diff --git a/lapv5.c b/lapv5.c
index 143d785..34a5caf 100644
--- a/lapv5.c
+++ b/lapv5.c
@@ -24,6 +24,7 @@
 
 #include "v5x_internal.h"
 #include "v5x_protocol.h"
+#include "lapv5.h"
 
 #include <stdio.h>
 #include <string.h>
@@ -73,9 +74,6 @@
 #define LOGLI(li, level, fmt, args ...) \
 	LOGP(DLLAPD, level, "(%s): " fmt, (li)->name, ## args)
 
-#define LOGTEI(teip, level, fmt, args ...) \
-	LOGP(DLLAPD, level, "(%s-T%u): " fmt, (teip)->li->name, (teip)->tei, ## args)
-
 #define LOGSAP(sap, level, fmt, args ...) \
 	LOGP(DLLAPD, level, "(%s): " fmt, (sap)->dl.name, ## args)
 
@@ -92,85 +90,24 @@ const struct lapd_profile lapd_profile_lapv5dl = {
 	.short_address	= 0
 };
 
-typedef enum {
-	LAPD_TEI_NONE = 0,
-	LAPD_TEI_ASSIGNED,
-	LAPD_TEI_ACTIVE,
-} lapd_tei_state;
-
-const char *lapd_tei_states[] = {
-	"NONE",
-	"ASSIGNED",
-	"ACTIVE",
-};
-
-/* Structure representing an allocated TEI within a LAPD instance. */
-struct lapd_tei {
-	struct llist_head list;
-	struct lapd_instance *li;
-	uint8_t tei;
-	lapd_tei_state state;
-
-	struct llist_head sap_list;
-};
 
 /* Structure representing a SAP within a TEI. It includes exactly one datalink
  * instance. */
-struct lapd_sap {
-	struct llist_head list;
-	struct lapd_tei *tei;
-	uint8_t sapi;
+struct lapv5_sap {
+	struct llist_head list;		/* list of SAP within instance */
+	struct lapv5_instance *li;	/* back-pointer */
+	uint16_t dladdr;		/* V5-Data Link Address */
 
-	struct lapd_datalink dl;
+	struct lapd_datalink dl;	/* the actual data link */
 };
 
-/* Resolve TEI structure from given numeric TEI */
-static struct lapd_tei *teip_from_tei(struct lapd_instance *li, uint8_t tei)
-{
-	struct lapd_tei *lt;
-
-	llist_for_each_entry(lt, &li->tei_list, list) {
-		if (lt->tei == tei)
-			return lt;
-	}
-	return NULL;
-};
-
-/* Change state of TEI */
-static void lapd_tei_set_state(struct lapd_tei *teip, int newstate)
-{
-	LOGTEI(teip, LOGL_INFO, "LAPD state change on TEI %d: %s -> %s\n",
-		teip->tei, lapd_tei_states[teip->state],
-		lapd_tei_states[newstate]);
-	teip->state = newstate;
-};
-
-/* Allocate a new TEI */
-struct lapd_tei *lapd_tei_alloc(struct lapd_instance *li, uint8_t tei)
-{
-	struct lapd_tei *teip;
-
-	teip = talloc_zero(li, struct lapd_tei);
-	if (!teip)
-		return NULL;
-
-	teip->li = li;
-	teip->tei = tei;
-	llist_add(&teip->list, &li->tei_list);
-	INIT_LLIST_HEAD(&teip->sap_list);
-
-	lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED);
-
-	return teip;
-}
-
 /* Find a SAP within a given TEI */
-static struct lapd_sap *lapd_sap_find(struct lapd_tei *teip, uint8_t sapi)
+static struct lapv5_sap *lapv5_sap_find(struct lapv5_instance *li, uint16_t dladdr)
 {
-	struct lapd_sap *sap;
+	struct lapv5_sap *sap;
 
-	llist_for_each_entry(sap, &teip->sap_list, list) {
-		if (sap->sapi == sapi)
+	llist_for_each_entry(sap, &li->sap_list, list) {
+		if (sap->dladdr == dladdr)
 			return sap;
 	}
 
@@ -180,32 +117,29 @@ static struct lapd_sap *lapd_sap_find(struct lapd_tei *teip, uint8_t sapi)
 static int send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg);
 static int send_dlsap(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx);
 
-/* Allocate a new SAP within a given TEI */
-static struct lapd_sap *lapd_sap_alloc(struct lapd_tei *teip, uint8_t sapi)
+/* Allocate a new SAP within a given instance */
+static struct lapv5_sap *lapv5_sap_alloc(struct lapv5_instance *li, uint16_t v5dladdr)
 {
-	struct lapd_sap *sap;
+	struct lapv5_sap *sap;
 	struct lapd_datalink *dl;
-	struct lapd_instance *li = teip->li;
 	struct lapd_profile *profile;
 	char name[256];
 	int k;
 
-	snprintf(name, sizeof(name), "%s-T%u-S%u", li->name, teip->tei, sapi);
+	snprintf(name, sizeof(name), "%s-%u", li->name, v5dladdr);
 
-	sap = talloc_zero(teip, struct lapd_sap);
+	sap = talloc_zero(li, struct lapv5_sap);
 	if (!sap)
 		return NULL;
 
-	LOGP(DLLAPD, LOGL_NOTICE,
-	     "(%s): LAPD Allocating SAP for SAPI=%u / TEI=%u (dl=%p, sap=%p)\n",
-	     name, sapi, teip->tei, &sap->dl, sap);
+	LOGP(DLLAPD, LOGL_NOTICE, "(%s): LAPV5 Allocating SAP for V5_DLADDR=%u (dl=%p, sap=%p)\n",
+	     name, v5dladdr, &sap->dl, sap);
 
-	sap->sapi = sapi;
-	sap->tei = teip;
+	sap->dladdr = v5dladdr;
 	dl = &sap->dl;
 	profile = &li->profile;
 
-	k = profile->k[sapi & 0x3f];
+	k = profile->k[0];
 	LOGP(DLLAPD, LOGL_NOTICE, "(%s): k=%d N200=%d N201=%d T200=%d.%d T203=%d.%d\n",
 		name, k, profile->n200, profile->n201, profile->t200_sec,
 		profile->t200_usec, profile->t203_sec, profile->t203_usec);
@@ -218,24 +152,21 @@ static struct lapd_sap *lapd_sap_alloc(struct lapd_tei *teip, uint8_t sapi)
 	dl->t200_sec = profile->t200_sec; dl->t200_usec = profile->t200_usec;
 	dl->t203_sec = profile->t203_sec; dl->t203_usec = profile->t203_usec;
 	dl->lctx.dl = &sap->dl;
-	dl->lctx.sapi = sapi;
-	dl->lctx.tei = teip->tei;
+	dl->lctx.sapi = v5dladdr & 0xff;
+	dl->lctx.tei = v5dladdr >> 8;
 	dl->lctx.n201 = profile->n201;
 
-	lapd_set_mode(&sap->dl, (teip->li->network_side) ? LAPD_MODE_NETWORK
-							: LAPD_MODE_USER);
+	lapd_set_mode(&sap->dl, (li->network_side) ? LAPD_MODE_NETWORK : LAPD_MODE_USER);
 
-	llist_add(&sap->list, &teip->sap_list);
+	llist_add(&sap->list, &li->sap_list);
 
 	return sap;
 }
 
 /* Free SAP instance, including the datalink */
-static void lapd_sap_free(struct lapd_sap *sap)
+static void lapv5_sap_free(struct lapv5_sap *sap)
 {
-	LOGSAP(sap, LOGL_NOTICE,
-	     "LAPD Freeing SAP for SAPI=%u / TEI=%u (dl=%p, sap=%p)\n",
-	     sap->sapi, sap->tei->tei, &sap->dl, sap);
+	LOGSAP(sap, LOGL_NOTICE, "LAPV5 Freeing SAP for DLADDR=%u (dl=%p, sap=%p)\n", sap->dladdr, &sap->dl, sap);
 
 	/* free datalink structures and timers */
 	lapd_dl_exit(&sap->dl);
@@ -244,99 +175,21 @@ static void lapd_sap_free(struct lapd_sap *sap)
 	talloc_free(sap);
 }
 
-/* Free TEI instance */
-static void lapd_tei_free(struct lapd_tei *teip)
+/* General input function for any data received for this LAPV5 instance */
+int lapv5_receive(struct lapv5_instance *li, struct msgb *msg, int *error)
 {
-	struct lapd_sap *sap, *sap2;
-
-	llist_for_each_entry_safe(sap, sap2, &teip->sap_list, list) {
-		lapd_sap_free(sap);
-	}
-
-	llist_del(&teip->list);
-	talloc_free(teip);
-}
-
-/* Input function into TEI manager */
-static int lapd_tei_receive(struct lapd_instance *li, uint8_t *data, int len)
-{
-	uint8_t entity;
-	uint8_t ref;
-	uint8_t mt;
-	uint8_t action;
-	uint8_t e;
-	uint8_t resp[8];
-	struct lapd_tei *teip;
-	struct msgb *msg;
-
-	if (len < 5) {
-		LOGLI(li, LOGL_ERROR, "LAPD TEIMGR frame receive len %d < 5"
-			", ignoring\n", len);
-		return -EINVAL;
-	};
-
-	entity = data[0];
-	ref = data[1];
-	mt = data[3];
-	action = data[4] >> 1;
-	e = data[4] & 1;
-
-	DEBUGP(DLLAPD, "LAPD TEIMGR: entity %x, ref %x, mt %x, action %x, "
-		"e %x\n", entity, ref, mt, action, e);
-
-	switch (mt) {
-	case 0x01:	/* IDENTITY REQUEST */
-		DEBUGP(DLLAPD, "LAPD TEIMGR: identity request for TEI %u\n",
-			action);
-
-		teip = teip_from_tei(li, action);
-		if (!teip) {
-			LOGLI(li, LOGL_INFO, "TEI MGR: New TEI %u\n",
-				action);
-			teip = lapd_tei_alloc(li, action);
-			if (!teip)
-				return -ENOMEM;
-		}
-
-		/* Send ACCEPT */
-		memmove(resp, "\xfe\xff\x03\x0f\x00\x00\x02\x00", 8);
-		resp[7] = (action << 1) | 1;
-		msg = msgb_alloc_headroom(DLSAP_MSGB_SIZE, DLSAP_MSGB_HEADROOM, "DL EST");
-		msg->l2h = msgb_push(msg, 8);
-		memcpy(msg->l2h, resp, 8);
-
-		/* write to PCAP file, if enabled. */
-		osmo_pcap_lapd_write(li->pcap_fd, OSMO_LAPD_PCAP_OUTPUT, msg);
-
-		LOGTEI(teip, LOGL_DEBUG, "TX: %s\n", osmo_hexdump(msg->data, msg->len));
-		li->transmit_cb(msg, li->transmit_cbdata);
-
-		if (teip->state == LAPD_TEI_NONE)
-			lapd_tei_set_state(teip, LAPD_TEI_ASSIGNED);
-		break;
-	default:
-		LOGLI(li, LOGL_NOTICE, "LAPD TEIMGR: unknown mt %x action %x\n", mt, action);
-		break;
-	};
-
-	return 0;
-}
-
-/* General input function for any data received for this LAPD instance */
-int lapd_receive(struct lapd_instance *li, struct msgb *msg, int *error)
-{
-	int i;
 	struct lapd_msg_ctx lctx;
-	int rc;
-	struct lapd_sap *sap;
-	struct lapd_tei *teip;
+	struct lapv5_sap *sap;
+	uint16_t dladdr;
+	bool is_isdn;
+	int i;
 
 	/* write to PCAP file, if enabled. */
 	osmo_pcap_lapd_write(li->pcap_fd, OSMO_LAPD_PCAP_INPUT, msg);
 
 	LOGLI(li, LOGL_DEBUG, "RX: %s\n", osmo_hexdump(msg->data, msg->len));
 	if (msg->len < 2) {
-		LOGLI(li, LOGL_ERROR, "LAPD frame receive len %d < 2, ignoring\n", msg->len);
+		LOGLI(li, LOGL_ERROR, "LAPV5 frame receive len %d < 2, ignoring\n", msg->len);
 		*error = LAPD_ERR_BAD_LEN;
 		return -EINVAL;
 	};
@@ -346,55 +199,39 @@ int lapd_receive(struct lapd_instance *li, struct msgb *msg, int *error)
 
 	i = 0;
 	/* adress field */
-	lctx.sapi = LAPD_ADDR_SAPI(msg->l2h[i]);
-	lctx.cr = LAPD_ADDR_CR(msg->l2h[i]);
+	dladdr = v51_l3_addr_dec(msg->l2h[0] << 8 | msg->l2h[1], &is_isdn);
+	if (!is_isdn) {
+		LOGLI(li, LOGL_ERROR, "LAPV5 frame with single-octet addr not permitted\n");
+		*error = LAPD_ERR_BAD_LEN;
+		return -EINVAL;
+	};
 	lctx.lpd = 0;
-	if (!LAPD_ADDR_EA(msg->l2h[i])) {
-		if (msg->len < 3) {
-			LOGLI(li, LOGL_ERROR, "LAPD frame with TEI receive "
-				"len %d < 3, ignoring\n", msg->len);
-			*error = LAPD_ERR_BAD_LEN;
-			return -EINVAL;
-		};
-		i++;
-		lctx.tei = LAPD_ADDR_TEI(msg->l2h[i]);
-	}
-	i++;
+	lctx.tei = dladdr >> 8;
+	lctx.sapi = dladdr & 0xff;
+	lctx.cr = LAPD_ADDR_CR(msg->l2h[0]);
+	i += 2;
+
 	/* control field */
 	if (LAPD_CTRL_is_I(msg->l2h[i])) {
 		lctx.format = LAPD_FORM_I;
 		lctx.n_send = LAPD_CTRL_I_Ns(msg->l2h[i]);
 		i++;
-		if (msg->len < 3 && i == 2) {
-			LOGLI(li, LOGL_ERROR, "LAPD I frame without TEI "
-				"receive len %d < 3, ignoring\n", msg->len);
+		if (msg->len < 4) {
+			LOGLI(li, LOGL_ERROR, "LAPV5 I frame receive len %d < 4, ignoring\n", msg->len);
 			*error = LAPD_ERR_BAD_LEN;
 			return -EINVAL;
-		};
-		if (msg->len < 4 && i == 3) {
-			LOGLI(li, LOGL_ERROR, "LAPD I frame with TEI "
-				"receive len %d < 4, ignoring\n", msg->len);
-			*error = LAPD_ERR_BAD_LEN;
-			return -EINVAL;
-		};
+		}
 		lctx.n_recv = LAPD_CTRL_Nr(msg->l2h[i]);
 		lctx.p_f = LAPD_CTRL_I_P(msg->l2h[i]);
 	} else if (LAPD_CTRL_is_S(msg->l2h[i])) {
 		lctx.format = LAPD_FORM_S;
 		lctx.s_u = LAPD_CTRL_S_BITS(msg->l2h[i]);
 		i++;
-		if (msg->len < 3 && i == 2) {
-			LOGLI(li, LOGL_ERROR, "LAPD S frame without TEI "
-				"receive len %d < 3, ignoring\n", msg->len);
-			*error = LAPD_ERR_BAD_LEN;
-			return -EINVAL;
-		};
 		if (msg->len < 4 && i == 3) {
-			LOGLI(li, LOGL_ERROR, "LAPD S frame with TEI "
-				"receive len %d < 4, ignoring\n", msg->len);
+			LOGLI(li, LOGL_ERROR, "LAPV5 S frame receive len %d < 4, ignoring\n", msg->len);
 			*error = LAPD_ERR_BAD_LEN;
 			return -EINVAL;
-		};
+		}
 		lctx.n_recv = LAPD_CTRL_Nr(msg->l2h[i]);
 		lctx.p_f = LAPD_CTRL_S_PF(msg->l2h[i]);
 	} else if (LAPD_CTRL_is_U(msg->l2h[i])) {
@@ -409,26 +246,10 @@ int lapd_receive(struct lapd_instance *li, struct msgb *msg, int *error)
 	msgb_pull(msg, i);
 	lctx.length = msg->len;
 
-	/* perform TEI assignment, if received */
-	if (lctx.tei == 127) {
-		rc = lapd_tei_receive(li, msg->data, msg->len);
-		msgb_free(msg);
-		return rc;
-	}
-
-	/* resolve TEI and SAPI */
-	teip = teip_from_tei(li, lctx.tei);
-	if (!teip) {
-		LOGLI(li, LOGL_NOTICE, "LAPD Unknown TEI %u\n", lctx.tei);
-		*error = LAPD_ERR_UNKNOWN_TEI;
-		msgb_free(msg);
-		return -EINVAL;
-	}
-	sap = lapd_sap_find(teip, lctx.sapi);
+	sap = lapv5_sap_find(li, dladdr);
 	if (!sap) {
-		LOGTEI(teip, LOGL_INFO, "LAPD No SAP for TEI=%u / SAPI=%u, "
-			"allocating\n", lctx.tei, lctx.sapi);
-		sap = lapd_sap_alloc(teip, lctx.sapi);
+		LOGLI(li, LOGL_INFO, "LAPV5 No SAP for DLADDR=%u, allocating\n", dladdr);
+		sap = lapv5_sap_alloc(li, dladdr);
 		if (!sap) {
 			*error = LAPD_ERR_NO_MEM;
 			msgb_free(msg);
@@ -439,8 +260,7 @@ int lapd_receive(struct lapd_instance *li, struct msgb *msg, int *error)
 	lctx.n201 = lctx.dl->maxf;
 
 	if (msg->len > lctx.n201) {
-		LOGSAP(sap, LOGL_ERROR, "message len %d > N201(%d) "
-			"(discarding)\n", msg->len, lctx.n201);
+		LOGSAP(sap, LOGL_ERROR, "message len %d > N201(%d) (discarding)\n", msg->len, lctx.n201);
 		msgb_free(msg);
 		*error = LAPD_ERR_BAD_LEN;
 		return -EINVAL;
@@ -451,26 +271,21 @@ int lapd_receive(struct lapd_instance *li, struct msgb *msg, int *error)
 }
 
 /* Start a (user-side) SAP for the specified TEI/SAPI on the LAPD instance */
-int lapd_sap_start(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
+int lapv5_sap_start(struct lapv5_instance *li, uint16_t dladdr)
 {
-	struct lapd_sap *sap;
-	struct lapd_tei *teip;
+	struct lapv5_sap *sap;
 	struct osmo_dlsap_prim dp;
 	struct msgb *msg;
 
-	teip = teip_from_tei(li, tei);
-	if (!teip)
-		teip = lapd_tei_alloc(li, tei);
-
-	sap = lapd_sap_find(teip, sapi);
+	sap = lapv5_sap_find(li, dladdr);
 	if (sap)
 		return -EEXIST;
 
-	sap = lapd_sap_alloc(teip, sapi);
+	sap = lapv5_sap_alloc(li, dladdr);
 	if (!sap)
 		return -ENOMEM;
 
-	LOGSAP(sap, LOGL_NOTICE, "LAPD DL-ESTABLISH request TEI=%d SAPI=%d\n", tei, sapi);
+	LOGSAP(sap, LOGL_NOTICE, "LAPV5 DL-ESTABLISH request DLADDR=%u\n", dladdr);
 
 	/* prepare prim */
 	msg = msgb_alloc_headroom(DLSAP_MSGB_SIZE, DLSAP_MSGB_HEADROOM, "DL EST");
@@ -482,22 +297,17 @@ int lapd_sap_start(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
 }
 
 /* Stop a (user-side) SAP for the specified TEI/SAPI on the LAPD instance */
-int lapd_sap_stop(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
+int lapv5_sap_stop(struct lapv5_instance *li, uint16_t dladdr)
 {
-	struct lapd_tei *teip;
-	struct lapd_sap *sap;
+	struct lapv5_sap *sap;
 	struct osmo_dlsap_prim dp;
 	struct msgb *msg;
 
-	teip = teip_from_tei(li, tei);
-	if (!teip)
-		return -ENODEV;
-
-	sap = lapd_sap_find(teip, sapi);
+	sap = lapv5_sap_find(li, dladdr);
 	if (!sap)
 		return -ENODEV;
 
-	LOGSAP(sap, LOGL_NOTICE, "LAPD DL-RELEASE request TEI=%d SAPI=%d\n", tei, sapi);
+	LOGSAP(sap, LOGL_NOTICE, "LAPV5 DL-RELEASE request DLADDR=%u\n", dladdr);
 
 	/* prepare prim */
 	msg = msgb_alloc_headroom(DLSAP_MSGB_SIZE, DLSAP_MSGB_HEADROOM, "DL REL");
@@ -508,23 +318,15 @@ int lapd_sap_stop(struct lapd_instance *li, uint8_t tei, uint8_t sapi)
         return lapd_recv_dlsap(&dp, &sap->dl.lctx);
 }
 
-/* Transmit Data (DL-DATA request) on the given LAPD Instance / TEI / SAPI */
-void lapd_transmit(struct lapd_instance *li, uint8_t tei, uint8_t sapi,
-		   struct msgb *msg)
+/* Transmit Data (DL-DATA request) on the given LAPD Instance / DLADDR */
+void lapv5_transmit(struct lapv5_instance *li, uint8_t dladdr, struct msgb *msg)
 {
-	struct lapd_tei *teip = teip_from_tei(li, tei);
-	struct lapd_sap *sap;
+	struct lapv5_sap *sap;
 	struct osmo_dlsap_prim dp;
 
-	if (!teip) {
-		LOGLI(li, LOGL_ERROR, "LAPD Cannot transmit on non-existing TEI %u\n", tei);
-		msgb_free(msg);
-		return;
-	}
-
-	sap = lapd_sap_find(teip, sapi);
+	sap = lapv5_sap_find(li, dladdr);
 	if (!sap) {
-		LOGTEI(teip, LOGL_INFO, "LAPD Tx on unknown SAPI=%u in TEI=%u\n", sapi, tei);
+		LOGLI(li, LOGL_INFO, "LAPV5 Tx on unknown DLADDR=%u\n", dladdr);
 		msgb_free(msg);
 		return;
 	}
@@ -540,11 +342,9 @@ void lapd_transmit(struct lapd_instance *li, uint8_t tei, uint8_t sapi,
 static int send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg)
 {
 	struct lapd_datalink *dl = lctx->dl;
-	struct lapd_sap *sap =
-		container_of(dl, struct lapd_sap, dl);
-	struct lapd_instance *li = sap->tei->li;
+	struct lapv5_sap *sap = container_of(dl, struct lapv5_sap, dl);
+	struct lapv5_instance *li = sap->li;
 	int format = lctx->format;
-	int addr_len;
 
 	/* control field */
 	switch (format) {
@@ -567,16 +367,9 @@ static int send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg)
 		return -EINVAL;
 	}
 	/* address field */
-	if (li->profile.short_address && lctx->tei == 0)
-		addr_len = 1;
-	else
-		addr_len = 2;
-	msg->l2h = msgb_push(msg, addr_len);
+	msg->l2h = msgb_push(msg, 2);
 	msg->l2h[0] = LAPD_ADDR2(lctx->sapi, lctx->cr);
-	if (addr_len == 1)
-		msg->l2h[0] |= 0x1;
-	else
-		msg->l2h[1] = LAPD_ADDR3(lctx->tei);
+	msg->l2h[1] = LAPD_ADDR3(lctx->tei);
 
 	/* write to PCAP file, if enabled. */
 	osmo_pcap_lapd_write(li->pcap_fd, OSMO_LAPD_PCAP_OUTPUT, msg);
@@ -592,47 +385,42 @@ static int send_ph_data_req(struct lapd_msg_ctx *lctx, struct msgb *msg)
 static int send_dlsap(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx)
 {
 	struct lapd_datalink *dl = lctx->dl;
-	struct lapd_sap *sap =
-		container_of(dl, struct lapd_sap, dl);
-	struct lapd_instance *li;
-	uint8_t tei, sapi;
-	char *op = (dp->oph.operation == PRIM_OP_INDICATION) ? "indication"
-							: "confirm";
+	struct lapv5_sap *sap = container_of(dl, struct lapv5_sap, dl);
+	struct lapv5_instance *li;
+	const char *op = (dp->oph.operation == PRIM_OP_INDICATION) ? "indication" : "confirm";
+	uint16_t dladdr;
 
-	li = sap->tei->li;
-	tei = lctx->tei;
-	sapi = lctx->sapi;
+	li = sap->li;
+
+	dladdr = lctx->tei << 8 | lctx->sapi;
 
 	switch (dp->oph.primitive) {
 	case PRIM_DL_EST:
-		LOGDL(dl, LOGL_NOTICE, "LAPD DL-ESTABLISH %s TEI=%d "
-			"SAPI=%d\n", op, lctx->tei, lctx->sapi);
+		LOGDL(dl, LOGL_NOTICE, "LAPD DL-ESTABLISH %s DLADDR=%u\n", op, dladdr);
 		break;
 	case PRIM_DL_REL:
-		LOGDL(dl, LOGL_NOTICE, "LAPD DL-RELEASE %s TEI=%d "
-			"SAPI=%d\n", op, lctx->tei, lctx->sapi);
-		lapd_sap_free(sap);
+		LOGDL(dl, LOGL_NOTICE, "LAPD DL-RELEASE %s DLADDR=%u\n", op, dladdr);
+		lapv5_sap_free(sap);
 		/* note: sap and dl is now gone, don't use it anymore */
 		break;
 	default:
 		;
 	}
 
-	li->receive_cb(dp, tei, sapi, li->receive_cbdata);
+	li->receive_cb(dp, dladdr, li->receive_cbdata);
 
 	return 0;
 }
 
-/* Allocate a new LAPD instance */
-struct lapd_instance *lapd_instance_alloc2(int network_side,
+/* Allocate a new LAPV5 instance */
+struct lapv5_instance *lapv5_instance_alloc(int network_side,
 	void (*tx_cb)(struct msgb *msg, void *cbdata), void *tx_cbdata,
-	void (*rx_cb)(struct osmo_dlsap_prim *odp, uint8_t tei, uint8_t sapi,
-			void *rx_cbdata), void *rx_cbdata,
+	void (*rx_cb)(struct osmo_dlsap_prim *odp, uint16_t dladdr, void *rx_cbdata), void *rx_cbdata,
 	const struct lapd_profile *profile, const char *name)
 {
-	struct lapd_instance *li;
+	struct lapv5_instance *li;
 
-	li = talloc_zero(NULL, struct lapd_instance);
+	li = talloc_zero(NULL, struct lapv5_instance);
 	if (!li)
 		return NULL;
 
@@ -645,35 +433,25 @@ struct lapd_instance *lapd_instance_alloc2(int network_side,
 	li->name = talloc_strdup(li, name);
 	memcpy(&li->profile, profile, sizeof(li->profile));
 
-	INIT_LLIST_HEAD(&li->tei_list);
+	INIT_LLIST_HEAD(&li->sap_list);
 
 	return li;
 }
 
-struct lapd_instance *lapd_instance_alloc(int network_side,
-	void (*tx_cb)(struct msgb *msg, void *cbdata), void *tx_cbdata,
-	void (*rx_cb)(struct osmo_dlsap_prim *odp, uint8_t tei, uint8_t sapi,
-			void *rx_cbdata), void *rx_cbdata,
-	const struct lapd_profile *profile)
-{
-	return lapd_instance_alloc2(network_side, tx_cbdata, tx_cb, rx_cb, rx_cbdata, profile, NULL);
-}
-
 
 /* Change lapd-profile on the fly (use with caution!) */
-void lapd_instance_set_profile(struct lapd_instance *li,
-			       const struct lapd_profile *profile)
+void lapv5_instance_set_profile(struct lapv5_instance *li, const struct lapd_profile *profile)
 {
 	memcpy(&li->profile, profile, sizeof(li->profile));
 }
 
-void lapd_instance_free(struct lapd_instance *li)
+void lapv5_instance_free(struct lapv5_instance *li)
 {
-	struct lapd_tei *teip, *teip2;
+	struct lapv5_sap *sap, *sap2;
 
-	/* Free all TEI instances */
-	llist_for_each_entry_safe(teip, teip2, &li->tei_list, list) {
-		lapd_tei_free(teip);
+	/* Free all SAP instances */
+	llist_for_each_entry_safe(sap, sap2, &li->sap_list, list) {
+		lapv5_sap_free(sap);
 	}
 
 	talloc_free(li);
@@ -692,6 +470,7 @@ void lapd_instance_free(struct lapd_instance *li)
  * while the last octet (before msg->tail) points to the last FCS octet. */
 int lapv5ef_rx(struct v5x_link *link, struct msgb *msg)
 {
+	struct lapd_datalink *dl;
 	uint16_t efaddr, efaddr_enc;
 	bool is_isdn;
 
@@ -715,13 +494,26 @@ int lapv5ef_rx(struct v5x_link *link, struct msgb *msg)
 	switch (efaddr) {
 	case V51_DLADDR_PSTN:
 		/* hand-over to LAPD-DL instance for PSTN */
+		dl = &link->interface->pstn.dl;
+		/* TODO */
 		break;
 	case V51_DLADDR_CTRL:
 		/* hand-over to LAPD-DL instance for CTRL */
+		/* TODO */
+		dl = &link->interface->control.dl;
 		break;
 	case V52_DLADDR_BCC:
+		dl = &link->interface->bcc.dl;
+		/* TOOD: implement V5.2 */
+		msgb_free(msg);
+		break;
 	case V52_DLADDR_PROTECTION:
+		dl = &link->interface->protection[0].dl;
+		/* TOOD: implement V5.2 */
+		msgb_free(msg);
+		break;
 	case V52_DLADDR_LCP:
+		dl = &link->interface->lcp.dl;
 		/* TOOD: implement V5.2 */
 		msgb_free(msg);
 		break;
@@ -732,5 +524,8 @@ int lapv5ef_rx(struct v5x_link *link, struct msgb *msg)
 			return -EINVAL;
 		}
 		/* relay function for LAPD of user ports */
+		/* TODO */
 	}
+
+	return 0;
 }
diff --git a/lapv5.h b/lapv5.h
new file mode 100644
index 0000000..16829cf
--- /dev/null
+++ b/lapv5.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include <osmocom/abis/lapd.h>
+
+struct lapv5_instance {
+	struct llist_head list;		/* list of LAPV5 instances */
+	bool network_side;
+
+	void (*transmit_cb)(struct msgb *msg, void *cbdata);
+	void *transmit_cbdata;
+	void (*receive_cb)(struct osmo_dlsap_prim *odp, uint16_t dladdr, void *rx_cbdata);
+	void *receive_cbdata;
+
+	struct lapd_profile profile;	/* must be a copy */
+
+	struct llist_head sap_list;	/* list of SAP/datalinks in this instance */
+	int pcap_fd;			/* PCAP file descriptor */
+	char *name;			/* human-readable name */
+};
+
+int lapv5ef_rx(struct v5x_link *link, struct msgb *msg);
diff --git a/v5x_data.c b/v5x_data.c
new file mode 100644
index 0000000..ee27213
--- /dev/null
+++ b/v5x_data.c
@@ -0,0 +1,92 @@
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/linuxlist.h>
+
+#include "v5x_internal.h"
+
+static LLIST_HEAD(v5_instances);
+
+struct v5x_instance *v5x_instance_alloc(void *ctx)
+{
+	struct v5x_instance *v5i = talloc_zero(ctx, struct v5x_instance);
+	if (!v5i)
+		return NULL;
+
+	INIT_LLIST_HEAD(&v5i->interfaces);
+	INIT_LLIST_HEAD(&v5i->user_ports);
+	/* TODO: allocate ctrl_fi */
+
+	llist_add_tail(&v5i->list, &v5_instances);
+
+	return v5i;
+}
+
+static void v5x_ts_init(struct v5x_timeslot *v5ts, uint8_t nr, struct v5x_link *v5l, uint16_t l3_addr)
+{
+	v5ts->nr = nr;
+	v5ts->link = v5l;
+	v5ts->l3_address = l3_addr;
+}
+
+static void v5x_cchan_init(struct v5x_c_channel *v5cc, struct v5x_link *v5l, struct v5x_timeslot *v5ts, bool active)
+{
+	v5cc->link = v5l;
+	v5cc->ts = v5ts;
+	v5cc->active = active;
+}
+
+static void v5x_link_init(struct v5x_link *v5l, struct v5x_interface *v5if, uint8_t id)
+{
+	unsigned int i;
+
+	v5l->id = id;
+	v5l->interface = v5if;
+
+	for (i = 1; i < ARRAY_SIZE(v5l->ts); i++) {
+		v5x_ts_init(&v5l->ts[i], i, v5l, 0 /*l3_addr*/);
+	}
+
+	/* primary c-channel must always be present */
+	v5x_cchan_init(&v5l->c_channel[0], v5l, &v5l->ts[16], true);
+}
+
+struct v5x_interface *v5x_interface_alloc(struct v5x_instance *v5i, enum v5x_dialect dialect)
+{
+	struct v5x_interface *v5if = talloc_zero(v5i, struct v5x_interface);
+	//struct v5x_link *v5l;
+	struct v5x_c_channel *primary_c_chan;
+
+	v5if->instance = v5i;
+	v5if->dialect = dialect;
+
+	/* primary link must alwasy be present */
+	v5x_link_init(&v5if->links[0], v5if, 0);
+	v5if->primary_link = &v5if->links[0];
+
+	primary_c_chan = &v5if->primary_link->c_channel[0];
+
+	
+	/* TODO: allocate fi */
+
+	//lapd_dl_init2(&v5if->control.dl, k, v_rnage, maxf, "control");
+	v5if->control.c_chan = primary_c_chan;
+
+	//lapd_dl_init2(&v5if->pstn.dl, k, v_rnage, maxf, "pstn");
+	v5if->pstn.c_chan = primary_c_chan;
+
+	if (v5if->dialect == V5X_DIALECT_V52) {
+		//lapd_dl_init2(&v5if->lcp.dl, k, v_rnage, maxf, "lcp");
+		v5if->lcp.c_chan = primary_c_chan;
+
+		//lapd_dl_init2(&v5if->bcc.dl, k, v_rnage, maxf, "bcc");
+		v5if->bcc.c_chan = primary_c_chan;
+
+		//lapd_dl_init2(&v5if->protection[0].dl, k, v_rnage, maxf, "protection0");
+		v5if->protection[0].c_chan = primary_c_chan;
+
+		//protection[1] ? 
+	}
+
+	llist_add_tail(&v5if->list, &v5i->interfaces);
+
+	return v5if;
+}
diff --git a/v5x_internal.h b/v5x_internal.h
index 37d9d0e..637bf64 100644
--- a/v5x_internal.h
+++ b/v5x_internal.h
@@ -118,3 +118,6 @@ struct v5x_instance {
 	struct llist_head user_ports;		/* list of v5x_user_port */
 	struct osmo_fsm_inst *ctrl_fi;		/* common control FSM */
 };
+
+struct v5x_instance *v5x_instance_alloc(void *ctx);
+struct v5x_interface *v5x_interface_alloc(struct v5x_instance *v5i, enum v5x_dialect dialect);