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 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 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 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 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 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 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/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