Rate of growth on IPv6 not fast enough?

Mon Apr 19 22:03:20 UTC 2010

On 4/19/2010 14:07, Leo Bicknell wrote:
> e a few problems with your data....
> 
> I know of no platform that does hardware NAT.  Rather, NAT is a CPU
> function.  While this is another interesting scaling issue, it means
> this data is not going in the FIB (hardware forwarding database),
> but rather is stored in a CPU accessible database.
> 
> It's not that you need 3.1G/254G of memory in the FIB (which would
> be expensive) but rather that you need it in relatively cheap DRAM.
> Even if use your larger memory number of 254G that's only $10-15k
> of RAM cost these days, hardly a deal breaker.  The FIB would hold
> only one entry for the /17 (or similar) pointing it to the CPU.

Well thats true of some implementations now, but some others put it in
hardware.  I'd say to scale you need to have it in hardware.

> Secondly, you're playing to both extremes.  Yes, the point to point
> user will use 3500 entries and grandma checking e-mail may use 42
> entries.  Not everyone will run a point to point client, and not
> everyone will be grandma.  Using an average is a much better first
> start.  I suspect though the percentage of users using a point to
> point client is small though, and thus drives the average number
> even lower.

Yes, but I was showing what a great DDOS attack method it would be too ;)
The numbers were slightly better than something I pulled from my backside to
demonstrate why we can't nat an entire PDSN worth of customers.

> So, 3500 + 42 / 2 = 1751 entries on average per person.
> 
> 250,000 users * 1751 entries * 312 bytes/entry = ~136G of data.
> 
> 250,000 users * 1751 entries / 64000 ports/IP = 6939 IP's.
> 
> So a /19 provides headroom.  10 servers, each with 16G of RAM
> (160G total) could do the job with headroom.

Yea, but this is more along the lines of a science experiment at this point.
I can't expect a carrier to deploy this, even if it's the best solution.  The
average carrier is _dumb_ and stupidity takes care of stupidity at these
places.  They are not going to deploy something unless it's Blue or Green (or
purple).

> Not all users will be active at the same time, so 100k per user
> probably translates into a 1Mbps/sec rate, given the old 10:1 rule on
> end users.
> 
> 250,000 users * 100,000 bytes/sec = ~186Gigabits/sec.  Humm,
> 10 servers won't do that (18Gbps/sec per server of NAT, no way!).
> 40 servers though would be 4.65Gbps per box, which with 10GE seems
> reasonable.  But that also means each one only needs 1/4th the RAM
> from above.
> 
> In summary, to NAT 250,000 users:
> 
> 40 servers, each with:
>     CPU capable of NATing 4.65Gbps
>     4-8Gb of memory
>     2x10GE interfaces
> A /19 of address space.
> 
> I think a server like that could be had for $10k each, easy.  So
> 400k of servers, depreciated over 3 years, divided by 250,000 users:
> $0.53 per user per YEAR.  Or, $0.04 per month per user.  Even selling
> $20 packages ISP's should be able to absorb four cents per user.

This is a good example, but I really would like to do some work on testing how
much a given nat solution can scale.

> NAT scales just fine.  I find that quite unfortunate, personally,
> but I don't think there's a problem with the technology or economics.

It's a damn shame is what it is :(

-- 
Bryan Fields

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