SIP trunking is a service offered by Internet Service Providers (ISPs) which permits businesses to adopt Voice-over-IP (VoIP) with its attendant benefits and remain connected to others who rely on the PSTN. For the enterprise SIP trunks can offer significant cost savings, as they eliminate the need to purchase either the local PSTN gateway or costly ISDN BRIs (Basic Rate Interfaces) or PRIs (Primary Rate Interfaces). The local IP-PBX can be connected to the service provider's PSTN gateways over the Internet.

Ingate Firewalls and SIParators solve the Network Address Translation (NAT) traversal issues that are faced by businesses using a SIP trunk. All voice traffic (as well as data traffic) must traverse the enterprise firewall/NAT. However, SIP traffic cannot traverse traditional enterprise firewalls and NAT devices. This is because traditional firewalls do not differentiate between SIP traffic and unwanted traffic. As a result, the firewall/NAT device blocks all SIP traffic, which includes VoIP. Ingate products resolve this issue, enabling enterprises to utilize SIP trunks.

Ingate's fully SIP-capable, proxy-based Firewalls and SIParators also provide flexibility to interoperate with carrier-specific requirements like numbering plans and authentication. They establish least cost routing rules, which offers businesses the ability to use multiple service providers, and to switch between them depending on which offers the best possible rates (which may vary by time, day or location). Long distance calls cost the same as a local call, reducing expenses for businesses as well as their customers, partners, etc. trying to reach, for example, the corporate sales force.

SIP trunks further reduce costs as they eliminate the need for separate voice and data connections, expanding the potential for communications convergence using both voice and data together. SIP trunking also offers scalability so that, as a company grows, all necessary infrastructure to handle additional voice/data traffic is already in place.

Security Over The Public Internet

Ingate products are specifically designed to leverage all the security benefits available with SIP communications. Ingate's enterprise-class Firewalls secure data and SIP traffic, while SIParators secure SIP media while leaving the traditional firewall in place (working in parallel to the SIParator) to secure data traffic.

Both products feature Ingate's full SIP proxy technology, which allows for advanced filtering, verification, authentication and routing, as well as dynamic control of the opening and closing of media ports. Encryption of the signaling is done using Transport Layer Security (TLS) and of the media (voice, video, etc.) using Secure RTP (SRTP). With encryption, the sessions are kept private with no chance of eavesdropping.

They also secure full VoIP redundancy, as traffic can be routed to a back-up carrier if the primary carrier is unavailable. And Ingate's proxy-based solutions can be used to provide local call management if the service provider cannot be reached; and, if the enterprise has a local gateway installed, outgoing calls can be routed to the PSTN if all connections to the hosting provider are unavailable.

"SIP trunking offers enterprises the benefits of converged communications and saves substantial expense by eliminating the need to purchase their own PSTN gateway," said Steven Johnson, President, Ingate Systems. "NAT/firewall traversal is a critical issue in any SIP trunk deployment. Ingate's SIP-capable Firewalls and SIParators offer an elegant solution to this problem, while also securing voice traffic."

Connecting Remote Workers To The SIP Trunk Without VPN

SIP trunking, when used in conjunction with Ingate's Remote SIP Connectivity software module, allows remote users to traverse most SIP-unaware residential firewalls and NAT devices and use all the IP-PBX functions installed in the enterprise. Remote SIP Connectivity complements SIP trunks, as remote workers can use the software to interface with their corporate IP-PBX and, if they were making calls to outside the enterprise, do so using the SIP trunk.

For more information, please visit us at Ingate's VoiceCon booth #639, or online at www.ingate.com.