tcp: Add reference to initial CWND ietf draft.

Suggested by Alexander Zimmermann

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7118668..adfe6db 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -196,7 +196,7 @@
 /* TCP thin-stream limits */
 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
 
-/* TCP initial congestion window */
+/* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
 #define TCP_INIT_CWND		10
 
 extern struct inet_timewait_death_row tcp_death_row;