Re: [DNA] IMPORTANT: Combined DNA Solution draft

[Syam Madanapalli <smadanapalli@gmail.com>]

On 11/6/05, Christian Vogt <chvogt@tm.uka.de> wrote:
> >>> [...]
> >>>
> >>>   - If the RS has a landmark and the router recognizes it
> >>>     a short RA is possible.
> >>>   - If the RS has a landmark but the router doesn't
> >>>     understand it, the landmark is ignored and a complete RA is sent
> >>>     that the host can use to make an immediate decision.
> >>>   - If the RS has no landmark, then the router sends a
> >>>     complete RA that the host can again make use of immediately.
> >>
> >>
> >> Its agreed that if complete RAs can be used then there's
> >> really no issue (other than perhaps loss of a little bit of
> >> bandwidth, but I wouldn't worry about that). However, in
> >> your second case above, what happens if the RS has a landmark,
> >> the router doesn't implement them, and it can't fit all the
> >> prefixes in the complete RA? It seems that the router will
> >> make a "random" decision of what prefixes to include, and
> >> since it doesn't recognize the landmark option, it may not
> >> include the host's prefix. Will this cause a problem?
> >
> >
> > I don't think so.  The choice of prefixes to include is not quite
> > random, because the router is required to include the "LinkID" prefix.
> > That may not be the prefix that the host picked as a landmark, but
> > it will have been received by the host in any earlier RAs if movement
> > has not taken place.  Note that I removed the word optional in the
> > suggested text for the previous comment because the the language in
> > section 6 does not make the LinkID inclusion optional.
>
>
> I thought you agreed earlier during your discussion that Landmark and
> LinkID are optional for hosts only, but both mandatory for routers.
>
> If you change the draft in this regard, a router not understanding the
> Landmark option would consequently not support the DNA Protocol 3 at
> all.  But such a router would not support LinkID either, and the host
> would end up having to apply CPL logic anyway to arrive at a movement
> decision.
>
> The host recognizes that it must use CPL because it sent a Landmark
> option with the RS, but the solicited RA neither includes a Landmark
> option nor has the C flag set.
>
> This said, I don't see a reason why "case 2" (i.e., the RS has a
> landmark but the router doesn't understand it) need to be considered for
> this protocol at all.
>

I think it is good to mandate the routers to support Landmark option and it is
optional for hosts to use it. This will ease the implemention on host side.

Regards,
Syam