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Comment by tyingq | Hacker News Reader

Here's the growth over time: http://www.cidr-report.org/cgi-bin/plota?file=%2fvar%2fdata%...

And here's the past week. I suspect the big dip is where things actually broke...a little higher than 768k: http://www.cidr-report.org/cgi-bin/plota?file=%2Fvar%2Fdata%...

I believe there's another hardcoded hurdle at 1M IPV4 routes with some existing routers, like the ASR1001.

Guess IPV6 adoption isn't slowing IPV4 growth much.

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Right now IPv6 adoption is only supplementing v4 deployments. Even in the rare "IPv6 only" deployment there is a 64 gateway at the internet edge and at least some v4 is still being advertised to the world. When this becomes commonplace the v4 table will either shrink or at least stop growing and it'll pave the way to finally being able to just turn off v4 interop completely which is when the table will finally start to empty. This is still many years out.

My ISP puts the local router on IPv6 by default (resolved with a phone call fortunately), which I imagine is tunnelled through a number of IPv4 gateways as port forwarding doesn't work. It's the first time I've seen this.

Port forwarding on v6 or v4? You shouldn't be port forwarding on v6 but if it was v4 it's likely they are using CG-NAT which basically results in double NAT which breaks such things. NAT64 would break this as well but I've only ever seen it in corporate networks or mobile networks.

That dip is probably not related to the 768k limit. The limit doesnt remove all the current routes, it just doesnt allow for new ones to be installed in hardware. All the routing logic is done in software, so the routes will probably be propagated correctly but not forwarded correctly. See potaroo[0] for other route graphs that don't have the same dip.

The article somehow manages to avoid discerning between control plane and forwarding plane which is a key concept for this issue.

[0]: https://bgp.potaroo.net

Companies and organizations are de-aggregating larger space into multiple /24 (most often) to extend the usage of their v4 IP address space, as nicely covered in this article: https://labs.ripe.net/Members/stephen_strowes/visibility-of-...

768k is 786432 so there is still a few k prefixes left before we hit the threshold

IPv6 routes also take more TCAM space than IPv4, so IPv6 growth (unless strongly aggregated) is actually more expensive than IPv4.

The parenthetical in your sentence is the key of course. In theory IPv6 allows for much greater aggregation than IPv4, especially as the latter becomes increasingly fragmented due to address exhaustion.

Of course in practice things are not that simple. Network operators have a habit of de-aggregating their BGP advertisements for various reasons, including traffic engineering.

It's an interesting problem from a economic perspective. Using BGP for traffic engineering consumes resources from every network participant, but there is no formal mechanism for ensuring efficient allocation of those resources. So far this hasn't been big deal because routing table capacity has been able to stay ahead of demand without too much trouble. It will be interesting to see what happens when/if the supply of routing table entries falls short of demand. Will there be a fee per advertisement? How would that even work? Will operators seen as over-consumers start seeing their de-aggregated advertisements dropped?

As with IPv4 runout, people will refuse to even start thinking about economic incentives until the problem happens then lawyers will spend five years coming up with some kind of "technically it's not the FIB entry that you're paying for" solution.

ipv4 isn't really growing so much, since RIPE, ARIN and APNIC have exhausted available large contiguous chunks of v4 IP space to hand out, as people are de-aggregating to much smaller prefix sizes.

ISPs that were previously announcing /16 to /20 sized CIDR ranges to their peers and upstreams are breaking them down into /22, /23 and /24 sized pieces used for smaller downstream customers, and announcing those in a deaggregated fashion.

I predict that the ultimate end state of ipv4 will be a huge number of /22 to /24 pieces all over the world being announced, and further FIB growth requirement for big core routers.

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