Re: AS 701 local-pref answer.

[David Barak <thegameiam () yahoo com>]

Hi,

I don't think AS 701 (or any of its peers) are
particularly worried about different best-paths in
different regions.  This is the old
hot-potato/cold-potato discussion, which I don't see a
need to re-hash.  

Let's pretend that Bob's bait & tackle shop (AS
30,000) is multihomed to AS 701 and AS 1.  Bob would
probably want AS701 origin traffic to prefer his AS701
link, and his AS1 Origin traffic to prefer his Genuity
link.  No problem there - they both see a route 1
AS-hop away.  The question only comes when Bob wants
to have all other traffic prefer one link or the
other.  

If he chose to prepend his AS to AS701, then he would
run the risk of Genuity being the preferred path from
AS701, and AS701 would not advertise a path.  This
would be a useful situation if, for instance, the
Genuity link was a DS3, and the 701 link was a T1.  If
they were equal bandwidth links, and Bob was trying to
do traffic-sharing, then that would not be a good
solution. 

AS 701 does have mechanisa for customers to do this,
and their support people are more than happy to assist
customers with their routing needs.  

By the way, the gentleman who referred to "customers,
peers, and upstreams" as useful loc-pref settings
should remember that AS701 doesn't have upstreams.  :)

David Barak
I speak for myself only.
"Quis custodes ipsos custodiet?" - Juvenal

--- Mike Leber <mleber () he net> wrote:
> Not to be like Columbo... However, there's just one
> last question
> bothering me.  Well ok, more than one :)
>
> If it's like mentzer () mentzer org said and 701
> doesn't deterministicly
> prefer customer routes (customers and peer routes at
> the same local pref)
> wouldn't this mean that they wouldn't have
> consistent route announcments
> in various parts of their network?
>
> If a customer doesn't set the community to boost the
> local pref, and 701
> truly by default sets customers and peers to 100,
> then 701 would be
> announcing varying numbers of routes to the same
> peer at different
> locations.
>
> Do they expect consistent route annoucements from
> their peers?
>
> Many networks out there insist upon this as a
> requirement when peering.
>
> Mike.
>
> On Sun, 16 Dec 2001, Mike Leber wrote:
>
> > Thank you for pointing that out.  I was being
> dense and reading way too
> > much into the statements:
> >
> > smentzer () mentzer org wrote:
> > > All the responses I have gotten indicate that
> UUnet does indeed set
> > > local-pref on both customers and peers to 100
> (or leave default in this
> > > case).  Thanks for all the responses...
> >
> > Especially when the 701 communities were already
> provided by German
> > Martinez.  *DOH*
> >
> > In other words, 701 transit customers that
> actually want to ensure their
> > downstream customer routes are announced by 701
> had better set the
> > appropriate community so that local pref gets set
> above 100.  By default
> > this is not done.
> >
> > Pardon me while I get some much needed rest.
> >
> > Mike.
> >
> > On Sun, 16 Dec 2001, David Barak wrote:
> >
> > > Mike Leber wrote:
> > >
> > > > If they set local pref for both peers and
> customers
> > > > to 100 how do they
> > > > ensure that the customer transit routes are
> > > > announced to peers?
> > >
> > > > The reason I ask this is because if a customer 
> > > > announces a customer of
> > > > theirs to you that a peer also has as a
> customer >you
> > > will have equal
> > > > length routes for the same destination AS. 
> While
> > > > there are many ways to
> > > > deterministicly prefer customer routes, local
> pref
> > > > is the most common.
> > >
> > > AS 701 always announces the best route, as their
> > > routers know it.  Their average AS-path length
> is
> > > under 2, so it doesn't seem to be a problem.  If
> a
> > > customer of AS 701 wants to insure that his/her
> route
> > > is advertised in all cases, s/he could send a
> > > community which AS701 edge devices could use to
> > > manipulate local-preference upward.  [this was
> covered
> > > in a previous posting on this topic]  I leave it
> to
> > > your imagination whether peers would be
> permitted to
> > > do this.
> > >
> > > -David Barak
> > > I only speak for myself.
> > > "Quis custodes ipsos custodiet?" - Juvenal
> __________________________________________________
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>
> +------------------- H U R R I C A N E - E L E C T R
> I C -------------------+
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>     Voice 510 580 4100 |
> | Hurricane Electric       Web Hosting  Colocation  
>       Fax 510 580 4151 |
> | mleber () he net                                     
>      http://www.he.net |
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