4 ms·
Unlike with a lot of what they do, that resistance I appreciate. I don't think it's the right way either. I've seen firsthand how it's a crutch that lulls some
by Avamander 4y ago
Unlike with a lot of what they do, that resistance I appreciate. I don't think it's the right way either. I've seen firsthand how it's a crutch that lulls some network admins into thinking they can just think about v6 as it were v4.
- zamadatix 4y agoI've maintained and deployed dozens of IPv6 networks but I'm still not quite sure I follow what you mean. The Android teams reasoning was they didn't want networks to be able to disallow multiple addresses (particularly carriers, not Wi-Fi) but that doesn't really have anything to do with treating it like v4 being wrong.
- vetinari 4y agoExactly; DHCPv6 would allow to force the device to use just a single IP address. In IPv6, you need extra IP addresses for tethering; XLAT464 needs entire /96 prefix. Allowing DHCPv6 would allow network admins cripple functionality like this. It's not like IP addresses even in the smallest subnet (/64) are a scarce resource. For carriers, it is not necessary at all. LTE networks use different mechanism for communicating assigned IP addresses.
- zamadatix 4y agoDHCPv6 forces no such thing. 464XLAT can still be done via PD though it's really again a carrier thing, enterprises will know if they need 464XLAT the device doesn't need to force that it would be possible. Same story with tethering. LTE w/ PDN still uses DHCPv6 PD or SLAAC (or both) https://i.imgur.com/2dKAw5W.png https://i.imgur.com/2dKAw5W.png
- vetinari 4y ago> DHCPv6 forces no such thing it just allows for it. I wrote "would allow to force", not that it forces. > LTE w/ PDN still uses DHCPv6 PD or SLAAC (or both). Unless you are turning Android device into router, you won't need PD support there. What else you need prefix delegation for?
- zamadatix 4y ago> I wrote "would allow to force", not that it forces. Ah sorry, must have misread my bad. All the same I'm not seeing how this plays into why it should be forced, the phone is just half the story (the CLAT) and if the enterprise wanted to implement 464XLAT they can PD and run a NAT64 gateway. If they don't then it's not going to work just because the device has enough addresses to be a CLAT as there is no NAT64 gateway. Or if they just want their devices to dual stack or single stack v6 instead why does Android get to decide they need to support something they aren't using? > Unless you are turning Android device into router, you won't need PD support there. What else you need prefix delegation for? The prefix for 464XLAT or to allow tethering. DHCPv6-PD is how you do this when you're not using SLAAC.
- vetinari 4y ago> All the same I'm not seeing how this plays into why it should be forced, the phone is just half the story (the CLAT) and if the enterprise wanted to implement NAT64 and 464XLAT they can PD. If they don't then it's not going to work just because the device has enough addresses to be a CLAT. You are right. I've used that as an example of why a device would want more IP addresses than one. One of aspects of treating IPv6-as-IPv4 is the assumption, that one IP is enough. I get it, it simplifies logging/reverse resolution for example, but one IP might be not enough and the example, while not be the best, illustrates the point. > The prefix for 464XLAT or to allow tethering. DHCPv6-PD is how you do this when you're not using SLAAC. There is a difference in scope between PD and SLAAC: With PD you usually hand out /64 (or bigger) carved out of whatever larger subnet you have. So if your upstream gets you /48 or /56, this is the mechanism to hand out smaller subnets to routers downstream. SLAAC support allows any device in the subnet to claim any address inside the announced prefix it wants, unless it is already taken and other device objects. There is no limit on how many addresses it can claim, but claiming /64 or more would take a while :). Claiming a few is enough for tethering to work. SLAAC is what you get wit RA by default; only those that want to force DHCPv6 on their network disable it (yes, I tried that once when playing with it. That playing was great way to understand why it was a bad idea). With DHCPv6, even if it is supported in the network, doesn't mean you also get PD. It remains completely optional. This is a problem with many CPEs (i.e. with a class of devices it was designed for!), that are supposed to support PD, but the support is either buggy or non-existent, thus their users never have more than /64.
- megous 4y agoAll this achieves is that for people who want to subnet /64 it is not possible on Android without manual setting of the address. (and only on android) Yeah and android doesn't support manual setting of the IPv6 address in the UI, lol. What an OS.