OSPF multi-level hierarchy: Necessary at all?

Fri May 28 09:32:56 UTC 1999

Hmm. THis is the right direction for this discussion - if someone built 
telephone network over IP technology (even if it's not public internet), 
he need quite scalable IGP protocol.

Through you dont' need plain IGP schema - you have backbone (with 100 - 
300 nodes) and regional access networks - every not too large. It can be 
build just as any ISP+customers. It's not so beautiful as multi-level 
scheme, but well designed and work just fine (OSPF+IBGP backbone, 
OSPF+iBGP customers).

On Fri, 28 May 1999, Sean Donelan wrote:

> Date: Fri, 28 May 1999 3:01:16 -0500
> From: Sean Donelan <SEAN at SDG.DRA.COM>
> To: nanog at merit.edu
> Subject: Re: OSPF multi-level hierarchy: Necessary at all?
> 
> 
> avg at kotovnik.COM (Vadim Antonov) writes:
> >Well, actually it is not that bad.  The biggest number of locations is
> >probably found in AT&T phone network - 250 or so.  Sprint is in few
> >dozen.  The existing IGPs are quite happy with that kind of complexity,
> >so if you belong to the "one-router-per-POP" school of thought the
> >IGP complexity is a non-issue.
> 
> Well, the phone system is already hierarchial.  The top-level is pretty
> small, it is the second and third levels which are monsters.
> 
> There are about 100,000 NXX's in the country.  California has the largest
> state with about 12,000.  The Los Angeles LATA is the biggest at about 5,000.
> Within PacBell there are about 800 CLLI locations for the Los Angeles LATA,
> not including all the other CLECs who may have locations in LA.  Getting from
> the relatively few IXC access tandems to those 800 locations is the trick.
> 
> I may be doing something wrong, but I've found OSPF gets a bit cranky
> with far less than 800 routers and 5,000 routes in an area.
> -- 
> Sean Donelan, Data Research Associates, Inc, St. Louis, MO
>   Affiliation given for identification not representation
> 
> 

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