OSPF multi-level hierarchy: Necessary at all?
Alex P. Rudnev
alex at Relcom.EU.net
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,
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
Aleksei Roudnev, Network Operations Center, Relcom, Moscow
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