estimation of number of DFZ IPv4 routes at peak in the future

Joel Jaeggli joelja at
Sat Mar 12 01:17:19 CST 2011

I'm super-tired of the "but tcams are an expensive non-commodity part not subject to economies of scale". this has been repeated ad nauseam since the raws workshop if not before.

You don't have to build a lookup engine around a tcam and in fact you can use less power doing so even though you need more silicon to achieve increased parallelism.

RFC 4984 has a lot of useful insights in it but it was flat wrong about two things since 2007. The impact of rate of growth in the DFZ(for one thing churn failed to grow in lockstep), and the ability of the technology to keep up.

Not all the devices in your network need a 2 million route FIB, yet getting a device today that has one isn't that hard. and it'll be a lot easier in five years and it likely will do so without having a 144Mbit CAM ASIC.

I don't know  if we'll be using commercially viable MRAM implementations in place of SRAM cells in a decade or if we'll have more of the same only smaller and faster and much much wider, Or if the LISP religion will take over the world and we'll carry the state for diversely connected edges elsewhere in the stack. What I am confident of is that as an industry we'll be able to deliver something that works without jacking up the Internet routing system and replacing it, and without somehow altering the individual decision making processes in many tens of thousands of autonomous systems. I am also confident that the early adopters will pay more for the technology than the stragglers, that we will grumble about how much it costs and the inevitability of obsolescence, and that life will somehow go on.

Joel's widget number 2

On Mar 11, 2011, at 17:53, Owen DeLong <owen at> wrote:

> On Mar 11, 2011, at 5:43 PM, William Herrin wrote:
>> On Fri, Mar 11, 2011 at 6:39 PM, Justin Krejci <jkrejci at> wrote:
>>> On Wed, 2011-03-09 at 09:32 -0500, John Curran wrote:
>>>> On Mar 9, 2011, at 12:43 AM, Majdi S. Abbas wrote:
>>>>>   I suspect that as we reach exhaustion, more people will be
>>>>> forced to break space out of their provider's v4 aggregates, and
>>>>> announce them, and an unfiltered DFZ may well approach the 'million'
>>>>> entries some vendors now claim to support.
>>>> This matches my personal view (and could be viewed as
>>>> "success" compared to the 5M estimate of Mr. Herrin...)
>>> Are people going to be relying on using default-routing then in the
>>> future if they don't upgrade routers to handle large routing table
>>> growth? Or perhaps forgo dual-stack and have a separate physical IPv6
>>> BGP network from IPv4? Are there any other strategies?
>> Hi Justin,
>> IMHO, the most sensible strategy is to recognize that that cost of a
>> route has been dropping faster than the route count has been rising
>> for the past decade. Then recognize that with today's hardware,
>> building a route processor capable of keeping up with 10M routes
>> instead of 1M routes would cost maybe twice as much... 10M being
>> sufficient to handle the worst case estimates for the final size of
>> the IPv4 table in parallel with any reasonable estimate of the IPv6
>> table in the foreseeable future. Better CPU, more DRAM, bigger TCAM.
>> It could be built today.
> But the RP is the easy cheap part. It's the line cards and the
> TCAM/etc. that they use that gets pricey fast.
>> Finally, get mad at your respective router manufacturers for
>> engineering obsolescence into their product line by declining to give
>> you the option.
> The option of $60,000 line cards instead of $30,000 or
> even $25,000 instead of $12,000 does not seem like one
> that most would have found appealing.
>> But that's just my opinion...
> And the above is just mine.
> Owen

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