Some applications try to increase the buffers for performance reason. The QUIC Go implementation for instance tries to request a 2048 kiB buffer size. The kernel default depends on skubuf size (which is architecture dependent), but it is memory size independet and typically around 200 kiB (see [1]). Other network tuning guides suggest 16MiB for 1GB ethernet, as well as changing the default as well as maximum bufffer size (see [2]). This conservatively increases the maximum buffer size to 4MiB. [1]: https://elixir.bootlin.com/linux/v5.15.45/source/include/net/sock.h#L2742 [2]: https://nateware.com/2013/04/06/linux-network-tuning-for-2013/