[c-nsp] Cisco pushes 'network memory' to alleviate high-speed bottlenecks

[Hank Nussbacher]

<http://www.networkworld.com/news/2008/090908-cisco-network-memory.html?netht=ts_091008&nladname=091008dailynewspmal>

"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."

...

"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."

-Hank