Re: BGP Peers as basis of available routes

[Bill Woodcock <woody () pch net>]

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On Oct 18, 2011, at 11:46 PM, Nathanael C. Cariaga wrote:
> Is it safe to conclude that the web hosting provider's available routes would would depend on the peers who are 
> advertising their AS / network?  (i.e if web hosting provider claims that they are peering with telco a, b, c but as 
> seen from a third party looking glass, only C is seen advertising the web hosting provider network that would mean 
> web hosting provider is effectively utilizing c as their upstream??)

Modulo a lot of nit-picking caveats, this would indicate that they are purchasing transit from C, while they may or may 
not be peering with A and B.  If a customer of A or B is able to reach them in a single AS-hop, but A and B are not 
advertising a route to C to looking-glasses or their own peers or transit providers, then A and B are peers, but not 
transit providers, to the web host.

> I would need to determine the web hosting provider who has the most number of peers and most number of transit 
> providers?

A large number of transit providers has been shown, both theoretically and experimentally, to _decrease_ uptime, 
because of greater route-convergence times when there are more parallel paths to a destination.  Your mileage may vary, 
but the optimum number is usually somewhere around three transit providers.  The number of peers, though, and more to 
the point, the number of routes acquired through peering, is an excellent measure of how large and how long an ISP (in 
this case a web-hoster) has been in business.  That shouldn't be your only measure of quality, however.  It may be that 
reliability of power, competence of remote-hands, and flexibility to accommodate your needs are more important than how 
the packets get delivered.

                                -Bill




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