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1.0SIGTRAN protocol1ObjectivesSIGTRAN application in R4 networkSIGTRAN protocol structure and message introductionSIGTRAN signaling flowUpon completion of this course,you will be able to: 2Course ContentChap1 overviewChap2 SCTP protocolChap3 M3UA protocol introductionChap4 SIGTRAN application

3SIGTRAN 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).

4SIGTRAN stack is the protocol stack that supports transmission of Switched Circuit Network (SCN) signaling via IP network. This protocol stack supports the inter-layer standard primitive interface defined in SCN signaling protocol hierarchy model, so as to ensure utilization of the existing SCN signaling application without modification. It also uses the standard IP transport protocol as the transmission bottom layer, and satisfies the special transmission requirements of SCN signaling via adding its own functions.Introduction of M3UA

Course ContentChap1 overviewChap2 SCTP protocolChap3 M3UA protocol introductionChap4 SIGTRAN application

6Chap2 SCTP protocol1.1 overview 1.2 SCTP terms 1.3 SCTP function 1.4 SCTP message structure

7SCTP 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. 8SCTP 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.

9Chap2 SCTP protocol

1.1 overview 1.2 SCTP terms 1.3 SCTP function 1.4 SCTP message structure

10SCTP 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. 11Host and endpointA 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.12Association and stream

13An association is the logic relationship, or channel, established between two SCTP endpoints for data transmission, via the four-way handshake mechanism prescribed in SCTP.SCTP is characterized by Stream. In an SCTP association, stream is a uni-directional logic channel established from one endpoint to the other associated endpoint. The data to be delivered in sequence has to be conveyed within a stream.Association and stream

TSN and SSNTSNTransmission 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.14TSN 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.

dataTSNSSNA11B21C32D142D25215CWND 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. 16Chap2 SCTP protocol

1.1 overview 1.2 SCTP terms 1.3 SCTP function 1.4 SCTP message structure

17SCTP functionThe functions of SCTP mainly include: association startup and takedownsequenced delivery within streamsuser data fragmentationacknowledgement and congestion avoidancechunk bundlingpacket validationpath management. 18Chap2 SCTP protocol

1.1 overview 1.2 SCTP terms 1.3 SCTP function 1.4 SCTP message structure

19SCTP message

COMMON HEADERCHUNK20SCTP message typeMessage NameDescriptionDATAThe payload user dataINITThis chunk is used to initiate a SCTP association between two endpoints. INIT ACKThe INIT ACK chunk is used to acknowledge the initiation of an SCTP association. SACKThis 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. HEARTBEATAn 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 ACKAn endpoint should send this chunk to its peer endpoint as a response to a HEARTBEAT chunk. ABORTThe ABORT chunk is sent to the peer of an association to close the association. SHUTDOWNAn endpoint in an association MUST use this chunk to initiate a graceful close of the association with its peer. SHUTDOWN ACKThis chunk MUST be used to acknowledge the receipt of the SHUTDOWN chunk at the completion of the shutdown process. ERRORAn endpoint sends this chunk to its peer endpoint to notify it of certain error conditions. COOKIE ECHOThis 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 ACKIt is used to acknowledge the receipt of a COOKIE ECHO chunk. SHUTDOWN COMPLETEThis chunk is used to acknowledge the receipt of the SHUTDOWN ACK chunk at the completion of the shutdown process 21

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

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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. 23Course ContentTraining.huawei.comChap1 overviewChap2 SCTP protocolChap3 M3UA protocol introductionChap4 SIGTRAN application

24Chap3 M3UA protocol introduction

3.1 overview3.2 basic concept 3.3 M3UA message structure

25M3UA 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.26M3UA protocol introductionSEPsignal endpointSGsignal gatewayMGCmedia control

27M3UA protocol introduction(continue)

28M3UA protocol introductionM3UA also can be used to transfer signaling between two IPSP

29Chap3 M3UA protocol introduction

3.1 overview3.2 basic concept 3.3 M3UA message structure

30Basic conceptASA logical entity serving a specific Routing Key. ASPA process instance of an Application Server.IPSPA 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.31ASA 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.

Basic conceptM3UA link state transition

32Basic conceptRelationship among M3UA Link, Linkset, Route and Entity

33Basic conceptM3UA routeThe path from source entity to destination entity is called a M3UA route. One M3UA route corresponds to one M3UA Linkset at the home terminal. 34Basic conceptM3UA entityThe 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. 35Chap3 M3UA protocol introduction

3.1 overview3.2 basic concept 3.3 M3UA message structure

36M3UA message structureThe 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.

37M3UA message introductionManagement messagesTransfer messagesSS7 Signaling Network Management messagesASP State Maintenance messagesASP Traffic Maintenance messages

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Establishment procedure

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Data Transfer procedure

Determine 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.

40MTP_TRANSFER primitive handling at ASP

41MTP_TRANSFER handling at SGP

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Release procedure

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