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September 30, 2014

SIP Trunking and UC with Lync: The Role of the E-SBC


By Steven Johnson President, Ingate Systems, Inc.



Enterprise session border controllers play an important role in enabling SIP trunking and all unified communications applications with Lync. Ingate Systems’ E-SBC, the SIParator, is fully certified for use in Lync environments and meets or exceeds both the required and optional test parameters, making it one of the few ESBCs that can support TLS and other security features offered by Microsoft.


The E-SBC serves many roles in a Lync deployment, as it does in deployments with other IP PBXs. Microsoft Lync has several unique requirements when deployed for SIP trunking. First is the use of Transmission Control Protocol Transport.  The TCP Transport, as compared to User Datagram Protocol Transport, provides a more reliable means of communication between services and can be effective in unified communications. However, many SIP trunk service providers deploy SIP trunking only using the UDP Transport (referred to as a streaming protocol, as data is sent without confirmation of receipt/delivery, whereas TCP is sent in small segments and confirmation is sent before the next segment is sent). 

Another Lync requirement is the use of Fully Qualified Domain Names in many of the SIP addressing fields. Many SIP trunk service providers deploy SIP trunks using only IP addresses in the SIP addressing fields.

E-SBCs can solve these problems. E-SBCs can provide a seamless format conversion of UDP to TCP, and change IPs to FQDNs, enabling seamless interoperability between the SIP trunking service provider and Lync. 

E-SBCs sit at the edge of the network to provide control over the SIP traffic. Traditionally E-SBCs were seen as just providing NAT traversal and firewalling protection – the security – for SIP-based voice networks. Today’s E-SBCs provide that crucial, business-class security, and also resolve interoperability issues between other on-premises equipment such as the Microsoft Lync server, resulting in a fast, simplified, and robust installation.

Microsoft has a rigorous certification process for E-SBCs. Certified E-SBCs ensure a seamless and reliable use of Lync applications. However, not all certified E-SBCs have been qualified to include the same security options. Some only comply with the basic requirements.

Only a handful of Lync-certified E-SBCs have been successfully tested to support optional features such as TLS, SRTP, DNS load balancing, full failover and full consultative transfer, ensuring the secure connection between the SIP trunking service and the Microsoft Lync environment. Ingate E-SBCs include these optional features, and have also been used by SIP trunking service providers to offer Microsoft Lync-qualified SIP trunks, with or without additional security such as TLS and SRTP. 

The same Ingate product can also integrate PBXs and other UC solutions into the Microsoft Lync environment.

As Microsoft Lync gains market share, enterprises (and service providers) can be confident that with an Ingate SIParator as the E-SBC, Lync deployments will be quick and result in a robust and secure SIP trunking and unified communications environment.

Steven Johnson is president of Ingate Systems




Edited by Maurice Nagle
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