vijay gill writes:
This is probably going to be a somewhat unpopular opinion, mostly because people cannot figure out their COGS. If you can get transit for cheaper than your COGS, you are better off buying transit and not peering. There are some small arguments to be made for latency and 'cheap/free' peering if you are already buying transit at an exchange and your port/xconn fee is cheaper than your capital/opex for the amount of traffic you peer off.
The other factor worth considering is the level of control your business plan supports giving up to third parties. This is more of a problem for things like real-time voice or video, but the circumstance can exist that depending on two even very good carriers may be uncomfortable - particular the first time one of them has a systemic issue.
To be completely realistic, at current transit pricing, you are almost always better off just buying transit from two upstreams and calling it done, especially if you are posting to nanog asking about peering.
Yep. Joe