diff --git a/linux-kernel/linux-2.6.27.4-misdn-abis.diff b/linux-kernel/linux-2.6.27.4-misdn-abis.diff
new file mode 100644
index 0000000..3691eda
--- /dev/null
+++ b/linux-kernel/linux-2.6.27.4-misdn-abis.diff
@@ -0,0 +1,144 @@
+diff -Nru --exclude-from /sunbeam/home/laforge/scripts/dontdiff linux-2.6.27.4-clean/drivers/isdn/mISDN/layer2.c linux-2.6.27.4/drivers/isdn/mISDN/layer2.c
+--- linux-2.6.27.4-clean/drivers/isdn/mISDN/layer2.c	2008-10-26 00:05:07.000000000 +0200
++++ linux-2.6.27.4/drivers/isdn/mISDN/layer2.c	2008-12-23 16:16:29.000000000 +0100
+@@ -94,8 +94,10 @@
+ 	struct layer2 *l2 = fi->userdata;
+ 	va_list va;
+ 
++#if 0
+ 	if (!(*debug & DEBUG_L2_FSM))
+ 		return;
++#endif
+ 	va_start(va, fmt);
+ 	printk(KERN_DEBUG "l2 (tei %d): ", l2->tei);
+ 	vprintk(fmt, va);
+@@ -882,6 +884,8 @@
+ 	l2->va = 0;
+ 	l2->vr = 0;
+ 	l2->sow = 0;
++	l2->sapi = skb->data[0] >> 2;
++	set_channel_address(&l2->ch, l2->sapi, l2->tei);
+ 	clear_exception(l2);
+ 	send_uframe(l2, NULL, UA | get_PollFlag(l2, skb), RSP);
+ 	mISDN_FsmChangeState(fi, ST_L2_7);
+@@ -898,6 +902,7 @@
+ 	struct layer2 *l2 = fi->userdata;
+ 	struct sk_buff *skb = arg;
+ 
++	printk(KERN_DEBUG "l2_send_UA()\n");
+ 	send_uframe(l2, skb, UA | get_PollFlag(l2, skb), RSP);
+ }
+ 
+@@ -931,6 +936,8 @@
+ 	l2->va = 0;
+ 	l2->vr = 0;
+ 	l2->sow = 0;
++	l2->sapi = skb->data[0] >> 2;
++	set_channel_address(&l2->ch, l2->sapi, l2->tei);
+ 	mISDN_FsmChangeState(fi, ST_L2_7);
+ 	stop_t200(l2, 3);
+ 	mISDN_FsmRestartTimer(&l2->t203, l2->T203, EV_L2_T203, NULL, 3);
+@@ -982,6 +989,8 @@
+ 	} else if (l2->vs != l2->va) {
+ 		skb_queue_purge(&l2->i_queue);
+ 		pr = DL_ESTABLISH_IND;
++		//l2->sapi = skb->data[0] >> 2;
++		//set_channel_address(&l2->ch, l2->sapi, l2->tei);
+ 	}
+ 	stop_t200(l2, 5);
+ 	l2->vr = 0;
+@@ -1841,11 +1850,14 @@
+ 	u_int	l;
+ 	int	c = 0;
+ 
++	printk(KERN_DEBUG "ph_data_indication 0x%x 0x%x 0x%x\n", datap[0], datap[1], datap[2]);
++
+ 	l = l2addrsize(l2);
+ 	if (skb->len <= l) {
+ 		mISDN_FsmEvent(&l2->l2m, EV_L2_FRAME_ERROR, (void *) 'N');
+ 		return ret;
+ 	}
++#if 0
+ 	if (test_bit(FLG_LAPD, &l2->flag)) { /* Maybe not needed */
+ 		psapi = *datap++;
+ 		ptei = *datap++;
+@@ -1875,6 +1887,7 @@
+ 			return 0;
+ 		}
+ 	} else
++#endif
+ 		datap += l;
+ 	if (!(*datap & 1)) {	/* I-Frame */
+ 		c = iframe_error(l2, skb);
+@@ -1890,6 +1903,7 @@
+ 			ret = mISDN_FsmEvent(&l2->l2m, EV_L2_UI, skb);
+ 	} else if (IsSABME(datap, l2)) {
+ 		c = unnum_error(l2, skb, CMD);
++		printk(KERN_DEBUG "IsSABME() returned true, unnum_error=%d\n", c);
+ 		if (!c)
+ 			ret = mISDN_FsmEvent(&l2->l2m, EV_L2_SABME, skb);
+ 	} else if (IsUA(datap)) {
+@@ -2087,7 +2101,7 @@
+ 		test_and_set_bit(FLG_LAPD, &l2->flag);
+ 		test_and_set_bit(FLG_LAPD_NET, &l2->flag);
+ 		test_and_set_bit(FLG_MOD128, &l2->flag);
+-		l2->sapi = 0;
++		l2->sapi = 62;
+ 		l2->maxlen = MAX_DFRAME_LEN;
+ 		if (test_bit(OPTION_L2_PMX, &options))
+ 			l2->window = 7;
+diff -Nru --exclude-from /sunbeam/home/laforge/scripts/dontdiff linux-2.6.27.4-clean/drivers/isdn/mISDN/tei.c linux-2.6.27.4/drivers/isdn/mISDN/tei.c
+--- linux-2.6.27.4-clean/drivers/isdn/mISDN/tei.c	2008-10-26 00:05:07.000000000 +0200
++++ linux-2.6.27.4/drivers/isdn/mISDN/tei.c	2008-12-23 16:32:59.000000000 +0100
+@@ -830,18 +830,29 @@
+ 	int		tei, ri;
+ 	struct layer2	*l2;
+ 
++	printk(KERN_DEBUG "new tei request: tei=%d\n", dp[3] >> 1);
++
+ 	ri = dp[0] << 8;
+ 	ri += dp[1];
+-	if (!mgr->up)
+-		goto denied;
+-	tei = get_free_tei(mgr);
+-	if (tei < 0) {
+-		printk(KERN_WARNING "%s:No free tei\n", __func__);
++	if (!mgr->up) {
++		printk(KERN_DEBUG "mgr->up == NULL\n");
+ 		goto denied;
+ 	}
++	if (dp[3] != 0xff) {
++		/* This is a TEI request according to 3GPP TS 08.56 6.1.11.2 */
++		tei = dp[3] >> 1;
++	} else {
++		tei = get_free_tei(mgr);
++		if (tei < 0) {
++			printk(KERN_WARNING "%s:No free tei\n", __func__);
++			goto denied;
++		}
++	}
+ 	l2 = create_new_tei(mgr, tei);
+-	if (!l2)
++	if (!l2) {
++		printk(KERN_DEBUG "create_new_tei == NULL\n");
+ 		goto denied;
++	}
+ 	else
+ 		mISDN_FsmEvent(&l2->tm->tei_m, EV_ASSIGN_REQ, dp);
+ 	return;
+@@ -1159,12 +1170,14 @@
+ 		return -ENOTCONN;
+ 	if (skb->len != 3)
+ 		return -ENOTCONN;
++#if 0
+ 	if (skb->data[0] != 0)
+ 		/* only SAPI 0 command */
+ 		return -ENOTCONN;
++#endif
+ 	if (!(skb->data[1] & 1)) /* invalid EA1 */
+ 		return -EINVAL;
+-	tei = skb->data[1] >> 0;
++	tei = skb->data[1] >> 1;
+ 	if (tei > 63) /* not a fixed tei */
+ 		return -ENOTCONN;
+ 	if ((skb->data[2] & ~0x10) != SABME)