How Many IXes Per Metro?

Dr Peering -

What is the optimal number of IXes per metro?



Dan -

Dr Peering did an informal study with the peering community and they seemed to fall into two camps:

Camp 1 : Only 1 IX per metro. About half of the peering coordinators said that they preferred that there to be only one IX per metro, because more than one would splinter the peering community.

“Which IX to go to? If I go to IX A, I can peer with the population there, but I miss the participants that are only at IX B. If I go to both, I dilute my benefits from peering in that region since it will cost me twice as much. So everyone chooses one or the other or both, and the splintering continues until the two IXes interconnect, which presents a different set of issues.”

“I want to manage redundancy myself in my backbone. IX failures are so rare that I can handle the sub-optimal path during the short period that the IX is down. Peering is merely a local optimization.”

Camp 2: Exactly 2 IXes per metro. The other half of the peering community said that they preferred the resiliency of two IXes in a metro.

“I want two IXes run by two different parties using two different sets of operations practices, different security companies, different vendors for switches, etc. so we get the redundancy and resiliency of two heterogeneous environments. That way we reduce our systemic risk.”


The two camps uniformly said they did not want more the two IXes in a metro since that would splinter the community and provide little incremental benefits from diversity.


DrPeering [at] DrPeering [dot] net


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