AudioCodes Limited, based in Lod, Israel, recently announced a “solution set” that will facilitate connectivity between Microsoft unified communications and e-mail applications (Communications Server “14” and Exchange 2010) and virtually any SIP trunking service provider.
The solution set, dubbed UcSIPT, pairs the Mediant 1000 E-SBC (enterprise session border controller)—an appliance that AudioCodes developed over the past six months or so—with configuration information specific to pretty much any SIP trunking provider you’d be likely to choose.
So, why is special equipment required to connect a SIP application like Microsoft Communications Server with SIP trunking services?
“There are SIP service providers and there are SIP applications—many of each,” AudioCodes director of market development, Alan Percy told Enterprise VoIPplanet in a recent briefing, “and despite the fact that you’d think you could just plug a SIP service provider into a SIP application and they’d just work, that’s not the reality.”
The simple fact is that different SIP implementations are not necessarily interoperable with each another.
This is one of the issues that session border controllers (SBCs) are designed to address—taking care of all the little protocol translation and header manipulation tasks that are involved in getting different SIP implementations to talk to each other.
Now AudioCodes did a lot of the heavy lifting of matching PBX applications to service providers back when a lot of enterprises were trying to connect their TDM phone systems to SIP trunks, to save money. AudioCodes’ solution for this problem was the Mediant Digital Gateway product line.
But as the company worked in this space, “it became increasingly clear to us that the interoperability challenges were not SIP to TDM but SIP to SIP. And that’s how we came to put SBC logic inside our gateways,” Percy told Enterprise VoIPplanet.
In fact, the Mediant Gateway and the Mediant E-SBCs are distinct products, but they do share a hardware platform—that is, they run on the same box. This has two advantages: Due to the volume of gateways AudioCodes sells, they buy a lot of hardware, and this keeps product costs down; second, where appropriate, both can be combined in a single unit.
Sip-to-SIP interoperability isn’t the full story on the E-SBC, though. “The other important piece of what this solution does is that it also provides the security front end,” Percy explained.
(The quick and dirty explanation of the security issue around SIP is that it works very poorly with firewall that use NAT—network address translation. SBCs straighten out this mismatch. For a more elegant explanation see our article on SBC Functions. For a really deep look into SBC functionality see our entire series on Session Border Controllers.)
“Basically what the UcSIPT strategy is about for the Mcrosoft Communications Server and Exchange community is that we’ve taken the role of providing the interoperability and the security,” Percy said.
But in fact, there’s one more piece—what’s known in the industry as “survivability”—the ability to get calls out to (and from) the PSTN in case of a failure of the IP network. And the AudioCodes Mediant solution is unique in providing that capability in addition to the interoperability security functions.
Gateways and SBCs, as mentioned, run on similar hardware platforms—or in the case of the Mediant line—can be combined on the same hardware. “And that opens up some interesting options,” Percy explained, “where a customer could start with TDM trunking, add some SIP trunks—add the SBC function to the box—have both for a while, then if they decided the wanted to go pure SIP, they could slowly turn off or unplug the TDM interfaces”—or, of course, keep one or more for survivability.
“It’s a cool strategy,” Percy said. “They gateway guys can’t do it because they don’t have SBCs; the SBC guys can’t do it because they don’t’ have gateways.”
How does this work out from a cost standpoint? Percy pointed out to Enterprise VoIPplanet that there are two cost issues involved in SIP trunking conversions: the operational cost saving and the capital expenditure required to get those operational savings.
“We’ve essentially priced our E-SBCs at the roughly the same price as a digital gateway of the same density—which is considerably less than the SBCs of similar density from [heavyweights like] Acme Packet—less than half,” Percy said.
“The operational savings easily—in a matter of months—pays for the gateway or SBC that make it happen. RoI is usually under six months, depending on details.”