Signaling and switching equipment allows VoIP calls channel for signaling is established where messages are exchanged
and associated elements to travel within networks and between between network elements over 56- or 64-Kbps A-Links.
networks, as well as between customers who use network ser- In VoIP services, many voice calls must cross over from the
vices. These information elements are defined by signaling VoIP world to the PSTN word and vice versa; therefore, VoIP
protocols as well as transport methods that enable inter-func- service-provider hubs must “understand” SS7 signaling. This is
tionality between network components. The Public Switched facilitated by Signaling Transport (SIGTRAN), a suite of proto-
Telephone Network (PSTN) relies on these protocols to estab- cols and adaptation layers for transporting signaling informa-
lish circuit connections. Within VoIP itself, the prime duty of tion over IP-based networks. The key transport component in
signaling is to facilitate connectivity to the PSTN network while any distributed Voice over Packet architecture, SIGTRAN can be
offering the carrier flexibility in resetting ports and billing. integrated at any point in a next-generation network, such as at
Signaling System Number 7, or SS7 for short, is a common a signaling gateway (SG), media gateway controller (MGC), or
channel signaling system. SS7 is used in public switched net- an IP-based SCP, which functionally resembles an SS7 SCP.
works where large numbers of circuits must be switched be- A wide assortment of companies provide SS7 and related sig-
tween subscribers. A global standard, SS7 is used within net- naling systems solutions, platforms, and software. Let us meet
works as well as internationally between networks. some of the high-profile players in the signaling systems market
SS7 is marked both by high-speed circuit switching as well as out- and explore what platforms, products, and solutions they offer: of-band signaling that uses service switching points (SSPs), signal Adax: Signaling infrastructure solutions provider Adax offers transfer points (STPs), and service control points (SCPs), which solutions for SS7, IP, and ATM protocols. Adax signaling blades are collectively referred to as signaling points or SS7 nodes. It is im- can support a complete SS7 stack over T1/E1 interfaces and/or portant to note that SS7 signaling does not take place over the same SIGTRAN protocols over Ethernet ports, which provide the SS7 path as the data transfer or conversation. Instead, a separate digital transport over IP. They can also act as a single-board signaling gateway with SS7 transport over IP, enabling integration of existing SS7 intelligent nodes and databases with IP-based media gateways, signaling gateways, and softswitches. Adax signaling gateways include products for SS7/IP switching, routing, tunneling, and backhaul, as well as high availability and high density solutions. These products include HDC, high density narrowband channelized controller for all SS7 and SIGTRAN signaling protocols; ATM, a controller for real-time voice and video over ATM AAL2; signaling and IP over AAL5; and SDC, an IP signaling card for high-performance SIGTRAN, IPSec, and SIP applications. Adax is based in Berkeley, Calif., ( www.adax.com–510-548-7047). Cantata Technology: Based in Needham, Mass., Cantata Technology has a signaling systems-related product portfolio that includes solutions it acquired when it merged with Brooktrout Technology early in 2006. The Cantata Technology NS301 is an open systems hardware platform for carrier-grade network interface and packet processing applications. The NS301 is available in CompactPCI and PCI form factors with dual, quad, or octal T1/E1 network interfaces with optional Ethernet and up to 256
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