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Re: OSPF multi-level hierarchy: Necessary at all?

  • From: Alex P. Rudnev
  • Date: Fri May 28 07:18:42 1999

Btw. Flat network...

Routers now have - 128 or 256 MB RAM, 300 - 400 Mhz CPU. I guess you can 
built flat betwork with 5,000 routers withouth hard problems.

Through it's not the question. There is _already_ 2 levels; you can use 
multi-zone OSPF (independent OSPF networks connected by _redistribute_). 
The question was _is 2-level hierarchy enougph__?

On Fri, 28 May 1999, Alex Zinin wrote:

> Date: Fri, 28 May 1999 14:26:27 +0400
> From: Alex Zinin <zinin@amt.ru>
> To: Vadim Antonov <avg@kotovnik.com>, nanog@merit.edu
> Subject: Re: OSPF multi-level hierarchy: Necessary at all?
> 
> 
> At 11:35 27.05.99 -0700, Vadim Antonov wrote:
> >...
> >>but the main question is whether there is a demand
> >>for it or not.
> >
> >I guess the answer is pretty much not. The amount of interior
> >routing information in a properly designed backbone is quite
> >small even if there is no two-layer abstraction.  
> 
> If you do not use route-summarization on the area borders,
> your're gonna have flat network from the routing info's point
> of view, even though the topology info is abstracted. Flat
> networks are very well known to be not scalable.
> 
> >(Now, the
> >_exterior_ information is aplenty, but OSPF is useless for it
> >anyway).
> 
> The new approach could incorporate aggregating externals
> on level borders in addition to aggregating internal routing info.
> 
> >
> >If someone proposed simplifying and cleaning up OSPF i'd be
> >quite for it.  Building a protocol allowing to get rid of
> >iBGP hack would also help :)
> 
> In OSPFv6 an ASE-LSA can point to another LSA, which per D. Ferguson
> can contain BGP path attributes.
> The new approach (which could be intergrated in OSPF for IPv6 btw)
> could use a technique analogous to this one.
> 
> Rgds
> ------------------------------------------------------------------
> Alex D. Zinin, Consultant
> CCSI #98966
> CCIE #4015
> AMT Group / ISL 
> Cisco Systems Gold Certified Partner
> http://www.amt.ru
> irc: //EFNET/#cisco, //irc.msn.com/#NetCisco [Ustas]
> 
> 
> 

Aleksei Roudnev, Network Operations Center, Relcom, Moscow
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