On Thu, 31 Aug 2023 at 23:56, Eric Kuhnke <eric.kuh...@gmail.com> wrote:
> The best working theory that several people I know in the neteng community > have come up with is because Cogent does not want to adversely impact all > other customers on their router in some sites, where the site's upstreams and > links to neighboring POPs are implemented as something like 4 x 10 Gbps. In > places where they have not upgraded that specific router to a full 100 Gbps > upstream. Moving large flows >2Gbps could result in flat topping a traffic > chart on just 1 of those 10Gbps circuits. It is a very plausible theory, and everyone has this problem to a lesser or greater degree. There was a time when edge interfaces were much lower capacity than backbone interfaces, but I don't think that time will ever come back. So this problem is systemic. Luckily there is quite a reasonable solution to the problem, called 'adaptive load balancing', where software monitors balancing, and biases the hash_result => egress_interface tables to improve balancing when dealing with elephant flows. -- ++ytti
