file: /proc/sys/net/ipv4/tcp_limit_output_bytes
variable: net.ipv4.tcp_limit_output_bytes
Official reference

Controls TCP Small Queue limit per tcp socket. TCP bulk sender tends to increase packets in flight until it gets losses notifications. With SNDBUF autotuning, this can result in a large amount of packets queued in qdisc/device on the local machine, hurting latency of other flows, for typical pfifo_fast qdiscs. tcp_limit_output_bytes limits the number of bytes on qdisc or device to reduce artificial RTT/cwnd and reduce bufferbloat. Default: 262144