Why don't ISPs peer with everyone?

Mon Jun 6 19:53:54 UTC 2011

On Mon, 6 Jun 2011, rucasbrown at hushmail.com wrote:

> All the whole "don't peer with this guy" only makes your customers
> have worse latencies and paths to other people, making the Internet
> less healthy.

Not necessarily.  Peering with an ISP who wants to take the traffic 
between your network and theirs through a saturated pipe, an overloaded 
router, or across an MPLS pipe with 13 underlying hops (each of which 
could be a choke point themselves) will not make your end-to-end latencies 
any better.

As others have mentioned, some ISPs do have friendly peering policies. 
This is particularly true for ISPs that are co-located at the same IXP, 
because much of the opex is already baked into the ISP's relationship with 
the IXP.

The reason most of the larger ISPs, particularly those who live in the 
DFZ, have peering policies (especially for settlement-free peering) that 
could be construed as less friendly to smaller networks is because those 
guys want to sell you transit, rather than let you peer for free, or for 
less than a the full transit rate.  It doesn't make financial sense for 
them to exchange bits with you for free, when they can make money off of 
those same bits if you buy transit instead.

jms