Vyatta as a BRAS

Lamar Owen lowen at pari.edu
Wed Jul 14 13:49:47 CDT 2010


On Wednesday, July 14, 2010 08:39:50 am Dobbins, Roland wrote:
> And it's not *my* definition - 'hardware-based' vs. 'software-based' are the terms to describe these two fundamental architectural classes of router *within Cisco itself*.

[snip]

> There's a world of difference in packet-handling mechanisms and sheer performance between a 7200 and a CRS-1, or a GSR, or a CRS-3, or Juniper T-series - and not just one of 'more, faster processors', but of fundamental architecture. 

CEF is CEF is CEF, whether done on a 2600 or a 7200 or a GSR.  Now, don't get me wrong; the engineers who make massively parallel forwarding engines are creative and smart folks, and have come up with very elegant methods of moving the bits ever faster, but the fundamental forwarding architectures, even of these accelerated boxes, can be implemented in pure software, as evidenced by the Cisco Nexus 1000V.

> This is why 'hardware-based' vs. 'software-based' is a useful distinction; again, note that within Cisco, these are the common terms used to describe these general classes of device, with 7200s and ISRs being termed 'software-based', and the other models mentioned above described as 'hardware-based'.

Marketingspeak doesn't necessarily reflect reality.  The original draft of one of my replies in this thread  said this 'Let's run this rabbit, and dispel some marketing hype while we're at it.'  

The reality is that 'hardware-based' routers really are AMP (asymmetrical multiprocessing) software-based routers, with specialized processors running specialized software. And when implemented properly they are very good at what they do; I have GSR's, they work great, and regardless of what engine is on the linecard some software at some level running on some processor is making the forwarding decisions at the data plane, and they can even for certain things require a punt to the MIPS processor on the linecard (IPv6 on Engine 1, anyone?).  

Knowing the technology and its architecture, without blindly buying into marketingspeak, helps operators make better procurement decisions.  And Cisco's website has most of the information you need to make that decision, if you use their hardware, which is very good.  Dig deeply enough, and past the hardware versus software pseudodichotomy, and you can make very informed decisions indeed.  As a tongue in cheek example, remember the 'switching router' versus 'routing switch' distinction?

If a specialized network processing engine in an AMP router can protect the control plane CPU, then code running on different processors in an SMP system could do the same.  Perhaps not as efficiently, but the end result can be the same.  I mean, I wonder if Blue Gene or Jaguar could give a CRS series a run for its money in terms of routing power (especially on the control plane), and what the price/performance ratio would be to throwing something like Jaguar (224K Opteron processors, running Linux) at the relatively mundane task of throwing precisely metered bits around the wires. :-)

Regardless of recommendations, people are using commodity server-grade SMP hardware to run commodity OS's to get the job done, and given the people who have chimed in here, apparently are doing it without lots of problems.  The increase on this and other lists of questions about Mikrotik, Vyatta, and other nontraditional routing platforms is an interesting throwback to the days of Proteon routers, the original SUN, and Cisco's multibus roots, and it shows that people are deploying these newer and much faster boxen in the real world, bugs and all.

It's not a 'software-based = bad; hardware-based = good' world, even at the edge anymore; a few years ago, sure, I wouldn't dream of doing such a thing.  I for one love what a good parallel state machine in an FPGA can do to your software's performance (we're doing that here, doing interferometric correlation at 96Gb/s on a relatively inexpensive FPGA platform based on IBOB); or what GPU acceleration can do to graphics performance, but it is a help to realize that those activities, accelerated though they may be, are still software-based.

And while it's not a BRAS, one of the most exciting products I've seen in a long while from Cisco is the above-mentioned Nexus 1000V.  Pure software virtual switching for VMware.




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