M3UA

Patrick Sharp

M3UADrive to exploit the values of IP in

traditional telephone networks led to the creation of the SIGTRAN group in the IETF (Internet Engineering Task Force).

Need for protocols with best of both.

M3UAM3UA is a protocol for interfacing

legacy SS7 networks with IP.

M3UA – MTP3 User Adaptation Layer

Allows integration of existing networks with new technology.

SS7Signaling Support 7

An architecture for performing out-of-band signaling in support of the functions of the PSTN (Public Switched Telephone Network).

SS7PSTN functions Call-establishment Routing Billing Information exchange

SS7 SSP-telephone switches STP-packet switches SCP-databases

SS7

MTP3SS7 protocol is layered. We are

interested in the Message Transfer Part-Level 3.

Together with the Message Transfer Part-Level 2, referred to as the MTP (Message Transfer Part)

MTP3MTP3 extends MTP2, which provided

link-layer functionality. MTP3 adds network functionality.

Ensures that messages are delivered across the network regardless of whether or not the nodes are directly connected.

MTP3Capabilities: Node addressing Routing Alternate routing Congestion control

MTP3Sits between MTP2 and user parts

(ISUP, TUP, SCCP).

Made up of 2 parts: SMH (Signaling Message Handling) SNM (Signaling Network

Management)

MTP3SNM:Deals with the

general management of the MTP.

SHM:Deals with

discrimination, distribution and routing of signaling messages.

MTP3 User AdaptationM3UA allows for all the functionality

of MTP3 to be done over IP.

M3UASupports the transport of MTP3-User

signaling over IP. ISUP-ISDN User Part SCCP-Signaling Connection Control

Part TUP-Telephone User Part

M3UATransports the MTP3-User signaling

using the Stream Control Transmission Protocol (SCTP).

SCTP provides for unique needs of the telephony network.

SCTPProtocol that met the needs of

determinism, reliability and timeliness.

UDP: Best effort delivery, but not reliable.TCP: Guaranteed delivery, but not timely.SCTP: Deterministic, reliable and timely.

SCTP Deals with framed messages. Multi-homing support, end-points can be

more than one IP address. Delivers data in chunks in independent

streams, eliminates head-of-the line blocking.

Path selection of a primary path and monitoring of connectivity.

Validation and acknowledgment prevents flooding and missing/duplicated chunks.

M3UAM3UA is generally deployed in an

application server as an Application Server Process.

Provides a link between SS7 and IP, but can also be used to transport MTP3-User signaling between IP networks.

SS7/IP

SS7/IPM3UA can be used as a gateway, in

almost the same way as an SS7 STP.

SS7/IPAll SS7 elements above MTP3

remain the same, but routing and transport are replaced by IP.

This allows the same services to be offered but adds flexibility and efficiency.

IP/IP

IP/IPLess commonly used, but M3UA also

allows for the transport of MTP3-User parts between two IP applications.

M3UA ProtocolM3UA message format includes a

common header followed by zero or more parameters as determined by the type of message.

M3UA Protocol

Version: 8 bits, version number Class: 8 bits, message class Type: 8 bits, message type Length: 32 bits, length of message in bytes,

including header and parameter padding Data: variable, contains the parameters, if any

M3UA Protocol

M3UA ProtocolEach message class has different types.MGMT: ERR, NTFYTransfer: Payload DataSSNM: Destination

Unavailable/Available, Destination State Audit, Signaling Congestion, Destination User Part Unavailable, Destination Restricted

M3UA ProtocolASPSM: ASP Up/Down, Heartbeat,

ASP Up/Down Ack, Heartbeat AckASPTM: ASP Active/Inactive, ASP

Active/Inactive AckRKM: Registration

Request/Response, Deregistration Request/Response

M3UA ProtocolAll classes also have reserved types

for IETF use as well as reserved types for IETF defined extensions.

M3UA ProtocolEach message class and type has

zero or more parameters, far too many to list here.

Parameters contain message bodies, context information, configuration data, destination/origination codes, etc.

M3UA ProcedureA Signaling Gateway (SG) sends and

receives native signaling at the edge of the IP network. It appears to be a signaling point to the SS7 network.

A Signaling Gateway process is a process instance of the SG. It interacts with the ASP.

M3UA Procedure Establishment of traffic between an ASP

and SGP

M3UA ProcedureWhen the M3UA layer at the ASP gets a

TRANSFER request from the M3UA user it must:

Determines correct SGP Determine if the DATA field needs to be

filled Map the request into the Data field Send the DATA message to the SGP over

SCTP

M3UA ProcedureWhen the M3UA at the ASP receives

a DATA message it must: Evaluate the optional Data fields Map the Data field into an MTP-

TRANSFER primitive Pass the primitive to the user part

M3UA Procedure A single exchange between IP Server

Processes (IPSP)

M3UA SecurityGoals: Availability of reliable and timely

user data transport Integrity of user data transport Confidentiality of user data

Benefits of M3UA Replace physical SS7 links with virtual IP

associations Maintain deterministic qualities

demanded in signaling. Eliminate SS7 bandwidth restrictions Eliminate SS7 complexity Deploy existing SS7 call-setup and value

added service w/out legacy overhead Point to point or gateway configuration

Questions: What is the purpose of M3UA? How is M3UA commonly deployed? How can M3UA be configured?

Answers Allowing seamless use of MTP3-

User signaling between SS7 and IP. As an application server process

on an application server. Point to point or as a gateway.

References http://www.networksorcery.com/enp/rfc/rfc333

2.txt http://www.ulticom.com/html/products/sigtran/

m3ua.asp http://www.iec.org/online/tutorials/ss7/index.ht

ml http://www.hssworld.com/voip/stacks/sigtran/Si

gtran_M3UA/overview.htm http://www.networksorcery.com/enp/protocol/

m3ua.htm http://www.javvin.com/protocolMTP.html