The State of SBCs: Service Border Controllers Scale and Add Functionality

By Paula Bernier

Session border controllers are expanding their horizons. SBCs got their start ensuring security at service provider-to-service provider interconnection points. Carriers still rely on session border controllers to do that job, but these devices also are used increasingly between enterprise and service provider networks as well. At the same time, SBCs have expanded their scalability and functionality.

Addressing Scalability

Acme Packet recently unveiled a variety of new SBC solutions that address various aspects of these themes.

“With our service provider customers we’re pretty well entrenched with them,” says Jonathan Zarkower (News - Alert), director of product marketing for Acme Packet, which went from $116 million in revenues in 2008 to $184 million in revenues in 2009. “The growth that we’re seeing is purely in terms of traffic volume.”

To help carriers scale, Acme Packet earlier this year introduced a new product that enables service providers to “cluster” several SBCs so they can be managed as one.

This new product, known as the Net-Net Session-aware Load Balancer, runs on the Net-Net 4500 hardware platform and enables any combination of Acme Packet SBCs to cluster. Not only does it allow for umbrella management, but the SLB also provides adaptive load balancing of subscribers based on SBC state and subscriber capacity, load and session state.

“We can now scale delivery of our SBC capabilities up to 2 million subscribers,” says Zarkower.

Prior to the availability of this clustering feature, Acme Packet’s highest-end SBC, the Net-Net 9200, topped out at 128,000 concurrent sessions, he adds.

“We’re seeing a lot of growth, particularly with large customers like tier 1 service providers, who are looking to scale up their networks,” says Zarkower. “But they want to do so in a way that is cost effective and simple. So using the Session-aware Load Balancer, which is an access-side solution, allows them to do that very easily. You can add SBCs to clusters, remove them, and it basically allows you to fine-tune or fine-tailor your access-side capacity.”

Acme Packet also has come out with an addition to its element management system that allows customers to consolidate and manage their routing tables for Net-Net SBCs and session routing proxies. The Net-Net Route Manager Central consolidates and automates the management and distribution of up to 2 million routes per Acme Packet SBC or SRP.

Adding Functionality

Alan Percy, director of marketing development for AudioCodes (News - Alert), which got into the SBC space nearly four years ago through the acquisition of Netrake, says session border controllers have been morphing over time to be part of larger solutions.

When AudioCodes did the Netrake deal in 2006, he says, the company’s plan was to pair the SBC technology with that of its existing media gateways to introduce a hybrid product. The company now offers that product under the name Mediant 1000.

The company has been expanding its capabilities ever since.

Percy says when AudioCodes talked to businesses about their needs they voiced interest in SIP services, but were reluctant to jump into the SIP pool with both feet. Instead, businesses wanted to ensure survivability, so if a SIP trunk went down they could revert to the PSTN, or if pricing shifted they could decide which service provider offered the best deal. As a result of this customer feedback, AudioCodes about a year ago added IP-to-IP features inside of its gateway. That includes a back-to-back user agent and mediation functionality.

As a result, the AudioCodes gateway can terminate both PSTN circuits as well as IP sessions from SIP trunking providers, which Percy says has been a key differentiator for the company in the marketplace. More businesses want to do SIP trunking and thus need to terminate SIP trunks onto enterprise SBCs and control the traffic that flows into and out of them, so there’s been strong growth on the “enterprise SBC” front, as Percy refers to it.

Elsewhere on the product development front, Zarkower says that Acme Packet’s R&D and new product development has always been extremely pragmatic. An example of that pragmatism, he says, is the Net-Net SIP Multimedia-xpress, aka the SMX. The company introduced the SMX, which is an add-on to the company’s Net-Net SBC, in response to customers telling it that the IMS architecture is too costly to deploy and asking how Acme Packet could leverage its know-how of upper-layer protocol to simply that.

“’You’re already functioning in our network as a P-CSCF, you’re already functioning in our network as a border gateway, the IMS-AGW function in IMS. What can you add to that to allow us to further consolidate?’” Zarkower says customers asked. “So we’re adding capabilities to our SBC such as the ability to have a SIP registrar, an Emergency Services CSCF (E-CSCF)” and at the same time ramp up volumes of traffic.

That simplifies things by concentrating more functionality into single elements within IMS rather than distributing all of the functions described by the architecture, says Zarkower. As a result, he explains, service providers have lower capital costs as well as decreased signaling and other operational costs because there are fewer separate network elements.

And the SMX can support IMS and other next-generation networking architectures for about $2 to $3 per subscriber for as few as 100,000 subscribers.

Tori Downes, principal technologist for the network protocols division at Metaswitch Networks, says the two most prominent trends on the SBC front are feature creep and the ability to run session border controller functionality in a variety of form factors.

The SBC solution offered by the side of Metaswitch for which Downes works includes between 300 and 400 features, she says, so can address a wide variety of service provider needs. But the vast majority of service providers are deploying SBCs using a relatively small number of those features today, she says.

While Metaswitch’s carrier systems division sells an SBC box, the network protocols division also has an SBC product, which is basically a software component it offers OEMs, which can run it on a blade or appliance. Downes says such embedded SBCs can be more cost-effective than standalone SBCs with set features.

Initially, she says, there were just one or two manufacturers offering embedded SBC capabilities “now this is really picking up.” IT

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