Question on peering strategies

Mon May 16 17:46:20 UTC 2016

Dear Nanogers,

I have a question about common/best network interconnection practices.
Assume that two networks (let's refer to them as AS-a and AS-b) are present
in a colocation facility say Equinix LA. As many of you know, Equininx runs
an IXP in LA as well. So AS-as and AS-b can interconnct
1) using private cross-connect
2) through the public IXP's switching fabric.
Is it a common/good practice for the two networks to establish connections
both through the IXP and also using a private cross-connect?

I was thinking considering the cost of cross-connects (my understanding is
that the colocation provider charges the customers for each cross-connect
in addition to the rent of the rack or cage or whatever), it would not be
economically reasonable to have both. Although, if the cross-connect is the
primary method of interconnection, and the IXP provides a router-server the
public-peering over IXP would essentially be free. So it might makes sense
to assume that for the private cross-connect, there exists a back-up
connection though the IXP. Anyway, I guess some discussion may give more
insight about which one is more reasonable to assume and do.

Now my last question is that if the two connections exist (one private
cross-connect and another back-up through the IXP), what are the chances
that periodically launched traceroutes that pass the inter-AS connection in
that colo see both types of connection in a week. I guess what I'm asking
is how often back-up routes are taken? Can the networks do load balancing
on the two connection and essentially use them as primary routes?

Best Regards
Reza Motamedi (R.M)
Graduate Research Fellow
Oregon Network Research Group
Computer and Information Science
University of Oregon