Hacker News Reader

Does anyone know why AWS's jumbo frame MTU is 9001 octets? Every other system I've worked on used an MTU of 9000 for jumbo frames. The only reason I can speculate is to force the use of Path MTU Discovery when using Direct Connects (similar to how Microsoft added spaces to common paths to force correct filename handling).

View on HN

9216 is the typical supported mtu for ethernet. But earlier iterations of their network used devices whose jumbo mtu length was like 9100 bytes.

Aws uses A LOT of different overlay technologies which are implemented through encapsulation(aka overhead).

To enable cross region vpc connectivity, additional encryption and encapsulation can be layered on top of the existing encapsulation.

9001 bytes was the absolute max they could give to customers and still be able to do packet shenanigans.

Reply on news.ycombinator.com