Re: [DNA] Comments on draft-shim-dna-proactive-00.txt

[Gregory Daley <Greg.Daley@eng.monash.edu.au>]

Hi Zhigao, 

----- Original Message -----
From: Zhigao Chen <zgchen@psl.com.sg>
Date: Tuesday, March 2, 2004 12:38 pm
Subject: [DNA] Comments on draft-shim-dna-proactive-00.txt

> 
> 
> -----Original Message-----
> From: Zhigao Chen [mailto:zgchen@psl.com.sg] 
> Sent: Tuesday, March 02, 2004 11:35 AM
> To: 'Alper Yegin'
> Subject: RE: [DNA] Comments on draft-shim-dna-proactive-00.txt
> 
> 
> > > > When there is no
> > > > hint, at most what a host would need to do is the same: send a
> > > > multicast RS.
> > > >
> > > 
> > > In the absence of a hint, the sending of the multicast RS
> > > might not be triggered so fast.
> > 
> > The link-up trigger prompts the RS to be sent. This is
> > equivalent to the reachability test you mentioned above.
> > 
> > Alper
> > 
> 
> I get your point after realizing that you make a distinction between
> trigger and hint in your draft. The gain of doing reachability test
> (with unicast RS/RA) in the case of weak hint could be less signaling
> overhead, especially in the downlink, and less disruption to
> routers/hosts. Consider that RS/RA exchange between hosts and 
> routers is
> changed from one-multiple-multiple to one-one-one.

I agree that the issue of multiple response is one 
which may be useful to check in the case 

Indeed, it may make sense for a router not to do
any delay when sending an RA in response to unicast RS
(if indeed it is suitable for a router to receive
unicast RS (I need to read 2461 again)).

Depending on the network topology and technology, 
the number of routers (which in many cases will be 
small) may not matter, but the cost of multicast response
may be large (uniform bandwidth consumption on all cells
in the link).

I'd like to think that the issue of whether a router responds
unicast is determined by the access network administrator.
This assumes that the admin knows best for their network.
Therefore, the host won't have control of whether the router
responds unicast or multicast.

Using RS/RA exchange in this case may not be one-one-one,
but it may not matter.

Significantly, it may be worthwhile determining if there are
network topologies which make sense that don't have large numbers
of RA responders in short time frames (perhaps on the slow responding
router, a multicast RA can be scheduled at a lower rate), and what
happens to hosts when the advertisement intervals for multiple
routers on a link are skewed.

In this case, we could set up access networks where it is always
alright to send an RS to all-routers group, without causing
significant performance hits on wireless links.

Greg