Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why IPv6 is so complicated

github.com

Post reply on HN
Print view View original

351–360 of 519 posts

Re: Why IPv6 is so complicated

#351

Post by convolvatron »

hackthemack wrote: post #337
MaKey wrote: post #322

Earlier quoted context omitted.

Your proposal (translation) is addressed as point 3B in the article.

I went and re-read point 3B. I agree that some hypothetical ipv42 faces a translation problem. But it does not follow that address design is irrelevant. The structure of the address space directly determines whether translation can be stateless and alogrithmic. In a hypothetical ipv42 design that preserves a deterministic embedding relationship between old and new addresses, translation at the edges could be largely…

I agree with you about the embedded addresses, and I don't understand why the space was moved to all zeros to a bunch of other mappings.

but the utility of this isn't that high. we already know how to handle 4-4 and 6-6 traffic just fine. but if a 4 host wants to talk to a 6 host, it just doesn't have the extra bits in order to describe it, so this just doesn't facilitate 4-6 endpoint communication at all. this is true even you substitute v6 with any other layer 3 with a larger address space.

where it does help is in a unified routing backbone, that would allow v4 prefixes to be announced in the v6 routing system. which is arguably useful.

Re: Why IPv6 is so complicated

#352

Post by t43562 »

I think we've been shunted into an alternate universe by NAT - one which reinforces the power of large companies because we essentially cannot communicate computer to computer without going through some service.

As for security.........are we really that secure running code in our browsers that we downloaded from who knows where? Is nat really saving us?

And now here we are with IPv6 and the real age of the network could begin.

Re: Why IPv6 is so complicated

#353

Post by convolvatron »

thayne wrote: post #349
Galanwe wrote: post #276

Earlier quoted context omitted.

Its not just NAT, it's also DHCP. Somehow the nerds creating IPv6 decided to not only add bytes (which is what people wanted), but also "fix" DHCP and NAT, which nobody asked for.

When ipv6 was first created DHCP and NAT were new and not widely deployed. They weren't trying to "fix" them, they solved the same problems independently. And if you need NAT or DHCP, there isn't any reason you can't use them with ipv6. DHCP6 had been around for a long time.

that's not at all true. DHCP was very much part of the operational canon of the internet at the time, which is why it persisted as a model. V6 really wanted to back that out so that networks 'just worked' without depending on an administrator to manage that local service.

NAT was already in use, and a substantial motivation for the IPv6 work was to provide an alternative before it got too entrenched, which sadly failed.

Re: Why IPv6 is so complicated

#354

Post by calvinmorrison »

hackthemack wrote: post #316
Plasmoid wrote: post #290

Earlier quoted context omitted.

> keeping backward operational compatibility It is not possible to be backwards compatibility with a larger address space

You are right that a 32 bit ipv4 stack can not understand a 64 bit packet format. The thing I am trying to get at is not native compatibility, it is operational compatibility via translation. I know, I know, you will probably say that is what ipv6 bridges do. But in an ipv42 type setup, you would have determnistic embedding so that every ipv4 address is represented inside the larger address space. This would allow tr…

I don't see how it matters we forced people into ipv6 as well. Who cares. It's more about the difference in mental models that prevented adoption especially among those who run the services that are on the internet.

Re: Why IPv6 is so complicated

#356

Post by zadikian »

doctorpangloss wrote: post #311
zadikian wrote: post #299

I disagree that it would've been just as hard anyway. The people who say "I just wanted v4 with more bits" have a point that most of these arguments completely ignore, but this one touches on it: Actually, we tried that: the "IPv4-Compatible IPv6 address" format was defined in [RFC3513] but deprecated by [RFC4291] because it turned out to be of no practical use for coexistence or transition. The practical use would'v…

they have no point. some random aesthetic aspect of a standard is not why it does or does not get adopted. it's an evolutionary standard that offers no direct incentives for adoption. the real obstacle was enterprise sales, that is, someone had to pay Microsoft, Google, Amazon, etc. as a major customer of theirs to implement correct IPv6, which takes time. the people at Microsoft working on ipv6 for customers, they'r…

Despite the lack of incentive for some, it's gotten pretty far. Pretty much every network device and host supports it in a minimal way. It's just that people/corps don't want to switch because it introduces a lot of risk and changes in unexpected areas. Like you can fully understand the spec without knowing what the routes and reputation will look like.

Re: Why IPv6 is so complicated

#357

Post by izacus »

Plasmoid wrote: post #290
hackthemack wrote: post #288

I think this is the kind of the topic that can be endlessly debated because you can not easily go back in time and test out alternate hypothesis. I will say that I do not like ipv6 because it tried to fix multiple accumulated problems. I know! How contrarian! How can you be against trying to fix things. But all of those issues made ipv6 a dual stack solution that replaced ipv4. Address exhaustion, Routing table scala…

> keeping backward operational compatibility It is not possible to be backwards compatibility with a larger address space

This is a fake argument. Noone is arguing for backwards compatibility.

But there was also no necessity to demand reshaping networks and changing address assignment in a way that made migration extremely work intensive and hard to deploy in parallel.

Re: Why IPv6 is so complicated

#358

Post by izacus »

api wrote: post #270
evilmonkey19 wrote: post #269

Personally, i feel it is complicated because ISPs are highly afraid of trying it. I understand that such novel technology would be risky to use. But after 20+ years there are still many countries, like Spain, which are barely using it. After that much time has passed, it is already well battle-tested. At this point, you don't want to make the move either because you are too afraid of anything or you have commercial r…

IT and telecom tend to have an ultra conservative if it’s not broke don’t fix it attitude. It won’t get deployed until enough customers ask for it or it’s required for something important.

That's because they actually get paid for providing a reliable service, not for ipv6.

Re: Why IPv6 is so complicated

#359

Post by Fabricio20 »

Personal experience that I see noone talk about with IPv6 is how much more expensive hardware that handles it correctly is for datacenters. On IPv4 your usual unit of allocation is a /32 for customers - that means a simple hashmap `1.1.1.1=destination mac` works wonderfully and is cheap (single memory lookup), but for ipv6 your usual unit is a /64 so its longest prefix match instead, which requires parsing the address to group it back into the /64 and alot of switches and routers that are already expensive still have very low limits on LPM memory banks.

Expensive switch at work we have can only do 3000 route entries for example on ipv6. If we did /128s it's basically infinite though, because it goes from a LPM to exact match, which has much much more memory available.

Doesn't help as well that for example, to be able to do SLAAC or even DHCPv6 (which barely works reliably in my experience) you need to do a /64 at minimum, those mechanisms dont even work otherwise, so for ISPs who can easily have more than 3000 downstream customers doing routed ipv6 is such an increase in hardware cost vs just doing NAT which they were already doing anyway.

Re: Why IPv6 is so complicated

#360

Post by kstrauser »

Fabricio20 wrote: post #359

Personal experience that I see noone talk about with IPv6 is how much more expensive hardware that handles it correctly is for datacenters. On IPv4 your usual unit of allocation is a /32 for customers - that means a simple hashmap `1.1.1.1=destination mac` works wonderfully and is cheap (single memory lookup), but for ipv6 your usual unit is a /64 so its longest prefix match instead, which requires parsing the addres…

Why on earth would you ever want to route something smaller than a /64? At the ISP level, you'd only be concerned about your customers' /48 or maybe /56 networks.
Post reply on HN