Dimuro An SG contains a set rff one or more unique Signalling Gateway Processes, of which one or more is normally actively processing traffic. See the ITU-T recommendations http: However, in the context of an SG, the maximum octet block size must be followed when interworking to a SS7 network that does not support the transfer of larger information blocks to the final destination. Prerequisites for this release can be found in the release notes for cisco media gateway controller software release 9. The treatment of unallocated traffic is implementation dependent. M3UA reports the status of an AS. Rfc ss7 mtp3user adaptation layer september linkset a number of signalling links that directly interconnect two signalling points, which are used as a module.
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Morneault Cisco J. Please refer to the current edition of the "Internet Official Protocol Standards" STD 1 for the standardization state and status of this protocol. Distribution of this memo is unlimited.
All Rights Reserved. Table of Contents 1. M3UA Protocol Elements Examples of M3UA Procedures Security Considerations IANA Considerations Document Contributors Sidebottom, et. The AS contains a set of one or more unique Application Server Processes, of which one or more is normally actively processing traffic. Note that there is a relationship between an AS and a Routing Key. Failover - The capability to reroute signalling traffic as required to an alternate Application Server Process, or group of ASPs, within an Application Server in the event of failure or unavailability of a currently used Application Server Process.
Failover also applies upon the return to service of a previously unavailable Application Server Process. Layer Management - Layer Management is a nodal function that handles the inputs and outputs between the M3UA layer and a local management entity. An example scenario is where an SG appears as an element in multiple separate national SS7 networks and the same Signaling Point Code value may be reused in different networks.
Network Byte Order: Most significant byte first, a. Routing Key: A Routing Key describes a set of SS7 parameters and parameter values that uniquely define the range of signalling traffic to be handled by a particular Application Server.
Routing Context - A value that uniquely identifies a Routing Key. Routing Context values are either configured using a configuration management interface, or by using the routing key management procedures defined in this document.
It serves as an active, backup, load-sharing or broadcast process of a Signalling Gateway. An SG contains a set of one or more unique Signalling Gateway Processes, of which one or more is normally actively processing traffic. Stream - A stream refers to an SCTP stream; a unidirectional logical channel established from one SCTP endpoint to another associated SCTP endpoint, within which all user messages are delivered in-sequence except for those submitted to the unordered delivery service.
Standards Track [Page 6] RFC SS7 MTP3-User Adaptation Layer September - Explicit packet-oriented delivery not stream-oriented , - Sequenced delivery of user messages within multiple streams, with an option for order-of-arrival delivery of individual user messages, - Optional multiplexing of user messages into SCTP datagrams, - Network-level fault tolerance through support of multi-homing at either or both ends of an association, - Resistance to flooding and masquerade attacks, and - Data segmentation to conform to discovered path MTU size.
Under certain scenarios, such as back-to-back connections without redundancy requirements, the SCTP functions above might not be a requirement and TCP MAY be used as the underlying common transport protocol. However, in the case where an ASP is connected to more than one SG, the M3UA layer at an ASP should maintain the status of configured SS7 destinations and route messages according to the availability and congestion status of the routes to these destinations via each SG.
However, in the context of an SG, the maximum octet block size must be followed when interworking to a SS7 network that does not support the transfer of larger information blocks to the final destination. The provisioning and configuration of the SS7 network determines the restriction placed on the maximum block size.
Some configurations e. The M3UA layer at an ASP keeps the state of the routes to remote SS7 destinations and may initiate an audit of the availability, the restricted or the congested state of remote SS7 destinations.
An SG may be logically partitioned to operate in multiple SS7 network appearances. In such a case, the SG could be addressable with a Point Code in each network appearance, and represents a set of nodes in the IP domain into each SS7 network.
Alias Point Codes [ 8 ] may also be used within an SG network appearance. Note: It is possible for the SGP Routing Key configuration data to be temporarily out-of-sync during configuration updates. SG-to-SG communication i. Inter-SGP protocol is outside of the scope of this document.
The following example shows a signalling gateway partitioned into two network appearances. A Routing Key is essentially a set of SS7 parameters used to filter SS7 messages, whereas the Routing Context parameter is a 4-byte value integer that is associated to that Routing Key in a relationship. The particular information used to define an M3UA Routing Key is application and network dependent, and none of the above examples are mandated.
It is not necessary for the parameter range values within a particular Routing Key to be contiguous. A Routing Key may be configured statically using an implementation dependent management interface, or dynamically using the M3UA Routing Key registration procedure.
Other implementation dependent distribution algorithms may be used. To support this message distribution, the SGP might, for example, maintain the equivalent of a network address translation table, mapping incoming SS7 message information to an Application Server for a particular application and range of traffic.
These ASPs provide dynamic status information regarding their availability, traffic handling capability and congestion to the SGP using various management messages defined in the M3UA protocol. The list of ASPs in an AS is assumed to be dynamic, taking into account the availability, traffic handling capability and congestion status of the individual ASPs in the list, as well as configuration changes and possible failover mechanisms. Normally, one or more ASPs are active i.
Broadcast, loadsharing and backup scenarios are supported. Possible solutions are to provide a default Application Server at the SGP that directs all unallocated traffic to a set of default ASP s , or to drop the message and provide a notification to layer management.
The treatment of unallocated traffic is implementation dependent. This is accomplished by observing the Destination Point Code and possibly other elements of the outgoing message such as the SLS value. Each ASP in this set may be active, inactive or unavailable. The function could optionally be used to control the start of traffic on to a newly available SCTP association.
It also provides network status information to one or both sides of the network. In addition, as an implementation and network option, restricted destinations are communicated from MTP network management to the local M3UA-resident management function. From ITU Q. For forward compatibility, all Message Types may have attached parameters even if none are specified in this version. The supported versions are the following: 1 Release 1. All the parameters contained in a message are defined in a Tag Length-Value format as shown below.
Parameter Tag: 16 bits unsigned integer The Tag field is a bit identifier of the type of parameter. It takes a value of 0 to Common parameters used by adaptation layers are in the range of 0x00 to 0x3f. M3UA-specific parameters have Tags in the range 0x to 0x02ff.
The parameter Tags defined are as follows: Common Parameters. Values other than those defined in specific parameter description are reserved for use by the IETF. Parameter Length: 16 bits unsigned integer The Parameter Length field contains the size of the parameter in bytes, including the Parameter Tag, Parameter Length, and Parameter Value fields. Thus, a parameter with a zero-length Parameter Value field would have a Length field of 4.
The Parameter Length does not include any padding bytes. The Parameter Value field contains the actual information to be transferred in the parameter. If the length of the parameter is not a multiple of 4 bytes, the sender pads the Parameter at the end i. The length of the padding is NOT included in the parameter length field. The receiver MUST ignore the padding bytes.
In other cases the parameter may be configured to be present for the use of the receiver. Where the optional Network Appearance parameter is present, it must be the first parameter in the message as it defines the format of the Protocol Data field. Where multiple Routing Keys and Routing Contexts are used across a common association, the Routing Context MUST be sent to identify the traffic flow, assisting in the internal distribution of Data messages.
User Protocol Data. Includes: MTP3-User protocol elements e. Service Indicator: 8 bits unsigned integer The Service Indicator field contains the SI field from the original SS7 message justified to the least significant bit. Network Indicator: 8-bits unsigned integer The Network Indicator contains the NI field from the original SS7 message justified to the least significant bit. The MP bits are aligned to the least significant bit.
As an implementation option the SG may suppress the sending of subsequent "response" DUNA messages regarding a certain unreachable SS7 destination for a certain period to give the remote side time to react.
Affected Point Codes that are less than bits, are padded on the left to the bit boundary. Including multiple Affected PCs may be useful when reception of an MTP3 management message or a linkset event simultaneously affects the availability status of a list of destinations at an SG. Identifying a contiguous range of Affected DPCs may be useful when reception of an MTP3 management message or a linkset event simultaneously affects the availability status of a series of destinations at an SG.
The Mask parameter is an integer representing a bit mask that can be applied to the related Affected PC field. The bit mask identifies how many bits of the Affected PC field are significant and which are effectively "wildcarded". For example, a mask of "8" indicates that the last eight bits of the PC is "wildcarded". A mask of "3" indicates that the last three bits of the PC is "wildcarded".
A mask value equal or greater than the number of bits in the PC indicates that the entire network appearance is affected - this is used to indicate network isolation to the ASP.
M3UA RFC 3332 PDF