diff --git a/kernel/Kconfig b/kernel/Kconfig
index 78bd4a89..e9ad6ee0 100644
--- a/kernel/Kconfig
+++ b/kernel/Kconfig
@@ -105,6 +105,15 @@ config MARS_SEPARATE_PORTS
 	If unsure, say Y.
 
 
+config MARS_IPv4_TOS
+	bool "use TOS / DSCP in IPv4"
+	depends on MARS_SEPARATE_PORTS
+	default y
+	---help---
+	Tag IP traffic differently for different ports.
+	In certain private networks, this can improve certain
+	network bottlenecks.
+
 config MARS_MEM_RETRY
 	bool "make MARS memory allocation more robust"
 	depends on MARS
diff --git a/kernel/mars_net.c b/kernel/mars_net.c
index 7ad50328..bccf7e32 100644
--- a/kernel/mars_net.c
+++ b/kernel/mars_net.c
@@ -189,7 +189,9 @@ void _set_socketopts(struct socket *sock, struct mars_tcp_params *params)
 	sock->sk->sk_reuse = 1;
 	_setsockopt(sock, SOL_SOCKET, SO_SNDBUFFORCE, params->tcp_window_size);
 	_setsockopt(sock, SOL_SOCKET, SO_RCVBUFFORCE, params->tcp_window_size);
+#ifdef CONFIG_MARS_IPv4_TOS
 	_setsockopt(sock, SOL_IP, IP_TOS, params->ip_tos);
+#endif
 	_setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, params->tcp_nodelay);
 	_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, x_true);
 	_setsockopt(sock, IPPROTO_TCP, TCP_KEEPCNT, params->tcp_keepcnt);