I suppose the persistence of IPv4 has broken all of our brains, but with IPv6 you can just Not Have NAT, and just have normal end-to-end connectivity to any random box in your home from outside.
(And yes, I do this. Works great.)
(And yes, I do this. Works great.)
But if you set your sights higher and want to build true p2p apps for non-techies, or if you want “roaming” servers (say an FTP server on your laptop), there are more obstacles than NAT, in practice:
- Opening up ports in both a residential router and sometimes the OS or 3p firewall. Most people don’t know what a port is.
- DNS & certs which require a domain name and a fixed connection (if the peer moves around across networks, eg a laptop or phone, DNS is not responsive enough)
Right.
> It unlocks the type of use case where technical people can host something from home for fun, although many can’t access it because both parties need ipv6.
At this point, that's an obstacle, but at some future point hopefully IPv6 will hit a critical mass and network effects will take off because there'll be enough stuff that _doesn't work without IPv6_, so customers will demand it.
> if you set your sights higher and want to build true p2p apps for non-techies
Definitely.
Restoring the universal endpoint-to-endpoint connectivity on the IP network overcomes a _major hurdle_, a hurdle that's so big and longstanding that people have come to just assume its existence and fear and removal… but it certainly doesn't solve all the problems.
> or if you want “roaming” servers (say an FTP server on your laptop)
https://en.wikipedia.org/wiki/Multipath_TCP will take a big dent out of this, I think.
> - Opening up ports in both a residential router and sometimes the OS or 3p firewall. Most people don’t know what a port is.
I mean, UPnP makes big improvements in this area, but a lot of devices stupidly don't handle it, or block it for alleged security reasons. Frustrating.
> - DNS & certs which require a domain name and a fixed connection (if the peer moves around across networks, eg a laptop or phone, DNS is not responsive enough)
There's no real reason why TLS clients _must_ only trust certs when they see that the CN or SAN matches the _domain name_ through which they looked up the IP address. I think that with a better issuing infrastructure and UX, a TOFU-based (https://en.wikipedia.org/wiki/Trust_on_first_use) approach to self-signed certs for peer-to-peer services could be both comprehensible for non-techies and highly secure.
Unfortunately most ISP's in my area don't dish out IPv6 addresses without ridiculous monthly charges. I hope one day it becomes more commonplace.
That's the job of a firewall and is unchanged between ipv4 and IPv6. Theyre both equally vulnerable to denial of service attacks
If you've got an IPv4 address that responds to ICMP, HE's https://tunnelbroker.net/ offers free IPv6 ranges (a bunch of /64s and a /48) for free. You can configure a tunnel to work through many routers, but with some setup you could also have something like a Raspberry Pi announce itself as an IPv6 router.
Sites like Netflix treat HE tunnels as VPNs, though, so if you run into weird playback errors, consider configuring your device's DNS server/network not to use IPv6 for that.
As for your questions:
> how you do this
Open port 8888 to (prefix):abcd:ef01:2345:56, or whatever IP your device obtains, in your firewall. It's the same process as with IPv4, except you can use the same port on multiple devices.
> And how do you prevent someone spamming your devices or is the risk so low you don't care?
While some services have started scanning IPv6, a home network from a semi-competent ISP will contain _at least_ 2^64 IPv6 addresses. Scanning the entire IPv6 network is unfeasible for most automated scanners.
What do you mean by spamming? People are scanning the Internet the whole time to see what's there, and it isn't a threat unless you are doing something terribly insecure. Scanning IPv6 is impossible in practice anyway, due to the high number of available addresses.
Also can you get an tls cert for a ipv6 number address? Or are you punching through using only ssh or unencrypted stuff?
IPv6 lets you do this -- nearly every client will use privacy addressing, so your (default) source address rotates daily. However you can still connect to the machine on its main (non-privacy protected) IPv6 address.
CGNat adds a layer of privacy that a public /32 (ipv4) or /64 (ipv6) doesn’t give.
SLAAC? Literally a hack that accidentally caught on because some vendor implemented it sooner than DHCPv6 for some reason. It was intended that everyone would use DHCP just like before. And that's the biggest difference from v4 other than the address format.
They might sound minor but in practice they violate assumptions that are really crucial for implementations. Everyone who deals with addresses must make decisions about how and what to do in face of these quirks.
Another example is the zone identifier string. So how do you store them efficiently in memory or a db? Golang did a really clever thing with netip but the implementation was not easy. Oh well maybe we can always ignore and strip it? Maybe, depends on the use case.
The point is going from exactly 32 bit to 128 bit + sometimes maybe a variable length string (max length, encoding, allowed chars?) is not a small change for something so important and ubiquitous as ip.
The history I recall is very much a academics designing theoretical standards vs operators who actually implement the damn things.
The academics designed the standards around the use of SLAAC deliberately and intentionally. DHCPv6 was the ‘hack’ that operators implemented after the fact.
I’m sure there’s an RFC somewhere that’ll prove this one way or another, if anyone else reading this cares enough to determine for sure (Duty Calls).
With ipv6 you can match IPs realistically to a single household across multiple sites.
Access porn.com from 12.34.56.78 and you are one of dozens of households. Just because Bob Bobson who logged into Netflix is on the same IP it doesn’t mean that house was on porn.com.
Access from 2100:1234:5678:abcd:: and you are accessing from one specific household, even if the lower 64 bits differ. You’ll likely keep the same ip for longer than in cgnat anyway (and by design you keep it until your isp changes)