diff --git a/include/osmocom/hnodeb/hnb_prim.h b/include/osmocom/hnodeb/hnb_prim.h
index ba3223d..be5cba2 100644
--- a/include/osmocom/hnodeb/hnb_prim.h
+++ b/include/osmocom/hnodeb/hnb_prim.h
@@ -188,7 +188,7 @@ enum hnb_audio_prim_type {
 /* HNB_AUDIO_PRIM_CONN_ESTABLISH, UL */
 #define HNB_MAX_RFCIS 64
 #define HNB_MAX_SUBFLOWS 7
-struct hnb_audio_conn_establish_req_param {
+struct hnb_audio_conn_establish_req_param_v0 {
 	uint32_t context_id;
 	uint16_t remote_rtp_port;
 	uint8_t spare1;
@@ -204,6 +204,16 @@ struct hnb_audio_conn_establish_req_param {
 	uint8_t IPTIs_present; /* 1=present; 0=not present */
 	uint8_t IPTIs[HNB_MAX_RFCIS]; /* values range 0-15, 4 bits */
 } __attribute__ ((packed));
+struct hnb_audio_conn_establish_req_param_v1 {
+	struct hnb_audio_conn_establish_req_param_v0 v0;
+	uint8_t rfci[HNB_MAX_RFCIS]; /* values range 6 bits */
+} __attribute__ ((packed));
+struct hnb_audio_conn_establish_req_param {
+	union {
+		struct hnb_audio_conn_establish_req_param_v0 v0;
+		struct hnb_audio_conn_establish_req_param_v1 v1;
+	} __attribute__ ((packed));
+} __attribute__ ((packed));
 
 /* HNB_AUDIO_PRIM_CONN_ESTABLISH, DL */
 struct hnb_audio_conn_establish_cnf_param {
diff --git a/include/osmocom/hnodeb/llsk.h b/include/osmocom/hnodeb/llsk.h
index d9e1a69..bde531a 100644
--- a/include/osmocom/hnodeb/llsk.h
+++ b/include/osmocom/hnodeb/llsk.h
@@ -51,8 +51,9 @@ struct hnb_iuh_prim *hnb_iuh_makeprim_conn_data_ind(uint32_t context_id,
 struct hnb_iuh_prim *hnb_iuh_makeprim_unitdata_ind(const uint8_t *data, uint32_t data_len);
 
 #define LLSK_SAPI_AUDIO_VERSION_MIN 0
-#define LLSK_SAPI_AUDIO_VERSION_MAX 0
+#define LLSK_SAPI_AUDIO_VERSION_MAX 1
 extern const struct value_string hnb_audio_prim_type_names[];
+int llsk_audio_sapi_version_confirmed(uint16_t sapi_version);
 int llsk_rx_audio(struct hnb *hnb, struct osmo_prim_hdr *oph);
 int llsk_audio_tx_conn_data_ind(struct rtp_conn *conn, uint8_t frame_nr, uint8_t fqc, uint8_t rfci,
 				const uint8_t *payload, uint32_t len);
diff --git a/src/osmo-hnodeb/llsk.c b/src/osmo-hnodeb/llsk.c
index b56cae7..f2d778f 100644
--- a/src/osmo-hnodeb/llsk.c
+++ b/src/osmo-hnodeb/llsk.c
@@ -167,6 +167,8 @@ static int llsk_rx_sapi_version_cb(struct osmo_prim_srv *prim_srv, uint32_t sapi
 			return -1;
 		if (rem_version > LLSK_SAPI_AUDIO_VERSION_MAX)
 			return LLSK_SAPI_AUDIO_VERSION_MAX;
+		if (llsk_audio_sapi_version_confirmed(hnb->llsk.sapi_version_audio) < 0)
+			return -1;
 		hnb->llsk.sapi_version_audio = rem_version;
 		break;
 	default:
diff --git a/src/osmo-hnodeb/llsk_audio.c b/src/osmo-hnodeb/llsk_audio.c
index a9fe858..a545ee7 100644
--- a/src/osmo-hnodeb/llsk_audio.c
+++ b/src/osmo-hnodeb/llsk_audio.c
@@ -68,6 +68,24 @@ const struct value_string hnb_audio_prim_type_names[] = {
 	{ 0, NULL }
 };
 
+int llsk_audio_sapi_version_confirmed(uint16_t sapi_version)
+{
+	/* Update primitive size expectancies based on SAPI version: */
+	switch (sapi_version) {
+	case 0:
+		llsk_audio_prim_size_tbl[PRIM_OP_REQUEST][HNB_AUDIO_PRIM_CONN_ESTABLISH] =
+			sizeof(struct hnb_audio_conn_establish_req_param_v0);
+		break;
+	case 1:
+		llsk_audio_prim_size_tbl[PRIM_OP_REQUEST][HNB_AUDIO_PRIM_CONN_ESTABLISH] =
+			sizeof(struct hnb_audio_conn_establish_req_param_v1);
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
 static struct hnb_audio_prim *hnb_audio_prim_alloc(enum hnb_audio_prim_type ptype, enum osmo_prim_operation op, size_t extra_len)
 {
 	struct osmo_prim_hdr *oph;
@@ -159,34 +177,35 @@ static int llsk_rx_audio_conn_establish_req(struct hnb *hnb, struct hnb_audio_co
 	union u_addr loc_uaddr = {0};
 	uint16_t loc_port = 0;
 	struct rtp_conn *conn = NULL;
+	struct hnb_audio_conn_establish_req_param_v0 *v0 = &ce_req->v0;
 
-	rc = ll_addr2osa(ce_req->remote_rtp_address_type, &ce_req->remote_rtp_addr, ce_req->remote_rtp_port, &rem_osa);
+	rc = ll_addr2osa(v0->remote_rtp_address_type, &v0->remote_rtp_addr, v0->remote_rtp_port, &rem_osa);
 	if (rc < 0) {
 		LOGP(DLLSK, LOGL_ERROR, "Rx AUDIO-CONN_ESTABLISH.req: ctx=%u with unexpected address type %u\n",
-		     ce_req->context_id, ce_req->remote_rtp_address_type);
-		return _send_conn_establish_cnf_failed(hnb, ce_req->context_id, 1);
+		     v0->context_id, v0->remote_rtp_address_type);
+		return _send_conn_establish_cnf_failed(hnb, v0->context_id, 1);
 	}
 	osmo_sockaddr_to_str_buf(rem_addrstr, sizeof(rem_addrstr), &rem_osa);
 
 	LOGP(DLLSK, LOGL_INFO, "Rx AUDIO-CONN_ESTABLISH.req ctx=%u rem_addr=%s\n",
-	     ce_req->context_id, rem_addrstr);
+	     v0->context_id, rem_addrstr);
 
-	if ((af = ll_addr_type2af(ce_req->remote_rtp_address_type)) < 0) {
+	if ((af = ll_addr_type2af(v0->remote_rtp_address_type)) < 0) {
 		LOGP(DLLSK, LOGL_ERROR, "Rx AUDIO-CONN_ESTABLISH.req: ctx=%u with unexpected address type %u\n",
-		     ce_req->context_id, ce_req->remote_rtp_address_type);
-		return _send_conn_establish_cnf_failed(hnb, ce_req->context_id, 1);
+		     v0->context_id, v0->remote_rtp_address_type);
+		return _send_conn_establish_cnf_failed(hnb, v0->context_id, 1);
 	}
 
-	ue = hnb_find_ue_by_id(hnb, ce_req->context_id);
+	ue = hnb_find_ue_by_id(hnb, v0->context_id);
 	if (!ue) {
 		LOGP(DLLSK, LOGL_ERROR, "Rx AUDIO-CONN_ESTABLISH.req: UE not found! ctx=%u rem_addr=%s\n",
-		     ce_req->context_id, rem_addrstr);
-		return _send_conn_establish_cnf_failed(hnb, ce_req->context_id, 2);
+		     v0->context_id, rem_addrstr);
+		return _send_conn_establish_cnf_failed(hnb, v0->context_id, 2);
 	}
 	if (!ue->conn_cs.active) {
 		LOGUE(ue, DLLSK, LOGL_ERROR, "Rx AUDIO-CONN_ESTABLISH.req: CS chan not active! rem_addr=%s\n",
 		      rem_addrstr);
-		return _send_conn_establish_cnf_failed(hnb, ce_req->context_id, 3);
+		return _send_conn_establish_cnf_failed(hnb, v0->context_id, 3);
 	}
 
 	/* Create the socket: */
@@ -194,22 +213,22 @@ static int llsk_rx_audio_conn_establish_req(struct hnb *hnb, struct hnb_audio_co
 	if ((rc = rtp_conn_setup(conn, &rem_osa, ce_req)) < 0) {
 		LOGUE(ue, DLLSK, LOGL_ERROR, "Rx AUDIO-CONN_ESTABLISH.req: Failed to set up audio socket rem_addr=%s\n",
 		      rem_addrstr);
-		return _send_conn_establish_cnf_failed(hnb, ce_req->context_id, 4);
+		return _send_conn_establish_cnf_failed(hnb, v0->context_id, 4);
 	}
 
 	/* Convert resulting local address back to LLSK format: */
-	if (osa2_ll_addr(&conn->loc_addr, &loc_uaddr,  &loc_port) != ce_req->remote_rtp_address_type) {
+	if (osa2_ll_addr(&conn->loc_addr, &loc_uaddr,  &loc_port) != v0->remote_rtp_address_type) {
 		LOGUE(ue, DLLSK, LOGL_ERROR, "Rx AUDIO-CONN_ESTABLISH.req: Failed to provide proper local address rem_addr=%s\n",
 		      rem_addrstr);
-		rc = _send_conn_establish_cnf_failed(hnb, ce_req->context_id, 4);
+		rc = _send_conn_establish_cnf_failed(hnb, v0->context_id, 4);
 		goto release_sock;
 	}
 
 	/* Submit successful confirmation */
 	LOGUE(ue, DLLSK, LOGL_INFO, "Tx AUDIO-CONN_ESTABLISH.cnf: error_code=0 rem_addr=%s loc_addr=%s\n",
 	      rem_addrstr, osmo_sockaddr_to_str(&conn->loc_addr));
-	audio_prim = hnb_audio_makeprim_conn_establish_cnf(ce_req->context_id, conn->id, 0, loc_port,
-							   ce_req->remote_rtp_address_type, &loc_uaddr);
+	audio_prim = hnb_audio_makeprim_conn_establish_cnf(v0->context_id, conn->id, 0, loc_port,
+							   v0->remote_rtp_address_type, &loc_uaddr);
 	if ((rc = osmo_prim_srv_send(hnb->llsk.srv, audio_prim->hdr.msg)) < 0) {
 		LOGUE(ue, DLLSK, LOGL_ERROR, "Failed sending AUDIO-CONN_ESTABLISH.cnf error_code=0\n");
 		goto release_sock;
diff --git a/src/osmo-hnodeb/rtp.c b/src/osmo-hnodeb/rtp.c
index c0d96a9..422e043 100644
--- a/src/osmo-hnodeb/rtp.c
+++ b/src/osmo-hnodeb/rtp.c
@@ -31,30 +31,33 @@
 
 #define HNB_IUUP_MSGB_SIZE 4096
 
-static struct osmo_iuup_rnl_prim *llsk_audio_ce_to_iuup_rnl_cfg(void *ctx, const struct hnb_audio_conn_establish_req_param *ce_req)
+static struct osmo_iuup_rnl_prim *llsk_audio_ce_to_iuup_rnl_cfg(struct rtp_conn *conn, const struct hnb_audio_conn_establish_req_param *ce_req)
 {
 	struct osmo_iuup_rnl_prim *irp;
 	struct osmo_iuup_rnl_config *cfg;
 	unsigned int i;
+	const struct hnb_audio_conn_establish_req_param_v0 *v0 = &ce_req->v0;
+	const struct hnb *hnb = conn->ue->hnb;
 
-	irp = osmo_iuup_rnl_prim_alloc(ctx, OSMO_IUUP_RNL_CONFIG, PRIM_OP_REQUEST, HNB_IUUP_MSGB_SIZE);
+	irp = osmo_iuup_rnl_prim_alloc(conn, OSMO_IUUP_RNL_CONFIG, PRIM_OP_REQUEST, HNB_IUUP_MSGB_SIZE);
 	cfg = &irp->u.config;
-	cfg->transparent = !!ce_req->transparent;
+	cfg->transparent = !!v0->transparent;
 	cfg->active = true;
-	cfg->data_pdu_type = ce_req->data_pdu_type;
-	cfg->supported_versions_mask = ce_req->supported_versions_mask;
-	cfg->num_rfci = ce_req->num_rfci;
-	cfg->num_subflows = ce_req->num_subflows;
-	cfg->IPTIs_present = ce_req->IPTIs_present;
+	cfg->data_pdu_type = v0->data_pdu_type;
+	cfg->supported_versions_mask = v0->supported_versions_mask;
+	cfg->num_rfci = v0->num_rfci;
+	cfg->num_subflows = v0->num_subflows;
+	cfg->IPTIs_present = v0->IPTIs_present;
 	OSMO_ASSERT(cfg->num_rfci <= ARRAY_SIZE(cfg->rfci));
 	OSMO_ASSERT(cfg->num_subflows <= ARRAY_SIZE(cfg->rfci[0].subflow_sizes));
 	for (i = 0; i < cfg->num_rfci; i++) {
 		cfg->rfci[i].used = true;
-		cfg->rfci[i].id = i; /* Assume RFC ID from position, llsk_audio doesn't provide info */
+		/* llsk_audio v0 doesn't provide info, assume RFC ID from position: */
+		cfg->rfci[i].id = (hnb->llsk.sapi_version_audio > 0) ? ce_req->v1.rfci[i] : i;
 		if (cfg->IPTIs_present)
-			cfg->rfci[i].IPTI = ce_req->IPTIs[i];
+			cfg->rfci[i].IPTI = v0->IPTIs[i];
 		if (cfg->num_subflows > 0)
-			memcpy(&cfg->rfci[i].subflow_sizes[0], &ce_req->subflow_sizes[i][0], cfg->num_subflows*sizeof(uint16_t));
+			memcpy(&cfg->rfci[i].subflow_sizes[0], &v0->subflow_sizes[i][0], cfg->num_subflows*sizeof(uint16_t));
 	}
 
 	cfg->t_init = (struct osmo_iuup_rnl_config_timer){ .t_ms = IUUP_TIMER_INIT_T_DEFAULT, .n_max = IUUP_TIMER_INIT_N_DEFAULT };