On Wed, Nov 20, 2013 at 4:08 PM, Michael Richardson <[email protected]>wrote:
> Athanasios Douitsis <[email protected]> wrote: > > Indeed in a scenario where all the requesting routers connecting to a > > delegating router (BNG) would have PD_EXCLUDE capability, using the > > Framed-IPv6-Prefix to infer what to put into the OPTION_PD_EXCLUDE > field is > > sufficient. > > > But if there is a mix of PD_EXCLUDE-capable and not capable > requesting clients, > > the situation becomes more complex. The fundamental problem is that > Prefix > > Delegation usually happens after the RADIUS exchange, so the RADIUS > server > > cannot really know whether the customer is exclude-capable or not. > > Note that CPEs ought to be smart enough to exclude the subnet that their > WAN > link is in, but it's certainly the case that many are not yet that smart. > (the dnsmasq PD implementation was missing related smarts at first) > > > If, for example, the client is not exclude-capable, then having the > RADIUS > > return a Framed-IPv6-Prefix that is part of the (greater) > > Delegated-IPv6-Prefix is problematic for obvious reasons. In fact, > I, for one, > > cannot wrap my head around a way to cover both cases > (exclude-capable and > > non-exclude-capable) using only the two existing RADIUS attributes > *and* at the > > same time maintain backwards compatibility with old customers. > > If the CPE is not EXCLUDE capable, and not smart enough to avoid the WAN > link, then it doesn't matter what the set of attributes returned is, does > it? > Assuming simple minded prefix assignment by CPEs, if they start at subnet > "1", then using subnet "0" probably works. But, using subnet "ff" for the > WAN link is perhaps simpler. Hello Michael, When I said "problematic" yesterday, I meant problematic for the delegating router. If the other side (requesting router - CPE) is not exclude-capable then is it not illegal for the delegating router to delegate a prefix and at the same time use part of it to enumerate one its interfaces? So a set of attributes where the Framed-IPv6-Prefix is contained in the Delegated-IPv6-Prefix may result in error. Apologies if I didn't understand correctly what you are saying. Kind regards, -- Athanasios Douitsis
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