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