RE: Question on peering strategies

[Nick Ellermann <nellermann () broadaspect com>]

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
 
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-----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