Are you thinking of a scenario where the ISP customers share a single prefix? This would be contrary to all the estabilished best practices and deployment guidance for IPv6 since it wouldn't let you easily subnet. And may get the ISP in trouble with your RIR since it's just extorting customers for access to v6 addresses.
And connection tracking gets expensive at scale.
But CPU/memory is going down in cost way faster than bandwidth demand is increasing.
Regardless, its way way cheaper than buying IPv4 blocks clearly, otherwise people wouldn't be doing it.
Edit: ok, the problem isn't hardware, it's comedy license fees. https://itprice.com/juniper-price-list/cgn.html
$470k for a license to do CGNAT at 100gbit/sec. Surely these guys are opening themselves up to be replaced with some cheaper open source based software solution?
Good. CGNAT needs to die. Addressing is fundamental and customers deserve not just an address, but their own RANGE, especially now that it's feasible.
a man can dream.
Having said that, I’m often equally baffled at just how expensive modern networking hardware is, but as it’s pretty much all of these carrier grade networking solutions being this expensive, I’m assuming it’s somewhat justified.
That doesn’t take away the fact that NAT just adds an expensive layer of complexity on top of it, and I can imagine that in the long term, IPv6 is starting to become much more attractive.
in a sense, yes. People claiming software based solutions can match performance of hardware basic ASIC's are simply not thinking about the scale and speeds of modern core routers and switches.
For instance, taken from the blog of ivan pepaljnak[0] > It’s hard to imagine how fast switching ASICs have to work – a modern data center switching ASIC can forward billions of packets per second. For example, the throughput of Broadcom Tomahawk 31 is 12.8 Tbps, and it can switch 8 billion packets per second, or 8 packets every nanosecond.
Another thing which makes routing at large scales with large traffic flows expensive is the separation of the control and data plane. most modern datacenter routers can continue forwarding traffic inside the ASIC while its control plane encounters a failure. (usually for a few 100ms to a second, after that the forwarding table will become stale, and this cannot be refreshed without a control plane).
Having a redundant control plane isn't that expensive, but it becomes harder and harder to keep this failover fast enough if your forwarding plane is pushing more and more individual traffic flows.
Then there are still other items which one can add to a modern router to make it do more but also cost more. (think about accelerated IPsec encryption, MACsec at line rate or DWDM functionality).
[0]: https://blog.ipspace.net/2022/06/data-center-switching-asic-...
And you can charge them an extra $10 per month for 'pro' internet and let them have 1000 connections for 'all the family'.
But that's besides the point. Your home router can easily have millions of connections open (if they didn't skimp on the ram anyway), but if you have CGNAT boxes that do the same for tens of thousands of customers you also have to take into account that they have to move a lot of traffic. This means routing and doing NAT in software won't cut it anymore, but you need dedicated hardware coupled with very fast specialized memory to handle that traffic.
I bet across even an ISP network of a million users, 80% of the traffic at any point in time is within 10,000 connections.
So you propose constantly swapping in and out connections from “hardware NAT” to “software NAT”? What heuristic will you use to decide which connections go where?
Such a heuristic will probably look a lot like QoS, which is even more (much more!) resource hungry than NAT.
At which point will the obvious conclusion be, “maybe the carriers who actually deal with these problems have a point, NAT is indeed a significant amount of complexity, and let’s be happy IPv6 starts to make actual economic sense?”
You’ve basically proposed an absolutely horrible solution, for both the end-user and the ISP. Something tells me you haven’t actually done any actual low level network engineering, and just brush all this off as “how hard can it be”.
The point is, the really fast part doesn't need to be more complex.
The part that handles new connections needs to be marginally more complicated, but not enough that it should really matter.
Also, in some countries ISP's need to map the use of a specific ip address to a specific subscriber for law enforcment purposes. GCNAT is no exception to this and creates a large amount of overhead because the public IPV4 prefix space is shared between multiple customers.
But it’s a solved problem with mature solutions, decades old. Is it really financially expensive?
For instance, most Core/Edge routers (my experience is mainly with juniper MX series, but i assume the model is roughly the same for other vendors), you need specific licenses or interface card's to do stateful services like NAT.
Compared to doing IPv6, which is "just forwarding packets" and doesn't require the hardware to track state in nearly the same manner.
Most serious core/edge hardware vendors also do not put IPv6 behind licenses compared to CGNAT and other NAT-like features, because packet based forwarding is the most basic functionality a router should provide.
Routers which are able to do less state, also are frequently far less expensive.
So ipv6 support might be saving you costs already in a dual stack setting.
Until there is a bunch of exclusive v6 stuff customers will be up in arms over missing, the answer of which thing to prioritize is obvious.
Also, one of the reasons to do satellite internet is lower latency which is a bit hurt by CGNAT infrastructure.
Last, generally brand new ISPs are in the situation that they have a hard time of getting ipv4 address space. The incumbents, especially the older ones, were around when ipv4 addesses were still plenty so they usually have way less problems with ipv4 address space. Starlink only has 166k ipv4 addresses according to https://ipinfo.io/AS14593 . Compare this to AT&T which has over a hundred million for their AS 7018 https://ipinfo.io/AS7018 alone, and there are other AS numbers they have like AS20057 with 7 million ipv4s. This roughly matches the number of AT&T customers while Starlink has more than double the number of subscribers than its number of public IPs, with growth ahead.
And v6 connections help drop the pressure on NAT resources - and sites that are optimizing for mobile connections are already going to be on IPv6 where possible (due to mobile networks prioritizing v6 traffic for various reasons, including licensing - and NAT resource costs)
The problem is with end user devices that do not use a stable DUID and when the client hits the reset button, it changes. We are probably going to work around this by responding from the closest hop and taking the MAC into account.