Transcript 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.
M3UA – MTP3 User Adaptation Layer
Allows integration of existing networks
with new technology.
SS7
Signaling Support 7
An architecture for performing out-ofband signaling in support of the
functions of the PSTN (Public Switched
Telephone Network).
SS7
PSTN functions
 Call-establishment
 Routing
 Billing
 Information exchange
SS7
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SSP-telephone switches
STP-packet switches
SCP-databases
SS7
MTP3
SS7 protocol is layered. We are
interested in the Message Transfer PartLevel 3.
Together with the Message Transfer PartLevel 2, referred to as the MTP
(Message Transfer Part)
MTP3
MTP3 extends MTP2, which provided linklayer functionality. MTP3 adds network
functionality.
Ensures that messages are delivered
across the network regardless of
whether or not the nodes are directly
connected.
MTP3
Capabilities:
 Node addressing
 Routing
 Alternate routing
 Congestion control
MTP3
Sits between MTP2 and user parts (ISUP,
TUP, SCCP).
Made up of 2 parts:
 SMH (Signaling Message Handling)
 SNM (Signaling Network Management)
MTP3
SNM:
Deals with the general
management of the
MTP.
SHM:
Deals with
discrimination,
distribution and
routing of signaling
messages.
MTP3 User Adaptation
M3UA allows for all the functionality of
MTP3 to be done over IP.
M3UA
Supports the transport of MTP3-User
signaling over IP.
 ISUP-ISDN User Part
 SCCP-Signaling Connection Control Part
 TUP-Telephone User Part
M3UA
Transports the MTP3-User signaling using
the Stream Control Transmission
Protocol (SCTP).
SCTP provides for unique needs of the
telephony network.
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.
SCTP
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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.
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 MTP3User signaling between IP networks.
SS7/IP
SS7/IP
M3UA can be used as a gateway, in almost the
same way as an SS7 STP.
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.
IP/IP
IP/IP
Less commonly used, but M3UA also
allows for the transport of MTP3-User
parts between two IP applications.
M3UA Protocol
M3UA message format includes a
common header followed by zero or
more parameters as determined by the
type of message.
M3UA Protocol
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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 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
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
M3UA Protocol
All classes also have reserved types for
IETF use as well as reserved types for
IETF defined extensions.
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.
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.
M3UA Procedure
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Establishment of traffic between an ASP and
SGP
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
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 MTPTRANSFER primitive
 Pass the primitive to the user part
M3UA Procedure
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A single exchange between IP Server
Processes (IPSP)
M3UA Security
Goals:
 Availability of reliable and timely user
data transport
 Integrity of user data transport
 Confidentiality of user data
Benefits of M3UA
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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:
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What is the purpose of M3UA?
How is M3UA commonly deployed?
How can M3UA be configured?
Answers
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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
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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