> Because NAT breaks a lot of services.

Which ones? I'm here and everything works right now. Literally everything works just fine. Please name exactly one service I have right now that is broken because of NAT.

You might not but NAT has many different flavors, and many people don't get to choose which is used on their network.

https://serverfault.com/questions/208522/what-is-strict-mode...

This can particularly play havoc with sensitive protocols like STUN. I believe many game consoles make use of this when in multiplayer matches. I have personally run into this using OpenBSD's pf, but I'm fortunate enough to have access and the known-how to fix it for my consoles.

It's one of those things that's fine until you run into "edge cases," and unfortunately NAT configurations can introduce a lot of undefined behavior from the user perspective.

VoIP.

Two peers, each behind a CG-NAT (or other symmetric NAT), depend on somebody running a relay in order to be able to communicate.

This makes it very expensive (and sometimes risky, since unrestricted relays can be used for all kinds of nefarious things too) to deploy any new VoIP service.

I'd call that "broken by NAT".

> everything works right now.

Yes, everything that works right now works right now, but that's a tautology, not proof of anything. The things that don't exist because they wouldn't work in a predominately NATted world don't work, because we live in a predominately NATted world.

Doesn't that present a privacy issue? One can _casually_ infer who you are talking to merely by examining network traffic.

You're always free to use a relay for privacy reasons. Many common VoIP solutions allow just that.

IPv6 (or more generally, the absence of NAPT) just changes the switch label from "try [not] to use direct connections, unless NAT gets in the way" to "[always|never] use direct connections".

In other words, it cleanly separates the two distinct concerns of privacy and connection topology. I think that's a good thing.

I remember having to do a lot of port forwarding to get certain things to work behind a nat. Certainly doable but beyond the competence of a non-expert.

And that's entirely out of your control if your ISP is doing the NATing.

Not even your ISP - it could be university, business, shared internet for apartments, etc.

And sometimes, entire nations. Qatar used to share a single IPv4 address, which I found out when news articles started reporting that the entire country could no longer edit Wikipedia without an account, which at the time, was also restricted if your IP was banned from anonymous edits. If you didn't create an account prior to the ban, you were completely blocked from editing.

https://en.wikipedia.org/wiki/User:82.148.97.69

https://techcrunch.com/2007/01/01/wikipedia-bans-qatar/

This isn't entirely about static port-forwarding. As others have pointed out, STUN, VoIP, PASV, etc rely on deterministic NAT behavior to work. That is not always guaranteed, and often out of your control.

The existence of PASV mode and STUN/TURN is because the end-to-end addressibility of the IP protocol was broken with CGNAT.

Furthermore, in populous countries like India, ISPs enforce extremely aggressive timeouts on IPv4 connections in order to keep the 5-tuples on the egress side of things manageable. Trying to make a request that takes 10 seconds to process (like a user requesting a report consisting of multiple SQL queries)? You get a connection reset.

I must also must point out the HN guidelines because you bring a combative tone to this entire conversation which is not helping it.

> Be kind. Don't be snarky. Converse curiously; don't cross-examine.

> The existence of PASV mode and STUN/TURN is because the end-to-end addressibility of the IP protocol was broken with CGNAT.

But isn't all that still necessary as long as the typical user isn't going to be opening their firewall on those ports to arbitrary incoming connections? That's the whole point here.

STUN yes (since you'll need to coordinate outbound traffic which creates the appropriate inbound rules), TURN no (since STUN will always succeed with stateful but non-translating firewalls).

And STUN scales almost infinitely better than TURN.

>> The biggest one is people seem to equate NAT = router/firewall. This is absolutely not the case,

I dont think anyone equate that, but IPv6 proponents refuse to recognize that decades and decades, especially in home users, and SMB space, NAT was a layer of the security model, often times one of the biggest

Right or wrong is irrelevant, that is/was the reality

Just tossing IPv6 as a replacement for ipv4 with out factoring that in while simply screaming into the void "NAT IS NOT A FIREWALL" will be of little comfort to the elderly retiree that has their home computer ransomwared, or the small business that is put under due to a cyber attack because the ipv6 address was strait on the public internet

Home router NAT "layer of security" is equivalent to closing all ports.

If an IPv6 home router closes all ports by default, then the same level of security is achieved.

That's a big "if."

> Randomized, temporary IPv6 public addresses are a nice feature, and mostly turned on by default

I really do not want this.

> I really do not want this.

Then disable it. IPv6 SLAAC privacy extensions are device-controlled, meaning neither your ISP nor your router can force you to use/not use them (unless they're so incompetent that they do things like hand out /128s).

Well, what I do is disable ipv6. I don't want the possibility that this is misconfigured, especially if the defaults tend to be wrong. Maybe my router doesn't even respect my firewall settings, like this: https://community.verizon.com/t5/Fios-Internet-and-High-Spee... Maybe the customer is wrong, but this shouldn't even be a question.

The rare times I want something publicly accessible, I use DMZ or port forwarding.

It isn't a big if, it is literally the same connection tracking stack except without the address and port mapping.

If you take away the mapping the tracking doesn't go away. Inbound traffic still needs to match to to a session created by outbound traffic.

Yes, and every router has to do it properly by default, which so far they haven't really been. NAT is a lot harder to do wrong, cause the local IPs aren't even addressible.

Its not harder to do wrong, its just less noticeable when done wrong, it's been a security consideration since NAT was created, and a persistent issue since then:

https://datatracker.ietf.org/doc/html/rfc2993#page-22

https://threatpost.com/remote-attackers-internal-network-dev... https://www.anvilsecure.com/blog/dhcp-games-with-smart-route...

It's defense in depth. I don't understand if and how this exploit allows an attacker to hit port 80 on my PC for instance, but either way it looks like a pretty sophisticated attack only discovered in 2021, and I still don't see panic over it.

If they haven't really been, then NAT wouldn't be working either, that's the point I'm making. NAT requires connection tracking to function, because NAT is actually an extra step on top of a basic stateful firewall, and the mapping part isn't the part that provides security, it is the connection tracking part.

> That's a big "if."

Not really. Many home routers used to assign all ports to the first device to connect to the router, and you'd need to setup NAT just for your second computer. Eventually the default settings wised up.

It is much more probable that security defaults will be much tighter today than they were when ADSL initially took off.

> Just tossing IPv6 as a replacement for ipv4 with out factoring that in while simply screaming into the void "NAT IS NOT A FIREWALL" will be of little comfort to the elderly retiree that has their home computer ransomwared, or the small business that is put under due to a cyber attack because the ipv6 address was strait on the public internet

This is definitely what I'm seeing. IPv4 is really engrained in us - I actually had a really hard time conceptualizing how things worked until I forced myself to learn by deploying dual-stack and ipv6-only networks.

The major downside I see right now is that "addresses are harder to memorize," but there are solutions to that as well.

> The major downside I see right now is that "addresses are harder to memorize," but there are solutions to that as well.

Definitely. That DNS thing sounds promising!

So we're supposed to do things wrong forever because some router vendors are too incompetent to set a firewall as well as NAT? That doesn't seem like a good approach to me.

Right and wrong in this context is subjective there are many things in IPv6 that I find to be wrong convoluted and overly complex

When IPv6 was created they had the opportunity to just make it an expansion of the IPv4 space they chose not to do that and instead they added in a bunch of wish list items that were not needed to accomplish the goal that they were seeking to do which was prevent the exhaustion of IPv4 addresses

Absent address space exhaustion I massively prefer working with IPv4 than I do IPv6

> Yes. You no longer need NAT, so port negotiation is much easier (even when inbound is blocked)

In practice someone can still configure NAT on IPv6 same as on IPv4 at least on Linux and some vendors, even if IETF resists standardizing it.

https://blogs.infoblox.com/ipv6-coe/you-thought-there-was-no...

So you might still see CGNAT if someone is determined to configure it.

Yes this is absolutely possible, but I do like that IPv6 doesn't mandate NAT.