You'd be surprised exactly how much functionality is written in vanilla C and pushed down the stack to raw packet handling. There is hardware acceleration in NI

You'd be surprised exactly how much functionality is written in vanilla C and pushed down the stack to raw packet handling. There is hardware acceleration in NICs, but voice is actually a tiny, almost insignificant amount of the workloads involved in some parts of the world. Think hyperscaler-style SDN, but largely on-premises.