On Mon, 1 Nov 2010 09:20:41 -0700 Owen DeLong <o...@delong.com> wrote:
> > On Nov 1, 2010, at 2:28 AM, Mark Smith wrote: > > > On Sun, 31 Oct 2010 21:32:39 -0400 > > Christopher Morrow <morrowc.li...@gmail.com> wrote: > > > >> On Sun, Oct 31, 2010 at 3:10 PM, David Conrad <d...@virtualized.org> wrote: > >>> On Oct 31, 2010, at 6:45 AM, Christopher Morrow wrote: > >>>>>> "If Woody had gone straight to a ULA prefix, this would never have > >>>>>> happened..." > >>>>> Or better yet, if Woody had gone straight to PI, he wouldn't have this > >>>>> problem, either. > >>>> ula really never should an option... except for a short lived lab, > >>>> nothing permanent. > >>> > >>> Seems to me the options are: > >>> > >>> 1) PI, resulting in no renumbering costs, but RIR costs and routing table > >>> bloat > >>> 2) PA w/o ULA, resulting in full site renumbering cost, no routing table > >>> bloat > >>> 3) PA w/ ULA, resulting in externally visible-only renumbering cost, no > >>> routing table bloat > >>> > >>> Folks appear to have voted with their feet that (2) isn't really viable > >>> -- they got that particular T-shirt with IPv4 and have been uniformly > >>> against getting the IPv6 version, at last as far as I can tell. > >>> > >>> My impression (which may be wrong) is that with respect to (1), a) most > >>> folks can't justify a PI request to the RIR, b) most folks don't want to > >>> deal with the RIR administrative hassle, c) most ISPs would prefer to not > >>> have to replace their routers. > >>> > >>> That would seem to leave (3). > >>> > >>> Am I missing an option? > >> > >> I don't think so, though I'd add 2 bits to your 1 and 3 options: > >> 1) we ought to make getting PI easy, easy enough that the other > >> options just don't make sense. > > > > Surely your not saying "we ought to make getting PI easy, easy enough > > that the other options just don't make sense" so that all residential > > users get PI so that if their ISP disappears their network doesn't > > break? > > > He may or may not be. I don't think it's such a bad idea. > How about algorithmically generating these addresses, so that they're near unique, instead of having the overhead of a central registry, and a global routability expectation? > > Recently we've seen somebody (on either nanog or ipv6-ops) proposing to > > set valid lifetimes of 24 hours on ISP GUA prefixes. While a 24 hour > > outage is unusual for a always connected broadband service, it isn't > > for intermittently connected nodes and networks. > > > The upstream valid lifetime doesn't have a lot to do with what happens on > the internal network if you're smart. > Residential end-users aren't "smart" and aren't network engineers - they pay people like us so that they don't have to be. > > In effect people who suggest using PA GUAs or PI for all IPv6 addressing > > are saying you can't run IPv6 unless you have an available IPv6 ISP > > connection or you must be able to afford to be able to thrust upon the > > world occupation of a global route table slot. They're not realistic > > requirements for all potential users of IPv6. > > > No...PI does not require an available IPv6 ISP connection at all. This > is a misstatement that does not become any less false no matter how > many times you repeat it. > What if you don't have an IPv6 ISP connection? Where do you get your PA from? Link local isn't good enough, because it can't span more than a single link. Homes in the future are likely to have multiple networks - visitor segments, multicast segments for video, children segments, 6LowPAN for home sensor networks etc. You've stated you use link locals for this sort of thing, yet you'd be specifying the interface to use as well. That isn't much different to using a subnet number, embedded in the address, to specify either directly attached or remotely reachable subnets. The nice thing about doing it that way is that IPv6 applications are addressing scope agnostic - they just use the address supplied, and ask the underlying OS, which uses the local route table, to direct where the packets go and therefore select the outgoing interface. Link locals + interfaces is more complicated, because now socket options have to be invoked, and only in the case of when a link local address is specified, which also means performing an address type check for the interface option. This code has to be present in ever application, instead of letting the underlying OS taking care of how application packets are directed towards their destinations, and the applications not having to care. > > For the most common and scalable case of PA, external addressing > > dependencies reduce reliability, because you can't control them. > > Completely relying on external connectivity and addressing for your > > internal networks reduces their reliability and availability. > > > This is also false if you use any form of sanity in applying the assigned > PA prefix to your network. > I suppose since they don't have the expertise, you could consider residential end-users insane. You can't make the insane sane just by telling them to be so. Preventing their "insanity" from breaking their Internet service, causing them to call your helpdesk, is the sane thing to do. That is achieved by making their Internet service work with the absolute least operational intervention on their part. It's hard enough to get them to enter their username/password via an embedded web server - to the point where some vendors supply setup CDs to automate the discovery of the device, avoiding the end user having to type an IP address URL into their browser. > > In this common case of PA, how are you going to justify that "no IPv6 > > without an IPv6 ISP" view to people who are very remote, such that even > > intermittent Internet access is very occasional; to people who run IPv6 > > sensor networks and don't ever want them connected to the Internet; or > > 3rd world countries where just local connectivity provides a very > > significant benefit, when global connectivity just isn't affordable? > > These and similar are cases where only ISP PA or PI aren't acceptable. > > > Nobody is trying to. This is a fallacy of logic that you keep pushing, > but, it's still false. If I wire a PA prefix into my router, it doesn't go > away just because the ISP does. All that happens is that I can't > reach the internet from it, which is kind of true regardless of the > address space used at the point where your ISP goes away. > You haven't ever tried to get a majority of residential end-users to update their firmware have you? You'll have the same luck getting a majority of them to "wire a PA prefix into" their routers. > > Permanent connectivity to the global IPv6 Internet, while common, > > should not be essential to being able to run IPv6, and neither should > > PI. All you should need to run IPv6 reliably is stable internal > > addressing. Global connectivity should be optional, and possibly only > > occasional. > > > Why shouldn't PI if it was easy to get? I still don't understand the > perceived advantage of ULA vs. PI other than the perception that > it is easier to get. If PI is just as easy to get, why is it a problem? > It seems to me your main criticism of ULAs is that people would expect it to be globally routed if they paid enough money. Now you're saying that if PI is really easy to get, people *won't* have a global routing expectation of PI routability? I certainly would if I was given PI. What would be worse is that this "non-routable" PI won't come out of a specific prefix so that it can easily filtered, unlike ULAs. > >> 2) ULA brings with it (as do any options that include multiple > >> addresses) host-stack complexity and address-selection issues... 'do I > >> use ULA here or GUA when talking to the remote host?' > >> > > > > There's an app for that (or rather a library routine called > > getaddrinfo() and an optional table it consults), and there's soon going > > to be a way to distribute it via DHCPv6 if the defaults don't suit - > > > > http://tools.ietf.org/html/draft-fujisaki-dhc-addr-select-opt-09 > > > Sure, now, how many applications have been coded to actually > pay attention to what getaddrinfo is telling them about address > selection order? > All the ones I use - they all seem to use the first getaddrinfo() response. They should be attempting to successively connect() to all responses in the order that getaddrinfo() returns as connect() failures occur. I don't know if they are (as destination reachability is usually good), however if they aren't, then the application developers haven't used getaddrinfo() correctly. That behaviour wouldn't be exclusive to IPv6 though - IPv4 applications should also be attempting to connect() to successive addresses when multiple are returned. IOW, applications coping with multiple responses to getaddrinfo() is not an exclusive issue to IPv6. I actually override the current default IPv6 address rules. Here's my /etc/gai.conf, which makes ULAs override GUAs as that currently isn't in the default address selection rules, and makes tunnelled IPv6 preferred over native IPv4, as I don't currently have native IPv6. The MRS entries are the non-defaults, the rest are from the gai.conf manual page. -- # Used for selecting source addresses # # label <prefix> <label> # label ::1/128 0 label ::/0 1 label 2002::/16 2 label 2000::/3 2 # MRS label ::/96 3 label ::ffff:0:0/96 4 label fc00::/7 5 # ULA - MRS # Used for sorting destination addresses # # precedence <prefix> <precedence> # precendence ::1/128 50 precendence ::/0 40 precendence fc00::/7 35 # ULA - MRS precendence 2000::/3 30 # MRS precendence 2002::/16 30 precendence ::/96 20 precendence ::ffff:0:0/96 10 --
