diff --git a/src/rlc.cpp b/src/rlc.cpp
index f6d6f4a..4f62f23 100644
--- a/src/rlc.cpp
+++ b/src/rlc.cpp
@@ -55,6 +55,22 @@
 	m_v_b.reset();
 }
 
+void gprs_rlc_dl_window::set_sns(uint16_t sns)
+{
+	OSMO_ASSERT(sns >= RLC_GPRS_SNS);
+	OSMO_ASSERT(sns <= RLC_MAX_SNS);
+	/* check for 2^n */
+	OSMO_ASSERT((sns & (-sns)) == sns);
+	m_sns = sns;
+}
+
+void gprs_rlc_dl_window::set_ws(uint16_t ws)
+{
+	OSMO_ASSERT(ws >= RLC_GPRS_SNS/2);
+	OSMO_ASSERT(ws <= RLC_MAX_SNS/2);
+	m_ws = ws;
+}
+
 int gprs_rlc_dl_window::resend_needed()
 {
 	for (uint16_t bsn = v_a(); bsn != v_s(); bsn = mod_sns(bsn + 1)) {
@@ -172,6 +188,22 @@
 		m_v_n[i] = GPRS_RLC_UL_BSN_INVALID;
 }
 
+void gprs_rlc_ul_window::set_sns(uint16_t sns)
+{
+	OSMO_ASSERT(sns >= RLC_GPRS_SNS);
+	OSMO_ASSERT(sns <= RLC_MAX_SNS);
+	/* check for 2^n */
+	OSMO_ASSERT((sns & (-sns)) == sns);
+	m_sns = sns;
+}
+
+void gprs_rlc_ul_window::set_ws(uint16_t ws)
+{
+	OSMO_ASSERT(ws >= RLC_GPRS_SNS/2);
+	OSMO_ASSERT(ws <= RLC_MAX_SNS/2);
+	m_ws = ws;
+}
+
 /* Update the receive block bitmap */
 void gprs_rlc_ul_window::update_rbb(char *rbb)
 {