Since they first appeared, session border controllers have been objects of controversy. Some say they are a single point of failure in a network. Others revile them as the antiSIP, interfering with peer-to-peer communication.
Still others suggest session border controllers really aren’t needed as separate entities and their functions soon will be subsumed into various network elements, such as gateways and routers.
But, as vendors of session border controllers might say, “Reports of our demise have been greatly exaggerated.”
Indeed, session border controllers have a higher profile than ever. Further, the product category is continuing to evolve as customers ask for new features and vendors take advantage of new technological developments in the products.
Recent carrier requests for proposals (RFPs) are asking for different features than in the past, say vendors. “A lot of carriers are getting to the point where they are transitioning from the lab to the field. They are no longer concerned about core functions, but rather deployment issues,” says Dan Dearing, vice president of marketing at NexTone Communications Inc.
One of those issues is transcoding, of both codecs and protocols, says Steve Baechle, director of technical services at Newport Networks Ltd. “A lot of carriers want to make their core networks ‘pure’ or uniform. They don’t want to support every protocol and every codec. They want to support, say, G.711 only and SIP only, and not just SIP, but RFC 3261 SIP. ...And where a session border controller sits is perfect for them.”
Dearing says the action of moving from the lab to the field means exposure to different types of Internet threats. “So now they are concerned about DoS attacks and new threats that always have been Internet threats, like spam. What do they do when hackers become VoIP savvy and start doing spit and spim? So they want to make sure that anything they deploy today is capable of adapting to new threats.”
However, session border controller vendors have to be judicious in what they choose to include in the product, says Mark Neider, director of product management and marketing at Netrake. “We support a long list of video codecs and voice codecs, but I don’t know if transcoding really fits within the scope. That has yet to be driven by customers, so we are waiting on customer direction on that. I don’t see a large demand based on who we are talking with.” Also, he adds, transcoding functions also are done by media servers with their extensive DSP resources.
Instead Netrake has decided “to move down the security-gateway path with wireless companies to do wireless LAN security for dual-mode phones,” says Neider. Netrake is exploring with partners and customers “how this high-level security and IPsec are converging into the session border controller and how we can create new products that support different market areas. “Adding intelligence to the SBC is an area that makes a lot of sense,” he adds. “An SBC today in the core reminds me of a tandem switch that is IP-enabled. It has routing intelligence, can manipulate digits, add and take away least cost routing, so it makes a lot of sense for that to be a major function of the device.”
Border Controllers and IMS
Session border controller vendors say their wares definitely have a role in IMS (IP Multimedia Subsystem) architectures.
Netrake has functions in its border controller that replicate two elements defined in the IMS architecture: a P-CSCF (like a proxy server) and a BGF (border gateway function). “We are using a building-block model,” says Mark Neider, director of product management and marketing. Working with partners “we have certain functions and they have certain functionality.” He adds that Netrake is finding opportunity “in wireless LAN to support that and to support the UMA (unlicensed mobile access) model to provide security to dual-mode phones. So we have two products, one is a security gateway and one is an SBC.”
Newport Networks Ltd. already has defined its product in a way that complies with IMS. “IMS says you have to have a separate signaling plane and a separate media plane and MEGACO in between,” says Steve Baechle, director of technical services at Newport Networks. “We have a signaling plane and media plane and we use MEGACO (H.248) as a protocol in the box to talk between the two. So if you have SIP signaling and RTP in the media, we use H.248 internally.”
ATCA: Ready for SBCs?
The Advanced Telecom Computing Architecture (ATCA) is a new standards-based chassis that border controller vendors are evaluating intensively for possible migration.
ATCA goes hand-in-hand with IMS, says Dan Dearing, vice president of marketing at NexTone Communications Inc. “What is apparent with IMS and ATCA is the desire by the carrier and the enterprise to drive cost out of the network. They want an open standard solution, and IMS gives that capability at the system level, and ATCA does on a platform basis. Those two things drive out a lot of the cost of building a network,” he says. “And you can have one network support multiple services and applications.”
As promising as the new ATCA platform is for border controller vendors, there are still questions. One is about the raw bandwidth of the current crop of boards for handling intensive tasks, such as encryption. The ATCA design with 14 slots, some of which can operate at 4gbps and some at 2gbps, does not have the bandwidth for functions such as encryption of media, says Steve Baechle, director of technical services at Newport Networks Ltd. “That architecture has potential for the future, but it’s not there yet for what an SBC has to do, particularly going into the future.”
| Links |
| Netrake (no Inc.) www.netrake.com Newport Networks Ltd. www.newport-networks.com NexTone Communications Inc. www.nextone.com |
