Re: [routing-wg]On Vince's talk

[Iljitsch van Beijnum iljitsch@localhost]

On 4-okt-2006, at 16:10, Joao Damas wrote:

> In addition, while watching Vince's presentation, and seeing how  
> the little IPv6 would contribute to the total sum of routes one  
> would be seeing announced to the Internet (internal routes are each  
> ISP's problem in this context, to some extent) I was wondering what  
> would actually happen towards the time around which *new* IPv4  
> addresses would become scarce and people are forced to change the  
> way IPv4 is used (eg, by splitting current allocations and trading  
> those smaller chunks).
Well, obviously that wouldn't be good. The question is how bad it  
would get? I think the current trends in routing table growth would  
continue more or less the same as before in the years immediately  
following the depletion of the free IPv4 address pools, as the  
underlying need remains the same and people will still find a way to  
get an address block, even though they probably won't get it from a  
RIR and it's going to be smaller than they'd like.
(Although the RIRs will get address space back from people that don't  
need it anymore, so they'll likely be able to continue to give out  
small blocks. 90% of all allocations are responsible for only 10% of  
the address space = less than a /8 a year.)
> Then the question might become, what would the mess look like if  
> there is no IPv6 deployment? and does the picture Vince hinted at  
> become any worse in the absence of IPv6 deployment, even with the  
> less than perfect routing solutions currently available?
Ah, but there already is IPv6 deployment. I use it every day. A  
quarter or so of the traffic generated at RIPE meetings is IPv6. 0.1%  
of all traffic flowing over the AMS-IX is IPv6. Going out on a limb  
here, that figure suggests that 3% of all systems exchanging traffic  
over the AMS-IX are IPv6-enabled. Logic: for 97% of all systems, 100%  
of their traffic is IPv4, but for the other 3%, 97% would be IPv4 and  
3% IPv6, for a total of 0.97 + 0.03 * 0.97 = 0,999% of all traffic  
being IPv4. There is probably something else that generates the  
majority of the 130 Mbps of IPv6 traffic on AMS-IX, but it's still an  
average of 130 Mbps, which is probably more than the IPv4 traffic 15  
years ago.
Coming back to routing: seeing recent developments in address  
policies and given the notion that the same people who made a mess of  
the IPv4 routing table will be running IPv6 at some point, I think  
the basic problem will remain the same. The routing table for IPv6 +  
IPv4 will probably be quite similar to the one for IPv4 without IPv6,  
at least until either the effects of massive IPv4 scarcity or  
retiring of IPv4 in favor of IPv6 will/would become noticeable,  
either of which will be a long way off.
Last year the routing table increased by 16%. That gives us (in  
thousands):
2007 ~ 210
2008 ~ 240
2009 ~ 280
2010 ~ 325
2011 ~ 375
2012 ~ 435
2013 ~ 500

So if I were to buy an expensive router I would certainly want it to  
be able to carry half a million prefixes in its FIB table, and have  
enough RP memory for several million BGP table entries. Linecards  
with 512 MB RAM can be had today, and assuming that a FIB entry is  
less than a kilobyte seems reasonable but of course assumptions are  
dangerous. The problem is probably the jump to 64 bit RP CPUs because  
the 2 gigabyte barrier will be a problem in the forseeable future.
I agree that internal routes can be a problem in large ASes, but  
that's just a question of proper engineering: unlike in inter-domain  
routing, in internal routing there are aggregation mechanisms that  
can be made to work effectively.
I would be nice if we could create similar mechanisms for BGP. The  
whole notion that when someone in Nairobi starts announcing a bunch  
of more specifics to his neighbor, EVERY BGP router in the world must  
process these extra prefixes and then search through them for every  
packet that is forwarded, is seriously broken.
As for my comments during Vince's talk:

(Ugh, I think the APNIC website has an IPv6 PMTUD problem, pages take  
forever to load... Works better with javascript disabled.)
http://www.apnic.net/news/hot-topics/index.html#ip-addressing