Joe Greco wrote:
Now, the question is, if you're sending all these prefix requests up to the ISP's router, why is *that* device able to cope with it, and why is the CPE device *not* able to cope with it?
The CPE cannot cope with it due to lack of a chaining standard and the lack of customer understanding of configuring a router. An ISP, as currently designed will manually assign prefix lengths and how they are handed out at each layer of the network. A home user should not be expected to understand this level of complexity. A CPE would have to be told HOW to divide it's variably received prefix to assign it's own networks and then issue prefixes to other routers behind it.
That doesn't seem like a problem from the set of unsolvable problems. We have current protocols that do substantially more complicated things in a standard and interoperable way. Your average current everyday IPv4 CPE has a DHCP server on it, for example, which very roughly approximates the complexity of the issue.
What is missing, unless I've missed a protocol (which is always possible), is an automated way for a CPE to assign it's networks, pass other networks out to downstream routers in an on-need basis. I say on-need, as there may be 3 routers directly behind the CPE and each of those may get additional routers and so on and so forth. A presumption could be made that route efficiency is not necessary at this level. ie, would it be practical or expected that an automatically configured network support > 100 routes or whatever a CPE can normally handle?
Actually, my own belief is that this /would/ be practical, and it might even be made to work efficiently. A "home router" maintains a list of space that it has been delegated, and a list of actually-used space (assigned to directly connected interfaces, along with any routed blocks). Upon receipt of a delegation request, the router starts an algorithm to see what it can do. Because it has been allocating out of a /56, the "primary" /64 was delegated at offset 0. Two requests from secondary routers came in, one was offered a /64 at offset 128, one at offset 192. That ought to make reasonable sense. The first "secondary" router learns that it has a bunch of downstream routers, and in the worst case asks for a delegation one at a time for each. The primary router assigns the subnet at offset 129, updates its route to the larger netmask, and away it goes. There's actually no increase in the number of forwarding entries, and this can be done a number of times. Further, if the primary router decides that it is allocating a lot of space to a secondary router, it can assign a larger hunk of space, saving some setup time, or it can try to optimize for bit boundaries. Not all cases will be this optimal. However, it seems reasonable to try.
Of course, if this support is built at a CPE level, there's no reason the protocol can't be extended and supported at the ISP level as well for those who wish to utilize it. An ISP, would of course prefer prefix aggregation and controls to set minimum and maximum aggregate space for a customer.
Exactly.
You have an ISP network, with a large amount of space available, and a lesser amount of space dedicated to the POP.
This setup in the ISP network is handled by hopefully clueful engineers and probably not automatically assigned by some cool protocol that routers speak (which would be cool, though, even if impractical).
Yes, but I'm really just talking about the idea of doing meaningful aggregation and simplification.
So what we want is something that can intelligently handle delegation in an automatic fashion, which probably includes configurable settings to request/register delegations upstream, and to accept/manage them downstream. There's no reason that this shouldn't be basic router capabilities.
For the home router, I believe that this is mandatory if we wish to continue to allow self configuring networks for home users.
Oh, yeah, let me say: I am assuming that it *is* mandatory that we come to a solution of some sort. It may not need to be day 1, but it ought to be.
A little extended logic and it can also be useful in larger networks, possibly even to the point of an enterprise network able to completely number itself (including renumbering itself as necessary).
A little pie in the sky, but I *want* to see that as an option. Not to trivialize Real Network Engineers(tm), but not everything has to be super complicated. I would like to see IPv6 reach a point where a mildly clueful person could plug in a "workgroup switch" into a managed corporate network, maybe even a few of them daisy-chained, and run a little web setup GUI that allows some basic network setup in fairly abstract terms, such as setting up a "protected" printer network that was only accessible to certain parties. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.