Some ISP’s tend to use different strategies or priorities in handling traffic across Backbone, some maybe because running out of capacity or by policy. In hot-potato routing, an ISP hands off traffic to a downstream ISP as quickly as it can “closest exit routing”. In opposite way Cold-potato routing ISP carries traffic as far as possible on its own network before deliver it to a downstream ISP “best exit routing”. In general, an ISP’s routing policy would follow an hot-potato or cold-potato routing.
Following a small diagram with an Cold-potato (blue) and Hot-potato (red) flows