On 2 Jun 2013, at 17:10, Ted Lemon <[email protected]> wrote: > On Jun 2, 2013, at 11:59 AM, Owen DeLong <[email protected]> wrote: >> You are assuming that all of the subordinate routers will act as DHCP relays >> rather than doing PD. >> That is certainly one possible solution, but, not necessarily ideal in all >> cases. >> In cases where the subordinate routers should receive delegations and >> perform their own PD for their subordinate routers, having a larger bit >> field can be useful for greater flexibility. > > No, there is no use case where this is better than doing the delegations from > the router that received the initial delegation (since we're apparently just > arguing by vigorous assertion). > >> Thus, providing 16 bits to the end site is, IMHO, worth while. > > And hence, this conclusion is not supported. > > You are welcome, of course, to contradict me by stating such a use case, but > bear in mind that when you delegate prefixes for further sub-delegation, > topology changes in the homenet become impossible. So your use case for > doing this would have to enable some pretty awesome functionality before it > would be worth doing. Also make sure you think about how it would work > during a renumbering event, with sub-delegations and sub-sub-delegations all > having different lifetimes. > > (I've got nothing against delegating /48's to the home, but the reason we did > that was to maintain flexibility, not because we really expect a typical > homenet to have 65,536 subnets. At least for most reasonable values of > "we.")
Well, this is why the homenet arch says that prefix delegation should be efficient. Using DHCP-PD forces a structure to the delegations, and thus potential inefficiency. The OSPF-based solution doesn't have that limitation, but then has to handle potential clashes. In terms of allocations, the homenet arch simply points to RFC6177. Tim
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