Global routeability doesn't automatically mean global reachability.
Many consumer and professional routers will block inbound TCP connections, and incoming UDP traffic without at least similar outbound UDP traffic preceding it, so you will still need hole punching.
Hole punching does get significantly more easy with v6, though, since there's really only one way to do "outbound connections only" firewalling (while there's several ways to port translate, some really hostile to hole punching).
Arguably one thing that's missing is a very simple, implicit standard that allows signalling a willingness to accept an inbound TCP connection from a given IP/port that such stateful firewalls can honor, similar to how they already implicitly do it for UDP, but with HTTP 3 running over UDP, the point might well be moot soon.
Simultaneous initiation is only slightly more complex, as is shown in
figure 8. Each TCP cycles from CLOSED to SYN-SENT to SYN-RECEIVED to
ESTABLISHED.
TCP A TCP B
1. CLOSED CLOSED
2. SYN-SENT --> <SEQ=100><CTL=SYN> ...
3. SYN-RECEIVED <-- <SEQ=300><CTL=SYN> <-- SYN-SENT
4. ... <SEQ=100><CTL=SYN> --> SYN-RECEIVED
5. SYN-RECEIVED --> <SEQ=100><ACK=301><CTL=SYN,ACK> ...
6. ESTABLISHED <-- <SEQ=300><ACK=101><CTL=SYN,ACK> <-- SYN-RECEIVED
7. ... <SEQ=101><ACK=301><CTL=ACK> --> ESTABLISHED
Simultaneous Connection Synchronization
Figure 8.
You could slap a UDP header on top of the TCP header and get the benefits of TCP with the hole-punching capabilities of UDP, provided you implemented some kind of keep-alive functionality and an out-of-band way of telling the "server" to establish an outbound connection with the "client". Or use QUIC, assuming it fits the use case.
But it's often disabled for the same reason as having router-level firewalls in the first place.
Yeah, anything that allows hosts to signal that they want to accept connections, is likely the first thing a typical admin would want to turn off.
It’s interesting because nowadays it’s egress that is the real worry. The first thing malware does is phone home to its CNC address and that connection is used to actually control nodes in a bot net. Ingress being disabled doesn’t really net you all that much nowadays when it comes to restricting malware.
In an ideal world we’d have IPv6 in the 90’s and it would have been “normal” for firewalls to be things you have on your local machine, and not at the router level, and allowing ports is something the OS can prompt the user to do (similar to how Windows does it today with “do you want to allow this application to listen for connections” prompt.) But even if that were the case I’m sure we would have still added “block all ingress” as a best practice for firewalls along the way regardless.
But how much of this is because ingress is typically disabled so ingress attacks are less valuable relative to exploiting humans in the loop to install something that ends up using egress as part of it's function.
[Don't get me wrong, if you just wanted to make your own as a learning project or because its fun, that's cool too]
As with any network protocol design, the tradeoff is slighty gained from versatility over loss of privacy. So it depends on your triage of needs: security, privacy, confidentiality.
Now with the latest "quadage", unobservability (plausible deniability).
Still a fascinating protocol, doomed to be used exclusively as a weird middle layer for websockets and as a carrier protocol for internal telco networks.
Cryptography can't be thought of as an optional layer that people might want to turn on. That bad idea shows up in many software systems. It needs to be thought of as a tool to ensure that a behavior is provided reliably. In this case, that the packets are really coming from who you think they are coming from. There is no reason to believe that they are without cryptography. It's not optional; it's required to provide the quality of service that the user is expecting.
DTLS and QUIC both immediately secure the connection. QUIC then goes on to do its stream multiplexing. The important thing is that the connection is secured in (or just above) the network layer. Had OSI (or whoever else) gotten that part right, then all of these protocols, like SCTP, would actually be useful.
This article focuses on the transport-layer design, not a torrent client replacement. The goal is to provide a reusable IPv6-native P2P connection layer (QUIC-based, NAT-free) that existing clients or new applications can integrate without touching their higher-level logic.
Feedback on design trade-offs is very welcome.
The project is very impressive, as is https://github.com/TheusHen/ternary-ibex and having papers: https://orcid.org/0009-0009-5055-5884
What's the education path for a 14 year old that does this stuff?
Would it be possible to use a dozen of IPv6 addresses at the same time? Like send one UDP packet over certain IPv6 interface, next packet over another IPv6 interface, and so on. If both sending and receiving end have access to multiple IPv6 addresses I can see how this significantly increases complexity for tracking.
Could you split up the traffic across dozens or hundreds of IPv6 source addresses?
Yes
> I can see how this significantly increases complexity for tracking
Not really. You just track at some prefix level. In general, the ISP will hand out a /64 per consumer so that's what you can track. From there, you can build more complex and more precise grouping rules for tracking.
I feel this would create significant struggles for any surveillance software because most firewalls I know are modeled on a source address / target address basis.
If you have access to enough source IPv6 addresses you might even put your whole wireguard traffic into ICMP packet payload?
In theory I could rent an IPv4 /29 (of which 6 addresses are usable) for like 20 euros a month from my home ISP to cause the same confusion but I doubt it'd confuse trackers to use those.
Re: renaming all the prefixes, that's why I use a ULA within my home network. Not as useful if you want your services available from the outside if you move ISPs (NAT66 can help on the inside but you'd still need to update all DNS records to use the new prefix). I'll stick with my ULA + VPN fallback for now, I don't expect the prefix to change more than once every five or six years.
If you want a static prefix with a changing prefix, you're probably better off with getting a Hurricane Electric tunnel. Or if you want to go hard on the IPv6 homelab hobby, get your personal IPv6 address space and a bring-your-own-IP business ISP.
Regardless, my point is that allocations narrower than /64 exist in the wild for better or worse. So do IPv6 NAT implementations for that matter. If you assume either of those things don't exist then you might be in for a surprise.
What I'd like to have is a single service dynamically using many network interfaces with randomized packet timings and randomized packet scheduling (5 packets on first interface, pause on 2nd, some on third interface, sometimes send traffic simultaneously).
I realize it's intended to be an unsupported edge case but I'm curious. What happens in the event a NAT is present along the IPv6 network path? Do you just forward a port the same as you would with the various IPv4 solutions and move on? Or does it break catastrophically? Something else?
What's the landscape today?
I don't believe those are synonymous.