M3UA

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M3UA

• Patrick Sharp

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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.

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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.

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SS7

• 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

• PSTN functions
• Call-establishment
• Routing
• Billing
• Information exchange

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SS7

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

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SS7
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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)

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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.

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MTP3

• Capabilities
• Node addressing
• Routing
• Alternate routing
• Congestion control

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MTP3

• 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

• SNM
• Deals with the general management of the MTP.

• SHM
• Deals with discrimination, distribution and
  routing of signaling messages.

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MTP3 User Adaptation

• M3UA allows for all the functionality of MTP3 to
  be done over IP.

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M3UA

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

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M3UA

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

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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.

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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.

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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.

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SS7/IP
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SS7/IP

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

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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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IP/IP
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IP/IP

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

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M3UA Protocol

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

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

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M3UA Protocol
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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

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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

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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, context
  information, configuration data,
  destination/origination codes, etc.

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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.

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M3UA Procedure

• Establishment of traffic between an ASP and SGP

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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

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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

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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 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

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Questions

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

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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.

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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/Sigtra
  n_M3UA/overview.htm
• http//www.networksorcery.com/enp/protocol/m3ua.ht
  m
• http//www.javvin.com/protocolMTP.html