Problem: encryption, cloud compute, and everything over port 443 is making it very difficult to manually steer heavy traffic (video, backups, etc) to a specific WAN link.
Proposal: use session tracking to create an automatic/feedback filter. For example, any session that uses more than a configurable amount of megabytes causes the server IPv4 address to entered into a lightweight filter. (Perhaps a bloom filter?) Then a “heavy traffic” outbound policy can do a simple/fast check against that filter to assign a WAN link for future connections.
Practical considerations: this wouldn’t be perfect but the alternative (manual policies) is basically an endless/thankless game of “whac-a-mole”. Personally, the false negatives would be tolerable (IPs that have never been “heavy” before) and the false positives should be low with the right filter algorithm.
Programmer considerations: I’d probably have two bloom filters: “old” and “new” and rotate them out infrequently (once a month or once a quarter). The “heavy traffic” outbound policy would check both but only the “new” filter would be learning from current sessions, thus allowing former “heavy” IP addresses to expire from the filter but without all of the memory and compute intensive logic to age out individual hash table entries.