diff --git a/include/osmocom/sgsn/rest_octets.h b/include/osmocom/sgsn/rest_octets.h
new file mode 100644
index 0000000..0dbe7ae
--- /dev/null
+++ b/include/osmocom/sgsn/rest_octets.h
@@ -0,0 +1,139 @@
+#ifndef _REST_OCTETS_H
+#define _REST_OCTETS_H
+
+#include <stdbool.h>
+#include <osmocom/sgsn/gsm_04_08.h>
+#include <osmocom/gsm/sysinfo.h>
+
+/* generate SI1 rest octets */
+int rest_octets_si1(uint8_t *data, uint8_t *nch_pos, int is1800_net);
+int rest_octets_si2quater(uint8_t *data, struct gsm_bts *bts);
+int rest_octets_si6(uint8_t *data, bool is1800_net);
+
+struct gsm48_si_selection_params {
+	uint16_t penalty_time:5,
+		  temp_offs:3,
+		  cell_resel_off:6,
+		  cbq:1,
+		  present:1;
+};
+
+struct gsm48_si_power_offset {
+	uint8_t power_offset:2,
+		 present:1;
+};
+
+struct gsm48_si3_gprs_ind {
+	uint8_t si13_position:1,
+		 ra_colour:3,
+		 present:1;
+};
+
+struct gsm48_lsa_params {
+	uint32_t prio_thr:3,
+		 lsa_offset:3,
+		 mcc:12,
+		 mnc:12;
+	unsigned int present;
+};
+
+struct gsm48_si_ro_info {
+	struct gsm48_si_selection_params selection_params;
+	struct gsm48_si_power_offset power_offset;
+	uint8_t si2ter_indicator;
+	uint8_t early_cm_ctrl;
+	struct {
+		uint8_t where:3,
+			 present:1;
+	} scheduling;
+	struct gsm48_si3_gprs_ind gprs_ind;
+	/* SI 3 specific */
+	uint8_t si2quater_indicator;
+	/* SI 4 specific */
+	struct gsm48_lsa_params lsa_params;
+	uint16_t cell_id;
+	uint8_t break_ind;	/* do we have SI7 + SI8 ? */
+};
+
+
+/* Generate SI3 Rest Octests (Chapter 10.5.2.34 / Table 10.4.72) */
+int rest_octets_si3(uint8_t *data, const struct gsm48_si_ro_info *si3);
+
+/* Generate SI4 Rest Octets (Chapter 10.5.2.35) */
+int rest_octets_si4(uint8_t *data, const struct gsm48_si_ro_info *si4, int len);
+
+enum pbcch_carrier_type {
+	PBCCH_BCCH,
+	PBCCH_ARFCN,
+	PBCCH_MAIO
+};
+
+/* TS 03.60 Chapter 6.3.3.1: Network Mode of Operation */
+enum gprs_nmo {
+	GPRS_NMO_I	= 0,	/* CS pagin on GPRS paging or traffic channel */
+	GPRS_NMO_II	= 1,	/* all paging on CCCH */
+	GPRS_NMO_III	= 2,	/* no paging coordination */
+};
+
+/* TS 04.60 12.24 */
+struct gprs_cell_options {
+	enum gprs_nmo nmo;
+	/* T3168: wait for packet uplink assignment message */
+	uint32_t t3168;	/* in milliseconds */
+	/* T3192: wait for release of the TBF after reception of the final block */
+	uint32_t t3192;	/* in milliseconds */
+	uint32_t drx_timer_max;/* in seconds */
+	uint32_t bs_cv_max;
+	uint8_t  supports_egprs_11bit_rach;
+	bool ctrl_ack_type_use_block; /* use PACKET CONTROL ACKNOWLEDGMENT */
+
+	uint8_t ext_info_present;
+	struct {
+		uint8_t egprs_supported;
+			uint8_t use_egprs_p_ch_req;
+			uint8_t bep_period;
+		uint8_t pfc_supported;
+		uint8_t dtm_supported;
+		uint8_t bss_paging_coordination;
+	} ext_info;
+};
+
+/* TS 04.60 Table 12.9.2 */
+struct gprs_power_ctrl_pars {
+	uint8_t alpha;
+	uint8_t t_avg_w;
+	uint8_t t_avg_t;
+	uint8_t pc_meas_chan;
+	uint8_t n_avg_i;
+};
+
+struct gsm48_si13_info {
+	struct gprs_cell_options cell_opts;
+	struct gprs_power_ctrl_pars pwr_ctrl_pars;
+	uint8_t bcch_change_mark;
+	uint8_t si_change_field;
+	uint8_t pbcch_present;
+
+	union {
+		struct {
+			uint8_t rac;
+			uint8_t spgc_ccch_sup;
+			uint8_t net_ctrl_ord;
+			uint8_t prio_acc_thr;
+		} no_pbcch;
+		struct {
+			uint8_t psi1_rep_per;
+			uint8_t pb;
+			uint8_t tsc;
+			uint8_t tn;
+			enum pbcch_carrier_type carrier_type;
+			uint16_t arfcn;
+			uint8_t maio;
+		} pbcch;
+	};
+};
+
+/* Generate SI13 Rest Octests (Chapter 10.5.2.37b) */
+int rest_octets_si13(uint8_t *data, const struct gsm48_si13_info *si13);
+
+#endif /* _REST_OCTETS_H */