Aculab offers SS7 and SIGTRAN as part of its extensive range of signalling protocols, allowing users to directly connect switching, media processing and signalling platforms to a carrier’s network – via TDM and/or IP-based signalling transport. The SS7 and SIGTRAN protocols are suitable for worldwide deployment over TDM, IP or hybrid TDM/IP transport environments as needed. They are available for use with the complete range of Aculab’s cPCI, PCI and PCIe boards – either E1/T1 trunk only (digital network access) boards or those from the Prosody range, combining media processing resources for both IP and TDM environments – to bring tremendous value for developers and systems integrators. For TCAP applications not requiring media processing functionality, Aculab’s SIGTRAN software can be licensed for use in a host PC without an Aculab board.

Applications
The implementation of Aculab's SS7 and SIGTRAN signalling protocol software is intended to assist developers and integrators designing value-added solutions for public telephony networks. These may range from CRBT, signalling gateways, and messaging applications, to prepaid calling board platforms and other added value, revenue generating services, for example. In addition, the SS7 signalling monitor is ideal for lawful interception (LI) mediation and delivery platforms.

Many applications also require media processing resources, such as record, playback, DTMF handling and echo cancellation. These functions are available with Aculab's Prosody platforms, which can be combined with SS7 and SIGTRAN on a single board to deliver powerful, cost-effective, computer-based solutions.

SIGTRAN is a stepping stone for cost-effective migration to an IP multimedia subsystem (IMS) at the signalling layer and provides increased capacity over IP – resulting in reduced link quantity requirements, more efficient bandwidth utilization and reduced transport cost. Together, these benefits allow operators to offer their customers new, more advanced services at competitive prices.

Protocol support and APIs
Aculab's SS7 and SIGTRAN signalling software supports M3UA (over SCTP), MTP, ISUP, SCCP and TCAP protocol procedures. The availability of the TCAP and SCCP allows multiple network-based application sub-systems to be addressed explicitly, enabling advanced access database query services and global title translation.

At the API, on a per call basis, the user has access to and control of many of the ISUP or TCAP protocol parameters. The API also provides a lower level of access to ISUP parameters. For power users requiring more complex control, direct access to raw data ISUP parameters, through ‘flexible ISUP’ extensions to the generic call control API, is provided.

The product presents a standard TCAP API to developers to support both TCAP structured and unstructured dialogues, as required by CAMEL or GSM-MAP applications, for example. The TCAP API includes ASN.1 codec 'helper' functions, which obviate the need for expensive, 3rd party APIs, compilers or toolkits.

ISUP and TCAP present the same APIs, whether they are to be used over MTP in a TDM scenario or via SIGTRAN M3UA in an IP-based network. Beneficially, this means applications can be readily used in either environment or indeed in a hybrid environment (e.g., ISUP over TDM and TCAP over IP) without the need for rework, protecting development investments.

An SS7 maintenance API provides user functions for the activation and deactivation of any configured link and the maintenance block/unblock of configured circuits, in addition to retrieval of essential state information from all configured hosts.

Multi-threaded applications
The Aculab TCAP API includes supporting software that enables easy construction of multi-threaded applications, with mechanisms that automatically manage thread pools and route TCAP traffic to individual threads for processing. In addition, many of the system facilities required for a multi-threaded application that are normally operating system specific, such as threads libraries, are presented in an operating system independent interface. This makes for easier portability of applications between platforms.

Capacities
Connection to a TDM network is supported by any Aculab board with an optional or fitted primary rate trunk interface, which carries user-defined 64kbit/s timeslots for signalling links. Timeslots within the trunks on Aculab boards that are not used for signalling are available as voice/data bearer circuits, thereby leading to maximum cost efficiency. Prosody X board variants using PMXC modules can support up to 128 signalling links, which can be freely allocated over the trunks on the board.

Connection to an IP network is supported by the host NIC or via the dual redundant Ethernet LAN connections on Prosody X board variants. The available LAN bandwidth, together with the licensed SIGTRAN capacity, limits the signalling message throughput. Aculab offers cost-effective, high performance licence options from 200 to 3200 transmit messages per second. Contact sales@aculab.com for other requrements.

The software supports an unrestricted number ISUP and TCAP hosts, including an unrestricted number of E1/T1 bearer circuits. Whether for traditional SS7 over TDM or using IP transport with SIGTRAN, Aculab offers an ideal option for high throughput messaging applications such as SMS and prepaid using CAMEL, GSM-MAP or ANSI 41 D (IS-41D).

See table for more details.

Signalling scalability and resilience
Signalling links can operate in fully associated signalling mode (F-links) or quasi-associated mode and form one or more link sets. Signalling links within the same link set can reside on more than one Aculab board within a system, ensuring that a single board level failure does not cause a loss of signalling connectivity to the SS7 network. Because of this, the product can be connected to one or more service switching points (SSPs) or one or more signal transfer points (STPs) in the network and resilience is achieved in that there is no reliance on a single delivery trunk from the network.

For added reliability, a dual resilient MTP3 allows an active/active, auto-failover, load sharing configuration, with the signalling links split between boards in two chassis, appearing as a single network node – and local point code. A single link set can be split between the two MTP3 systems or separate link sets used to connect each system to a different STP.

The dual redundant architecture applies equally to M3UA configurations, with signalling associations established via SCTP to adjacent network nodes from each host. The dual M3UA hosts provide the same high level of resilience expected of traditional SS7 network connections with the advantages of greater bandwidth and reduced transport costs.

In addition, for large systems, the ISUP and TCAP architecture allows boards providing bearer channel terminations to be installed or implemented in multiple, distributed chassis/nodes, each sharing a single point code. The distributed architecture applies to both ISUP and TCAP applications in TDM environments and IP or hybrid TDM/IP configurations. All of which enables excellent scalability and application resilience, because problems with a single ISUP/TCAP node won't affect the operation of the rest of the system.

Protocol standards
Aculab is continually expanding its coverage of SS7 and SIGTRAN protocol standards and country-specific variants. In addition to general market requirements, a request for change system is used to define customer priorities for additions and changes to products. Contact your Account Manager or sales@aculab.com for information about protocol development plans or individual feature requests.

See table for more details on conformance of individual protocol specifications.

Recommended reading
Aculab’s SS7 developer’s guide is available from the technical documents pages.

Related links:

Product pages Digital network access SS7 signalling monitor E1/T1 PCI E1/T1 cPCI Prosody X PCI Prosody X cPCI Prosody X PCIe Prosody PCI Prosody cPCI Media processing resources Protocols and approvals Press release SS7 monitoring solutions Comsys press release   Technical documents     Software downloads     Deployment notes     Technical details Features An old protocol refuses to budge Lawful interception     Case studies Globitel Comsys' hosting platform enhanced by Prosody X with SS7

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