Delivering Highly Available Voice Services Using Technology and Carrier Diversity
When prioritizing the delivery of highly available voice services, technology and carrier diversity could be key.
SIP trunks have proven to drive costs savings, boost flexibility and address capacity challenges, but how do you ensure that your designs will deliver the high availability needs of your enterprise? Before completely retiring legacy TDM trunks, consider the benefits of blending them with your SIP trunks and taking advantage of technology diversity to drive higher availability. If your requirements demand ultrahigh availability, then take it a step further and consider carrier diversity.
In this article, we will cover a number of designs that blend the use of new and traditional technologies as well as multiple carriers to deliver highly available solutions for your voice environment. Regardless of your voice needs, technology and carrier diversity can provide simple and often cost effective ways to guard against downtime of voice services.
SIP Trunk Deployment Using Site Diversity
In a simple SIP trunk deployment, a carrier will provide inbound and outbound voice services over an IP Wide Area Network (WAN) connection (Typically MPLS or Internet). There are two deployment models in this case. The option you choose depends entirely on the carrier you procure your SIP trunk service from.
If you obtain SIP trunk services from your existing WAN MPLS vendor then you can simply consolidate voice and data services on the same physical links. This option produces some of the most attractive financial benefits, since you eliminate separate physical voice and data circuits. If you instead use different providers for SIP trunk and WAN services, then you'll need to deliver your voice service over-the-top of your WAN. In this case you need to provision separate physical links to your SIP trunk provider.
Regardless of your deployment strategy, one of the main advantages of using SIP trunking is the ability to terminate these services in multiple data centers. With this approach you provide a very simple, cost-effective and highly available solution.
In the following diagram you can see how voice services from a single carrier are delivered to multiple data centers to create high availability through site diversity.
With this design, it's also important to split the call control function across the two data centers and maintain heartbeat via a back channel (in this example Metro Ethernet). This ensures that both call control and carrier services remain available in the event of a single data center failure.
External or off-net calls are delivered to and from remote offices via the data center trunks by routing this traffic over-the-top of the second carrier MPLS WAN. Enterprise Session Border Controllers (E-SBCs) provide the enterprise security boundary between you and the voice service provider, while carrier Session Board Controllers (SBCs) provide the security boundary between you and other enterprises. E-SBCs, in this case, also provide additional benefits like addressing fax issues, manipulating SIP headers, and protocol interworking. See my September article titled "Enterprise SBCs: Why they're so Important" for additional information on the value of E-SBCs.
Next page: SIP Trunk and PRI Technology Diversity