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Software router on server cluster delivers 40 Tbps throughput

With their RouterBricks project, Intel researchers have substantially increased the potential throughput of software routers. Software-based routers, which used to be limited by the processing power of a single server, could now theoretically deliver up to 40 terabits per second of throughput by linking multiple servers together.

Researchers from Intel say they have built a prototype for a software-based router built on clustered x86 servers that could deliver up to 40 terabits per second (Tbps) of throughput if scaled properly.

Intel's prototype project, RouterBricks, would enable enterprises to deploy low-cost software routers in their data center cores using commodity servers, delivering IP routing to the wide area network (WAN) at a price much lower than companies currently pay for enterprise routers.

"This is positioned directly at Cisco's proprietary medium-performance routers. Once this matures, and if it's provided by a branded vendor like Hewlett-Packard or IBM, it could be very attractive to enterprises," said Rob Enderle, principal analyst at Enderle Group. "Enterprises tend to be very price-focused, and they don't like to be locked into any one vendor." Having a high-performance software router available could create a dynamic similar to that which exists in the general-purpose server market, where enterprises can frequently pit one vendor against another to get the best price.

Nehalem processors enable high-throughput, software-based routers

Sylvia Ratnasamy, a researcher with Intel Research Berkeley, said Intel's Nehalem processors made the RouterBricks concept possible. The processors enable servers that can process packets at up to 20 or 30 Gbps. By clustering multiple servers on a single forwarding plane and reserving one for the control plane, Intel is able to scale throughput linearly. Using a valent load balancing algorithm, researchers have clustered four servers together into a prototype router that has a throughput of 80 Gbps, Ratnasamy said.

"We take a cluster of servers and put them together, and we have the cluster act as a router," she said."This gives us an architecture that is incrementally scalable. If I want to build a faster router, I just have to add a few more servers to my cluster. We have a prototype that does about 80 Gbps using four servers. If I add a fifth server, I get 100 Gbps; and if I add a sixth one, I get 120 Gbps."

Ratnasamy said the upper limit of a RouterBricks cluster's power will be determined by the limits of fan-out, such as how many links one can have on each server, and constraints of the processing power of each server.

"We think we can get to the 20 or 30 terabits per second range," she said. "We haven't looked beyond that point."

This clustering technology could attract several vendors to the software router market. So far, startup Vyatta has had the market mostly to itself. It has developed open source router software that runs on commodity servers and makes revenue by packaging the software with optimized and certified servers and by selling support. But Vyatta's software router is constrained by the power of an individual server. The clustered approach could offer Vyatta and other vendors the opportunity to deliver a high-throughput router at a fraction of the cost of leading enterprise routers from Cisco and Juniper Networks.

Software-based routers offer feature-rich flexibility, lower-cost upgrades

Ratnasamy said a software router can be much more programmable and flexible than a hardware-based enterprise router. Programmability in routers is becoming much more important to enterprises and service providers, she said.

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"If you look at how networks have been traditionally built, they rely very heavily on specialized hardware, where the processing is done in ASICs or specialized software in a closed platform," she said. "And that technology is designed to do a very narrow job: to move packets around. In modern networks, we increasingly see networks take on a lot of functionality. A network operator today doesn't just have a switch or a router. You have appliances like WAN optimizers, intrusion prevention systems and firewalls. We're seeing a growing sophistication of what networks can do, but the traditional way we built networks doesn't really support all that specialization. It's still very narrowly defined hardware and software."

In addition to programmability, software routers offer an easier upgrade path when enterprises need more power from a core router.

"Right now, to scale up using proprietary gear, it's a forklift," said Kelly Herrell, CEO of Vyatta. "The only answer proprietary vendors give you is to get rid of the old one and get a bigger box that comes at a really high price. It's not uncommon for a chassis trade-up to be two to three times what you paid for the previous one. What if you could put your x86 infrastructure in there? My workload requires four Vyattas, and I'll distribute them across this [RouterBricks] fabric. The next day you come in and say, 'My workload has increased.' Just start up more Vyattas in the system. It's like adding pistons to your car as you need them."

Risk-averse to stay away from software routers?

Zeus Kerravala, distinguished research fellow with Yankee Group, said many enterprises might balk at introducing software routers on commodity hardware into sensitive parts of their networks.

"At the end of the day, I think the router plays too critical a role in the network," Kerravala said. "It connects networks together. There's a risk-reward issue here. How much money are you going to save? Considering the importance of the router, if it were not working, the downside is the network being down for extended periods of time, costing the company thousands or millions of dollars. For the critical role they play, routers are not that expensive."

Kerravala said software-based routers can offer costs savings, but he doesn't hear many companies complaining about the prices of enterprise routers from Cisco and Juniper. And if they are complaining, there are lower-cost alternatives out there from vendors such as 3Com (now HP Networking).

Herrell, whose company's open source routers depend on commodity servers to deliver its products, said specialized hardware is overrated in routers.

"The bottom line is [that] networking is software," he said. "The question is what kind of hardware you're running it on. Hardware is a decision that you can make. Once you divorce hardware from software, you're putting yourself on a structurally more efficient hardware cost model."

Let us know what you think about the story; email: Shamus McGillicuddy, News Editor

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