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Cisco pushes 'network memory' to alleviate bottlenecks

Engineer cited for work on combining load balancing, caching algorithms
  • Jim Duffy (Network World)
  • 10 September, 2008 10:07

A Cisco engineer has been recognized for his work on scaling router and switch performance with algorithms he developed at a start-up Cisco acquired three years ago.

Sundar Iyer was recently cited in Technology Review Magazine as an innovator, under the age of 35, in the area of scaling router performance. Iyer began exploring the topic during his doctoral work at Stanford University on "network memory" -- alleviating performance problems caused by router memory access and storage bottlenecks in 10/40/100Gbps networks.

Iyer then co-founded Nemo Systems in 2004, where he was CTO and principal architect. Cisco acquired Nemoin October 2005. Nemo's network memory algorithms will be implemented in 27 Cisco product instances slated for commercial availability in 2009 or early 2010, Iyer says.

The problem occurs in high-speed networks, including the Internet backbone. Packets arrive on routers much faster than commodity memory can support.

"Systems have to handle hundreds of thousands of tiny packets stored and accessed from memory at very high speeds," Iyer says.

On a 10Gbps link, for example, packets can arrive approximately every 50ns, while commodity memory -- for example, DRAM memory -- can only be accessed once every 50ns. Packets can also arrive in any order and require unpredictable, or random access to memory.

Yet it takes two memory operations per packet every 50ns on a 10Gbps link: one to write the packet, another to read. If the memory can only do one operation every 50ns, it can't keep up; and as link rates increase, the router vs. memory performance gap widens and the problem only becomes worse.

Then end result is that routers cannot support the needs of real-time applications such as voice, video conferencing, multimedia and gaming that require guaranteed performance because it cannot ensure that packets can be written to or read from memory on time, at high line rates.

But adding memory capacity in the form of specialized 10Gbps SRAMs or reduced latency DRAMs are "extremely high in cost and unwieldy" in the number of components and power required per system, Iyer says. They also are unable to keep up with 40Gbps rates, he says.

Moreover, they may not alleviate virus attacks that can infiltrate a system based on the packet memory management pattern. If the attacker figures out this pattern, they can repeat it over and over, causing router or switch memory to be overwhelmed.

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The solution, according to Iyer, are network memory algorithms that combine load balancing and caching algorithms on commodity memory. Load balancing distributes the load over slower memories, and guarantee that memory is available when data needs to be accessed; caching guarantees that data is available in cache memory 100% of the time.

"They provide hard guarantees, mathematical guarantees that performance would never fail," Iyer says.

Applications for network memory include buffering, NetFlow accounting and quality-of-service (QoS).

For buffering, routers must make sure that the packets it needs are always in the cache. With a small SRAM cache inside a packet processing ASIC and a slow commodity DRAM, it is possible to build a huge, fast, low power packet buffer using network memory algorithms, Iyer says.

For QoS, network memory enables routers to better provide strict performance guarantees for critical applications, such as remote surgery and supercomputing. And they help maintain state for applications such as NetFlow, which collects IP traffic information for monitoring purposes.

Network memory techniques are currently being designed in Cisco's next generation port speeds of 10G and 40Gbps, Ethernet switches and enterprise routers, Iyer says. They are also being designed into the company's next generation 100Gbps router line cards, he says.

In addition to making memory more efficient and enhancing router performance on high-speed links, the algorithms reduce board space real estate by reducing pin counts on packet processing ASICs, and reducing the number of on-board ASICs, Iyer says. That, in turn, approximately halves the physical area to build a router line card, leading to considerable reduction in power requirements for high-speed systems, he says.

Still, network memory technology will need to continue to evolve as routers become faster and more complex, and memory requirements attempt to keep pace with new applications designed to harness higher and higher speeds, Iyer notes. This will require continued improvement and innovation in caching and load balancing technology, he says.