TSN

Optional/Variable-Length

Parameters

Advertised Receiver Window Credit

Trunk

Flag

Number Of Inbound

Streams


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Format of DATA Chunk

32bit

Type=0 Reserve UU B Length

Stream ID SSN

Payload Protocol Identifier

User Data

E

TSN


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Format of SACK Chunk32bit

Type=3 Length

Cumulative TSN Ack

Number Of GapAck Blocks = N

Duplicate TSN #1

Advertised Receiver Window Credit

Trunk

Flag

Number OfDuplicate TSNs = X

Gap Ack Block #1

Start

Gap Ack Block #1

End

Duplicate TSN #x

Gap Ack Block #n

Start

Gap Ack Block #n

End


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Contents

2 SCTP Protocol


2.2 SCTP Terms

2.3 SCTP Functions




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INIT_ACK

SACK

Initialization

Four-wayhandshake

INIT

COOKIE ECHOCOOKIE ACK

DATA

SACK

DATA

Data

transmission

Initial Tag, OS, MIS

State COOKIE, Tag

State COOKIE

TSN, SSN, Stream ID

SCTP Association Initialization and

Data TransmissionEndpoint A Endpoint B


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SHUTDOWNSHUTDOWN ACK

SHUTDOWN COMPLETE

Endpoint A Endpoint B

Graceful Close of SCTP

Association


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Summary

The basic information of SCTP is introduced in this chapter,

such as the SCTP features, main function and startup and

takedown of SCTP association. The concepts include

transport address, association, stream, TSN, SSN, etc.

These are very useful to understand SCTP and SIGTRAN.


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Contents


2. SCTP Protocol

3. M2UA Protocol

4. M3UA Protocol


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Contents

3 M2UA Protocol

3.1 Concepts and Functions

3.2 Messages and Procedures

3.3 State Transition

3.4 Implementation of M2UA


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M2UA Overview

M2UA is SS7 MTP2 User Adaptation Layer protocol.

M2UA is defined by RFC3331.

M2UA transport SS7 MTP2 user message over IP using SCTP as

the underlying transport protocol.

M2UA is applied to transport signaling between Signaling

Gateway (SG) and Media Gateway Controller (MGC).


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Primitives defined by M2UA:

Primitives between M2UA and MTP3

Primitives between M2UA and MTP2

Primitives betweenM2UA and SCTP

Primitives between M2UA and Layer

Management

MTP3

M2UA

SCTP

IP

LM

The primitives interaction between M2UA and MTP2 is

implemented by NIF. From protocol view, M2UA is a middle layer

between MTP3 and MTP2. The signaling message of M2UA is

transfer through SCTP.

M2UA Protocol Stack


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M2UA Protocol Stack

SEP MGC

ISUP

MTP3

MTP2

MTP1

ISUP

MTP3

M2UA

SCTP

IP

M2UA

SCTP

IP

MTP2

MTP1

SS7 SIGTRANSG

PSTN IP(NIF)


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Application Server (AS)

A logical entity serving a specific application instance. An AS is modeled as an

ordered list of one or more related Application Server Processes.

Application Server Process (ASP)

A process instance of an Application Server. Examples of Application Server

Processes are active or standby MGC instances. Only the active ASP provides

service.

M2UA Terms


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Signalling Gateway (SG)

An SG is a signaling agent at the edge of the IP network. An SG appears to the

SS7 as one or more Signaling Link Terminals that are connected to one or more

Signaling Data Links in the SS7 network. An SG contains a set of one or more

unique Signaling Gateway Processes, on which one or more is normally actively

processing traffic. Where an SG contains more than one SGP, the SG is alogical entity.

Signalling Gateway Process (SGP)

A process instance that uses M2UA to communicate to and from a Signaling LinkTerminal. It serves as an active, backup or load-sharing process of a Signaling

Gateway.

M2UA Terms


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Interface IdentifierIID

The Interface Identifier identifies the physical interface at the SG for which the

signaling messages are sent/received. The format of the IID parameter can be

text or integer. The values used are of local significance only, coordinated

between the SG and ASP.

Stream 1

AS

ASPNo.7 Link1

Interface ID ASP

No.7 Link2Stream 2

Interface ID

Active

Inactive

Logical view of relationship in an SGP

Note:1. IID is mapped to an SCTP association/stream.

2. A SGP MAY support more than one AS. An AS MAY support more than one IID.

M2UA Terms


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SG MGC

NIF

MTP2 M2UA

SCTP

M2UA

SCTP

MTP3

UP

MTP2 M2UA primitive

M2UA SCTP primitive

M2UA message

SCTP M2UA primitive

M2UA MTP3 primitive

M2UA Services and Functions


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M2UA Services

Support for MTP Level 2 / MTP Level 3 interface

boundary

It provides the equivalent set of services to its users as

provided by the MTP2 to MTP3.

Support for communication between Layer

Management modules on SG and MGC

The M-ERROR message is used to indicate an error with a

received M2UA message in order to facilitate reporting of

errors that arise because of the backhauling MTP Level 3

scenario.



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M2UA Services

Support for management of active associations between SG

and MGC

A set of primitives between M2UA layer and the Layer Management

are defined to help the Layer Management manage the associations

between the SG and the MGC.

Maintenance of SCTP/ASP/AS status

The M2UA layer may need to inform the status of the SCTP

association(s) to the Layer Management. The Layer Management

may also need to inform the M2UA layer of an AS/ASP status (i.e.,

failure, active, etc.) .



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M2UA Functions

Mapping

Support for the management of SCTP associations between

the SGPs and ASPs

Maintenance of ASP status on SGP

SCTP Specifics

SCTP Stream Management

Seamless SS7 Network Management Interworking

Flow Control / Congestion

Audit of SS7 Link State



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Contents

3 M2UA Protocol






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M2UA Message Format

M2UA message contains Common Message Header, M2UA Message Header

and several M2UA messages with variable length.

32bit

Common Message

Header

M2UA Message

Header

M2UA

Message 0

Spare8Message length32

Tag16

Message class(8) Message typ8Version8

Length16Interface identifier32

Parameter tag16 Parameter length16Parameter value

Parameter tag16 Parameter length16Parameter value

Parameter length16 M2UAMessage n

M2UA M


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M2UA Messages

Message Type DescriptionDATA It contains an SS7 MTP2-User Protocol Data Unit (PDU)

(mandatory) and Correlation Id (optional).

Data Acknowledge It acknowledges data message with Correlation Id.

Establish Request When the MGC desires the SS7 link to be in-service, it will send the

EstablishRequest message to SGP and start a timer.

Establish Confirmation SGP sends it to MGC to indicate SS7 link is established.Release (Request,

Indication,

Confirmation)

Request is used to release the channel. Confirm and Indication

messages are used to indicate that the channel has been released.

State Request The State Request message can be sent from a MGC to cause an action

on a particular SS7 link supported by the SGP.

State Confirm The State Confirm message will be sent by the SGP in response to a

State

Request from the MGC.

State Indication It is sent from a SGP to an ASP to indicate a condition on a SS7 link.

MTP2 User Adaptation Messages

M2UA M


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M2UA Messages

Message Type Description

Congestion Indication It is sent from a SGP to an ASP to indicate the congestion status and

discard status of a SS7 link.

Retrieval Request The MTP2 Retrieval Request message is used during the MTP Level 3

changeover procedure to request the BSN, to retrieve PDUs from the

transmit and retransmit queues or to flush PDUs from the retransmit queue.

Retrieval Confirm The MTP2 Retrieval Confirm message is sent by the SG in response to a

Retrieval Request message.

Retrieval Indication The Retrieval Indication message is sent by the SG with a PDU from the

transmit or retransmit queue.

Retrieval Complete

Indication

It is exactly the same as the MTP2 Retrieval Indication message except that

it also indicates that retrieval is complete.

MTP2 User Adaptation Messages


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M2UA Messages


ASP Up It is used to indicate to a remote M2UA peer that the Adaptation

layer is ready to receive traffic or maintenance messages.

ASP Up Ack It is used to acknowledge an ASP Up message received from a

remote

M2UA peer.

ASP Down It is used to indicate to a remote M2UA peer that the adaptation

layer is not ready to receive traffic or maintenance messages.

ASP Down Ack It is used to acknowledge an ASP down message received from a

remote M2UA peer.

Heartbeat The Heartbeat message is optionally used to ensure that the

M2UA peers are still available to each other.

Heartbeat Ack The Heartbeat ACK message is sent in response to a BEAT

message.

ASP Maintenance Messages


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M2UA Messages


ASP Active It is sent by an ASP to indicate to an SG that it is Active and

ready to be used.

ASP Active Ack It is used to acknowledge an ASP-Active message Received

from a remote M2UA peer.

ASP Inactive It is sent by an ASP to indicate to an SG that it is no longer an

active ASP to be used from within a list of ASPs.

ASP Inactive Ack It is used to acknowledge an ASP-Inactive message Received

from a remote M2UA peer.

ASP Maintenance Messages

Establishment Procedure of M2UA


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ASP ACTIVE

ASP UP

ASP UP ACK

ASP ACTIVE ACK

ASP 1. SCTP association must be

established between SGP

and ASP before the

establishment of M2UA

service environment.

2. ASP is the client, which willfirst send the request to

establish the environment.

Once the environment is

ready, the M2UA data, ASP

maintenance messages,

and layer managementmessages can be

transmitted between the

peers.

SGP

C S

Establishment Procedure of M2UA

Service Environment


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SS7 Link

Alignment

State Req (STATUS_EMER_SET)Emer Req

M2UAASP M2UASGP MTP2SGP

Emer Req

Emer CfmState Cfm (STATUS_EMER_SET)Emer Cfm

Establish ReqStart Req

Start Req

In Serv IndEstablish CfmIn Serv Ind

DataSend MSU

Send MSU

Receive MSUData

Receive MSU

Release ReqStop Req

Stop Req

Out of Serv IndRelease Cfm

Out of Serv Ind

Data

Transfer

SS7 Link

Release

MTP3ASP

Data Transfer Procedure


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ASP DOWN

ASP INACTIVE

ASP INACTIVE ACK

ASP DOWN ACK

ASP SGP

C S

Release Procedure of M2UA

Service Environment

Switch Over Procedure of


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ASP Inactive

ASP1 SGP ASP2

ASP Inactive Ack

NTFY(AS-PENDING)

NTFY(ASPENDING)

ASP Active

ASP Active Ack

NTFY(AS-ACTIVE)

NTFY(AS-ACTIVE)

Switch Over Procedure of

Active/Standby ASP


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Contents

3 M2UA Protocol






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ASP State Transition Diagram

ASP-ACTIVE

ASP-INACTIVE

ASP-DOWN

ASP ACTIVE ASP INACTIVE

ASP UPASP DOWN

SCTP CDI

SCTP RI

Other ASP in

AS OverridesASP DOWN

SCTP CDI

SCTP RI

M2UA State Transition


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AS State Transition Diagram

AS-INACTIVE AS-ACTIVE

AS-DOWNAS-PENDING

queuing

One Asp

Trans to

ASP-Inactive

All Asp

Trans to

ASP-Down

One Asp

trans to

ASP-Active

One Asp

Trans to

ASP-Active

Last ACTIVE Asp

Trans to

ASP-Inactive

Or ASP-Down

(Start Tr)

Tr expiry and no ASP

In ASP-Inactive

Tr expiry, At Least One

ASP In ASP-Inactive

M2UA State Transition

Tr = Recovery Timer


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Contents

3 M2UA Protocol






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Implementation of M2UA

TMG provides the SGfunction

Be suitable for simple

network structure

Support for interworking

between the PSTN and IP

network

MGC

IP network

MGW/SG

H.248/M2UA

BSSAP

H.248/M2UA

BSCPSTN

ISUP

MGW/SG


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Summary

This Chapter mainly focus on the basic concepts , functions,message format and main procedures of M2UA.


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Contents


2. SCTP Protocol

3. M2UA Protocol

4. M3UA Protocol


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Contents

4 M3UA Protocol

4.1 Introduction and Concepts

4.2 Services and Functions

4.3 Message Format

4.4 Implementation


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M3UA Introduction

M3UA is SS7 MTP3 User Adaptation Layer protocol. It is one kind ofuser adaptation protocol of SIGTRAN. It is defined by RFC3332.

M3UA supports the transport of any SS7 MTP3-User signaling (e.g.,

ISUP and SCCP messages) over IP using the services of the Stream

Control Transmission Protocol. It also enables a seamless operation ofthe MTP3-User peers in the SS7 and IP domains.

This protocol would be used between a Signaling Gateway (SG) and a

Media Gateway Controller (MGC) or IP-resident Database, or between

two IP-based applications.


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Primitives defined by M3UA:

Primitives between M3UA and MTP3-

User

Primitives between M3UA and SCTP

Primitives between M3UA and Layer

Management

MTP3 Users

M3UA

SCTP

IP

LM

The M3UA Layer provides the equivalent set of primitives to the MTP3-Users as

provided by the MTP Level 3 to its local MTP3-Users at an SS7 SEP.

M3UA Protocol Stack


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SG is a signaling agent that receives/sends SCN native

signaling at the edge of the IP network.

SEP MGC

ISUP

MTP3

MTP2

ISUP

M3UA

SCTP

M3UA

SCTPMTP2

SS7 SIGTRANSG

PSTN IP

MTP3

NIF

MTP1 MTP1 IP IP

M3UA Protocol Stack


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Application Server (AS)

A logical entity serving a specific Routing Key. An example of an Application

Server is a virtual switch element handling all call processing for a unique

range of PSTN trunks, identified by an SS7 SIO/DPC/OPC/CIC-range.

Application Server Process (ASP)

A process instance of an Application Server. An Application Server Process

serves as an active or backup process of an Application Server (e.g., part of a

distributed virtual switch or database).

M3UA Terms


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Signaling Gateway (SG)

An SG is a signaling agent that receives/sends SCN native signaling at the

edge of the IP network . An SG appears to the SS7 network as an SS7

Signaling Point. An SG contains a set of one or more unique Signaling

Gateway Processes, of which one or more is normally actively processing

traffic. Where an SG contains more than one SGP, the SG is a logical entity

and the contained SGPs are assumed to be coordinated into a single

management view to the SS7 network and to the supported Application

Servers.

Signaling Gateway Process (SGP)

A process instance of a Signaling Gateway. It serves as an active, backup,

load-sharing or broadcast process of a Signaling Gateway

M3UA Terms


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IP Server Process (IPSP)

A process instance of an IP-based application. An IPSP is essentially the same

as an ASP, except that it uses M3UA in a point-to-point fashion. Conceptually,

an IPSP does not use the services of a Signaling Gateway node.

Routing Key

A routing key describes a set of SS7 parameters and parameter values (such

as DPC, SIO + DPC, SIO + DPC + OPC, and SIO + DPC + OPC + CIC) that

uniquely define the range of signaling traffic to be handled by a particular

application server. Parameters within the routing key cannot extend across a

single destination point code .

M3UA Terms


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Routing Context

A value that uniquely identifies a Routing Key. Routing Context values are

either configured using a configuration management interface, or by using the

routing key management procedures defined in this document.

Entity is the unit which implement the specified function, like AS , SG, or MTP

entity (signaling point).

Each M3UA entity identified by its own signaling point code.

M3UA Entity

M3UA Terms

C


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Contents

4 M3UA Protocol

4.1 Introduction and Concepts


4.3 Message Format

4.4 Implementation

M3UA S i d F i


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Transport the MTP3 users messages

Native management function

Interworking with MTP3 network management

functions

Association management Management of connections to multiple SGPs

SS7 signaling point indicator

Route context and Route key

SS7 and M3UA Interworking at the SG

Redundancy Models

Flow control

SCTP stream mapping

Functions

Services



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Interworking with MTP3 Network Management Functions

At the SGP, the M3UA layer provides interworking with MTP3 management

functions to support seamless operation of the user SCN signaling

applications in the SS7 and IP domains

Network Management Indications

Providing an indication to MTP3-Users at an ASP that a destination in the

SS7 network is not reachable.

Providing an indication to MTP3-Users at an ASP that a destination in the

SS7 network is now reachable.

Providing an indication to MTP3-Users at an ASP that messages to a

destination in the SS7 network are experiencing SS7 congestion.

Providing an indication to MTP3-Users at an ASP that a MTP3-User peer is

unavailable.

M3UA Services

M3UA S i


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Management of connection to multiple SGPs

SGP1

SGP2

SGPn

SGP1

SGP2

SGPn

ASP1

ASP2

ASPn

ASP1

ASP2

ASPn

Host1 Host3

M3UA Service

An ASP may be connected to multiple SGPs. In such a case a

particular SS7 destination may be reachable via more than one

SGP and/or SG, i.e., via more than one route.

C t t


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Contents

4 M3UA Protocol4.1 Introduction and Concepts


4.3 Message Format4.4 Implementation

M3UA M St t


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M3UA Message Structure

The general M3UA message format includes a Common Message Header

followed by zero or more parameters as defined by the Message Type.

Common

Header

M3UA

Messageclass 1

32bit

Spare8 Message class(8) Message typ8Version8

Parameter tag16 Parameter length16

Parameter value

Parameter tag16 Parameter length16Parameter length16

M3UA

Message

class nParameter value

Message length32

M3UA M T


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M3UA Message Types

Message Type DescriptionManagement (MGMT) messages (MGMT)

Error (ERR) The ERR message is used to notify a peer of an error event

associated with an incoming message

Notify (NTFY) The NTFY message is used to provide an autonomousindication of M3UA events to an M3UA peer.

M3UA Transfer Messages

Data The DATA message contains the SS7 MTP3-User protocol

data, including the complete MTP3 routing label.

M3UA M T


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M3UA Message Types

M3UA Signaling Network Management (SSNM)

Destination Unavailable (DUNA) The DUNA message is sent from an SGP in an SG to all concerned ASPs to indicate

that the SG has determined that one or more SS7 destinations are unreachable. It is

also sent by an SGP in response to a message from the ASP to an unreachable SS7

destination.

Destination Available (DAVA) The DAVA message is sent from an SGP to all concerned ASPs to indicate that the SG

has determined that one or more SS7 destinations are now reachable (and not

restricted), or in response to a DAUD message if appropriate.

Destination State Audit (DAUD) The DAUD message may be sent from the ASP to the SGP to audit theavailability/congestion state of SS7 routes from the SG to one or more affected

destinations.

Signaling Congestion (SCON) The SCON message can be sent from an SGP to all concerned ASPs to indicate that an

SG has determined that there is congestion in the SS7 network to one or more

destinations, or to an ASP in response to a DATA or DAUD message as appropriate.

Destination User Part Unavailable

(DUPU)

The DUPU message is used by an SGP to inform concerned ASPs that a remote peer

MTP3-User Part (e.g., ISUP or SCCP) at an SS7 node is unavailable.

Destination Restricted (DRST) The DRST message is optionally sent from the SGP to all concerned ASPs to indicate

that the SG has determined that one or more SS7 destinations are now restricted from

the point of view of the SG, or in response to a DAUD message if appropriate.

M3UA M T


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M3UA Message TypesMessage Types Description

M3UA ASP State Maintenance Message (ASPSM)

ASP Up (UP) The ASP Up message is used to indicate to a remote M3UA

peer that the adaptation layer is ready to receive any

ASPSM/ASPTM messages for all Routing Keys that the ASP

is configured to serve.

ASP Down (DOWN) The ASP Down message is used to indicate to a remote

M3UA peer that the adaptation layer is NOT ready to receive

DATA, SSNM, RKM or ASPTM messages.

Heartbeat (Beat) The BEAT message is optionally used to ensure that the

M3UA peers are still available to each other.

ASP Up Acknowledgement (UP

ACK)

The ASP UP Ack message is used to acknowledge an ASP

Up message received from a remote M3UA peer.

ASP Down Acknowledgement

(DOWN ACK)

The ASP Down Ack message is used to acknowledge an ASP

Down message received from a remote M3UA peer.

Heartbeat Acknowledge (BEAT

ACK)

The BEAT Ack message is sent in response to a received

BEAT message. It includes all the parameters of the received

BEAT message, without any change.

M3UA Message T pes


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M3UA Message Types

Message Type DescriptionM3UA ASP Traffic Maintenance Message (ASPTM)

ASP Active (ASPAC) The ASP Active message is sent by an ASP to indicate to a remote

M3UA peer that it is ready to process signaling traffic for a

particular AS. The ASP Active message affects only the ASP state

for the Routing Keys identified by the Routing Contexts, if present.

ASP Inactive (ASPIA) The ASP Inactive message is sent by an ASP to indicate to a

remote M3UA peer that it is no longer an active ASP to be used

within a list of ASPs. The ASP Inactive message affects only the

ASP state in the Routing Keys identified by the Routing Contexts, if

present.

ASP Active Acknowledgement

(ASPAC ACK)

The ASP Active Ack message is used to acknowledge an ASP

Active message received from a remote M3UA peer.

ASP Inactive

Acknowledgement (ASPIA

ACK)

The ASP Inactive Ack message is used to acknowledge an ASP

Inactive message received from a remote M3UA peer.

Transfer Message Format: Data


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a s e essage o at ata

Message

The DATA message contains the SS7 MTP3-User protocol data, including the complete MTP3

routing label. The DATA message contains the optional Network Appearance (not in use

temporarily), optional Routing Context, mandatory Protocol data, and optional Correlation ID

parameters.

Tag = 0x0200 Length =8

Network

Appearance

Tag = 0x0006

Routing Context

Protocol Data

Correlation ID

Length =8

Length

Length =8

Tag = 0x0210

Tag = 0x0113

DATA Message-Protocol Data


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DATA Message Protocol DataOPCReserved

DPCReserved

SI Reserved Reserved SLSNI

User Protocol Data

Field Description

OPC Originating Point Code: 32 bits (unsigned integer)

DPC Destination Point Code: 32 bits (unsigned integer)

SI (Service Indicator)The Service Indicator field contains the SI field from the

original SS7 message justified to the least significant bit.

NI (Network Indicator)The Network Indicator contains the NI field from the original

SS7 message justified to the least significant bit.

SLS (Signaling Link

Selection)

The Signaling Link Selection field contains the SLS bits from

the routing label of the original SS7 message justified to the

least significant bit and in Network Byte Order.

Protocol data MTP-User information from the original SS7 message

SS7 Signaling Network Management


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g g g

(SSNM) Messages - DUNATag = 0x0200 Length =8

Network

Appearance

Tag = 0x0006

Routing Context

Length

LengthTag = 0x0012

INFO string

LengthTag = 0x0004

Affected PC1Mask

Affected PCnMask

SS7 Signaling Network Management


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(SSNM) Messages-DUPUTag = 0x0200 Length =8

Network

Appearance

Tag = 0x0006

Routing Context

Length

Length = 8Tag = 0x0012

INFO string

LengthTag = 0x0004

Affected DPCMask=0

Length =8Tag = 0x0204

UserCause

Value Meaning

0x0000-

0x0002

Reserved

0x0003 SCCP

0x0004 TUP

0x0005 ISUP

0x0006-

0x0008Reserved

0x0009 Broadband ISUP

0x000a Satellite ISUP

0x000b Reserved

0x000c AAL2 Signaling

0x000d BICC

Media Gateway

Contents


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Contents

4 M3UA Protocol4.1 Introduction and Concepts


4.3 Message Format

4.4 Implementation

M3UA Implementation


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MGC

IPBackbone Network

No.7Trunk Circuit

No.7 Signaling

Network

MGW/SG

PSTN

M3UALinkMTPLink

STPSG

M3UALink

M3UALink

M3UA Implementation

M3UA Implementation


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SEP/STP ASPSGP

(NIF)

MTP1

MTP2

MTP3

SCCP/ISUP

MTP1

MTP2

MTP3

IP

SCTP

M3UA

IP

SCTP

M3UA

SCCP/ISUP

M3UA Implementation

M3UA Implementation


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SEP/STP ASPSGP

MTP1

MTP2

MTP3

SCCP/ISUP

MTP1

MTP2

MTP3

IP

SCTP

M3UA

IP

SCTP

M3UA

SCCP/ISUPSCCP

M3UA Implementation

M3UA Implementation


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IPSP1 IPSP2

IP

SCTP

M3UA

SCCP/ISUP

IP

SCTP

M3UA

SCCP/ISUP

M3UA Implementation

Summary


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Summary

This chapter mainly focus on introduction of the relatedconcepts , functions and main procedures of M3UA.


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Thank youwww.huawei.com

Documents

SIGTRAN Signaling Analysis