1. Banners – whatever banner which has any file on our servers (in your hosted solution) e.g. image/pdf/replicated site. In this case 1 impression uses as much bandwidth as the size of the particular file (image/pdf/replicated site) is.
2. Click, sale/lead, impression tracking – why? – because the integration code has to be loaded, which also has some size. However, this used to consume on average 4% of your bandwidth. Of course, if you have really large traffic, then it can consume a lot more bandwidth.
3. Login, browsing the merchant/affiliate panel – this is also the part of bandwidth consumption, since some scripts must be loaded, requests must be handled. However, this uses only a very low percentage of your bandwidth. It would be significant if a merchant had e.g. 1000 affiliates who keep logging in and out on daily bases.