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