Being a little pedantic here...my understanding is that a host never knows a subnet length, per se. What the host knows is a list of on-link prefixes, which it matches against outbound traffic. A minimal implementation might not keep a list of on-link prefixes and send everything to its default router; redirects would do the rest...
- Ralph, who is sorry if he missed something earlier in the thread and is now pedanting up the wrong tree On Aug 19, 2010, at 3:31 PM 8/19/10, Jared Mauch wrote: > > On Aug 19, 2010, at 3:07 PM, Thomas Narten wrote: > >> Brian E Carpenter <brian.e.carpen...@gmail.com> writes: >> >>> Jared, >> >>> On 2010-08-16 13:06, Jared Mauch wrote: >>> ... >> >>>> Is there a legitimate operational reason a host should not know >>>> the subnet length it sits on? >> >> A host should not be *required* to know the subnet length. Very >> simple devices may have "simple" stacks. And indeed, for a simply >> host, all you need to know is a first hop router address. Redirects >> can do the rest. > > If they can't handle to know an extra byte (mask) plus 128 bits for 'default' > gateway, I certainly understand small embedded solutions having limited space > but implementing the redirect codebase, aging, etc.. seems like a lot more > effort than knowing a mask and default gateway. > >> This may not be the ideal situation, but it is one the architecure >> allows for. > > Just because something is 'allowed' does not mean it should be encouraged. > I could announce vanity information in AS_PATH, but it's certainly not > encouraged. > >> It is also fine for more sophisticated implementations to know what >> the subnet length is. > > - Jared > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
