Reza, You maybe overthinking this one a bit. The economics are something to consider, however all public exchanges have different economics. With Equinix you pay pretty much a flat rate for a single 1Gbps/10Gbps link that includes the cost of facility cross-connect and public exchange access. It is a nice one to many connection for all those various network and content networks your end users would appreciate direct connectivity. Depending on the public exchange you either have a single BGP session or a BGP session per network you are peering. Really after that, it's just BGP routing and route management. You do need to be careful about not being too overly dependent on a single public switch link, in some cases like at Equinix you may want multiple connections to redundant public exchange switches at that site. There is a balance you want to seek of number of paid upstream network transit providers you are connected to versus how many direct peering arrangements you have setup. It's not usually practical for a smaller network to have loads of BGP peers. There are lots of good articles online about this fine balance and some good advice from experienced network operators. To your later questions. For your simple example, if AS-a and AS-b were both already on the public IX, and the link wasn't too overly critical then using the public IX switch maybe a good first step. However as that relationship matures, they most likely in a real world example may look to split the cost of the private cross-connect. If it was mutually beneficial. There is much more to public peering and transit than the technical conversation. Most of the larger networks on the public switches won't peer privately with anyone or only with extremely larger networks. To get a provider such as this to peer both privately and on the public exchange is not a technical issue, it's more of a business overhead and management issue. If you have a couple of quality upstream transit providers, they will be excellent failovers to a public switch outage. Plan for the public switch to have as many problems as any upstream provider. Sincerely, Nick Ellermann – CTO & VP Cloud Services BroadAspect E: nellermann@broadaspect.com P: 703-297-4639 F: 703-996-4443 THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. -----Original Message----- From: NANOG [mailto:nanog-bounces+nellermann=broadaspect.com@nanog.org] On Behalf Of Reza Motamedi Sent: Monday, May 16, 2016 1:46 PM To: nanog@nanog.org Subject: Question on peering strategies 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