View source for M3UA

'''M3UA''' is a [[Communication protocol|communication protocol]] of the [[Organization:SIGTRAN|SIGTRAN]] family, used in [[Engineering:Telephone network|telephone network]]s to carry [[Engineering:Signaling (telecommunications)|signaling]] over [[Internet Protocol]] (IP).  M3UA enables the SS7 protocol's User Parts (e.g. [[ISDN User Part|ISUP]], [[Signalling Connection Control Part|SCCP]] and TUP) to run over virtually any network technology breaking its limitation to telephony equipment like [[T-carrier]], [[E-carrier]] or [[Asynchronous Transfer Mode]] (ATM), which highly improves [[Scalability|scalability]] of the signaling networks.

'''M3UA''' stands for MTP Level 3 (MTP3) User Adaptation Layer as defined by the [[IETF]] [[Organization:SIGTRAN|SIGTRAN]] working group in {{IETF RFC|4666}} (which replaces and supersedes {{IETF RFC|3332}}).  Like other adaptation protocols, M3UA uses [[Stream Control Transmission Protocol|SCTP]] to transmit messages between its network elements.

== Implementation scheme ==

<imagemap>
Image:M3UA-scheme.svg|404x404px|thumb|M3UA: Transmitting MTP-3 messages: on the left is the [[Time-division multiplexing|TDM]]-network for SS7. On the right is the IP network with SIGTRAN as a transport.|center
rect 1 1 100 72 Point code

rect 1 90 593 123 [[ISDN User Part|ISUP]]
rect 1 123 593 160 [[Signalling Connection Control Part|SCCP]]

rect 1 160 100 232 MTP-3
rect 1 232 100 445 MTP-2
rect 1 445 100 515 MTP-1

rect 248 1 347 72 Point code

rect 199 160 296 232 MTP-3
rect 199 232 296 445 MTP-2
rect 199 445 296 515 MTP-1

rect 298 160 397 232 [[M3UA]]
rect 298 232 397 302 SCTP
rect 298 302 397 372 [[Internet Protocol|IP]]
rect 298 372 397 445 [[Data link layer|L2]]
rect 298 445 397 515 [[Physical layer|L1]]

rect 493 1 593 72 Point code

rect 493 160 593 232 [[M3UA]]
rect 493 232 593 302 SCTP
rect 493 302 593 372 [[Internet Protocol|IP]]
rect 493 372 593 445 [[Data link layer|L2]]
rect 493 445 593 515 [[Physical layer|L1]]

rect 15 522 85 565 ISDN
rect 248 522 347 565 Signaling gateway
rect 493 522 580 565 [[Media Gateway Controller]]

</imagemap>

=== Typical scheme ===
<pre>
________                   _________                __________ 
|      |                   |       |                |     MGC|
|  SP  |<----------------->|  SGW  |<---------------|-->(AS) |
|______|   SS7 network     |_______|   IP network   |________|
  MTP3
point-code                         common point-code
   PC1                                    PC2
</pre>

=== Use SGW as STP===
Several AS owns PC itself and uses SGW as STP (transit pointcode).
<pre>
________                 _____________               ___________ 
|      |                 |    SGW    |               |      MGC|
|      |                 |           | /-------------|-->(AS)  | point-code PC3
|  SP  |<----------------|-->(STP)<--|-              |         |
|      |                 |           | \-------------|-->(AS)  | point-code PC4
|______|  SS7 network    |___________|   IP network  |_________|
  MTP3                    point-code
point-code                   PC2                         
   PC1
</pre>

== Protocol ==
M3UA uses a complex state machine to manage and indicate states it's running. Several M3UA messages are mandatory to make an M3UA association or peering fully functional (ASP UP, ASP UP Acknowledge, ASP Active, ASP Active Acknowledge), some others are recommended (Notify, Destination Audits (DAUD)).

== Additional info ==

An open implementation of the M3UA standard can be found at OpenSS7's web site.<ref>[http://www.openss7.org/m3ua.html OpenSS7 web site]</ref>

[[Software:Wireshark|Wireshark]] is shipped with a dissector for M3UA, sample packets can be found in Wireshark's wiki page, which shows ISUP Packet samples (including M3UA<ref>[http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=view&target=isup.cap Wireshark wiki page]</ref>).

==References==
{{Reflist}}


[[Category:Internet protocols]]
[[Category:Internet Standards]]

{{Sourceattribution|M3UA}}