[86184] in North American Network Operators' Group
Re: What is multihoming was (design of a real routing v. endpoint
daemon@ATHENA.MIT.EDU (Pekka Savola)
Tue Oct 25 06:12:24 2005
Date: Tue, 25 Oct 2005 13:11:43 +0300 (EEST)
From: Pekka Savola <pekkas@netcore.fi>
To: Michael.Dillon@btradianz.com
Cc: nanog@nanog.org
In-Reply-To: <OFEA70FFB3.E5549892-ON802570A4.00307875-802570A4.00318F14@btradianz.com>
Errors-To: owner-nanog@merit.edu
On Mon, 24 Oct 2005 Michael.Dillon@btradianz.com wrote:
> A single tier-2 ISP who uses BGP multihoming with several
> tier 1 ISPs can provide "multihoming" to it's customers
> without BGP. For instance, if this tier-2 has two PoPs
> in a city and peering links exist at both PoPs and they
> sell a resilient access service where the customer has
> two links, one to each PoP, then it is possible to route
> around many failures. This is probably sufficient for most
> people and if the tier-2 provider takes this service seriously
> they can engineer things to make total network collapse exteremely
> unlikely.
From RFC 3582, this is not multihoming (see the defs below). The above
is referred to as "multi-connecting" or multi-attaching (also see
RFC 4116).
I agree, this is sufficient for many sites. Especially in academic
world, many universities are just multi-connected, trusting the
stability of their NREN's backbone and transit providers. Lots of
commercial sites do it too, but some are wary due to events like
L3/Cogent, L3 backbone downtime, etc.
.....
A "multihomed" site is one with more than one transit provider.
"Site-multihoming" is the practice of arranging a site to be
multihomed.
and:
A "transit provider" operates a site that directly provides
connectivity to the Internet to one or more external sites. The
connectivity provided extends beyond the transit provider's own site.
A transit provider's site is directly connected to the sites for
which it provides transit.
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
