M3UA SIGTRAN

8/12/2019 M3UA SIGTRAN

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SIGTRAN-M3UA

Ziad El Samad


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Introduction

The drive to exploit the values of IP in traditional

telephone networks led to the creation of the

SIGTRAN group in the IETF (Internet EngineeringTask Force).

Need for protocols with best of both.


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SS7 (Review)

Signaling Support 7

An architecture for performing out-of-band signaling

in support of the functions of the PSTN (Public

Switched Telephone Network).


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SS7 (Review)

PSTN functions

Call-establishment

Routing

Billing

Information exchange


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SS7 (Review)

SSP-telephone switches

STP-packet switches

SCP-databases


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SS7 (Review)


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MTP3 (Review)

SS7 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)


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MTP3 (Review)

MTP3 extends MTP2, which provided link-layer

functionality. MTP3 adds network functionality.

Ensures that messages are delivered across thenetwork regardless of whether or not the nodes are

directly connected.


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MTP3 (Review)

Sits between MTP2 and user parts (ISUP, TUP,

SCCP).

Made up of 2 parts:

SMH (Signaling Message Handling) SNM (Signaling Network Management)


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MTP3 (Review)

SNM:

Deals with the

general

management of theMTP.

SHM:

Deals with

discrimination,

distribution androuting of signaling

messages.


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M3UA

M3UA supports the transport of SS7 MTP3-User

signaling (ISUP and SCCP messages) to an IP

Signaling Point (IPSP).

M3UAMTP3 User Adaptation Layer

Allows integration of existing networks with newtechnology.


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SCTP

UDP: Best effort delivery, but not reliable.

TCP: Guaranteed delivery, but not timely.

SCTP: Deterministic, reliable and timely.


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SCTP Services

Multi-Homing: End-points can be more than one IPaddress.

Multi-streaming (Chunking): Allows for multiple virtualconnections on the same physical line.

Block-Level: Unlike TCP in which transmission isviewed as a continuous stream of data, SCTP

transmits blocks.

Sequenced Delivery: Allows for messages to bedelivered in the order in which there were sent.


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SCTP Services (Continued)

Heartbeat Messages: SCTP uses periodic heart-beatmessages to confirm status of each endpoint.

Self-Fragmentation: SCTP uses MTU path discoveryto ensure that messages are not fragmented byintermediate nodes.


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M3UA

M3UA is generally deployed in an Application

Server (IPSP) as an Application Server Process.

Provides a link between SS7 and IP, but can also

be used to transport MTP3-User signaling betweenIP networks.


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M3UA - SS7/IP


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M3UA - SS7/IP

M3UA can be used as a gateway, in almost the

same way as an SS7 STP.


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M3UA - SS7/IP

All 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.


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M3UASS7/IP

M3UA is IP aware in that it translates the contents

of the incoming SS7 MSU using a Routing Key (aglorified routing table) to map to the relevant IP

address.


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M3UASS7/IP

When using M3UA, IPSPs (ASs) may, or may not,

require point codes:

If the application uses SCP functionality then the SSNmay be used to address the required IPSP without any

need for Point Codes.

If the application is a VoIP gateway (an SSP) whose

point code is visible within the SS7 network then clearlya point code is required at the IPSP (AS).


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M3UASS7/IP

The SS7 SG in the M3UA scenario functions as an

STP and can provide SCCP based services which

could include Golbal Title Translation which maycause redirection to either the SS7 or IP network.

MTP3 and M3UA provide routing capabilities. MTP3 routes from point code to point code.

M3UA maps and routes point codes to IP addresses

and vice versa using a Routing Key.


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M3UASS7/IP

The Nodal Inter-working Function (NIF) allows

messages to be routed to a local SCCP based

service, such as Global Title Translation, or to an

IPSP based on a Routing Key. When a message arrives at the SG, MTP3 or M3UA

examines the SIO/DPC/OPC set and routes the

message via the NIF to the appropriate location.

If the DPC is the same as the SG's Point Code, the

message is sent to the layer above.

If the DPC differs from the SG's Point code, the message is

routed by the SG to its proper destination via the NIF.


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M3UASS7/IP

In the SG, if the result of an application request or a GTT

yields an SCP address located in the SS7 domain or the IP

domain, the resulting request is sent to the local MTP3 or

M3UA respectively for proper routing.

M3UA provides functionality similar to MTP3 but routing is IP

aware through the use of the Routing Key.

Less commonly used, but M3UA also allows for the transport

of MTP3-User parts between two IP applications.


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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, includingheader and parameter padding

Data: variable, contains the parameters, if any


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M3UA Protocol


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M3UA Protocol

All classes also have reserved types for IETF use

as well as reserved types for IETF defined

extensions.


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M3UA Protocol

Each message class and type has zero or more

parameters, far too many to list here.

Parameters contain message bodies, contextinformation, configuration data, error code, status,

congestion indication, destination/origination

codes, etc.


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M3UA Procedure

A single exchange between IP Server

Processes (IPSP)


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M3UA Security

Goals:

Availability of reliable and timely user data

transport

Integrity of user data transport

Confidentiality of user data


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Benefits of M3UA

Replace physical SS7 links with virtual IPassociations

Maintain deterministic qualities demanded insignaling.

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


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References

http://www.networksorcery.com/enp/rfc/rfc3332.txt

http://www.ulticom.com/html/products/sigtran/m3ua.asp

http://www.iec.org/online/tutorials/ss7/index.html

http://www.hssworld.com/voip/stacks/sigtran/Sigtran_M3UA/overview.htm

http://www.zytrax.com/tech/ss7/sigtran_intro.html

http://www.informit.com/library/content.aspx?b=Signalin

g_System_No_7&seqNum=127 http://www.networksorcery.com/enp/protocol/m3ua.htm

http://www.javvin.com/protocolMTP.html
http://www.networksorcery.com/enp/rfc/rfc3332.txthttp://www.ulticom.com/html/products/sigtran/m3ua.asphttp://www.iec.org/online/tutorials/ss7/index.htmlhttp://www.hssworld.com/voip/stacks/sigtran/Sigtran_M3UA/overview.htmhttp://www.hssworld.com/voip/stacks/sigtran/Sigtran_M3UA/overview.htmhttp://www.zytrax.com/tech/ss7/sigtran_intro.htmlhttp://www.informit.com/library/content.aspx?b=Signaling_System_No_7&seqNum=127http://www.informit.com/library/content.aspx?b=Signaling_System_No_7&seqNum=127http://www.networksorcery.com/enp/protocol/m3ua.htmhttp://www.javvin.com/protocolMTP.htmlhttp://www.javvin.com/protocolMTP.htmlhttp://www.networksorcery.com/enp/protocol/m3ua.htmhttp://www.informit.com/library/content.aspx?b=Signaling_System_No_7&seqNum=127http://www.informit.com/library/content.aspx?b=Signaling_System_No_7&seqNum=127http://www.zytrax.com/tech/ss7/sigtran_intro.htmlhttp://www.hssworld.com/voip/stacks/sigtran/Sigtran_M3UA/overview.htmhttp://www.hssworld.com/voip/stacks/sigtran/Sigtran_M3UA/overview.htmhttp://www.iec.org/online/tutorials/ss7/index.htmlhttp://www.ulticom.com/html/products/sigtran/m3ua.asphttp://www.networksorcery.com/enp/rfc/rfc3332.txt

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M3UA SIGTRAN