diff --git a/openbsc/src/rest_octets.c b/openbsc/src/rest_octets.c
new file mode 100644
index 0000000..6efd475
--- /dev/null
+++ b/openbsc/src/rest_octets.c
@@ -0,0 +1,393 @@
+/* GSM Mobile Radio Interface Layer 3 messages on the A-bis interface,
+ * rest octet handling according to
+ * 3GPP TS 04.08 version 7.21.0 Release 1998 / ETSI TS 100 940 V7.21.0 */
+
+/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include <openbsc/gsm_data.h>
+#include <openbsc/bitvec.h>
+#include <openbsc/rest_octets.h>
+
+/* generate SI1 rest octets */
+int rest_octets_si1(u_int8_t *data, u_int8_t *nch_pos)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 2;
+
+	if (nch_pos) {
+		bitvec_set_bit(&bv, H);
+		bitvec_set_uint(&bv, *nch_pos, 5);
+	} else
+		bitvec_set_bit(&bv, L);
+
+	bitvec_spare_padding(&bv, 15);
+	return 0;
+}
+
+/* Append selection parameters to bitvec */
+static void append_selection_params(struct bitvec *bv,
+				    const struct gsm48_si_selection_params *sp)
+{
+	if (sp->present) {
+		bitvec_set_bit(bv, H);
+		bitvec_set_bit(bv, sp->cbq);
+		bitvec_set_uint(bv, sp->cell_resel_off, 6);
+		bitvec_set_uint(bv, sp->temp_offs, 3);
+		bitvec_set_uint(bv, sp->penalty_time, 5);
+	} else
+		bitvec_set_bit(bv, L);
+}
+
+/* Append power offset to bitvec */
+static void append_power_offset(struct bitvec *bv,
+				const struct gsm48_si_power_offset *po)
+{
+	if (po->present) {
+		bitvec_set_bit(bv, H);
+		bitvec_set_uint(bv, po->power_offset, 2);
+	} else
+		bitvec_set_bit(bv, L);
+}
+
+/* Append GPRS indicator to bitvec */
+static void append_gprs_ind(struct bitvec *bv,
+			    const struct gsm48_si3_gprs_ind *gi)
+{
+	if (gi->present) {
+		bitvec_set_bit(bv, H);
+		bitvec_set_uint(bv, gi->ra_colour, 3);
+		/* 0 == SI13 in BCCH Norm, 1 == SI13 sent on BCCH Ext */
+		bitvec_set_bit(bv, gi->si13_position);
+	} else
+		bitvec_set_bit(bv, L);
+}
+
+
+/* Generate SI3 Rest Octests (Chapter 10.5.2.34 / Table 10.4.72) */
+int rest_octets_si3(u_int8_t *data, const struct gsm48_si_ro_info *si3)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 5;
+
+	/* Optional Selection Parameters */
+	append_selection_params(&bv, &si3->selection_params);
+
+	/* Optional Power Offset */
+	append_power_offset(&bv, &si3->power_offset);
+
+	/* Do we have a SI2ter on the BCCH? */
+	if (si3->si2ter_indicator)
+		bitvec_set_bit(&bv, H);
+	else
+		bitvec_set_bit(&bv, L);
+
+	/* Early Classmark Sending Control */
+	if (si3->early_cm_ctrl)
+		bitvec_set_bit(&bv, H);
+	else
+		bitvec_set_bit(&bv, L);
+
+	/* Do we have a SI Type 9 on the BCCH? */
+	if (si3->scheduling.present) {
+		bitvec_set_bit(&bv, H);
+		bitvec_set_uint(&bv, si3->scheduling.where, 3);
+	} else
+		bitvec_set_bit(&bv, L);
+
+	/* GPRS Indicator */
+	append_gprs_ind(&bv, &si3->gprs_ind);
+
+	return bitvec_spare_padding(&bv, (bv.data_len*8)-1);
+}
+
+static int append_lsa_params(struct bitvec *bv,
+			     const struct gsm48_lsa_params *lsa_params)
+{
+	/* FIXME */
+}
+
+/* Generate SI4 Rest Octets (Chapter 10.5.2.35) */
+int rest_octets_si4(u_int8_t *data, const struct gsm48_si_ro_info *si4)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 11; /* FIXME: up to ? */
+
+	/* SI4 Rest Octets O */
+	append_selection_params(&bv, &si4->selection_params);
+	append_power_offset(&bv, &si4->power_offset);
+	append_gprs_ind(&bv, &si4->gprs_ind);
+
+	if (0 /* FIXME */) {
+		/* H and SI4 Rest Octets S */
+		bitvec_set_bit(&bv, H);
+
+		/* LSA Parameters */
+		if (si4->lsa_params.present) {
+			bitvec_set_bit(&bv, H);
+			append_lsa_params(&bv, &si4->lsa_params);
+		} else
+			bitvec_set_bit(&bv, L);
+
+		/* Cell Identity */
+		if (1) {
+			bitvec_set_bit(&bv, H);
+			bitvec_set_uint(&bv, si4->cell_id, 16);
+		} else
+			bitvec_set_bit(&bv, L);
+
+		/* LSA ID Information */
+		if (0) {
+			bitvec_set_bit(&bv, H);
+			/* FIXME */
+		} else
+			bitvec_set_bit(&bv, L);
+	} else {
+		/* L and break indicator */
+		bitvec_set_bit(&bv, L);
+		bitvec_set_bit(&bv, si4->break_ind ? H : L);
+	}
+
+	return 0;
+}
+
+/* GPRS Mobile Allocation as per TS 04.60 Chapter 12.10a:
+   < GPRS Mobile Allocation IE > ::=
+     < HSN : bit (6) >
+     { 0 | 1 < RFL number list : < RFL number list struct > > }
+     { 0 < MA_LENGTH : bit (6) >
+         < MA_BITMAP: bit (val(MA_LENGTH) + 1) >
+     | 1 { 0 | 1 <ARFCN index list : < ARFCN index list struct > > } } ;
+
+     < RFL number list struct > :: =
+       < RFL_NUMBER : bit (4) >
+       { 0 | 1 < RFL number list struct > } ;
+     < ARFCN index list struct > ::=
+       < ARFCN_INDEX : bit(6) >
+       { 0 | 1 < ARFCN index list struct > } ;
+ */
+static int append_gprs_mobile_alloc(struct bitvec *bv)
+{
+	/* Hopping Sequence Number */
+	bitvec_set_uint(bv, 0, 6);
+
+	if (0) {
+		/* We want to use a RFL number list */
+		bitvec_set_bit(bv, 1);
+		/* FIXME: RFL number list */
+	} else
+		bitvec_set_bit(bv, 0);
+
+	if (0) {
+		/* We want to use a MA_BITMAP */
+		bitvec_set_bit(bv, 0);
+		/* FIXME: MA_LENGTH, MA_BITMAP, ... */
+	} else {
+		bitvec_set_bit(bv, 1);
+		if (0) {
+			/* We want to provide an ARFCN index list */
+			bitvec_set_bit(bv, 1);
+			/* FIXME */
+		} else
+			bitvec_set_bit(bv, 0);
+	}
+	return 0;
+}
+
+static int encode_t3192(unsigned int t3192)
+{
+	if (t3192 == 0)
+		return 3;
+	else if (t3192 <= 80)
+		return 4;
+	else if (t3192 <= 120)
+		return 5;
+	else if (t3192 <= 160)
+		return 6;
+	else if (t3192 <= 200)
+		return 7;
+	else if (t3192 <= 500)
+		return 0;
+	else if (t3192 <= 1000)
+		return 1;
+	else if (t3192 <= 1500)
+		return 2;
+	else
+		return -EINVAL;
+}
+
+static int encode_drx_timer(unsigned int drx)
+{
+	if (drx == 0)
+		return 0;
+	else if (drx == 1)
+		return 1;
+	else if (drx == 2)
+		return 2;
+	else if (drx <= 4)
+		return 3;
+	else if (drx <= 8)
+		return 4;
+	else if (drx <= 16)
+		return 5;
+	else if (drx <= 32)
+		return 6;
+	else if (drx <= 64)
+		return 7;
+	else
+		return -EINVAL;
+}
+
+/* GPRS Cell Options as per TS 04.60 Chapter 12.24
+	< GPRS Cell Options IE > ::=
+		< NMO : bit(2) >
+		< T3168 : bit(3) >
+		< T3192 : bit(3) >
+		< DRX_TIMER_MAX: bit(3) >
+		< ACCESS_BURST_TYPE: bit >
+		< CONTROL_ACK_TYPE : bit >
+		< BS_CV_MAX: bit(4) >
+		{ 0 | 1 < PAN_DEC : bit(3) >
+			< PAN_INC : bit(3) >
+			< PAN_MAX : bit(3) >
+		{ 0 | 1 < Extension Length : bit(6) >
+			< bit (val(Extension Length) + 1
+			& { < Extension Information > ! { bit ** = <no string> } } ;
+	< Extension Information > ::=
+		{ 0 | 1 < EGPRS_PACKET_CHANNEL_REQUEST : bit >
+			< BEP_PERIOD : bit(4) > }
+		< PFC_FEATURE_MODE : bit >
+		< DTM_SUPPORT : bit >
+		<BSS_PAGING_COORDINATION: bit >
+		<spare bit > ** ;
+ */
+static int append_gprs_cell_opt(struct bitvec *bv, struct gprs_cell_options *gco)
+{
+	int t3192, drx_timer_max;
+
+	t3192 = encode_t3192(gco->t3192);
+	if (t3192 < 0)
+		return t3192;
+
+	drx_timer_max = encode_drx_timer(gco->drx_timer_max);
+	if (drx_timer_max < 0)
+		return drx_timer_max;
+
+	bitvec_set_uint(bv, gco->nmo, 2);
+	bitvec_set_uint(bv, gco->t3168 / 500, 3);
+	bitvec_set_uint(bv, t3192, 3);
+	bitvec_set_uint(bv, drx_timer_max, 3);
+	/* ACCESS_BURST_TYPE: Hard-code 8bit */
+	bitvec_set_bit(bv, 0);
+	/* CONTROL_ACK_TYPE: Hard-code to RLC/MAC control block */
+	bitvec_set_bit(bv, 1);
+	bitvec_set_uint(bv, gco->bs_cv_max, 4);
+
+	/* hard-code no PAN_{DEC,INC,MAX} */
+	bitvec_set_bit(bv, 0);
+
+	/* no extension information (EDGE) */
+	bitvec_set_bit(bv, 0);
+
+	return 0;
+}
+
+static void append_gprs_pwr_ctrl_pars(struct bitvec *bv,
+				      struct gprs_power_ctrl_pars *pcp)
+{
+	bitvec_set_uint(bv, pcp->alpha, 4);
+	bitvec_set_uint(bv, pcp->t_avg_w, 5);
+	bitvec_set_uint(bv, pcp->t_avg_t, 5);
+	bitvec_set_uint(bv, pcp->pc_meas_chan, 1);
+	bitvec_set_uint(bv, pcp->n_avg_i, 4);
+}
+
+/* Generate SI13 Rest Octests (Chapter 10.5.2.37b) */
+int rest_octets_si13(u_int8_t *data, const struct gsm48_si13_info *si13)
+{
+	struct bitvec bv;
+
+	memset(&bv, 0, sizeof(bv));
+	bv.data = data;
+	bv.data_len = 21;
+
+	if (0) {
+		/* No rest octets */
+		bitvec_set_bit(&bv, L);
+	} else {
+		bitvec_set_bit(&bv, H);
+		bitvec_set_uint(&bv, si13->bcch_change_mark, 3);
+		bitvec_set_uint(&bv, si13->si_change_field, 4);
+		if (0) {
+			bitvec_set_bit(&bv, 0);
+		} else {
+			bitvec_set_bit(&bv, 1);
+			bitvec_set_uint(&bv, si13->bcch_change_mark, 2);
+			append_gprs_mobile_alloc(&bv);
+		}
+		if (!si13->pbcch_present) {
+			/* PBCCH not present in cell */
+			bitvec_set_bit(&bv, 0);
+			bitvec_set_uint(&bv, si13->no_pbcch.rac, 8);
+			bitvec_set_bit(&bv, si13->no_pbcch.spgc_ccch_sup);
+			bitvec_set_uint(&bv, si13->no_pbcch.prio_acc_thr, 3);
+			bitvec_set_uint(&bv, si13->no_pbcch.net_ctrl_ord, 2);
+			append_gprs_cell_opt(&bv, &si13->cell_opts);
+			append_gprs_pwr_ctrl_pars(&bv, &si13->pwr_ctrl_pars);
+		} else {
+			/* PBCCH present in cell */
+			bitvec_set_bit(&bv, 1);
+			bitvec_set_uint(&bv, si13->pbcch.psi1_rep_per, 4);
+			/* PBCCH Descripiton */
+			bitvec_set_uint(&bv, si13->pbcch.pb, 4);
+			bitvec_set_uint(&bv, si13->pbcch.tsc, 3);
+			bitvec_set_uint(&bv, si13->pbcch.tn, 3);
+			switch (si13->pbcch.carrier_type) {
+			case PBCCH_BCCH:
+				bitvec_set_bit(&bv, 0);
+				bitvec_set_bit(&bv, 0);
+				break;
+			case PBCCH_ARFCN:
+				bitvec_set_bit(&bv, 0);
+				bitvec_set_bit(&bv, 1);
+				bitvec_set_uint(&bv, si13->pbcch.arfcn, 10);
+				break;
+			case PBCCH_MAIO:
+				bitvec_set_bit(&bv, 1);
+				bitvec_set_uint(&bv, si13->pbcch.maio, 6);
+				break;
+			}
+		}
+	}
+	return bitvec_spare_padding(&bv, (bv.data_len*8)-1);
+}