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M3UA

M3UA. Patrick Sharp. M3UA. Drive 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. M3UA. M3UA is a protocol for interfacing legacy SS7 networks with IP.

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M3UA

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  1. M3UA Patrick Sharp

  2. M3UA Drive 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.

  3. M3UA M3UA is a protocol for interfacing legacy SS7 networks with IP. M3UA – MTP3 User Adaptation Layer Allows integration of existing networks with new technology.

  4. SS7 Signaling Support 7 An architecture for performing out-of-band signaling in support of the functions of the PSTN (Public Switched Telephone Network).

  5. SS7 PSTN functions • Call-establishment • Routing • Billing • Information exchange

  6. SS7 • SSP-telephone switches • STP-packet switches • SCP-databases

  7. SS7

  8. MTP3 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)

  9. MTP3 MTP3 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.

  10. MTP3 Capabilities: • Node addressing • Routing • Alternate routing • Congestion control

  11. MTP3 Sits between MTP2 and user parts (ISUP, TUP, SCCP). Made up of 2 parts: • SMH (Signaling Message Handling) • SNM (Signaling Network Management)

  12. SNM: Deals with the general management of the MTP. SHM: Deals with discrimination, distribution and routing of signaling messages. MTP3

  13. MTP3 User Adaptation M3UA allows for all the functionality of MTP3 to be done over IP.

  14. M3UA Supports the transport of MTP3-User signaling over IP. • ISUP-ISDN User Part • SCCP-Signaling Connection Control Part • TUP-Telephone User Part

  15. M3UA Transports the MTP3-User signaling using the Stream Control Transmission Protocol (SCTP). SCTP provides for unique needs of the telephony network.

  16. SCTP Protocol 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.

  17. 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.

  18. M3UA M3UA 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.

  19. SS7/IP

  20. SS7/IP M3UA can be used as a gateway, in almost the same way as an SS7 STP.

  21. 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.

  22. IP/IP

  23. IP/IP Less commonly used, but M3UA also allows for the transport of MTP3-User parts between two IP applications.

  24. M3UA Protocol M3UA message format includes a common header followed by zero or more parameters as determined by the type of message.

  25. 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

  26. M3UA Protocol

  27. M3UA Protocol Each message class has different types. MGMT: ERR, NTFY Transfer: Payload Data SSNM: Destination Unavailable/Available, Destination State Audit, Signaling Congestion, Destination User Part Unavailable, Destination Restricted

  28. M3UA Protocol ASPSM: ASP Up/Down, Heartbeat, ASP Up/Down Ack, Heartbeat Ack ASPTM: ASP Active/Inactive, ASP Active/Inactive Ack RKM: Registration Request/Response, Deregistration Request/Response

  29. M3UA Protocol All classes also have reserved types for IETF use as well as reserved types for IETF defined extensions.

  30. M3UA Protocol Each 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.

  31. M3UA Procedure A 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.

  32. M3UA Procedure • Establishment of traffic between an ASP and SGP

  33. M3UA Procedure When 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

  34. M3UA Procedure When 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

  35. M3UA Procedure • A single exchange between IP Server Processes (IPSP)

  36. M3UA Security Goals: • Availability of reliable and timely user data transport • Integrity of user data transport • Confidentiality of user data

  37. 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

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

  39. 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.

  40. 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.networksorcery.com/enp/protocol/m3ua.htm • http://www.javvin.com/protocolMTP.html

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