Re: [dhcwg] [radext] [homenet] PPP, DHCPv6 and Prefix Delegation

[Athanasios Douitsis <[e-mail]>]

On Wed, Nov 20, 2013 at 10:55 AM, Jouni Korhonen <[e-mail]>wrote:

> I don't think having multiple attributes brings any additional value. That
> would mean you allocate "just to be sure" a prefix from another block. What
> I would do in this specific case is just to halve delegated prefix and pick
> the single prefix from there and delegate the rest to the client. That
> wastes half of the delegated prefix but I as a delegating router am allowed
> to do so. This would make the logic/provisioning on the RADIUS server and
> the client always the same. The additional logic would be in the delegating
> router to device whether it halves the delegated prefix or not.


Hello,

Yes, using one prefix and halving it if necessary is simpler and more
elegant from a certain point of view. Admittedly allocating "just to be
sure" is by the same token ugly.

The only downside that I'd like to mention is that many administrators
generally like to do as much as possible in the RADIUS and rely on
specialized router features as little as possible. Not only is it easier to
add functionality and logic on the side of the RADIUS, but it makes one
more standards compliant and vendor independent in case one would like to
make a switch in the future. From that point of view, relying on the BNG to
halve (or in any other way modify) the prefixes if necessary can be
slightly disadvantageous. Especially if it is not possible to tell what
eventually happened with the prefix(es), even by looking at the radius
accounting records.

My regards and thanks very much,
-- 
Athanasios Douitsis