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It was thought in the 1990s that telephone companies would soon offload all of their voice calls from Public Switched Telephone Networks (PSTNs) to voice-over-Internet Protocol (VoIP) networks, since it’s less expensive to carry voice traffic over packet-switched Internet Protocol (IP) networks than over circuit-switched networks.

 

Circuit-switched telephone networks are still with us. They interface and exchange traffic with the growing number of IP networks, and they still use a signaling protocol called Common Channel Signaling System #7 (called SS7 or C7). In the PSTN, signaling end points send and receive SS7 signaling messages. There are three kinds of signaling end points: Service Switching Point (SSP or central office switch), Signal Transfer Point (STP) and Service Control Point (SCP)

 

In SS7 networks, ISUP (Integrated Services Digital Network [ISDN] User Part) signaling messages are used to setup, manage and release trunk circuits that carry voice calls between central office switches. ISUP messages also carry caller ID information, such as the calling party's telephone number and name. ISUP is used for both ISDN and non-ISDN calls between central office switches. TCAP (Transaction Capabilities Application Part) signaling messages support telephony services, such as calling cards, toll-free calls, Local Number Portability and mobile wireless roaming and authentication services.

 

VoIP networks can carry SS7-over-IP using protocols defined by Signaling Transport (sigtran) working group of the Internet Engineering Task Force (IETF), the international organization responsible for recommending Internet standards. The SIGTRAN protocols support the requirements for SS7/C7 signaling as defined by International Telecommunication Union (ITU) Telecommunication Standardization Sector. Given the growing worldwide patchwork of PSTN and IP networks, multi-purpose signaling gateways for SS7 and IP interworking are also becoming popular.

 

And now, Adax (News - Alert) Europe, a major provider of high performance signaling infrastructure, has launched the HDC3-Low Profile PCI Express (PCIe) four-port SS7 controller: HDC3-LPe. With four physical ports on board, rather than the normal two, Adax’s Low Profile PCIe card maximizes system density and helps to reduce points of failure by removing the need for Y cables ensuring NEBS certification isn’t affected when four connections are required.

The HDC3 is a high-density, high-performance solution suited for narrowband and broadband signaling applications and is being released following rigorous testing on many rack-mounted servers and trials by customers. Delivering up to 124 MTP2 links or four HSLs (Q.703 Annex A or ATM AAL5) per card, the HDC3-LPe board is able to perform many thousands of transactions per second, placing minimal load on the host, maximizing application performance and ensuring no degradation of service for the customer.

 

Increasingly providers such as Sun and HP are making only Low Profile PCI Express slots available in their rack-mount server ranges and the Low Profile PCIe format saves space, leaving server manufacturers more room for bigger and faster host CPUs. As a vendor that supports a single software driver and a common API across the whole range of board formats, the Adax HDC3 saves development time and provides a rapid return on investment.

 

The Adax HDC3 family is available in PMC (PCI Mezzanine Card), AMC (AdvancedTCA (News - Alert) Mezzanine Card), PCI/X and PCIe board formats. The board is dynamically configurable and can deliver up to 8 T1/E1 ports and 248 channels of multiple protocols, including SS7 MTP2, LAPB/D/V5, Frame Relay, X.25 and HDLC per card. ATM AAL5 is also supported for broadband SS7. With the ability to install multiple cards in a system, the HDC3 provides a totally scalable, flexible and cost-effective solution that is ideal for any signaling need.