Size the data centre border from north-south traffic volume, growth allowance and uplink speed.
North-south traffic is what the border routers, firewalls and load balancers have to carry, and it grows with user demand rather than with internal chatter. The uplink count is the projected load divided by the speed of one border link. Border devices are the most expensive per gigabit in the data centre, so knowing the projected figure prevents both a congested edge and a heavily over-built one.
North-South Traffic
north-south = total traffic × north-south share; projected = that × (1 + growth); uplinks = projected ÷ uplink speed, rounded up.
north-south = total traffic × north-south share; projected = that × (1 + growth); uplinks = projected ÷ uplink speed, rounded up. North-south traffic is what the border routers, firewalls and load balancers have to carry, and it grows with user demand rather than with internal chatter. The uplink count is the projected load divided by the speed of one border link.
Border devices are the most expensive per gigabit in the data centre, so knowing the projected figure prevents both a congested edge and a heavily over-built one.
This calculator takes 6 inputs: Servers in the fabric, Busy-hour traffic per server, Share that is north-south, Border capacity installed, Growth allowance, Border uplink speed. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.