PERFORMANCE TECHNOLOGIES EXTENDS SS-7 NETWORKS WITH IP
Transition of voice traffic to Internet protocol (IP) is expected to take years, but one company, Performance Technologies of Rochester, N.Y., already has applied IP technology to underlying Signaling System-7 (SS-7) control network. Company’s SEGway product is SS-7 to IP internetworking device that enables wireline and wireless carriers to offload SS-7 traffic to shared packet networks rather than use dedicated circuit for each link. Link Concentrator, 2nd product due next month, reduces need to add links to Signal Transfer Points (STPs) by concentrating SS-7 traffic onto fewer shared IP links. Both products use Internet Engineering Task Force (IETF) Stream Control Transmission Protocol (SCTP) to transport SS-7 messages over IP networks with same reliability as dedicated links, company said. Developed specifically for signaling data, SCTP is transport protocol operating on top of IP -- at best potentially unreliable connectionless packet service. SEGway product is transparent to SS-7 network and messages are transported without need for new SS- 7 point codes (addresses) or network reconfiguration upon installation, company said.
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Early customer of SEGway product is Comfone AG, GSM roaming broker based in Switzerland, which uses product to reach remote countries where SS-7 networks are unavailable or amount of SS-7 traffic doesn’t justify cost of dedicated leased line. Core of company business is ANSI-to-ITU standards conversion of SS-7 messaging between N. American GSM wireless networks and GSM operators outside N. America, Comfone spokesman Peter Zb?ren said. Roaming between standards required conversion of Mobile Application Part (MAP) messages. “Comfone processes all roaming messages between ANSI and ITU standards with more than 280 operators connected, including all ANSI GSM operators in North America,” Zbaren said. “Over time, our customer base increased remarkably and the associated signaling access in certain places of the world became more and more difficult.” Problems Comfone faced include: Lack of SS-7 networks, regulations hindering international roaming, high prices charged by incumbent operators, or existing SS-7 systems “not supporting certain functions like TT conversion.” “Based on the new SCTP protocol the connection of remote locations for GSM roaming became possible via the public Internet connection,” he said.
Unlike most small IP telephony equipment makers, Performance Technologies’ future isn’t tied to CLEC or independent telco rollouts of voice over IP. Although products use IP technology, each solves problems in existing circuit switched networks. “Products are geared to smaller carriers and wireless carriers that don’t have extensive SS-7 networks. In the latter case an IP link could be used to bring applications to wireless customers and bring SS-7 messages back to the STP,” Performance Technologies’ Robert Mason said. While SEGway product serves needs of international long-haul SS-7 links over IP, new Link Concentrator product will serve domestic need, he said. “A real concern where SS-7 networks are growing is port exhaustion.” In current U.S. telephone networks STP is packet switch with huge capacity -- typically single STP is provisioned per LATA together with redundant backup. “To replace the STP is a huge expense, as much as $8 to $10 million at a stage where capital is tight for the carriers,” Mason said. Link Concentrator acts as small STP in telephone network, concentrating and routing messages between nodes using SS-7 or IP signaling protocols, he said.