diff --git a/openbsc/src/gsm_04_11.c b/openbsc/src/gsm_04_11.c
index 68ccec6..6dac9d8 100644
--- a/openbsc/src/gsm_04_11.c
+++ b/openbsc/src/gsm_04_11.c
@@ -414,6 +414,9 @@
 	 * successfully received a SMS.  We can now safely mark it as
 	 * transmitted */
 
+	/* we need to look-up the transaction based on rph->msg_ref to
+	 * identify which particular RP_DATA/SMS-submit was ACKed */
+
 }
 
 static int gsm411_rx_rp_error(struct msgb *msg, struct gsm411_rp_hdr *rph)
@@ -422,6 +425,9 @@
 	 * successfully receive the SMS.  We need to investigate
 	 * the cause and take action depending on it */
 
+	/* we need to look-up the transaction based on rph->msg_ref to
+	 * identify which particular RP_DATA/SMS-submit failed */
+
 }
 
 static int gsm411_rx_rp_smma(struct msgb *msg, struct gsm411_rp_hdr *rph)