NPUs offer flexibility for Carrier Ethernet designs

Oct. 1, 2005

Like a rambunctious little brother, network processing units (NPUs) have long sought a place alongside-or, more often, as a replacement for-more mature and well-accepted silicon technologies such as ASICs and FPGAs within carrier class equipment. The advent of Carrier Ethernet represents another opportunity for the programmable devices to prove their value. NPU vendors say equipment developers have already begun to insert their products into metro Ethernet designs. However, the technology and its providers still must answer several questions before NPUs become a more prevalent choice for the upcoming generation of Carrier Ethernet designs.

NPUs combine the programmability of FPGAs with much of the performance and volume production pricing of ASICs. Equipment designers use them to perform a variety of packet processing functions, including classification, modification, queuing, management, and control. The ability to provide these functions flexibly via their programmability and multiple memory interfaces plays well in the Carrier Ethernet space, says Bob Wheeler, a senior analyst at the Linley Group (Mountain View, CA). That’s because while just about every carrier is introducing Ethernet into their networks, particularly in the metro, the form that Ethernet takes will differ among service providers-and even within a given network.

For example, a carrier may use Ethernet over SONET for virtual private LAN services to the customer but rely on MPLS closer to the core. The trick is to transition from one form of Ethernet carriage to another-a task that usually involves packet processing. “That’s where the network processors come into play-where you’re doing the interworking between protocols,” Wheeler says. He adds that these edge applications can be necessary at several points in the network, which broadens the potential applications for NPUs.

In particular, the chips should be well suited for hardware tasked with enforcing service-level agreements (SLAs) and providing quality of service. “At the edge, you also have to worry about doing policing and shaping down to whatever the guaranteed bandwidth rate is,” Wheeler explains. “So when you bring that in at the edge, you have to do shaping and policing to the guaranteed rates. And that’s something that the typical Ethernet switch isn’t going to be able to handle.”

NPU vendors say that multiservice provisioning platforms (MSPPs) do provide these functions-and that systems designers have come to them to investigate the benefits of NPUs. “We see a wave of a number of carriers moving from traditional MSPPs, which were TDM-based, to adding in a packet switching fabric to complement the need for not only the traditional services but all this new Ethernet capability that is demanded by their customers,” offers Bob Brand, a senior solutions architect at AMCC (San Diego).

In response, systems vendors also have started to use NPUs to create line cards that enhance fielded platforms. “Mostly the applications that we are seeing are the applications for line cards that normally have 10-Gig E ports or maybe even 20,” says Eli Fruchter, president and CEO of EZchip Technologies (Yokneam, Israel). That requires NPUs that can operate at 10 Gbits/sec, although Fruchter reports that his company’s 5-Gbit/sec device has found a home in “pizza box” systems used for traffic aggregation closer to the customer.

“What we see is people adding capability to existing platforms or in some cases extending capabilities,” agrees Gary Lidington, vice president of marketing at Xelerated (Santa Clara, CA), which makes an NPU capable of supporting 10 or more Gigabit Ethernet ports on the same line card as well. Lidington also sees a trend in next generation systems design toward integrating data capability throughout the system. “A lot of them were data-aware, but they are essentially evolving on this path of being more data-optimized,” he says.

The necessity to meet rapidly emerging requirements with fielded systems plays particularly well into the NPU’s strengths compared to an in-house ASIC effort, says Fruchter. “Network processors are available today off-the-shelf, and they can offer a solution for the metro. If [developers] have to start and develop an ASIC now, it’s going to take them 18-24 months,” he explains.

NPUs also meet the traffic management requirements that SLAs have created. “It is strategically important to do traffic management because of the service-level agreements that customers are asking for in the transport of their data,” says Brand. “Likewise, the carriers need to measure appropriately the amount of bandwidth they’re allocating to an assured service.”

However, the manner in which NPUs and associated processors provide this capability has begun to evolve. Traffic management used to be the province of a separate chip. Now, silicon companies are either integrating the functions into the switch-fabric interface or, in the case of EZchip, into the NPU itself. The resultant lower overhead streamlines design and lowers cost.

While NPU vendors believe their offerings provide a worthy solution to Carrier Ethernet design problems, system architects still express some skepticism. “We don’t have to do a lot of education around the value proposition of network processing, which is in contrast to what we had to do several years ago,” offers Lidington. “What we have to do more of is prove to them that we can hit a high-volume cost point or an Ethernet cost point and that the solution isn’t going to be overly complex.”

In Lidington’s mind, “complexity” refers to the programming the NPU requires. Designers want programming that produces predictable results; if presented with an NPU software package, they want something that works quickly and will not require significant debugging. It’s not the time to write the code, Lidington says, it’s the amount of effort it takes to optimize the device and get it to run reliably in the manner intended.

Fruchter says that for some companies, in-house development will always be preferred. But more companies are approaching NPUs with an open mind. “The question is, is it available and can it do what they need it to do? And I think that for metro, the answer is yes. I think that more and more customers will use NPUs for the metro,” he says.

Some of them already have. Xelerated has announced Atrica as a customer, and Lidington says the majority of his customers are working on metro Ethernet designs. Fruchter says that “about a third” of EZchips customers, including ZTE, are incorporating his devices into similar types of designs. As Ethernet switches and routers are redesigned to incorporate some degree of traffic management, more design slots may open for NPUs as well.

“Today, almost every vendor who is developing any metro Ethernet product is talking to NPU vendors,” Fruchter concludes.

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