Sigtran protocol

1.0

SIGTRAN protocol

Objectives

SIGTRAN application in R4 network

SIGTRAN protocol structure and message introduction

SIGTRAN signaling flow

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

Course Content

Chap1 overview

Chap2 SCTP protocol

Chap3 M3UA protocol introduction

Chap4 SIGTRAN application

SIGTRAN definition Two layers of protocols are included in the

SIGTRAN protocol stack, i.e., transmission protocols (such as SCTP/IP) and adaptation protocols (such as M3UA, IUA).

Introduction of M3UA

SEP MGC

ISUP

MTP3

MTP2

MTP1

ISUP

M3UA

SCTP

IP

M3UA

SCTP

IP

MTP2

MTP1

SS7 SIGTRANSG

PSTN IP

MTP3

NIF

Course Content

Chap1 overview

Chap2 SCTP protocol



Chap2 SCTP protocol

1.1 overview1.1 overview

1.2 SCTP terms

1.3 SCTP function

1.4 SCTP message structure

SCTP protocol introductionStream Control Transmission Protocol

(SCTP) is a reliable transport protocol that operates over a potentially unreliable connectionless packet service such as IP. SCTP is designed to transfer SCN

narrowband signaling over IP network. Compared with the TCP, SCTP features

higher reliability, real-time and multi-homed performance.

SCTP features Support for orderly/disorderly transmission of

subscriber datagram in the flow.Multiple streams can be established in one

association, and the data in the streams do not interfere with each other.

Multi-home can be supported at one end or both ends of the association to improve the reliability of the link.

The association must pass the COOKIE authentication before establishment to guarantee the security.

Chap2 SCTP protocol

1.1 overview

1.2 SCTP terms1.2 SCTP terms

1.3 SCTP function

1.4 SCTP message

structure

SCTP transmission addressA transport address of Stream Control

Transmission Protocol (SCTP) is defined by the combination of an IP address and an SCTP port number.

SCTP port number is used for the identification of the users at the same address, and it is identical to that of TCP port number in the concept.

Host and endpoint

A Host is a computer, configured with one or multiple

IP addresses. It is a typical physical entity.

Endpoint is one of basic concepts of SCTP. An

endpoint is the logical sender/receiver of SCTP

packets. It is a typical logical entity.

Association and stream

SCTPEndpointA

IP/SCTP-port

SCTPEndpointB

IP/SCTP-port

SCTPassociation

SCTPstream(sigleway)

TSN and SSNTSN

Transmission Sequence Number (TSN) is a 32-bit sequence number used internally by SCTP. One TSN is attached to each chunk containing user data to permit the receiving SCTP endpoint to acknowledge its receipt and detect duplicate deliveries. TSN is maintained on the basis of association.

SSNSSN is the acronym of Stream Sequence

Number. In each stream of an SCTP association, a 16-bit sequence number is assigned to each data chunk sent in the stream by the local end, in order to ensure the sequenced transmission in the stream. SSN is maintained on the basis of stream.

TSN and SSNTSN is maintained on the basis of association.For example: Endpoint A use two stream to connect

endpoint B. Now block A,B,C,D will be transmit, the sequence of transmission is as following :block A use stream1,block B use stream2, block C use stream3, block D use stream4. And block5 is divided into D1 and D2.

data TSN SSN

A 1 1

B 2 1

C 3 2

D1 4 2

D2 5 2

CWND and RWNDCWND: Congestion Window

An SCTP variable that limits the data, in number of bytes, a sender can transmit to a particular destination transport address before receiving an acknowledgement. SCTP is a sliding window protocol.

RWND: Receiver Window. An SCTP variable that a data sender uses to

store the most recently calculated receiver window of its peer, in number of bytes.

Chap2 SCTP protocol

1.1 overview

1.2 SCTP terms

1.3 SCTP function1.3 SCTP function

1.4 SCTP message

structure

SCTP function

The functions of SCTP mainly include: association startup and takedownsequenced delivery within streamsuser data fragmentationacknowledgement and congestion

avoidancechunk bundlingpacket validationpath management.

Chap2 SCTP protocol

1.1 overview

1.2 SCTP terms

1.3 SCTP function

1.4 SCTP message 1.4 SCTP message

structurestructure

SCTP message（ COMMON HEADER）＋（ CHUNK）

SCTP message type

Message Name Description

DATA The payload user data

INIT This chunk is used to initiate a SCTP association between two endpoints.

INIT ACK The INIT ACK chunk is used to acknowledge the initiation of an SCTP association.

SACK This chunk is sent to the peer endpoint to acknowledge received DATA chunks and to inform the peer endpoint of gaps in the received

subsequences of DATA chunks.

HEARTBEAT An endpoint should send this chunk to its peer endpoint to probe the reachability of a particular destination transport address defined

in the present association.

HEARTBEAT ACK An endpoint should send this chunk to its peer endpoint as a response to a HEARTBEAT chunk.

ABORT The ABORT chunk is sent to the peer of an association to close the association.

SHUTDOWN An endpoint in an association MUST use this chunk to initiate a graceful close of the association with its peer.

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

ERROR An endpoint sends this chunk to its peer endpoint to notify it of certain error conditions.

COOKIE ECHO 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 It is used to acknowledge the receipt of a COOKIE ECHO chunk.

SHUTDOWN COMPLETE This chunk is used to acknowledge the receipt of the SHUTDOWN ACK chunk at the completion of the shutdown process

Startup of association

The startup of SCTP association is a four-way handshake process, which has four message interactions: INIT, INIT ACK, COOKIE ECHO and COOKIE ACK

Termination of association

SCTP association can be terminated in two ways: One is GRACEFUL close, the other is UNGRACEFUL close.

Just as their names imply, the former means that all data in queue by either endpoint is delivered to the respective peers before the association is shut down.

The latter means that the association is directly aborted and the data is directly discarded.

Course Content

Training.huawei.com

Chap1 overview

Chap2 SCTP protocol




3.1 overview3.1 overview

3.2 basic concept

3.3 M3UA message

structure

M3UA functionM3UA (MTP3 User Adaptation) protocol

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.

Also, provision is made for protocol elements that enable a seamless operation of the 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.

M3UA protocol introduction

SEP ： signal endpoint SG ： signal gateway MGC ： media control

SEP MGC

ISUP

MTP3

MTP2

MTP1

ISUP

M3UA

SCTP

IP

M3UA

SCTP

IP

MTP2

MTP1

SS7 SIGTRANSG

PSTN IP

MTP3

NIF

M3UA protocol introduction(continue)

RNC

RANAP

SCCP

MTP-3b

SAAL

ATM

MGW

ATM

SAAL

MTP-3b M3UA

SCTP

IP

SERVER

RANAP

SCCP

M3UA

SCTP

IP

ATM IP

M3UA protocol introductionM3UA also can be used to transfer

signaling between two IPSP

IPMGC MGC

User

M3UA

SCTP

IP

User

M3UA

SCTP

IP


3.1 overview

3.2 basic concept3.2 basic concept

3.3 M3UA message

structure

Basic concept AS

A logical entity serving a specific Routing Key.

ASP

A process instance of an Application Server. 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.

Basic conceptM3UA link state transition

M3UA_LINK_INACTIVE

M3UA_LINK_UNESTABLISH

M3UA_LINK_DOWN

Asp Inactive/Asp Inactive Ack/

Asp Alt Notify

Asp Active/Asp Active Ack

M3UA backout successful/Sctp-CDI

M3UA_LINK_ACTIVE

SCTP-RI Asp Down orAsp Down Ackor SCTP-RI

SCTP-CDI

SCTPCDI

M3UA establish successful

Asp Up orAsp Up Ack

Basic concept Relationship among M3UA Link, Linkset, Route and Entity

SGP1

SGP2

SGP3

SGP1

SGP2

SGP3

SG1

SG2

MGC

M3UA link set

M3UA route

SP

ASP1

ASP2

ASP3

M3UA linkM3UA entity MTP link

Basic conceptM3UA route

The path from source entity to destination entity is called a M3UA route.

One M3UA route corresponds to one M3UA Linkset at the home terminal.

Basic conceptM3UA entity

The logical processing unit that accomplishes some special functions, such as AS, SP or a logic unit that only implements special message transfer function, such as SG can be classified as M3UA Entity. Each M3UA Entity is identified by a unique signaling point code.

M3UA LOCAL ENTITY: The logical entity to accomplish special function in local side.

M3UA DESTINATION ENTITY: The logic entity to accomplish special function in peer side.


3.1 overview

3.2 basic concept

3.3 M3UA message 3.3 M3UA message

structurestructure

M3UA message structure

The general M3UA message format includes a common message header followed by zero or more variable length parameters.The protocol messages for MTP3-User Adaptation require

a message structure, which contains a version, message class, message type, message length, and message contents.

All the parameters contained in a message are defined in a Tag Length-Value format as shown below.

Version(8) Reserved(8) Message Class(8) Message Type(8)

Message Length(32)

Parameter Length (16)

Parameter Value(32)

Parameter Tag (16)

M3UA message introduction

Management messages Transfer messages SS7 Signaling Network Management

messages ASP State Maintenance messages ASP Traffic Maintenance messages

Establishment procedure

SGP ASP

ASP UP

ASP UP ACK

AS INACTIVE NOTIFY

ASP ACTIVE

ASP ACTIVE ACK

AS ACTIVE NOTIFY

Data Transfer procedureDetermine the correct Destination Entity.If the destination Entity is Accessible, then get

the Available route to that destination entity.Get an Active Linkset belonging to this Route.Determine an Active Link in the given Linkset.Determine whether to complete the optional

fields of the DATA message.Map the MTP-TRANSFER request primitive into

the Protocol Data field of a DATA messageSend the DATA message to the remote M3UA

peer at the SGP, over the chosen M3UA link.

MTP_TRANSFER primitive handling at ASP

MTP_TRANSFER

ASP

Choose the rightlink and map

Transferprimitive to

DATA message

SGP

DATA message

MTP_TRANSFER handling at SGP

MTP_TRANSFER

ASP

Choose the right link and map

Transfer primitive to

DATA message

SGP

DATA message

Release procedure

SGP ASP

ASP INACTIVE

ASP INACTIVE ACK

AS PENDING NOTIFY

Pending Timer ExpiresAS INACTIVE NOTIFY

ASP DOWN

ASP DOWN ACK

AS DOWN NOTIFY

Technology

Sigtran protocol