[Cu-wireless] Re: Cu-wireless digest, Vol 1 #118 - 4 msgs

[David Young]

Oops.  When I wrote 10.0.5.11/0, I meant 10.0.5.11/32.

Dave

On Thu, May 02, 2002 at 01:32:49PM -0500, David Young wrote:
> 
> (Response below)
> 
> On Thu, May 02, 2002 at 07:53:24AM -0500, The Morenz Family wrote:
> > ###REPLY INLINE####
> > 
> > >From: David Young <dyoung at onthejob.net>
> > 
> > >I can understand the desire to keep the routing tables compact, but subnet
> > >routing seems unnatural for a wireless network. Will OSPF bog down if
> > >we do not use subnets? Every host in a subnet needs to be individually
> > >routed, anyway....
> > 
> > The whole idea of subnet routing is that things in a subnet are not
> > individually routed.  So, if you are individually routing to the
> > elements of a subnet then you are not using subnet routing.  Am I
> > missing something?
> > 
> 
>     I think that the way Zach conceives of the network, there are stations
>     Q1, Q2, Q3, ..., Qn; each routes/forwards. At some instant T, Q1 can
>     reach stations P11, P12, P13 with its radio, Q2 can reach stations
>     P21, P22, P23 with its radio, station Q3 can reach stations P31,
>     P32, P33, and so on. Stations P23 and P31 are the same station, and
>     stations P12 and P33 are the same station. No matter, we *arbitrarily*
>     lump the stations reachable by Q1 into a subnet, call it 10.0.5/24. We
>     also lump the stations reachable by Q2 into subnet 10.0.7/24. Stations
>     reachable by Q3 are in subnet 10.0.13/24.
> 
>     In this way, some station Q4 which is adjacent to Q1, Q2, and Q3
>     knows that when it receives a packet addressed to P12 (whose IP
>     number is 10.0.5.11, say), the next hop for that packet is over the
>     link to station Q1.
> 
>     What happens to the routes if the link from Q1 to P12 is broken?
>     That is not a rhetorical question, but I will try to answer it.
>     It seems to me that Q1 will advertise that it cannot any longer reach
>     all of the subnet 10.0.5/24, only hosts P11 and P13 on the subnet.
>     The route through Q3 to P12 via P33 (P12 and P33 are the same station)
>     takes effect.
> 
>     In the example I gave, a change in link state split a subnet in two,
>     and we ended up with a host route---or, if you prefer, a route to
>     a subnet of size 1, 10.0.5.11/0. =) I don't see the use of subnet
>     routing in a wireless network when a subnet falls apart with a change
>     of link state.
> 
>     Certainly OSPF can deal with a route 10.0.5.11/0 ?
> 
> Dave
> 
> -- 
> David Young             OJC Technologies
> dyoung at onthejob.net     Engineering from the Right Brain
>                         Urbana, IL * (217) 278-3933
> 
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-- 
David Young             OJC Technologies
dyoung at onthejob.net     Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933