Comment by mojuba
4 days ago
> Groups of zeros can be omitted with two colons, but only once in an address (i.e. 2000:1::1, but not 2000::1::1 as that is ambiguous)
Can someone explain why it's ambiguous?
On the subject, IPv6 is one of the strangest inventions on the internet. Its utility and practically are obvious no matter how you look at it except... just one thing.
Network-related things are generally easy to remember and then type from memory: IPv4, domain names, standard port numbers. Back in the day it was the phone numbers, again, easy to remember and dial when you need it. IPv6 is just too long and requires copy/paste all the time. This is the only real reason in my opinion, why IPv6 is doomed to be second-grade citizen for (probably) a few more decades.
2000:1::1 would expand to 2000:0001:0000:0000:0000:0000:0000:0001
2000::1::1 could be 2000:0000:0000:0000:0001:0000:0000:001, or 2000:00000000:0001:0000:0000:0000:001
There's ambiguity on where to fill in the five groups of 0000 in the second case.
The second address is invalid. You can only use :: once per address.
Edit: Whoops. Didn't read what the above post was in response to. My bad.
That exactly what was the question about and they explained why it is invalid…
> This is the only real reason in my opinion, why IPv6 is doomed to be second-grade citizen for (probably) a few more decades.
Except if you're using a mobile phone, in which case many telcos hand out only IPv6 addresses to handsets. 2018 NANOG presentation "T-Mobile's journey to IPv6":
* https://www.youtube.com/watch?v=d6oBCYHzrTA
From 2014, "Case Study: T-Mobile US Goes IPv6-only Using 464XLAT":
* https://www.internetsociety.org/deploy360/2014/case-study-t-...
But who cares about mobile phones, right? They're only second-grade devices.
my tmobile 5g modem has ipv4 but changes ip every single page load, it's wild
I'm used to cablemodems with static ipv4 for months basically until mac changes
Is it per chance 100.64.0.0/10?
* https://en.wikipedia.org/wiki/IPv4_shared_address_space
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Your IPv4 packets are getting tunneled to a CGNAT server which has an IP address pool.
Your website will load faster on cellphones if it supports IPv6. This is because the packets take more direct routes (because they don't go to the central CGNAT server) and because less processing is applied to them. Almost all mobile networks are now IPv6-only, with IPv4 traffic tunneled and CGNATted. Apparently T-Mobile is the rare exception.
> my tmobile 5g modem has ipv4 but changes ip every single page load, it's wild
They're probably using CG-NAT, though IP changes that often is a bit aggressive.
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I've said this since time immemorial, and networking people often dismiss it. "Just use DNS," say people who have never actually worked netops or devops.
The length of the addresses and the clunky nature of their ASCII representation is absolutely the #1 reason the IPv6 has taken this long. User experience is the most powerful force affecting large scale adoption, and IPv6 has poor UX.
I think the UX is partly fixable by creating less horrible ASCII representation, but this would take a lot of coordination that was hard even back then and is virtually impossible now. If someone told me in 500 years we're still running dual-stack IPv4/IPv6 absolutely unchanged, I'd believe it.
Half the reason (literally) the address looks so bad is not because of IPv6 but because everyone keeps choosing to implement randomized in-subnet addresses and cycle through them for privacy reasons.
E.g. 2600:15a3:7020:4c51::52/64 is not too horrible but 2600:15a3:7020:4c51:3268:b4c4:dd7b:789/64 is a monster by unrelated intent of the client.
This is pretty much on the money. IPv6 addressing can be pretty simple if you design your subnets and use low numbers for hosts. But hosts themselves will forgo that and randomly generate 64 bit random host addresses for themselves - some times for every new connection. Now you have thousands of IPv6 addresses for a single computer speaking out to the Internet.
"Modern" tooling in the consumer space is pretty dire for IPv6 support too. The best you can reasonably get is an IPv6 on the WAN side and then just IPv4 for everything local. At least from the popular routers I've experienced lately.
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Yes, I forgot about SLAAC and worthless privacy extensions.
Privacy extensions are worthless because there are just sooooo many ways to fingerprint and track you. If you are not at least using a VPN and a jailed privacy mode browser at a bare minimum, you are toast. If you’re serious about privacy you have to use stuff like Tor.
V6 privacy extensions are like the GDPR cookie nonsense: ineffective countermeasures with annoying side effects.
SLAAC sucks too. They should have left assignment up to admins or higher level protocols like with V4. It’s better that way.
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I said this in a previous post and was shot down hard. I think you are right. Every time I look at a ipv6 address my brain goes “fack this”.
IPv4 isn't perfect, but it was designed to solve a specific set of problems.
IPv6 was designed by political process. Go around the room to each engineer and solve for their pet peeve to in turn rally enough support to move the proposal forward. As a bunch of computer people realized how hard politics were they swore never to do it again and made the address size so laughably large that it was "solved" once and for all.
I firmly believe that if they had adopted any other strategy where addresses could be meaningfully understood and worked with by the least skilled network operators, we would have had "IPv6" adoption 10 years ago.
My personal preference would have been to open up class E space (240-255.*) and claw back the 6 /8s Amazon is hoarding, be smarter about allocations going forward, and make fees logarithmic based on the number of addresses you hold.
> IPv4 isn't perfect, but it was designed to solve a specific set of problems.
IPv4 was not designed as such, but as an academic exercise. It was an experiment. An experiment that "escape the lab". This is per Vint Cerf:
* https://www.pcmag.com/news/north-america-exhausts-ipv4-addre...
And if you think there wasn't politics in iPv4 you're dead wrong:
* https://spectrum.ieee.org/vint-cerf-mistakes
> IPv6 was designed by political process.
Only if by "political process" you mean a bunch of people got together (physically and virtually) and debated the options and chose what they thought was best. The criteria for choosing IPng were documented:
* https://datatracker.ietf.org/doc/html/rfc1726
There were a number of proposals, and three finalists, with SIPP being chosen:
* https://datatracker.ietf.org/doc/html/rfc1752
> I firmly believe that if they had adopted any other strategy where addresses could be meaningfully understood and worked with by the least skilled network operators, we would have had "IPv6" adoption 10 years ago.
The primary reason for IPng was >32 bits of address space. The only way to make them shorter is to have fewer bits, which completely defeats the purpose of the endeavour.
There was no way to move from 32-bits to >32-bits without every network stack of every device element (host, gateway, firewall, application, etc) getting new code. Anything that changed the type and size of sockaddr->sa_family (plus things like new DNS resource record types: A is 32-bit only; see addrinfo->ai_family) would require new code.
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Imo they should have just clawed 1 or 2 bits out of the ipv4 header for additional routing and called it good enough
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IPv6 is literally just IPv4 + longer addresses + really minor tweaks (like no checksum) + things you don't have to use (like SLAAC). Is that not what you wanted? What did you want?
And what's wrong with a newer version of a thing solving all the problems people had with it...?
There are more people than IPv4 addresses, so the pigeonhole principle says you can't give every person an IPv4 address, never mind when you add servers as well. Expanding the address space by 6% does absolute nothing to solve anything and I'm confused about why you think it would.
> Every time I look at a [long] ipv6 address my brain goes “fack this”.
I do get that but I also get 'There are so many I could have all I wanted ... or I could if any of our fiber ISPs would support it, that is'
I finally clicked when I worked out it was 2^64 subnets . You have a common prefix of you /48, which isn’t much longer than an ipv4 address - especially as it seems everything is 2001::/16, which means you basically have to remember a 32 bit network prefix just like 12.45.67.8/32.
That becomes 2001:0c2d:4308::/48 instead
After that you just need to remember the subnet number and the host number. If you remember 12.45.67.8 maps to 192.168.13.7 you might have
2001:0c2d:4308:13::7
So subnet “13” and host “7”
It’s not much different to remebering 12.45.67.8>192.168.13.7
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> Network-related things are generally easy to .. type from memory [but] IPv6 is just too long
I was reminded of this 2d ago; I was testing one IPv6 WAN from another. DDNS had failed so I didn't have my usual crutch to lean on.
> Can someone explain why it's ambiguous?
Because you don’t know how many zeroes are on each side around the 0001 in the middle.
It can be 2000:0000:1:0000:0000:0000:0000:1 or 2000:0000:0000:0000:0000:1:0000:1 etc.
This shortcut system of ipv6 only makes it worse. It's too hard to remember how it works.
Is it really hard to remember? A hint is in the syntax itself. What's in between the two colons '::'? Nothing. In other words, all zeros.
IPv4 also has a similar, though rarely documented or utilized, shortcut system. Try `ping 1.1` for example. It expands to 1.0.0.1.
":: is all zeros" is too hard??
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> IPv6 is just too long and requires copy/paste all the time.
That is only true for autogenerated/SLAAC IPs. In contrast, manually assigned IPs are often much simpler and easier to remember in IPv6 than in IPv4. I have one common subnet prefix that can be uniformly split to end networks and last number in IP address for such network always end with 0 (and therefore the first device is xxx::1). While in IPv4 i had multiple prefixes, each split non-uniformly based on how many devices was expected to be on that end network, and because most end network prefixes were smaller than /24 (say /26-28), the last number of IP address varies between these networks.
I mean yes, but there’s no escape from the fact that ip addresses need to be longer as amount of devices on the internet already exhausted the pool of IPv4 addresses by multiple orders of magnitude.
I guess it could be possible to implement sort of mnemonic phrases for addresses, à la bip-39, but it would be just trading one kind of pain for another.
whats the rule to say where the first 1 floats between the 2000: and the :1 at the end? the :: rule says "all zeros" but not how long.
It’s a really complicated rule called “subtraction”. Addresses are always 128 bits long, or 8 groups of four hex digits. 2000::1 is two groups, so you need six groups in between to make 2000:0000:0000:0000:0000:0000:0000:1. But I don’t know why people always ask this, because it’s always the computer you are typing addresses in to that does the subtraction. You never ever have to type out the whole address. Just type the shortened version, because 2000::1 _is_ the whole address.
They were answering the question of why "2000::1::1" would be ambiguous if it was allowed.
the :1 is short for :0001 basically and then just put that bit of the address at the very end and put the first bit of the address at the front, and then just fill each missing group inbetween with 0000
"just"
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My answer was too terse. IF there was two :: in the address, then the length of EACH :: denoted section is not known. It can be either longest left :: or longest right :: and that wasn't defined, because the rule is THERE IS ONLY ONE :: section.
Posed as a question, disingenuously.