All incoming traffic to your Linode is free.
Transfer quotas are soft caps and if you go over by a few GB we usually won’t invoice. We also send an e-mail when you reach 80% of your monthly quota. Transfer is pooled among all of the Linodes under your account. If you believe you will have overages consistently, you can purchase additional transfer or upgrade to the next plan level. Additional transfer is $0.10/GB.