Soft exchange packet protocol foundation

xiaoxiao2021-03-06 17

SigTran

Keywords: SigTran M2UA NIF SCTP MTP2

Abstract: This article introduces the SigTran protocol, focusing on the M2UA protocol part used in NGN networking, for NGN's concept and protocol to see "Softswitch Protocol Basis - NGN and Softswitch Protocol V2.0 "Document.

Abbreviated language list:

English nouns explain Chinese interpretation SIGTRAN Signalling Transport signaling M2UAMTP2 User Adaption LayerMTP2 User Adaptation Layer SCTP Stream Control Transport Protocol Stream Control Transmission Protocol SG Sigaling Gateway Signaling Gateway Media Gateway MG Media Gateway MGC Media Gateway Controller Media Gateway Controller AS Application Server The application server represents a certain resource. For SG, a combination of interface identifies on the SG. The ASP Application Server Process application server process is a process instance for one or more AS services, and the entity NIF Node Interworking function node interworking function for communication with SG's process instance is the conversion between narrowband signaling protocol modules and UA. Adaptation layer.

Reference list:

table of Contents

Chapter 1 SigTran brief introduction ... 1-2

1.1 SigTran Getting Started Introduction .. 1-2

1.2 SigTRAN protocol stack structure introduction. 1-2

1.2.1 SigTRAN protocol stack structure. 1. 1-2

1.2.2 SigTRAN application model. 1-2

Chapter 2 M2UA Basic Concepts and Business Functions ... 2-2

2.1 M2UA networking application. 2-2

2.2 SigTran Features - "Seamless Connection". 2-2

2.3 M2UA basic concepts and business features .. 2-2

2.3.1 M2UA's basic concepts.. 2-2

2.3.2 M2UA business features .. 2-2

2.3.3 Support Transfer MTP2 / MTP3 interface primitive function .. 2-2

2.3.4 Supports communication between the layer management modules on SG and MGC. 2-2

2.3.5 Supports management of SCTP coupling between SG and ASPs. 2-2

2.4 M2UA internal features .. 2-2

2.4.1 Mapping .. 2-2

2.4.2 ASP status .. 2-2

2.4.3 SCTP stream map. 2-2

2.4.4 Seamless network management interworking. 2-2

2.4.5 IP Congestion Management .. 2-2

2.4.6 link query .. 2-2

Chapter 3. Getting Started with Agreement Messages ... 3-2

3.1 General Message Head Structure. 3-2

3.1.1 Version (8bits) .. 3-2

3.1.2 Message Category (8bits) .. 3-2

3.1.3 Message Type (8bits) .. 3-2

3.1.4 Message Length .. 3-2

3.1.5 M2UA Message can be structural. 3-2

3.2 m2ua message header .. 3-2

3.3 Example Description .. 3-2

3.3.1 Processing of the ASPUP message .. 3-2

3.3.2 Processing of Aspactive Messages .. 3-2

3.3.3 Processing of AspinActive Messages .. 3-2

3.3.4 Processing of Aspdown Messages .. 3-2

Chapter 4 M2UA Protocol Process and Network Application ... 4-2

4.1 M2UA protocol process example. 4-2

4.1.1 M2UA Business Environment Establishment Process (Construction Chain): .. 4-2

4.1.2 M2UA business interrupt process (broken link): .. 4-2

4.2 SigTran protocol in the NGN network .. 4-2

Chapter 1 SigTRAN Brief Introduction

& Knowledge points:

1. Understand the application background and implementation of the SigTran protocol;

2. Understand the basic concepts of the SigTran protocol, constitute structures;

SigTran beginners, through reading this chapter, you can understand its basic concepts and applications. By understanding the basic concepts of SigTran, you can enter the role faster. If you are familiar with the SCN signaling protocol (such as SS7), it will be helpful for understanding the SigTran protocol. The basic concepts of the SigTRAN protocol will be described below.

The SigTRAN protocol stack is a protocol stack that supports the transmission of SCN signaling protocols through an IP network. The protocol stack supports the inter-layer standard primitive interface in the definition of the SCN signaling protocol hierarchical model, ensuring that the existing SCN signaling application can be used without modification, and also uses the standard IP transport protocol as the transfer underlayer. Add your own features to meet the special transmission requirements of SCN signaling.

1.1 SigTran Getting Started Introduction

When we talk about SigTran, we can't involve its application background. Figure 1-1 shows this very well.

Figure 1-1 SigTRAN Application Model

With the rapid development of IP packets, the interoperability of IP networks and circuit switched networks (SCNs) has become a problem that must face. Under the promotion of this requirement, the gateway with the interoperability appears at the IP network and the SCN network junction, ie the media gateway MG, the signaling gateway SG, each completion of the bearer transfer and conversion between the different media streams and the different signaling. Among them, the signaling gateway SG and the media gateway controller MGC pass through the SigTRAN transmission letter. This requires SG and MGC to support the SigTran protocol. The following two points illustrate the functionality of SigTran in Figure 1-1:

(1) Use SigTran between SG and MGC to transmit SCN signaling. Between the MG and MGCs, SigTran may also be used between the SIGC and between SGs and between SGs.

(2) SigTRAN supports a plurality of SCN protocols, does not include any SCN protocol translation / conversion function, but is performed at the endpoint of the translation / conversion function in the signaling transfer, and it is only positioned in the letter. Order transfer.

1.2 SigTran protocol stack structure introduction

1.2.1 SigTRAN protocol stack structure

SigTRAN consists of two layers: transport layer and UA layer.

Transport layer protocol uses stream control transmission protocol SCTP, providing reliable message package transmission on IP online;

The UA layer, the adaptation of each layer protocol in the protocol hierarchical model of SCN signaling, responsible for the transmission of interlayer primitives located in SCN and IP. For example, M2ua is the user adaptation layer of MTP2, its role supports the primitive interface between MTP2 and MTP3, which is a link between MTP3 and SG on the MGC in the IP network.

Figure 1-2 SigTRAN protocol stack structure

Figure 1-2 has appeared in many documents, which is the structure of the entire SigTRAN. In fact, this picture also contains several levels of meaning:

A. Why is this painted in the middle of SCTP? Because the UA layer includes many members such as M2UA, M3UA, IUA, V5UA, and they all need to be based on SCTP, so the SCTP layer is more wider, and the importance of SCTP can be seen. Introduce SCTP's protocol situations here:

SCTP's development history and prospects: SCTP actually begins with TCP protocol, many protocol processes, such as congestion control, and TCP. But starting SCTP positioning in signaling transmission, so some considers of real-time and security, overcoming some of TCP's inherent defects. Its birth is a simple control transmission protocol based on UDP. After the development of the 13 versions, when the RFC is formed, it is definitely not a simple agreement, and the major communications companies have conducted multiple Bake OFF tests, the rationality and practicality of the SCTP protocol have been fully tested. And SCTP has far exceeded the advantages of TCP, and its application has far exceeded SigTran. On the one hand, in many places in VoIP, the role of the transport protocol, such as BICC, MGCP has the trend of SCTP, on the other hand in general transmission There are more TCP protocols on the protocol, and IETF has discussed a variety of SCTP-based application feasibility including HTTP protocols, and launched a draft of SCTP's socket interface. B, Figure 1-2 In the back of V5UA, there is an omitted number, which indicates that the UA member of the SigTran protocol stack is still increasing. Not only contains M2UA, M3UA, V5UA, etc., other protocols are likely to transmit on IP online through the SigTRAN protocol, and the condition is that its UA protocol is to support the SCTP protocol, and the SCTP is created with the SCTP.

1.2.2 SigTRAN application model

As shown in Figures 1-3, the SigTRAN can evolve the integrated SS7 into the interlayer separated SS7. SigTRANs can separate SS7 interlayer separation, guaranteeing the complete transmission of the IP online, in fact, the complete transfer of the IP online, is guaranteed to be in the IP online. An important feature of SigTran seamlessly is reflected in the process of signaling. The second chapter will explain the specific content of the seamless connection.

Figure 1-3 SigTRAN application model

& Description

Summary: Through Chapter 1, you should have a clear understanding of the SigTran application background. And for the concept of SigTran, SCTP, etc. should have a preliminary understanding.

Chapter 2 M2UA Basic Concepts and Business Functions

& Knowledge points:

1. Understand the application of M2ua and "seamless connection";

2, master the basic concepts and functions of M2ua;

We talked about the SigTran protocol stack composition in Chapter 1, where the UA layer is the adaptation of each layer protocol in the protocol hierarchy model of SS7, which is responsible for the layers of two-layer protocols in SCN and IP networks. Language transmission. This chapter focuses on the M2UA protocol of typical applications in softswitch systems.

2.1 M2UA networking application

Figure 2-1 shows the M2UA application networking: Typically, the M2UA application occasion is when the SG function entity is within the MGU, you need to send the SS7 MTP2 user signaling message to the MGC, that is, the signaling backhaul, such as Down shown. The green portion is M2ua, the blue part is MTP functional level.

Figure 2-1 M2UA application networking network

2.2 SigTran Features - "Seamless Connection"

From Figure 2-1, we can clearly see that SigTran is inserted between MTP1, MTP2, MTP3. In the traditional circuit switched network, MTP1, MTP2, MTP3 is transmitted in E1 in order, and now the SigTRAN is inserted between MTP2 and MTP3, so that MTP signaling messages are possible in IP networks! The so-called seamless connection means that MTP2, MTP3 will not know the existence of SigTran. Figure 2-1 The leftmost light blue part is the original MTP transport layer. And the light blue part of the middle and right is also MTP members. What is the difference between it and the leftmost MTP member? We can find that MTP1 and MTP2 are still tightly tight, while the MTP2 and MTP3 are running on the SigTran on the IP. MTP2 is originally passed to MTP3 through interlayer primitives, in fact, is transmitted to SigTran because SigTRAN can support MTP2 and MTP3 inter-layer primitive function. SigTRAN passes the MTP2 to the MTP3 after IP network, and the MTP3 receives the MTP2 message through the interlayer primitive, and passes to the upper user TUP, ISUP, etc. In fact, MTP2 and MTP3 do not know that they are separated from a layer of SigTran, upper TUP, ISUP, and other application layer modules. So there is no connection and association between SigTran and MTP upper users.

Similarly, the signaling message transmitted by the upper user on the MGC side is passed to the SigTRAN through the MTP3, and the IP network is passed to MTP2, and MTP3 is directly sent to MTP2, and MTP2 is called MTP3. MTP2 and MTP3 are isolated from SigTRAN in the figure, while MTP2 and MTP3 do not know that there is such a slit between them!

This is the so-called "seamless connection" of SigTran.

& Description

"Seamless connection" is characterized by understanding the important content of SigTran (M2UA). Figure 1-3 is a typical M2UA application network diagram, which is very helpful for M2UA.

2.3 basic concepts and business features of M2UA

As everyone understands the "seamless connection" characteristics of the M2ua protocol. The implementation of M2UA seamless connection has been mentioned above, relying on it to support MTP2 and MTP3 inter-layer primitive function. So this section will explain several concepts of M2ua and the business functions that can be provided.

2.3.1 M2UA Basic Concept

M2ua: (SS7 MTP2-User Adaptation Layer) SS7 MTP2 User Adaptation Layer, M2UA Termination MTP2 The User Message (MTP3 Message) of MTP2 is forwarded to MTP3 (MGC) located in the packet network.

M2ua is primarily applied to signaling and media to pass through the same E1 / T1 to MG direct connection, and is basically an embedded signaling gateway.

(1) Interface (interface)

Signaling links of SS7 in M2UA.

(2) (MTP2-User (MTP2 users)

Refers to the protocol of the business using MTP2, ie MTP3.

(3) Interface Identifier (interface ID)

The interface identifier refers to the physical interface identifier transmitted and received on the SG side, which is only a logical identifier, or a number, or a string, for M2UA, it can be considered to correspond to a 7th letter. Let the link, which only have local meaning, use between SG and ASP.

(4) Application Server (Application Server, Abbreviation AS)

A logic entity for a particular application entity, for example, the MGC that handles call processing can be considered as an AS, which can view AS on the SG side as a combination of one or more services of the relevant service. (5) Application Server Process (Application Server Process, ASP)

A process instance of an AS, status is activated / standby. Each ASP contains a SCTP endpoint that can handle multiple AS services. At the m2ua layer, AS represents a set of MTP signaling links, and an ASP process is a message of a set of signaling links. A SCTP connection 1 is established between the ASP1 and SG, and a SCTP connection 2 is established between the ASP2 and SG, 5 MTP signaling links on the SG, 1, 2 signaling links are processed by ASP1; 3, 4, 5 The signaling link is processed by ASP2. You can view the M2UA process on the MGC as an ASP, then the message of the 1, 2 signaling link is handed over from the M2UA process 1 (ie, ASP1) to the MTP3; 3, 4, 5 link messages by M2UA process 2 (ie ASP2) ) Handed over to MTP3 processing.

(6) Fail-over (fault recovery)

When the current ASP is not arrival or failure, the service can reselect the ASP, which can also handle the ASP (or alternate ASP) transmission of the link service. This ability is called fault recovery. The fault recovery means can be used to switch to the previously unreachable process.

(7) Layer Management (Layer Management)

It is the function of processing input and output between the M2UA protocol stack and the local management entity. If local management can use the stack by the Layer Management Configuration Stack, the fault of the protocol stack is notified local management and so on.

(8) Link Keyword (Link Key)

The link key is locally used to determine a signal link and a unique identifier of its peer.

(9) Signaling link terminal (Signalling Link Terminal)

The signaling link terminal refers to an entity that enables the specific execution details and enables the various functions specified by the MTP2.

2.3.2 M2UA business function

The M2UA task is to make seamless connections between MTP2 in the SG side and the MTP3 on the ASP side, that is, for MTP2, M2ua represents the interface of MTP3, for MTP3, M2ua represents MTP2 Interface.

& Description

Do "seamless connection", M2UA must support the following features:

Support transfer MTP2 / MTP3 interface primitive

Supports communication between layer management modules located on SG and MGC, respectively

Support for SCTP coupling between SG and ASPs (ie, connection, connected in national standard is called coupling).

2.3.3 Support Transfer MTP2 / MTP3 Interface Property

M2UA translates MTP2 / MTP3 interface primitive to M2UA corresponding message is transmitted over the IP network via SCTP connection, and then converts the M2UA message to the corresponding MTP2 / MTP3 interface primitive to MTP3 after reaching the peer. M2ua supports all primitives specified in the MTP2 and MTP3 protocol, including the following categories:

Establish

Used to request a signal to start positioning, and indicate and confirm the result of successful link positioning.

RELEASE

Used to request to remove the result of the previously established signaling link, indicate and confirm the result of the chain, and the link positioning failed report.

Data

Used to request to transmit the MSU message, send it to the MSU to MSU to MSU on the SG side MTP2, send MSU to MGC side MTP3 request;

Data Retrieval

Data recovery class, the recycling process for link data.

State

Link status requests, instructions, and confirmation, for MTP3 to understand and control link status.

2.3.4 Supports communication between the layer management modules located on the SG and MGCs at MTP2, MTP3, on the same device, because MTP2, MTP3 share the same layer management together, so there is no problem. When MTP2, MTP3 is located on different devices. When M2UA communicates with the IP network, there is a layer management in both sides. In order to truly seamlessly connect, the communication problem management of both sides must be considered.

On the SG side, when the ASP is discovered, M2UA is responsible for notifying SG management, at which point M2ua's action taken by MTP2, the MTP specification is followed, and the M2UA protocol does not make regulations.

When M2UA receives an error message from the peer, the local layer management report error needs to be reported (such as an interface ID that does not know on the SG side).

2.3.5 Support for SCTP coupling between SG and ASP

The SG side M2UA layer must maintain the availability status of all configured remote ASPs to see if the ASP is enabled or downtime; in order to manage SCTP coupling and service between SG and ASP, SG side M2ua must maintain remote ASP Activate / unactivated state, activated ASP is used to process the service sent by the SG.

Local management can command the SG or ASP side of the M2UA layer to establish SCTP coupling to the peer M2UA node. It can create SCTP coupling to peer M2UA nodes by using M-SCTP ESTABLISH requests, instructions and confirming primitives.

The M2UA layer can also use the M-SCTP STATUS request and indication of the original language to the local layer management to notify the SCTP coupled state, for example: M2UA can notify the local management of the reasons for the SCTP coupling release, determined by the local M2UA layer or SCTP release of.

The M2UA layer can also notify the ASP availability status to local management, which informs the ASP status by using M-ASP Status primitives.

2.4 M2UA internal function

2.4.1 mapping

M2UA needs to maintain mapping between SS7 physical links and interface identifiers, both of which are one-to-one correspondence.

2.4.2 ASP status

Due to the need to support redundancy between ASPs, different service processing methods between ASPs are supported, and the M2UA on the SG side must maintain the status of the ASP. SG and ASPs are managed by ASPM messages.

2.4.3 SCTP flow map

Guidelines for SCTP flow maps:

(1) Finally mapping the business to the SCTP stream is done by the adaptation layer;

(2) The mapping benchmark is the interface ID;

(3) Ordered business must be guaranteed in the same streaming;

(4) The flow rate 0 is used to transmit management messages and cannot be used to transmit the MAUP message.

2.4.4 Seamless network management interoperability

M2ua provides seamless interworking between SG and ASP, and SG side M2ua should notify the local layer management notify the local layer management notification MTP3 when the ASP moves out of the activation state, and the SG m2ua is subject to the measures taken by MTP2, follow the related MTP specifications, The draft protocol did not make a regulation.

2.4.5 IP Congestion Management

When the IP network occurs, SCTP will notify M2UA, M2ua's processing of network congestion can be based on implementation, and the M2UA protocol is not specified.

2.4.6 link query

When an inverting occurs between ASP, the M2UA on the newly activated ASP may query the SGL link state to ensure the consistency of both ends, so the SG side M2ua will report the state of the current link as to the ASP.

Chapter 3 Protocol Message Getting Started

In the M2UA protocol message, give you the classification and composition of the M2UA protocol message. If you are interested in more specific message content, please refer to the protocol text.

& Description

M2UA news is divided into the following three categories:

(1) MAUP: M2UA user adaptation message

(2) ASPM: ASP Maintenance Message (3) MGMT: Managing Messages

3.1 Universal Message Head Structure

It should be noted that any M2UA message must include the M2UA universal message header, which is as follows:

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2

- - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - -

| Message Length |

- - - - - - - - - - - - - - - -

M2UA's general message header includes: version, message category, message type, message length. Let's explain the message heads above.

3.1.1 Version (8bits)

The version now supported is 1.0, so the value of this domain can only be 01.

1. Keep field (8bits)

Fill in 00 in the actual news

3.1.2 Message Category (8bits)

SigTRAN's message category is unified, that is, this general message header is supported by various UA protocols in all SigTran families. For M2ua, you can only be the following:

0 Management Message (MGMT: Management Message) [IUA / M2UA / M3UA / SUA]

3 ASP Status Maintenance Message (ASPSM: ASP State Maintenance Messages)

[IUA / M2UA / M3UA / SUA]

4 ASP Business Maintenance Message (ASPTM: ASP Traffic Maintenance Messages)

[IUA / M2UA / M3UA / SUA]

6 MTP2 User Adaptation Message (MAUP: M2ua] [M2ua]

(Note: The latter square bracket indicates which UA protocol supports this category, where 3 and 4 can be collectively referred to as an ASPM class message)

3.1.3 Message Type (8bits)

The message type refers to a specific instance corresponding to the message category. For example, fruit is a "message category", and Apple is a message type of such message category, and pears are also a message type of such message category.

Management Class Message (Message Class = 0) has the following message type: 0 Error Message (ERR)

1 Notify Message (NTFY)

MTP2 user adaptation message (Message Class = 6) has the following message type:

0 reserved

1 Data

2 ESTABLISH REQUEST

3 Establish Confirm

4 Release Request

5 RELEASE CONFIRM

6 Release Indication

7 State Request

8 State Confirm

9 State INDICATION

10 Data Retrieval Request

11 Data Retrieval CONFIRM

12 Data Retrieval Indication

13 Data Retrieval Complete IND Information

14 Congestion Indication

ASP Status Maintenance Message (Message Class = 3) has the following message type:

1 ASP UP (Up)

2 ASP Down (Down)

3 reserved

4 ASP UP ACK (UP ACK)

5 ASP DOWN ACK (Down Ack)

ASP Business Maintenance Message (MSAGE CLASS = 4) has the following message type:

1 ASP ACTIVE (ACTIVE)

2 asp inactive (inactive)

3 ASP ACTIVE ACK (ACTIVE ACK)

4 Asp Inactive Ack (Inactive Ack)

3.1.4 Message Length

Message length defines the length of the message (in an eight-bit group), including the length of the message header and the length of the padding.

3.1.5 M2UA message can be variable length parameters

The parameter format in the M2UA message contains the length of the message tag, the length of the parameter, parameter content, referred to as the TLV format.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

- - - - - - - - - - - - - - - -

Parameter Tag | Parameter Length |

- - - - - - - - - - - - - - - -

/// Parameter Value /

/ /

- - - - - - - - - - - - - - - -

Parameter TLV format

In addition to the universal message header, each parameter is in this TLV format, and the M2ua message is accumulated by these one or more parameters, or there is no parameters. The TAG value is a sign of different parameters. For details, please refer to the protocol text.

3.2 M2ua Message Head

In addition to the universal message, the MAUP message has a specific message header called the M2ua message header. In such messages, the M2ua message is tightened to follow the general message head. The M2UA message head contains an interface identifier, the format of the M2ua message head is as follows:

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

- - - - - - - - - - - - - - - -

| TAG (0x1) | Length |

- - - - - - - - - - - - - - - -

| Interface Identifier (Integer) |

- - - - - - - - - - - - - - - -

M2UA message header (when the interface identifies is a digital type)

3.3 Example Description

The process of establishing a M2UA business environment between the two ends is as follows:

SG ASP

| <------------- ASP UP --------------

| ----------- ASP-UP ACK ----------> || <------ ASP ACTIVE ----------- ---- |

| ---- ASP ACTIVE ACK ------------> |

(1) ASPUP message package: (below is 16)

01 00 03 01 00 00 00 08

ASPUP message only has a general message header, 01 indicates version number, 00 is a reserved field, 03 is a message category (ASP status maintenance message), 01 is an ASPUP message, 00 00 00 08 is the length of the entire message package.

(2) ASPUP ACK message package:

01 00 03 04 00 00 00 08

The ASPUP ACK message is also only a universal message header.

(3) ASP ACTIVE message package

01 00 04 01 00 00 18 | 00 0B 00 08 00 00 01 | 00 01 00 08 00 00 00 00 00 00 00 00 00

The ASP Active message includes a universal message header and a M2UA message header and parameter, 01 indicates version number, 00 is a reserved field, 04 is a message category (ASP service maintenance message), 01 is an ASP Active message, 00 00 00 18 is the entire message package length. 00 0b is a TAG value indicating that the transmission mode (main standby or load sharing), 00 08 indicates the length of this parameter, 00 00 01 is represented by a load balance, 00 01 is also a TAG value, indicating the IF_ID value, 00 08 Indicates the length of this parameter, 00 00 00 is the IF_ID configured in our end.

The rest of the messages can also be split in units of 8 bytes, and then look up the protocol text according to different TAG values.

3.3.1 Processing of ASPUP Messages

When the SCTP connection is established, the ASP sends an ASP UP message to the SG (the message is always sent by the ASP). SG will write down the identifier of the ASP (if any in the message), tag the ASP in the inactive status and returns an ASP UP ACK message.

For the ASP side, if the timeout is not accepted, the upper layer (specific implementation) is retransmitted or notified. Other ASP messages cannot be sent on the ASP side before receiving returns.

For the SG side, if the ASP has been labeled as an ASP_ACTIVE or ASP_ACTIVE or ASP_STANDBY state after receiving the ASP UP message, send the "UnexPerCted Message" error message to the peer while returning the ASP UP message, and modify the ASP The status is ASP_INACTIVE.

For the SG side, if the ASP has been marked as ASP_INACTIVE, only the ASP UP ACK message is returned.

3.3.2 Processing of Aspactive Messages

Whenever, the ASP receives an ASP UP ACK, and the ASP will send an ASP Active to SG. After the SG receives the ASP Active, even if the status of the ASP is marked as Active, it will still return it to a confirmation, and change its own status, and notify the LM to open the business. ASP cannot send any data messages before the ASP Active Ack is not returned. After returning, the LM is notified. The timeout is returned. 3.3.3 Processing of AspinActive Messages

When an ASP does not want to carry an AS business, it will send an ASP INACTIVE message to the SG. The message may be that the LM is issued by m_asp_inactive primitives or by the M2UA management mechanism. SG usually returns a confirmation inactive ACK. The ASP INACTIVE timeout is returned. The transmission mode parameters also included in the ASP INACTIVE message. However, if the SG discovery is not the same as the current mode of the AS in the SG, the SG will return an error message.

For the AS of the active and standby interchange mode, the new ASP takes over the AS transmission before the SG accepts the ASP_INACTIVE message of the ASP, then the SG at this time has already considered an inactive state. The ASP will receive a confirmation message

3.3.4 Processing of Aspdown Messages

After the SG accepts the ASP DOWN message, the ASP status is ASP_DOWN. Notify the LM (indicated by m-asp_down indicator), returns an ASP Down ACK message. No matter what the ASP is in, the SG returns to the ASP Down ACK message.

For the ASP side, the LM is notified after receiving the ASP DOWN ACK message. However, if the ASP does not issue an ASP Down message, it is subject to the ASP Down ACK message, it will think it is in the ASP_DOWN state. If the ASP is previously in the ASP-ACTIVE or ASP_INACTIVE state, the ASP at this time will re-return yourself to the state. For the ASP side, if you do not receive a confirmation, it is repeatedly reused or notified that the LM is implemented.

Chapter 4 M2UA Protocol Process and Network Application

& Knowledge points:

1, master the Message process such as M2ua construction chain, broken link;

2, understand the role of SigTran in the NGN network;

4.1 M2UA protocol process example

In the NGN network, SG and MG are located at the junction of the packet network and the SCN network, and SG communicates with the SigTRAN protocol and MGC (soft exchange), and MG communicate via H.248 protocol and MGC. Where SG acts as a signaling gateway, it can be a separate device or in TMG or SofTX (ie, MGC).

4.1.1 M2UA Business Environment Establishment Process (Concrete Chain):

SG MGC

| <------------- ASP UP --------------

| ----------- ASP-UP ACK ----------> |

| <------- ASP ACTIVE --------------- |

| ---- ASP ACTIVE ACK ------------> |

4.1.2 M2UA business interrupt process (broken chain):

SG MGC

| <------------ ASP inactive -------- |

| -------- ASP inactive ACK -------> |

| <------- ASP Down ------------- || ---- ASP Down ACK ------------> |

M2ua messages mainly include ASP UP, ACK, ASP INACTIVE, ASP ACTIVE ACK, ASP INACTIVE, ASP INACTIVE ACK, ASP DOWN, ASP DOWN ACK, etc.

4.2 SigTRAN protocol in NGN networking

Figure 4-1 SigTRAN in the NGN network

Figure 4-1 is a protocol architecture for our NGN network, you can see the network structure of the distributed media gateway, IP telephone gateway is separated into three parts: signaling gateway SG, media gateway MG and media gateway controller MGC (Ie softx).

SG is responsible for processing signaling messages, ending, translating or relaying; MG is responsible for processing media streams, sending media streams from narrowband network packages to IP network or receives after receiving the package after receiving the package; SoftX is responsible for MG Registration and management of resources, as well as call control.

& Description

In the NGN distributed gateway architecture, the H.248 protocol is employed between the MG and SOFTX.

SigTran protocols are used between SG and SOFTX.

转载请注明原文地址:https://www.9cbs.com/read-51015.html

9cbs

New Post(0)