Re: router-router NHRP

[Yakov Rekhter <[e-mail]>]

Dimitry,

> > We certainly failed to communicate. The R2R proposal I sent to the ROLC
> > list certainly allows to accomplish what you are asking for - the
> > ability of a router to augment (on demand) its existing routing
> > information (acquired via conventional routing protocols) with
> > additional routing information acquired via NHRP.
> > 
> > So, for example an OSPF router that is not in area 0 could just
> > maintain routes to the destinations within its own area, and a single
> > default route to all other destinations. 
> 
> What is the next hop of such a default route?

The next hop is controlled by OSPF. The default route is likely to
be injected into the area by the area's border router. So, a path
from within the area to a destination outside the area will traverse
through that area border router.

> > Perhaps it would help if you'll give me an example of what you think
> > the current NHRP R2R proposal can't do.
> > 
> 
> OK. Let assume a *transient* routing domain with around 300 forwarding
> devices (this example is not quite arbitrary but is based on an existing
> FR network).  This domain must be aware of up to 40,000 external networks.
> These external networks are distributed behind the forwarding devices in
> such a way that no high scale aggregation is possible. 
>  
> Every forwarding device/router is inexpensive lower-end box that is
> capable to handle a few thousand (~5000) packet streams at a time,
> can support forwarding cache of a few thousand entries (10,000 max), but
> unable to maintain a full set of potential target (i.e. 40,000 routes).
> 
> To make our task easier, let assume that we can convince the domain owner
> to install 20-30 high end routers to handle routing load.
> 
> Can you explain how your R2R proposal will handle the described setup?
> I realy try to understand your proposal and hope your explonations would help
> me. Sorry if I am the only one on the list who doesn't see the obvious.

I'll be glad to explain how the R2R proposal would handle the described
setup, but I need one more piece of information from you. Specifically,
I'd like to understand how do you plan to organize routing without shortcuts
(without NHRP) in the scenario you described. Remember that NHRP is just a 
mechanism to discover shortcuts, and that routing should be able to work 
correctly (although without shortcuts) in the absence of NHRP.

Yakov.