[73949] in North American Network Operators' Group
Re: ISP Policies
daemon@ATHENA.MIT.EDU (Jeff Kell)
Thu Sep 9 01:24:07 2004
Date: Thu, 09 Sep 2004 01:17:07 -0400
From: Jeff Kell <jeff-kell@utc.edu>
To: Tulip Rasputin <tulip_rasputin@yahoo.ca>
Cc: bmanning@vacation.karoshi.com, nanog@merit.edu
In-Reply-To: <001001c49627$c834a200$e90218ac@Floyd>
Errors-To: owner-nanog-outgoing@merit.edu
Tulip Rasputin wrote:
> So can you give me an example of why and when would an ISP *not* want
> its traffic to flow via some other AS(es). Is it a normal policy to
> have, and do most of the ISPs have such policies in place?
If you don't have a transit agreement and aren't sitting in the top tier
peering list, you will not want traffic to flow via some other AS(es) as
they may be blocking your advertisements inbound. This is really a
"tier" question. Most end-node ASNs you will find do not want to
provide transit traffic between their upstream ISPs (asking for trouble
and bandwidth saturation) or at least make it a short-term emergency act
of altruism.
You may have "dedicated" circuits or bandwidth or CIRs for certain
services from YOUR ASN only. They may not accept traffic that doesn't
originate in your ASN and you're wasting time to try. Part marketing,
part business, part political as what transit you will support (and what
transit your upstream(s) support).
In more practical terms, we have dedicated circuits for H.323 video, an
IPSec link to our parent campus with the university-wide SAP/R3 traffic,
another link restricted to ESNet (immediate peers only). For a
commercial ISP your mileage may vary as you are, above a certain level,
providing transit between different administrative domains (or ASNs, or
whatever). You can do this with statics, with policy routing (or null
routing), or in a local OSPF or whatever routing mechanism you have at
your border.
Jeff
